ICQF-17 / 1

3rd International Conference

Quantum Foundations 2017

(ICQF-17)

04-09 December, 2017

Program and Book of Abstracts

Venue: Hotel Panache, Patna

Organised by

Department of Physics

National Institute of Technology Patna

India

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ICQF-17 / 3

PROGRAM

4th

December 2017

Event Timing (IST)

REGISTRATION 09:00 - 10:00

INAUGURATION 10:00 - 10:30

TEA BREAK 10:30 -11:00

Name of the

speaker

Title of the talk Timing (IST) Duration**

(minutes)

Chair: G. S. AGARWAL

P. Busch* Quantum Uncertainty Regions – Theory and

Experiment

11:00 - 11:45 45

D. Home* Generalised Weak Measurement assisted Remote

State Preparation and Demonstration of Hidden

Nonlocality

11:45 - 12:30 45

M. Pawlowski Random access codes - a review 12:30 - 13:05 35

Lunch (13:05 - 14:30) #

Chair: P. GHOSE

S. M. Roy* Contractive Quantum States 14:30 - 15:15 45

C. Branciard Multipartite quantum processes and correlations

with no definite causal order

15:15 - 15:50 35

Y. C. Liang What can we learn from the apparent violation

of the nonsignaling conditions?

15:50 - 16:25 35

Tea break (16:25 - 16:50)

Chair: D. HOME

A. R. Usha Devi Asymptotic limit of diffusive quantum

trajectories

16:50 - 17:25 35

H. F. Hofmann Superpositions of causality: an analysis of the

mechanisms of control in the quantum limit

17:25 - 18:00 35

Dinner (19:00 - 21:00) ##

5th

December 2017

Chair: P. BUSCH

G. S. Agarwal* Subradiance to Hyperradiance in Strong

Coupling Cavity QED

9:30 - 10:30 60

P. Ghosh Quantum and Classical Mechanics: Building A

Bridge

10:30-11:05 35

P. K. Panigrahi Quantum coherence, Holevo Bound and

Quantum Discord

11:05 – 11:40 35

Tea Break (11:40 - 12:00)

Chair: A. R. USHA DEVI

Y. Shikano Quantum Phase through Quantum Tunneling 12:00 - 12:35 35

S. Banerjee Aspects of Non-Markovianity In Quantum

Walks

12:35 - 13:10 35

Lunch (13:10 - 14:20) Chair: L. MACCONE

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D. Rohrlich* What is nonlocal in “counterfactual

communication”?

14:20 - 15:05 45

G. Kar Quantum nonlocality does not demand all-out

randomness in measurement choice

15:05 - 15:40 35

A. Matzkin Strong and weak single particle nonlocality

induced by time dependent boundary conditions

15:40 - 16:15 35

Tea break (16:15 - 16:35)

Chair: P. K. PANIGRAHI

U. Sinha Correlated photonic qutrit pairs for quantum

information and communication

16:35 - 17:10 35

S. Sponer Measurement Uncertainty Relations: operator-

based, operational and information-theoretic

approaches studied in Neutron Optics

17:10 - 17:45 35

M. Banik Exclusivity principle and unphysicality of Garg-

Mermin correlation

17:45 - 18:05 20

Dinner (19:00 - 21:00)

6th

December 2017 Free day discussion session

7th

December 2017

Chair: A. JORDAN

L. Maccone* Quantum time and quantum spacetime 9:30 - 10:15 45

S. Ghosh Self-testing via nonlocality-without-inequality

arguments

10:15 - 10:50 35

E. Cavalcanti Bell and Kochen-Specker inequalities from no-

fine-tuning

10:50 - 11:25 35

Tea Break (11:25 - 11:45)

Chair: S. GHOSH

A. Majumdar Sharing of nonlocality 11:45 - 12:20 35

K. Edamatsu Nonlocal two-qubit measurement using spin

products

12:20 - 12:55 35

Lunch (12:55 - 14:15) Chair: A. MAJUMDAR

A. K. Pati* Tighter uncertainity and Reverse uncertainity

relation

14:15 - 15:00 45

F. Buscemi Secure Disposal of Information and Quantum

Private Decoupling

15:00 -15:35 35

Le Bin Ho Continuous pointer state approach to modular-value

amplification

15:35 - 15:55 20

POSTER SESSION (16:00-17:45)

CULTURAL PROGRAMME (18:00-19:30) CONFERENCE DINNER*#

(19:45 - 23:00)

8th

December 2017

Chair: A. K. PATI

A. Jordan* Strength in weakness: quantum trajectories,

foundations, and precision measurements

9:30 - 10:15 45

D. Sarkar Correlations in multipartite scenario 10:15 - 10:50 35

O. Maroney "What's Fine for Leggett & Garg? About

Macrorealisms & Measurement disturbances"

10:50 - 11:25 35

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Tea Break (11:25 - 11:50)

Chair: D. SARKAR

Arvind Protecting Quantum States of NMR Qubits 11:50-12:25 35

R. P. Singh Using non-separable state of light to find the

“lost” phase structure

12:25-13:00 35

Lunch (13:00 - 14:30)

Chair: M. GENOVESE

L. Vaidman* The past of a quantum particle 14:30 - 15:15 45

R. Shrikanth A quantum cryptographic route to the reality of

the quantum state

15:15 - 15:50 35

R. Rahman Quantum anonymous veto based on GHZ

correlations

15:50 - 16:25 35

Tea break (16:25 - 16:50)

Chair: G. KAR

J. Dressel Quantum Trajectories with Many Worlds 16:50 - 17:25 35

A. Avella Quantum measurement in weak coupling

regime: from non-contextuality in weak values to

protective measurements

17:25 - 18:00 35

Dinner (19:00 – 21:00)

9th

December 2017

Chair: L. VAIDMAN

M. Genovese* Time and quantum correlations: experimental

visualizations

9:30 - 10:15 45

A. Sen De Deterministic Quantum Dense Coding Networks 10:15 - 10:50 35

T. Qureshi Measuring Coherence in Multislit Interference 10:50 - 11:25 35

Tea Break (11:25 - 11:45)

Chair: ARVIND

N. Sakharwade Bidirectional Dense Coding and Teleportation in

Butterfly network

11:45 - 12:05 20

Aravinda S Combinatorial approach to non-classicality and

cryptographic security in single systems

12:05 - 12:25 20

R. Venkatrama Negations and Truth-Perspectives pertaining to

Qudits based Multi-valued Quantum Computational

Logics

12:25 - 12:45 20

G. Sharma Complementarity Relation for Coherence and

Disturbance

12:45 - 13:05 20

Closing Remark: 13:05 – 13:30

Lunch (13:30 - 14:30)

*Key note speaker

**Duration includes the time for discussions. The duration of discussions is 10 minutes for Keynote

speakers and 5 minutes for rest of the speakers. # Lunches (except 6

th December) will be served at the Conference Hotel (Panache Hotel) for all

participants. ##

Dinners (except 7th December) will be served at the same hotel/guest house where the

speaker/participant is accommodated.

**Conference Dinner will be served at the Hotel panache. All participants are invited to join.

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TITLE AND ABSTRACTS

Invited Talks

Name G. S. Agarwal

Affiliation Texas A&M University, USA

Title Subradiance to Hyperradiance in Strong Coupling Cavity QED

Abstract The collective behavior of an ensemble of atoms has been studied in-depth since the

seminal paper of Dicke where he demonstrated that a group of emitters in collective

states is able to radiate with increased intensity a phenomenon that he called

superradiance. Almost all studies of superradiance since then have been in the weak

coupling regime of the interaction. The strong coupling which one can routinely

achieve in cavity QED can lead to a variety of new behavior starting from

subradiance to hyperradiance. We discuss various mechanisms behind

hyperradiance and possible nonclassical nature of the emitted radiation.

Name Arvind

Affiliation IISER-Mohali, India

Title Protecting Quantum States of NMR Qubits

Abstract The talk will describe our recent work on generation, estimation and preservation of

novel quantum states of two and three qubit NMR systems. Quantum states which

display quantum correlations play a key role in performing specific quantum

information processing tasks. We have prepared several types of correlated quantum

states which are quite fragile and implemented various types of preservation

schemes on them. We use several pulse sequences based on dynamical decoupling

schemes to decouple system-bath interactions, thereby suppressing the decoherence

of the state under study. Our schemes have important implications for the realistic

protection of delicate quantum states.

Name A. Avella

Affiliation INRIM, Turin, Italy

Title Quantum measurement in weak coupling regime: from non-contextuality in

weak values to protective measurements

Abstract Quantum mechanics, one of the keystones of modern physics, has an unprecedented

success in predicting the behavior of nature, leading to a perfect agreement between

theoretical predictions and experimental results in a vast amount of fields. However,

until this day, there is a strong debate about the foundational concepts of quantum

mechanics [1-4].

Weak value measurements have recently given rise to a great amount of interest in

both the possibility of measurement amplification and the chance for further

quantum mechanics foundations investigation. In particular, a question emerged

about weak values being proof of the incompatibility between quantum mechanics

and non-contextual hidden variables theories (NCHVTs). A test to provide a

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conclusive answer to this question was given by Pusey [5] where a theorem was

derived showing the NCHVT incompatibility with the observation of anomalous

weak values under specific conditions. We realized this proposal, clearly pointing

out the connection between weak values and the contextual nature of quantum

mechanics [6].

Another very intriguing aspect of quantum mechanics that we have investigated by

means of weak measurements is the fact that variables might not have definite

values. A complete quantum description provides only probabilities to obtain

various eigenvalues of a quantum variable. In particular, the expectation value is

known to be a statistical property of an ensemble of quantum systems. In contrast to

this paradigm, we demonstrate a unique method allowing to extract information

about the expectation value of a physical variable on a single particle with a single

measure. Our experimental implementation corresponds to the first realization of

the quantum protective measurement [7][8].

Reference:

[1] M. F. Pusey et al., Nat. Phys. 8, 475 (2012).

[2] L. Hardy, Int. J. Mod. Phys. B 27, 1345012 (2013).

[3] M. Ringbauer et al.; Nat. Phys. 11, 249 2015).

[4] M. Genovese; Adv. Sci. Lett. 3, 249 (2010).

[5] M. F. Pusey; Phys. Rev. Lett. 113, 200401 (2014).

[6] F. Piacentini et al., Phys. Rev. Lett. 116 (18), 180401(2016).

[7] Y. Aharonov and L. Vaidman; Phys. Lett. A 178, 38 (1993).

[8] F. Piacentini et al.; Nature Physics doi:10.1038/nphys4223 (2017).

Name Subhashish Banerjee

Affiliation IIT Jodhpur

Title Aspects of Non-Markovianity In Quantum Walks

Abstract After motivating the need for a study of Open Quantum Systems, we introduce,

briefly, quantum operations and use it to discuss a few well known noise

processes. We then move to some recent developments in the efforts to understand

non-Markovian phenomenon. Our discussion about non-Markovian behaviour will

be made in the backdrop of some well-known non-Markovian processes. We show

how different sources of non-Markovianity could be disambiguated. All this is

done using the platform of Quantum Walks.

Name C. Branciard

Affiliation Institute of Neel, Grenoble, France

Title Multipartite quantum processes and correlations with no definite causal order

Abstract The notion of causality is deeply rooted in our understanding of the world we live

in: we typically understand the relationship between events in terms of causal

relations, where some earlier events are causes for later events. Now, we know that

the quantum world is full of weird phenomena. Cats can be in indefinite states, in a

quantum superposition of being alive and dead. It has been realised recently that

causal relations themselves can be indefinite, in some kind of quantum

superposition. However, a good understanding of quantum processes with indefinite

causal order, and of the correlations they may generate is still missing. In this talk I

will describe recent research on those new concepts, with a special focus on the

subtleties that arise in the multipartite case.

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Name F. Buscemi

Affiliation Nagoya University, Japan

Title Secure Disposal of Information and Quantum Private Decoupling

Abstract Correlations between an "object system" (accessible) and a "reference system"

(inaccessible) can be understood as the amount of information that one possesses

about the reference. When faced with the problem of erasing such information

(correlations), the direct approach is "to dump" them in the environment, that is,

hand them over to an eavesdropper. In order to give a model-independent

description of secure information disposal, I propose here the paradigm of "private

quantum decoupling," where the goal is to decouple the system from the reference,

by acting locally on the system and, at the same time, maintaining its local

environment decoupled from the reference.

In this framework, the concept of private local randomness naturally arises as a

resource, and total correlations are divided into "extrinsic" (disposable) and

"intrinsic" (non-disposable) ones. I show upper and lower bounds on the amount of

intrinsic correlations present in an arbitrary bipartite state, and show that, in

tripartite pure states, they satisfy a monogamy constraint, making apparent their

quantum nature. A relation with entanglement theory is provided, by showing that

intrinsic correlations constitute an entanglement parameter. Finally, I compute the

regularized intrinsic correlations and show that these equal the coherent

information, which is thus equipped with a new operational interpretation. This

implies, in particular, that separable correlations are all extrinsic. Reference: F.

Buscemi, "Private Quantum Decoupling and Secure Disposal of Information." New

J. Phys., vol. 11, 123002 (2009).

Name P. Busch

Affiliation University of York, UK

Title Quantum Uncertainty Regions – Theory and Experiment

Abstract Recent break-through results in the rigorous formulation of the joint measurement

aspect of Heisenberg’s uncertainty principle (which I reviewed in my talk at

ICQF15) have led to a boost of research activity into finding novel variants of

measurement uncertainty relations. Here I discuss the most comprehensive and

stringent way of casting such relations, namely in the form of uncertainty regions. I

will explain this concept, give examples both for preparation and measurement

uncertainty, and describe some recent experimental confirmations.

Name E. Cavalcanti

Affiliation Griffith University, Australia

Title "Bell and Kochen-Specker inequalities from no-fine-tuning"

Abstract Nonlocality and contextuality are at the root of conceptual puzzles in quantum

mechanics, and are key resources for quantum advantage in information-processing

tasks. Bell nonlocality is best understood as the incompatibility between quantum

correlations and the classical theory of causality, applied to relativistic causal

structure. Contextuality, on the other hand, is on a more controversial foundation.

In this work, I provide a common conceptual ground between nonlocality

and contextuality as violations of classical causality. First, I generalise a recent

work by Wood and Spekkens, who showed that all causal models for certain Bell-

inequality violations require fine-tuning of its causal parameters -- regardless of the

underlying causal structure. Here I show this result holds without two of the original

ICQF-17 / 10

assumptions, applies to all (bipartite) cases of Bell nonlocality, and remarkably,

does not require any extra assumption related to "free choice" or independence

between hidden variables and measurement settings, unlike all other derivations of

Bell inequalities. As a consequence, it can be applied to contextuality scenarios: all

causal models for violations of a Kochen-Specker-contextuality inequality

(involving two measurements per context) require fine-tuning. Thus the quantum

violation of classical causality goes beyond the case of space-like separated

systems, and manifests already in scenarios involving single systems.

Name Justin Dressel

Affiliation Chapman University, USA

Title Quantum Trajectories with Many Worlds

Abstract The usual formulation of quantum trajectory theory seems distinct from the standard

quantum theory at face value, since it involves stochastic master equations that

modify the unconditioned unitary dynamics. A careful analysis of a realistic

continuous measurement for a superconducting qubit corrects this misconception,

and highlights interesting subtleties like delayed choice measurements that are

hidden in the standard treatment. This analysis also makes clear how to understand

such a measurement from a purely unitary many worlds perspective.

Name K. Edamatsu

Affiliation Tohoku University, Japan

Title Nonlocal two-qubit measurement using spin products

Abstract A simple protocol for nonlocal and generalized two-qubit measurement is proposed.

It consists of measurements of nonlocal spin product operators [1] with the help of

shared entanglement as an ancillary resource. The protocol also realizes complete

and deterministic Bell state measurement between a pair of distant qubits, as well as

a complete Bell filter that transmits either one of the Bell states indicated by the

measurement outcome [2]. These schemes can be implemented using photon

polarization qubits by which measurement uncertainty relation for a single qubit is

investigated [3].

References

[1] A. Brodutch and E. Cohen, Phys. Rev. Lett. 116, 070404 (2016).

[2] K. Edamatsu, arXiv:1612.0857.

[3] K. Edamatsu, Phys. Scr. 91, 073001 (2016).

Name Marco Genovese Affiliation NRIM, Turin, Italy Title Time and quantum correlations: experimental visualizations

Abstract Quid est ergo tempus? si nemo ex me quaerat, scio; si quaerenti explicare velim,

nescio 1

As Aurelius Augustinus everybody has a clear perception of what time is, but a

clear physical definition of what it is still remains a debated task. The ―problem of

time‖ in present physics substantially stems from the fact that a straightforward

quantization of the general relativistic evolution equation and constraints generates

for the Universe wave function the Wheeler-De Witt equation [1], which describes

a static Universe. Page and Wootters [2] considered the fact that there exist states

of a system composed by entangled subsystems that are stationary, but one can

interpret the component subsystems as evolving: this leads them to suppose that the

global state of the universe can be envisaged as one of this static entangled state,

whereas the state of the subsystems (us, for example) can evolve.

Here I present two experiments addressed to visualise this phenomenon. The first is

ICQF-17 / 11

based on PDC polarisation entangled photons that allows showing with a practical

example a situation where this idea works, i.e. a subsystem of an entangled state

works as a "clock" of another subsystem [3]. However, the simple original Page and

Wootters model needs some extension for describing several time measurements

[4]. Similarly, in our first experiment the Use of a two-dimensional clock implies

that the time is discrete, periodic and can take only two values: 0 and 1. In a second

experiment [5], that I present here for the first time, we use a continuous system (the

position of a photon) to describe time, which gives us access to measurements at

arbitrary times and hence arbitrary two-time correlations.

[1] C.Rovelli, quant-gr0006061

[2] D.N. Page and W.K. Wootters, Phys. Rev. D 27, 2885 (1983); W.K. Wootters,

Int. J. Theor. Phys. 23, 701 (1984).

[3] E.Moreva,M.Gramegna,G.Brida,L.Maccone,M.Genovese, Phys. Rev. A 89,

052122 (2014).

[4] V.Giovannetti, S.Lloyd, L.Maccone, Phys. Rev. D, 92, 045033 (2015).

[5] E.Moreva, M.Gramegna, G. Brida, L. Maccone and M.Genovese, Phys. Rev.D

in press. (arXiv:1710.00707) 1What is the time? If nobody ask me, I know; whether I want to explain it to

somebody, I do not know.

Name Partha Ghose Affiliation INSA New Delhi, India Title Quantum and Classical Mechanics: Building A Bridge

Abstract It is first shown that when the Schrodinger equation for a system is written in the

Hamilton-Jacobi form, complete information about the system's quantum-ness is

separated out in a single term Q, the so called `quantum potential'. Based on this, an

operator formulation of classical statistical mechanics using complex wave

functions spanning a Hilbert space is then proposed, and its similarities and

differences with quantum mechanics are pointed out. The formulation goes beyond

standard classical statistical mechanics in predicting coherent superpositions of

classical states that do not exhibit any interference patterns and challenge deeply

held notions of classical-ness, quantum-ness, entanglement, macro realism and the

significance of violations of Bell-like and Leggett-Garg inequalities. It also provides

a more secure foundation to delve deeper into the area of quantum-classical

correspondence and information processing than exists at present.

Name Sibashish Ghosh Affiliation IMSc Chennai, India Title Self-testing via nonlocality-without-inequality arguments

Abstract Given any entangled state of a bipartite quantum system, shared between two far

apart parties, what is the best task it can offer? Self-testing provides one kind of

solution for such a task in the sense that if such a state is pure, it will violate a local-

realistic inequality maximally. Such an inequality -- referred

to as a `tilted Bell inequality' -- depends on a parameter which, in turn, depends on

the entanglement of the given pure state. Considering Hardy-type nonlocality-

without-inequality argument for two dichotomic measurement settings per site, we

provide here self-testing for any given two-qubit non-maximally entangled pure

state -- by appending at most one extra condition on the observed joint probabilities.

Similarly, by appending at most two extra conditions on the observed joint

probabilities, we provide here Cabello-type self-testing argument for any such state.

Finally, we try to provide a comparison of strengthness of the aforesaid self-testing

protocol with the associated protocol(s) expressed in terms of corresponding local-

realistic inequality.

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Name Holger F. Hofmann Affiliation Hiroshima University, Japan Title Superpositions of causality: an analysis of the mechanisms of control in the

quantum limit

Abstract Experimentally, quantum state preparation and measurement require extreme levels

of control over the dynamics of quantum systems. As a result, the procedures of

state preparation and measurement seem to produce separate "contextual" realities

of the same system, with paradoxical statistical relations between these separate

realities. Although much progress has been made to identify non-classical features

of quantum statistics, quantum theory only describes these phenomena, without

providing any satisfactory explanation in the form of unifying concepts or

principles. Here, I present a possible solution to the problem based on the

description of non-classical statistics by weak values and Dirac distributions. The

key to non-classical features is then found in the complex phases that relate the

effects of quantum interferences to reversible transformations of quantum states and

their associated statistics. I will argue that this relation provides us with a non-trivial

explanation of quantum physics that can resolve fundamental questions about the

origin and nature of quantum phenomena such as entanglement and quantum jumps.

In particular, this new perspective on quantum physics should motivate us to

investigate the actual processes involved in state preparation and the role played by

the physics of control in the available quantum technologies, significantly

improving our understanding of large scale quantum processes.

Reference: [1] H. F. Hofmann, "Quantum paradoxes originating from the nonclassical statistics

of physical properties related to each other by half-periodic transformations," Phys.

Rev. A 91, 062123 (2015).

[2] H.F. Hofmann, "On the fundamental role of dynamics in quantum physics," Eur.

Phys. J. D 70, 118 (2016).

[3] H. F. Hofmann "Quantum interference of position and momentum: A particle

propagation paradox," Phys. Rev. A 96, 020101(R) (2017).

Name Dipankar Home Affiliation Bose Institute, Kolkata, India Title Generalised Weak Measurement assisted Remote State Preparation and

Demonstration of Hidden Nonlocality

Abstract Taking cue from the standard weak measurement scenario, we generalise it by

introducing a finite strength coupling between an ancilla and one of the members

(referred to as Alice) of spatially separated correlated particles, followed by

postselection through projective measurement on the ancilla. Corresponding to each

postselected outcome on Alice’s side, we find that the state of the other member

(referred to as Bob) of the spatially correlated system can be prepared very close to

a target state of Alice’s choice. By choosing an appropriate fidelity measure that is

averaged over all pure target states on Alice’s side, we show that this protocol can

implement remote state preparation giving quantum advantage for all Bell diagonal

states.

A further significance of the novel scenario used for the above suggested remote

state preparation scheme is that it can also be used to reveal hidden nonlocality for a

class of bipartite qubit states that do not initially exhibit nonlocality. Indications will

be given of further studies for probing the usefulness of such a scheme.

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Name Andrew N. Jordan Affiliation University of Rochester, USA Title Strength in weakness: quantum trajectories, foundations, and precision

measurements

Abstract This overview talk will outline recent developments in quantum theory and

experiment, focusing on weak and continuous measurements. I will discuss the

basic theory behind this field, highlighting the recent stochastic path integral

approach to continuous measurements and the experiments now able to be routinely

done in order to check the accuracy of the theory. I will also discuss some of the

applications of this area of research, such as parameter estimation, state

tomography, and error correction. Finally, some foundational questions addressed

by this field of study will be raised, such as the simultaneous measurement of

noncommuting observables.

Name Guruprasad Kar Affiliation ISI Kolkata, India Title Quantum nonlocality does not demand all-out randomness in measurement

choice Abstract Nonlocality is one of the most intriguing features of quantum mechanics. John Bell,

in his seminal work of 1964, proved that local-realism imposes a bound on the

correlations among the measurement statistics of distant observers. Surpassing this

bound rules out the possibility of local-realistic description of microscopic

phenomena. For detecting Bell-nonlocality, it requires, in the simplest scenario, two

measurements to be performed randomly by each of the two distant observers. In

this work, we propose a novel framework where three measurements, two on

Alice’s side and one on Bob’s side, suffice to reveal quantum nonlocality and hence

does not require all-out randomness in measurement choice. Our method relies on a

very naive operational task in quantum information theory, namely, the minimal

error state discrimination. As a practical implication, this method constitutes an

economic entanglement detection scheme, which uses a less number of entangled

states compared to all such existing schemes. Moreover, the method applies to a

class of generalized probability theories containing quantum theory as a special

example.

Name Y-C. Liang Affiliation National Cheng Kung University, Taiwan Title What can we learn from the apparent violation of the nonsignaling conditions?

Abstract The device-independent approach to physics is one where conclusions are drawn

directly and solely from the observed correlations between measurement outcomes.

This operational approach to physics arose as a byproduct of Bell's seminal work to

distinguish quantum correlations from the set of correlations allowed by a particular

class of physical theories, namely, locally-causal theories. In practice, since one can

only perform a finite number of experimental trials, deciding whether an empirical

observation is compatible with some class of physical theories will have to be

carried out via the task of hypothesis testing.

In this talk, I will review some recent progress on this task based on the prediction-

based-ratio method and discuss how it may allow us to determine the statistical

evidence against some other classes of physical theories, such as those constrained

only by the nonsignaling principle, and those that are constrained to produce the so-

called "almost-quantum" set of correlations. As an application, we demonstrate how

this method allows us to unveil the apparent violation of the nonsignaling

ICQF-17 / 14

conditions in certain experimental data. The implication of this apparent violation

will be briefly discussed.

Name Lorenzo Maccone Affiliation Universita' di Pavia, Italy Title Quantum time and quantum spacetime

Abstract We give a consistent quantum description of time, based on Page and Wootters'

conditional probabilities mechanism, that overcomes the criticisms that were raised

against similar previous proposals. In particular we show how the model allows to

reproduce the correct statistics of sequential measurements performed on a system

at different times. We also give a mechanism to construct a quantum spacetime by

evaluating space and time through quantum rods and clocks. It provides a

framework to treat time and space as homogeneous degrees of freedom. To this

aim, we introduce the state of the system conditioned on a position in space whereas

the conventional formulation of quantum theory considers only states that are

conditioned on time.

Name Archan Majumdar Affiliation SNBCS Kolkata, India Title Sharing of nonlocality

Abstract We address the question as to whether the nonlocality of a single member

of an entangled pair of spin 1/2 particles can be shared among multiple observers on

the other wing who act sequentially and independently of each

other. We first show that the optimality condition for the trade-off between

information gain and disturbance in the context of weak or non-ideal measurements

emerges naturally when one employs a one-parameter class of positive operator

valued measures (POVMs). Using this formalism we then prove analytically that it

is impossible to obtain violation of the Clauser-Horne-Shimony-Holt (CHSH)

inequality by more than two Bobs in one of the two wings using unbiased input

settings with an Alice in the other wing. We finally consider the steering scenario

for two-qubits with two measurement settings for each observer. We show that the

Cavalcanti Foster-Fuwa-Wiseman (CFFW) inequality can be violated for an Alice

and at most two Bobs on the other side.

Name Owen Maroney Affiliation Oxford University, UK Title "What's Fine for Leggett and Garg? About Macrorealisms and Measurement

disturbances."

Abstract "In recent years the precise control involved in quantum measurements has allowed

the testing of Leggett-Garg Inequality violations in microscopic systems, and a

renewed interest in understanding precisely what such a violation implies. Doubts

have been raised whether such violations are a problem for macrorealism, as

Leggett and Garg thought, or are just a problem for non-invasive measurements,

and whether the Leggett Garg Inequalities themselves could be replaced with better

tests.

I will attempt to bring some clarity to this issue by presenting a root theorem that

incorporates both the Leggett-Garg Inequality and some of the suggestions for

replacing it, and argue that it is the possibility of an explanation in terms of non-

invasive measurements that is at stake in these tests. However, I will also show that

whenever a non-invasive explanation is possible, then a macrorealist non-invasive

model is also possible. This is analogous to the situation with Bell's inequality,

where it is local causality, rather than hidden variables, that is at stake, but that

whenever a locally causal explanation is possible, a locally causal hidden variable

ICQF-17 / 15

model is also possible. Finally I will show how macrorealism is no more committed

to non-invasive measureability than hidden variables are restricted to be locally

causal, and will briefly discuss how wider classes of macrorealist theories may yet

be experimentally ruled out by different kinds of experimental tests."

Name Paolo Mataloni Affiliation University Sapienza Of Rome, Italy Title Weak and strong non-Markovianity

Abstract The simulation of non-Markovian dynamics and the test of its main features have

been object of several experimental works in the last years, with relevant examples

mainly based on the use of all-optical systems. Generally, non-Markovian regimes

featuring environment to system backflow of information (strong non-

Markovianity) have been experimentally simulated. Using an all-optical setup we

have experimentally emonstrated the so-called regime of weak non-Markovianity

occurring even in absence of information backflow from the environment to the

system. In a further experiment we have studied non-Markovianity of open quantum

systems based on the so-called collisional model where the continuous time

evolution of an open quantum system is replaced by a stroboscopic one. I will

present the theoretical and experimental results obtained in the case of single and

two-photon entangled state evolution.

Name Alex Matzkin Affiliation CNRS, Univ. Cergy-Pontoise, France

Title Strong and weak single particle nonlocality induced by time dependent

boundary conditions

Abstract We investigate the issue of single particle nonlocality in a quantum system

subjected to time-dependent boundary conditions. First, we will see that contrary to

earlier claims, there is no strong nonlocality: a quantum state localized at the centre

of a well with moving walls is not modified by the wall's motion. We then show the

existence of a weak form of nonlocality: when a quantum state is extended over the

well, the wall's motion induces a current density all over the box instantaneously.

We indicate how this current density can in principle be measured by performing

weak measurements of the particle's momentum. We will also see how the wall's

motion generates the existence of a global geometric phase at every point of the

box.

Name P. Panigrahi Affiliation IISER-Kolkata, India Title Quantum coherence, Holevo Bound and Quantum Discord

Abstract We explicate the relationship between the information theoretic quantities in

quantum mechanics: quantum coherence, quantum discord and Holevo bound. The

main result of our paper can be summarized by the following two points:

• Equivalence of loss of information and loss of coherence: A physically

motivated resource theory of coherence under operations which do not use

coherence has been recently proposed. The operations which do not use coherence

have been identified as strictly incoherent operations [2]. We considered the task of

classical communication using quantum ensemble { } when the receiver is only

allowed to perform strictly incoherent operation and demonstrated the equivalence

between the loss of information about ( ) and the loss of

coherence due to mixing ∑ ( ) (∑ ) , according to relative entropy

measure of coherence. Here, is the Holevo Bound.

ICQF-17 / 16

• Complementarity of quantum discord and accessible information: We

consider a separable bipartite system ∑ , and proved that the

basis dependent quantum discord is bounded above by the loss of coherence on

Bob’s side; ∑ ( ) (∑ ) . We employed this relation to prove the

complementarity of quantum discord and accessible information on Bob’s side;

( ) ( ). Here, is the optimal measurement for

which accessible information is maximum on Bob’s ensemble. Hence, if Holevo

bound is achievable by performing certain measurement on Bob’s side, quantum

discord will be equal to zero.

Reference:

[1] A. K. Goswami, P. K. Panigrahi. arXiv:1703.08700.

[2] B.Yadin, J. Ma, D. Girolami, M. Gu, V.Vedral, Phys. Rev. X, 6, 041028 (2016).

Name A.K. Pati Affiliation HRI, Allahabad, India Title Tighter Uncertainty and Reverse Uncertainty Relations

Abstract We prove a few novel state-dependent uncertainty relations for product as well the

sum of variances of two incompatible observables. These uncertainty relations are

shown to be tighter than the Roberson-Schrodinger ¨ uncertainty relation and other

ones existing in the current literature. Also, we derive state dependent upper bound

to the sum and the product of variances using the reverse Cauchy-Schwarz

inequality and the Dunkl-Williams inequality. Our results suggest that not only we

cannot prepare quantum states for which two incompatible observables can have

sharp values, but also we have both, lower and upper limits on the variances of

quantum mechanical observables at a fundamental level.

Name Marcin Pawlowski Affiliation University of Gdańsk, Poland Title Random access codes - a review

Abstract Random access codes are one of the simplest communication tasks in which

quantum advantage can be witnessed. They have been formally introduced over a

decade ago but implicitly they were used even earlier. They have many applications

due to their simplicity and ease of generalization. The former also enabled many

teams to perform experimental realizations of them. In this review I will define the

codes formally and them describe many of their possible generalizations. For each

of them I will discuss applications which include: foundations of physics,

cryptography, computer science and pure mathematics.

Name Tabish Qureshi Affiliation Jamia Milia University, Delhi, India Title Measuring Coherence in Multislit Interference

Abstract A quantitative measure of quantum coherence was recently introduced in the

context of quantum information theory. This measure has also been argued to be a

good quantifier of the wave nature of quantum objects. However, actually

measuring coherence in an experiment is still considered a challenge. A procedure

for measuring coherence in a multislit interference is proposed here. It can be used

for experimentally testing duality relations for interference experiments involving

more than two slits.

ICQF-17 / 17

Name S. M. Roy Affiliation HBCSE, TIFR, Mumbai, India Title Contractive Quantum States

Abstract I prove rigorous quantum limits on contractive and expanding states of a free mass

and of an oscillator. Since a free electromagnetic field and a free boson field have

Hamiltonians which are sums of oscillator Hamiltonians with different frequencies,

there are immediate applications to such fields. In particular limits on contractive

and expanding quadratures of the electromagnetic field follow. The limits are

shown to be optimum by constructing states which saturate the limits.

Name Daniel Rohrlich Affiliation Ben Gurion University of the Negev, Israel Title What is nonlocal in “counterfactual communication”?

Abstract We present a paradox in which a neutron and a mirror exchange weak modular

angular momentum <Lz mod 2ħ >w even though there seems to be no local

interaction that could allow them to exchange <Lz mod 2ħ >w. We then demonstrate

that the neutron and mirror do interact locally, via a local current of Lz mod 2ħ.

However, Lz mod 2ħ is itself a nonlocal quantity. In this sense, we invert the

―interaction-free measurement‖ of Elitzur and Vaidman, in which two local

quantities (the positions of a photon and a bomb in the two arms of a Mach-Zehnder

interferometer) interact nonlocally; we exhibit it, instead, as two nonlocal quantities

(the modular angular momentum of a neutron and of a mirror) that interact locally

via their weak currents. We apply our result to show that so-called counterfactual

quantum communication arises from local interaction via a massless local current.

Name Ramij Rahaman Affiliation Allahabad University, India Title Quantum anonymous veto based on GHZ correlations

Abstract Anonymous Veto (AV) is one of the basic primitive for the cryptographic problems

like Dining cryptographers (DC) where the main aim is to hide the identity of the

senders of the messages. It can be achieved by classical methods where the security

is based either on computational hardness or on shared private keys. In this regard,

we present a secure quantum protocol for the AV problem by exploiting the GHZ

correlations. First, we solve a generalized version of the DC problem with the help

of multiparty GHZ state. This allow us to provide a secure quantum protocol for the

AV. Security of our protocol rely on some novel and fundamental features of GHZ

correlations related to quantum nonlocality.

Name Debasis Sarkar

Affiliation Calcutta University, India

Title Correlations in multipartite scenario

Abstract The increase in the number of non-interacting particles (N) together with use of

multipartite entanglement in an entanglement swapping network basically motivates

our present topic of discussion. To be specific, here we firstly focus on tripartite

entangled states. However, the discussion can be extended for $n-$ partite entangled

states. For our purpose we will introduce a general network scenario involving five

parties and three independent sources. We define such a network, characterized by

five partite correlation terms as a trilocal network scenario. We design a set of Bell-

type inequalities necessarily satisfied under source independence assumption known

as trilocal assumption. There exist families of tripartite entangled quantum states,

both pure and mixed which can generate nontrilocal correlations and hence capable

of exhibiting nonlocality (apart from standard Bell sense). Interestingly, genuine

entanglement is not a necessary requirement for generation of nontrilocality in a

ICQF-17 / 18

quantum network. This form of nonclassical phenomenon can also be observed in a

network using biseparable quantum states. Now, analyzing shareability of

correlations arising in any physical theory may be considered as a fruitful technique

of studying the theory. We will also discuss here an analogous approach of studying

quantum theory. For our purpose, we have deviated from the usual procedure of

assessing monogamous nature of quantum correlations in standard Bell-CHSH

scenario. We have considered correlations arising in a quantum network involving

independent sources. Precisely speaking, we will discuss monogamy of nonbilocal

correlations by deriving a relation restricting marginals.

Name Aditi Sen De Affiliation HRI, Allahabad, India

Title Determinstic Quantum Dense Coding Networks

Abstract I will talk about the scenario of deterministic classical information transmission

between multiple senders and a single receiver, when they a priori share a

multipartite quantum state -- an attempt towards building a deterministic dense

coding network. Specifically, I will show that in case of two or three senders and a

single receiver, generalized Greenberger-Horne-Zeilinger (GHZ) states are not

beneficial for sending classical information deterministically beyond the classical

limit, except when the shared state is the GHZ state. On the other hand, three and

four qubit generalized W states with specific parameters as well as the four qubit

Dicke states can provide quantum advantage in deterministic dense coding.

Name R.P. Singh

Affiliation PRL Ahmedabad India

Title Using non-separable state of light to find the “lost” phase structure

Abstract We generate optical vortices of different orders and scatter them through random

scattering media. We show that vortices can be recovered even after scattering with

far reaching applications in optical communication.

Name Urbashi Sinha Affiliation RRI, Bangaluru, India Title Correlated photonic qutrit pairs for quantum information and communication

Abstract In this talk, I will discuss ongoing experiments in our lab which deal with spatially

correlated photonic qutrits towards applications in quantum information and

communication. While twodimensional quantum systems known as qubits are

traditionally used for experiments in Quantum Computation, we are exploring

higher dimensional quantum systems called qudits. Maximally entangled qudits are

subjects of interest in many quantum information protocols and fundamental tests of

quantum mechanics. Transverse spatial correlation obtained from spontaneous

parametric down converted photons is one of the simplest methods that could be

readily implemented using slit based interferometric systems [1]. Recently, it was

shown that, the angular spectrum of the incident pump can be transferred to the

signal-idler bi-photon pair in SPDC process. Tapping on to this, we attempt to

harness qutrit- qutrit correlations in spatial degrees of freedom by making the pump

have a profile of a triple slit. We study how the idler profile is correlated with a

given signal and establish the qutrit-qutrit correlations for different experimentally

viable parameters [2]. Very recently, we have also been able to certify and quantify

entanglement between the qutrits, thus opening up a plethora of possibilities in

foundations based studies as well as quantum information based explorations. This

principle of generating spatially entangled photon qutrits could be easily extended

to n dimensional space and find wide applications, especially in Quantum

Computing. Demonstrating spatial correlations between two qutrits paves the way

ICQF-17 / 19

for using the spatial degree of freedom in experiments based on long distance

Quantum Communication. While our experiment is a proof of principle experiment

which demonstrates that spatial correlations can be quantified between qutrits, the

result will also be applicable when the photons are in larger physical separation than

inside the lab domain.

[1]P.Kolenderski, U.Sinha, M.Youning, T.Zhao, M.Volpini, A.Cabello,

R.Laflamme, T.Jennewein, Physical Review A 86 012321, (2012).

[2] D.Ghosh, T.Jennewein, P.Kolenderski, U.Sinha, arXiv: 1702.02581

Name Yutaka Shikano Affiliation Tokyo Institute of Technology, Japan Title Quantum Phase through Quantum Tunneling

Abstract The quantum tunnelling is one of the unique quantum-mechanical phenomena but

does not be well understood. In this talk, the quantum phase through quantum

tunnelling will be discussed physically and mathematically, respectively.

Name Stephan Sponar Affiliation Atominstitute, Vienna, Austria Title Measurement Uncertainty Relations: operator-based, operational

& information-theoretic approaches studied in Neutron Optics

Abstract Heisenberg’s uncertainty principle is without any doubt one of the corner stones of

modern quantum physics. However, the present perception of quantum mechanics

has deviated from Heisenberg’s empiristic assumptions, reflected in his famous

gamma-ray microscope where a measurement process is the source of uncertainty,

resulting in a version of the uncertainty relation expressed as a product of widths of

probability distributions, i.e., standard deviations (independent of any

measurement). These types of uncertainty relations set limits on how sharp the

values of two observables can be determined if measured separately, but provide no

information of the error when measuring one observable and the thereby induced

disturbance on another subsequently measured observable. However, a naive

product-type error-disturbance uncertainty relation (EDUR) is not valid in general.

In 2003, Ozawa thus proposed an improved EDUR, based on rigorous and general

theoretical treatments of quantum measurements which is usually referred to as an

operator-based approach. In my talk, I will give an overview of our neutron optical

approaches for investigation of EDUR via successive measurements of

incompatible neutron spin observables.

Another more recent experiment tests so called operational definitions of error and

disturbance developed by Busch and his co-workers. In this theoretical framework

error and disturbance are evaluated from the difference between output probability

distributions of the successive measurement and reference (ideal) measurements.

Despite the ongoing controversy of the two competing approaches, in the case of

projectively measured qubit observables, such as neutron spin components, both

approaches lead to the same outcomes.

In our most recent experiment information-theoretic, or entropic, definitions of error

(in this theoretical framework referred to as noise) and disturbance are studied.

Here, noise and disturbance are defined via correlations between the input states and

measurement outcomes. We successfully carried out an experimental test of a

newly derived, tight noise disturbance uncertainty relation for general qubit

measurements. For certain non-commuting spin observables, the tight relation is

saturated with projective measurements. However, there are also cases in which the

ICQF-17 / 20

relation is only tight for general quantum measurements (i.e., positive-operator

valued measures), as predicted theoretically by Branciard.

Name R. Srikanth Affiliation PPISR, Bangalore, India. Title A quantum cryptographic route to the reality of the quantum state

Abstract The insecurity of quantum bit commitment (QBC) in the standard non-relativistic

quantum cryptographic framework is a consequence of quantum (and more

generally, nonclassical) steering. We identify assumptions in the standard argument,

by relaxing which, the committer's malicious steering operation can be rendered

either indeterminable or inexistent. Further, we propose a QBC protocol in a

quantum teleportation setting, whose security would, without appeal to an

ontological framework, entail the reality of the quantum state, assuming the

exclusion of retro causality. Interestingly, this only requires remote steering and not

nonlocality, allowing our argument to be adapted to provide an ontological

interpretation even for Spekkens' toy model (101) in support of an epistemic

interpretation of quantum states!

Name A.R. Usha Devi Affiliation Bangalore University, India Title Asymptotic limit of diffusive quantum trajectories

Abstract Every record of detection (measurement data) made on the environmental system

determines a trajectory in the state space of a quantum system interacting with the

environmental system [1]. Averaging over all possible measurement record results

in the Gorini-Kossakawsi-Sudarshan-Lindblad (GKSL) master equation [2],

describing dissipative irreversible evolution of the quantum system. It has been

identified that Quantum trajectories, resulted via continuous monitoring on the

environmental system, are solutions of non-linear stochastic Schrodinger equations,

where continuous time detection records are modelled as random classical noise

processes [3]. In particular, quantum diffusive trajectories describe Brownian

motion of a quantum state in the Hilbert space. Early 80’s witnessed a renewed

interest in developing the theory of continuous time observations on a quantum

system interacting with an environment [4]. Quantum state trajectory approach

attracted further attention in the context of quantum measurement theory [5]. In this

talk I outline the historical origin of quantum stochastic evolution leading to a

quantum state diffusion equation and discuss its asymptotic limit [6].

Reference:

[1] E. Davies. Quantum Theory of Open Systems (Academic Press, 1976); M. D.

Srinivas and E. B. Davies, Opt. Acta 28 981 (1981).

[2] V. Gorini, A. Kossakowski, and E. C. G. Sudarshan, J. Math. Phys. 17, 821

(1976); G. Lindblad, Commun. Math. Phys. 48, 119 (1976).

[3] L. Diosi, Phys. Lett. A 129, 419 (1988); N. Gisin, and J. Percival, J. Phys. A

167, 315 (1992).

[4] R. L. Hudson, and K. R. Parthasarathy, Commun. Math. Phys. 93, 301 (1984);

K. R. Parthasarathy, An Introduction to Quantum Stochastic Calculus, (Birkhauser,

1992).

[5] V. Belavkin, Radiotekh. Electron. 25, 1445 (1980); A Barchielli, Phys. Rev. A

34, 1642 (1986); H. M. Wiseman, G. J. Milburn, Quantum Measurement and

Control (Cambridge University Press, 2010).

[6] K. R. Parthasarathy and A. R. Usha Devi, J. Math. Phys. 58, 082204 (2017); K.

R. Parthasarathy and A. R. Usha Devi, arXiv:1707.08157v2.

ICQF-17 / 21

Name Lev Vaidman Affiliation Tel Aviv University, Israel Title The past of a quantum particle

Abstract Textbooks of quantum mechanics lack the concept of the past of quantum systems.

Few years ago I proposed to define the past of a quantum particle according the

trace it leaves. While in many cases this definition provides a reasonable

description, for a nested Mach-Zehnder interferometer it leads to a picture

seemingly contradicting common sense: the particle leaves a trace in a place

through which it could not pass. I will discuss recent theoretical and experimental

studies of this controversial issue.

ICQF-17 / 22

Contributed Talks

Name Manik Banik Affiliation IMSc, Chennai, India Title Exclusivity principle and unphysicality of Garg-Mermin correlation

Abstract We address the question of physical realizability of a probability distribution.

Specker first pointed out that this question cannot be answered from Kolmogorov’s

axioms alone. In the recent past, this observation of Specker has motivated simple

principles (exclusivity principle/ local orthogonality principle) that can explain

quantum limitations on possible sets of experimental probabilities in nonlocality

and contextuality experiments. We study Specker’s observation in the simplest

scenario involving three inputs each with two outputs. Then using only linear

constraints imposed on joint probabilities by this principle we show unphysicality of

a correlation introduced by Garg and Mermin as a counterexample to a suggestion

of Fine that if the inequalities of Clauser and Horne hold, then there exists a hidden-

variable model for a spin-1/1 correlation experiment of the Einstein-Podolsky-

Rosen type. Our result establishes limitation of a recent claim made by different

group of researchers that local orthogonality principle at single copy level is

equivalent to the no-signaling condition.

Name Le Bin Ho Affiliation Osaka University, Osaka, Japan Title Continuous pointer state approach to modular-value amplification

Abstract In quantum mechanics, the concept of quantum modular values allows for the

description of a quantum system in pre- and post-selection states. This manner has

been studied so far theoretically and experimentally, but most of the studies carried

out to date are in discrete pointers. Here, we present a modular-value version in

which the measurement pointer is described in a continuous Gaussian state. We

show that the conditional post-selection probability of obtaining the momentum is

described and amplified by the modular value. Furthermore, to clarify the advantage

of the modular-value amplification (MWA), we discuss the momentum shift and the

signal-to-noise ratio (SNR) of a measured observable in the system and its

optimization. This might guide for the study of modular values with various

classical and nonclassical pointer states, as well as further investigations of the

optimal pointer states for MWA.

Name Claude Klöckl Affiliation IQOQI Vienna, Austria Title On the complementarity between monogamy of correlations and entropy

inequalities in the Bloch picture

Abstract We exploit the Bloch vector formalism to study the seemingly unrelated areas of

entropy inequalities for the linear or Tsallis-2-entropy and monogamy relations.

Thereby we derive several new entropy inequalities for the linear entropy: First, we

present a dimension-dependent analogue to strong subadditivity. The existence of

such analogues is remarkable since the classic version of strong subadditivity is

known not to hold for the linear entropy [1]. As a byproduct we obtain a similar

relation in analogy to subadditivity. Moreover, we propose a yet unknown quadratic

entropy inequality that generalizes the pseudo-additivity [2] of Tsallis q-entropies

from separable to all states. This relation is shown to be stronger than subadditivity

in some cases.

Finally, we define a new measure of correlations and show that it follows a quasi-

ICQF-17 / 23

monogamy relation for systems of arbitrary dimension. Similarly to the case of

strong subadditivity, we find that although the classical Coffman-Kundu-Wootters

inequality is known not to generalize to higher dimensions, our dimension-

dependent correlation measure obeys an analogous inequality for arbitrary

dimensions.

[1] KMR. Audenaert, Journal of Mathematical Physics, (2017)

https://arxiv.org/pdf/0705.1276.pdf

[2] S. Abe, Physics Letters A, Volume 271, 74-79, (2000)

https://arxiv.org/pdf/cond-mat/0005538.pdf

Name Aravinda S

Affiliation IMSc Chennai, India

Title Combinatorial approach to nonclassicality and cryptographic security in single

systems

Abstract The concept of compatibility of two measurements in a generalized probability

theory is usually identified with their joint measurability. Here we provide a

geometric interpretation in terms of ―congruence‖, the requirement that the polytope

associated with the maximal knowledge states of a pair of measurements forms a

simplex. A natural division then arises between ―transitive theories‖, where

congruence is transitive, and ―intransitive theories‖, where the congruence is in

general not transitive. Transitive theories of single systems can reproduce

nonclassical features like no-cloning and measurement disturbance, but not

contextuality, for which the intransitive property is required. Here we indicate the

difference between these two theory types from a cryptographic perspective.

Additionally, we point out that in the context of single systems that the essence of

Spekkens’ toy model (2017) is that it is a transitive (albeit non-convex) theory.

Name Gautam Sharma Affiliation HRI, Allahabad, India Title Complementarity Relation for Coherence and Disturbance

Abstract Quantum measurements necessarily disturb the state of physical system. Once we

perform a complete measurement, the system undergoes decoherence and loses its

coherence. If there is no disturbance, the state retains all of its coherence. It is

therefore natural to ask if there is trade-off between disturbance caused to a state

and its coherence. We present a coherence disturbance complementarity relation

using the relative entropy of coherence. For bipartite states we prove a

complementarity relation between the quantum coherence, entanglement and

disturbance. Similar relation also holds for quantum coherence, quantum discord

and disturbance for a bipartite state. We illustrate the trade-off between the

coherence and the disturbance for single qubit state for various quantum channels.

ArXiv:1708.03090

Name Nitica Sakharwade Affiliation Perimeter Institute, Canada Title Bidirectional Dense Coding and Teleportation in Butterfly network

Abstract Non-local correlations via entangled states have been known to be resources for

two-party communication tasks such as teleportation and dense-coding. We are

interested in optimizing many such two-party communication tasks in a quantum

network of many parties akin to the role the internet played in classical

communication tasks. Specifically, we choose the simplest non-trivial

communication task of two communication tasks simultaneously achieved between

two-parties, Alice and Bob, and find optimal protocols for bidirectional

ICQF-17 / 24

teleportation and bidirectional dense coding by embedding them in the butterfly

network and using a classical network coding protocol. Surprisingly, we find that a

one-qubit channel (or two-cbit channel) along with pre-shared entanglement is

sufficient for bidirectional teleportation (or dense-coding). We also find a general

boundary rule that prescribes which parties require pre-shared entanglement for a

given set of two-party tasks on a quantum network. These results have implications

for post-quantum theories like the indefinite causal theories.

Name Ranjith Venkatrama Affiliation ALOPHIS group, Univ. of Cagliari, Italy Title Negations and Truth-Perspectives pertaining to Qudits based Multi-valued

Quantum Computational Logics

Abstract In the present work certain peculiar aspects of the concept of negation in quantum

computation are explored in the framework of a continuous t-norms based fuzzy-

type representation of qudit based quantum computational multivalued logics.

ICQF-17 / 25

Posters

Name Raunaq Ahmad Affiliation Bangalore University, India Title Statistical distinguishability of two unknown rotations using Majorana

geometric representation of N-qubit symmetric states

Abstract Ability to discriminate two unknown rotations (or equivalently, two

unitary operations ( )) with better precision is an important

foundational task as this is directly linked with aligning reference frames between

spatially separated parties sharing a quantum state. We address this issue by

making use of the Majorana geometric representation for pure permutationally

invariant multiqubit states. We show that when two unknown rotations are

applied on a pure symmetric N-qubit state , belonging to an N +1

dimensional irreducible unitary representation (R) of rotations, it is possible to

discriminate ( ) and

( ) perfectly,

when there are 2j = N distinct Majorana spinors constituting the quantum state.

We also discuss the possibility of discrimination of rotations using symmetric N

qubit states constituted by distinct Majorana spinors.

Name Balwant Singh Airy Affiliation GBPUAT, Uttarakhand, India Title Protecting entanglement by using weak measurement and quantum

measurement reversal against one and two sided amplitude damping channel

Abstract In this paper we have studied the effect of one and two sided amplitude damping

decoherence on the entanglement of Bell’s state by measuring their concurrence

and compare them. We found that in the case of two sided amplitude damping

state shows more protection of entanglement compare to the state

to amplitude damping. While in the case of one sided amplitude

damping both state perform equally. We found that in the case of two sided

amplitude damping after applying weak measurement and quantum measurement

reversal, state is protected more compare to the state

and similar results are obtained in the case of one sided amplitude

damping.

Name Natasha Awasthi

Affiliation GBPUAT, Pantnagar, India

Title Universal quantum uncertainty relations between non-ergodicity and loss of

information

Abstract We establish uncertainty relations between information loss in general open

quantum systems and the amount of non-ergodicity of the corresponding

dynamics. The relations hold for arbitrary quantum systems interacting with an

arbitrary quantum environment. The elements of the uncertainty relations are

quantified via distance measures on the space of quantum density matrices. The

relations hold for arbitrary distance measures satisfying a set of intuitively

satisfactory axioms. The relations show that as the non-ergodicity of the dynamics

increases, the lower bound on information loss decreases, which validates the

belief that non-ergodicity plays an important role in preserving information of

quantum states undergoing lossy evolution. We also consider a model of a central

qubit interacting with a fermionic thermal bath and derive its reduced dynamics, to

ICQF-17 / 26

subsequently investigate the information loss and non-ergodicity in such

dynamics. We comment on the ―minimal‖ situations that saturate the uncertainty

relations.

Name Shreya Banerjee Affiliation IISER, Kolkata, India Title The Minimum Distance of PPT Bound Entangled States from the Maximally

Mixed State

Abstract Using a geometric measure of entanglement quantification based on Euclidean

distance of the Hermitian matrices [1], we obtain the minimum distance between a

bipartite bound entangled nqudit density matrix and the maximally mixed state.

This minimum distance for which entangled density matrices necessarily have

positive partial transpose (PPT) is obtained as

√ √ ( )

, which is also a

lower limit for the existence of 1-distillable entangled states. The separable states

necessarily lie within a minimum distance of

from the Identity [1],where R

is the radius of the closed ball homeomorphic to the set of density matrices, which

is lesser than the limit for the limit for PPT bound entangled states. Furthermore

an alternate proof on the non-emptiness of the PPT bound entangled states have

also been given.

[1] Aryaman A Patel and Prasanta K Panigrahi. Geometric measure of

entanglement based on local measurement. arXiv preprint arXiv:1608.06145,

2016.

Name Kishor Bharti Affiliation NUS, Singapore Title Quantum Contextuality for Continuous Variables

Abstract We analyse n-cycle non-contextuality inequalities and discuss the condition for

the quantum violation for odd as well as even n-cycle. The set of quantum states

for qutrits, which can violate odd n-cycle noncontextuality inequality, shrinks as

we increase n. In the infinite n scenario, the only qutrit which violates the

inequality is the maximally contextual state. For even cycle, the necessary

condition for quantum violation depends on the difference of the two largest

eigenvalues for the density matrix ρ.

Name Samyadeb Bhattacharya Affiliation HRI, Allahabad, India Title Dynamics and thermodynamics of a central spin immersed in a spin bath

Abstract An exact reduced dynamical map along with its operator sum representation is

derived for a central spin interacting with a thermal spin environment. The

dynamics of central spin shows high sustainability of quantum traits like

coherence and entanglement in low temperature regime. However, for sufficiently

high temperature and when the number of bath particles approaches the

thermodynamics limit, this feature vanishes and the dynamics closely mimics the

Markovian evolution. The property of long time averaged state and the tapped

information of initial state for the central qubit are also investigated in detail,

confirming that the non-ergodicity of the dynamics can be attributed to the finite

temperature and finite size of bath. It is shown that if a certain stringent resonance

condition the long-time averaged state retains quantum coherence, which can have

far reaching technological implications in engineering quantum device. An exact

time local master equation of the canonical form is derived. With the help of this

master equation, the non-equilibrium properties of central spin system are studied

ICQF-17 / 27

by investigating the detailed balance condition and irreversible entropy production

rate. The result reveals the central qubit thermalizes only in limit of very high

temperature and large number of bath spins.

Name Suchetana Goswami Affiliation SNBNCBS, Kolkata, India Title Selftesting of any non-maximally entangled pure two-qubit state in

one-sided-device-independent scenario

Abstract The certification of quantum devices through the observation of quantum

nonlocality has implications for both quantum information and foundations of

quantum theory. Some extremal nonlocal quantum correlations of two-binary-

inputs-two-binary-outputs Bell scenario can be witnessed by the maximal

violation of a tilted Bell-CHSH inequality. These nonlocal correlations were

shown to selftest any pure two-qubit entangled state in a device-independent way.

Device-independent selftesting is a quantum information task in which one wishes

know the quantum state and measurements from the observed correlations without

any assumption on the dimension of the physical system. Recently, selftesting of

maximally entangled two-qubit state in a one-sided device-independent way (in

which one can do state tomography on one side and the other side is treated as

black-box device) was proposed. In this context, the maximal violation of a

steering inequality which certifies the maximally entangled state was shown to

selftest the maximal entanglement in a one-sided device independent way.

Selftesting via quantum steering was shown to provide certain advantage over

device-independent selftesting.

In this work, we consider the problem of selftesting of any pure nonmaximally

entangled two-qubit state through quantum steering. We note that in the two-

setting steering scenario, the maximal violation of a fine-grained steering

inequality can be used to witness certain extremal steerable correlations, which

certify all pure two-qubit nonmaximally entangled states. Motivated by this

observation, we are interested in selftesting of any pure nonmaximally entangled

state with these extremal steerable correlations. We demonstrate that by using the

fine-grained steering inequality and analog CHSH necessary and sufficient

condition of steerability, one can selftest any pure nonmaximally entangled two-

qubit state in a one-sided device-independent way.

Name Kamil Kostrzewa Affiliation University of Gdansk, Poland Title Investigating nonclassicality of many qutrits by symmetric two-qubit

operators

Abstract We introduce a method of investigating qutrit nonclassicality by translating qutrit

operators to symmetric two qubit operators. We show that this procedure sheds

light on the discrepancy between maximal qutrit entanglement and maximal

nonclassicality of qutrit correlations. Namely, we express Bell operators

corresponding to qutrit Bell inequalities in terms of symmetric two-qubit operators

and analyze the maximal quantum violation of a given Bell inequality from the

qubit perspective. As an example, we show that the two qutrit Collins-Gisin-

Linden-Massar-Popescu (CGLMP) Bell inequality can be seen as a combination

of Mermin's and Clauser-Horne-Shimony-Holt (CHSH) qubit Bell inequalities,

and therefore the optimal state violating this combination differs from the one

which corresponds to the maximally entangled state of two qutrits. In addition, we

discuss the same problem for a three-qutrit inequality. We also demonstrate that

the maximal quantum violation of the CGLMP inequality follows from

complementarity of correlations.

ICQF-17 / 28

Name C S Sudheer Kumar Affiliation IISER, Pune, India Title Violation of space-time Bell-CHSH inequality beyond Tsirelson bound via

postselection and quantum cryptography

Abstract Here we show that, if we insert context dependent unitary evolutions into spatial

(i.e., normal) Bell-CHSH test, then it is possible to violate space-time Bell-CHSH

inequality maximally (i.e., up to 4). Correct context dependency can be achieved

via postselection. However this does not contradict Tsirelson quantum bound √ ,

because the latter has been derived without taking into consideration context

dependent unitary evolutions and/or postselection. As an important application,

this leads to a more efficient (in terms of resource (singlets) and classical

communication required) and more sensitive (to eavesdropping) quantum key

distribution protocol, compared to Ekert and Wigner QKD protocols.

Name Som Kanjilal Affiliation Bose Institute, Kolkata, India Title Quantifier of effective Resource State in Remote State Preparation

Abstract The nature and effectiveness of the resource determining the efficiency of a

quantum information task is crucial to our understanding of the protocol itself. In

an earlier work [2], it was shown that quantum discord is a legitimate resource for

remote state preparation - it was shown that fidelity achieved using the RSP

protocol they formulated was the same as the value of geometric discord for the

shared resource state. Using a newly suggested scheme for remote state

preparation of pure quantum qubit state (that will be briefly reviewed in this

poster), it has been argued that discord is not always a faithful resource as one can

achieve finite fidelity for even zero discord states. As an alternative to quantum

discord as an effective resource for such a scheme, we suggest here the use of the

simultaneous correlations that exist in two (C2) and three (C3) mutually unbiased

bases [1] as resources for the said RSP scheme. We show that both the quantities

C2 and C3 are monotonic functions of fidelity for classes of zero discord Bell-

diagonal states. On the other hand, for any general Bell diagonal state (that

includes both zero and non-zero discord states), we demonstrate that in addition to

the monotonocity of the dependence of C3 on fidelity, there is also an explicit

functional relationship between it and RSP fidelity. These results, we argue,

justify arguing for the use of measures of quantum correlations beyond discord for

quantifying the efficiency of such RSP schemes.

[1] Guo, Yu and Wu, Shengjun Sci. Rep. 1, 7179 (2014).

[2] B Dakic et al.,Nature Physics 8, 666670 (2012).

Name Swati Kumari Affiliation NIT, Patna, India Title Inequivalent Leggett-Garg Inequalities Abstract Fine [1] showed that for two parties, two inputs and two outputs only relevant

inequality is the CHSH one. In recent times, there is an upsurge of interest for

studying the issue of macrorealism and Leggett-Garg inequalities (LGIs). Various

formulations of LGIs have recently been proposed, for example, Wigner form of

LGIs (WLGIs), Clauser-Horne form of LGIs (CHLGIs). Standard Leggett-Garg

Inequalities (SLGIs) are often considered to be the temporal analogue of CHSH

Inequalities. In contrast to the CHSH scenario, here we show that for three and

ICQF-17 / 29

four-time measurement scenario, WLGIs and CHLGIs are inequivalent, and both

of them are stronger than SLGIs.

[1] A. Fine, Phys. Rev. Lett. 48, 291(1982).

Name Avijit Misra Affiliation IMSc Chennai, India Title Complementarity between tripartite quantum correlation and bipartite Bell-

inequality violation in three-qubit states

Abstract We find a single parameter family of genuinely entangled three-qubit pure states,

called the maximally Bell-inequality violating states (MBV), which exhibit

maximum Bell-inequality violation by the reduced bipartite system for a fixed

amount of genuine tripartite entanglement quantified by the so-called tangle

measure. This in turn implies that there holds a complementary relation between

the Bell-inequality violation by the reduced bipartite systems and the tangle

present in the three-qubit states, not necessarily pure. The MBV states also exhibit

maximum Bell-inequality violation by the reduced bipartite systems of the three-

qubit pure states with a fixed amount of genuine tripartite correlation quantified by

the generalized geometric measure, a genuine entanglement measure of multiparty

pure states, and the discord monogamy score, a multipartite quantum correlation

measure from information-theoretic paradigm. The aforementioned

complementary relation has also been established for three-qubit pure states for

the generalized geometric measure and the discord monogamy score, respectively.

The complementarity between the Bell-inequality violation by the reduced

bipartite systems and the genuine tripartite correlation suggests that the Bell-

inequality violation total tripartite correlation present in the entire system. in the

reduced two-qubit system comes at the cost of the total tripartite correlation

present in the entire system.

Name Shiladitya Mal Affiliation SNBNCBS, Kolkata, India Title Scheme for implementing dichotomic quantum measurements through non-

ideal Stern Gerlach setup

Abstract Positive operator valued measures (POVMs) are the most general class of

quantum measurements. There has been significant interest in the theory and

possible implementations of generalized measurement in the form of POVMs.

Such measurements are useful in the context of cryptography, state discrimination,

preparation of arbitrary states and for monitoring quantum dynamics. As argued

by P. Busch (Phys. Rev. D 33 (1986) 2253), the most general dichotomic POVMs

are characterised by two real parameters known as sharpness and biasedness of

measurements. While unbiased unsharp measurements have been demonstrated

experimentally, for example using the quantum feedback stabilization of number

of photons in a microwave cavity (Nature (London) 477, 73 (2011)), as well as in

the context of energy measurements of trapped ions, however, to the best of our

knowledge unsharp biased measurements has not yet been probed experimentally.

For this purpose, we propose in this work, an empirically realizable scheme using

non-ideal SG setup. The relevant formulation involves identifying one to one

correspondence between biasedness, unsharpness of measurements and the key

parameters characterising non-ideal SG setup. This study has the potentiality to be

useful for the implementations of various quantum information tasks as well as

experiments related to quantum foundational studies based on POVMs.

ICQF-17 / 30

Name Chiranjib Mukhopadhyay Affiliation HRI, Allahabad, India Title Quantum speed limit constraints on a nanoscale autonomous refrigerator

Abstract Quantum thermal machines have attracted renewed attention in last few years. We

propose a figure of merit for a model of quantum absorption refrigerator

considering the constraints on the speed of evolution. We show that this quantity,

hence termed the bounding second order cooling rate (BSOCR), is linearly

proportional to the strength of biasing interaction. We derive a bound on

efficiency at maximum value of this figure of merit in the high temperature limit.

We also study how the quantum zeno effect affects the BSOCR. We compare this

approach with another approach based on known a priori probability distributions

over steady state performance parameters, which itself is investigated here for the

first time for absorption refrigerators, and point out the similarity in the results

furnished by both approaches.

Name Sumit Nandi Affiliation IOP, Bhubaneswar, India Title Co-operative communication protocols

Abstract Quantum entanglement plays an important role in various communication

protocols, like teleportation, secret sharing, superdense coding, and quantum key

distribution. We consider the scenario when more than two parties are involved in

the protocol. One party wishes to communicate information with the help of other

parties. The information could be classical, a quantum state

or establishment of a secret key. A multipartite entangled state is shared between

many parties. Various parties make measurement or apply unitary transformations,

to allow sender, Alice, to communicate with receiver, Bob. We consider secret

sharing and Quantum key distribution to find conditions that a resource state must

satisfy for the protocol to work exactly.

Name Suma S P Affiliation University of Mysore, India Title Study on a class two qubit symmetric separable states in term of moments of

angular momentum operators.

Abstract We express PPT criterion for a system of 2-qubit symmetric states in terms of the

well-known Fano Statistical tensor parameters and prove that a large set of

separable symmetric states are characterized by real statistical tensor parameters

only. The physical importance of these states are brought out by employing the

trivariate representation of density matrix wherein the components of J namely Jx,

Jy, Jz are considered to be the three variates. We prove that this set of separable

states is characterized by the vanishing average expectation value of Jy and its

covariance with Jx and Jz.

Name Varad Pande Affiliation HRI, Allahabad, India Title Quantum Information Transfer Using Weak Measurements and Any Non-

product Resource State

Abstract Information about an unknown quantum state can be encoded in weak values of

projectors belonging to a complete eigenbasis. We present a protocol that enables

one party -- Bob -- to remotely determine the weak values corresponding to weak

measurements performed by another spatially separated party -- Alice. The

particular set of weak values contains complete information of the quantum state

encoded on Alice's ancilla, which enacts the role of the preselected system state in

ICQF-17 / 31

the aforementioned weak measurement. Consequently, Bob can determine the

quantum state from these weak values, which can also be termed as remote state

determination or remote state tomography. A combination of non-product bipartite

resource state shared between the two parties and classical communication

between them is necessary to bring this statistical scheme to fruition.

Significantly, the information transfer of a pure quantum state of any known

dimensions can be affected even with a resource state of low dimensionality and

purity with a single measurement setting at Bob's end.

Name Md Qutubuddin Affiliation NIT, Patna, India Title Improved quantum violation of macrorealist and noncontextual inequalities

Abstract In a recent paper [1] it is shown that for a qutrit system the maximum quantum

violation of three-time Leggett-Garg inequalities (LGIs) can exceed the L ̈der

bound if von Neumann collapse rule is invoked. Even, the violation can approach

to the algebraic maximum in the asymptotic limit of system size. We show that for

the case of qutrit system the quantum violation can be further improved by

suitably choosing the intermediate unitary evolutions between two measurements.

We then pointed out that the choice of basis for invoking the von Neumann

projective rule is not unique for a degenerate observable. We found that choice of

basis can improve the maximum quantum violation of LGIs. We further show that

the simplest non-contextual inequalities (NCIs) can also violated if von Neumann

rule is used as opposed the recent claim [1]. We provide a discussion about the

experimental verifiability of our results using optical setup.

[1] C. Budroni and E. Emary, [Phys.Rev.Lett.113, 050401 (2014)].

Name Arun Sehrawat Affiliation IISER Mohali, Punjab, India Title Quantum constraints stronger than uncertainty relations

Abstract Every statistical operator—that represents a quantum state—must follow the three

conditions Hermiticity, normalization, and positivity. These conditions give birth

to quantum constraints on the expectation values with the aid of Born’s rule,

which connects the mean values for any set of operators to a quantum state. The

quantum constraints specify a permissible region of the expectation values. For a

set of observables, the allowed region is a compact and convex set in a real space,

and all its extreme points come from pure quantum states. By defining an

appropriate concave function on the permitted region and then finding its absolute

minimum at the extreme points, one can establish a tight uncertainty relation. The

permissible region resides in every other region bounded by an uncertainty

relation. A point outside the admissible region—even if it satisfies a tight

uncertainty relation—does not correspond to any quantum state. In that sense, the

quantum constraints are optimal.

Name Ritabrata Sengupta Affiliation IISER, Berhampur, Odisha, India Title Extendability and complete extendability of states in Fock space

Abstract Motivated by the notion of k-extendability and complete extendability of the state

of finite level quantum system as described by Dorherty et al (Phys Rev A

69:022308), we introduce parallel definition in the context of Gaussian state using

only the properties of covariance matrices derive necessary and sufficient

ICQF-17 / 32

condition for their complete extendability. It turns out that the complete

extendability property is equivalent to separability property of bipartite Gaussian

state.

Following the proof of quantum de Finetti theorem as outlined in Hudson and

Moody (Z. Wahrscheinlichkeitstheorie und Verw. Gebiete 33(4):343-351), we

showed that separability is equivalent to complete extendability for a state in a

bipartite Hilbert space where at least one of which is of dimension greater than 2.

This, in particular, extends the result of Fannes, Lawis, Verbeure (Latt. Math.

Phys. 15(3): 155-260) to the case of an infinite dimensional Hilbert space whose

algebra of all bounded operators is not separable.

Name Ashutosh Singh Affiliation RRI, Bangalore, India Title Manipulation of entanglement sudden death in an all-optical experimental

setup

Abstract The unavoidable and irreversible interaction between an entangled quantum

system and its environment causes decoherence of the individual qubits as well as

degradation of the entanglement between them. Entanglement sudden death (ESD)

is the phenomenon wherein disentanglement happens in finite time even when

individual qubits decohere only asymptotically in time due to noise. Prolonging

the entanglement is essential for the practical realization of entanglement-based

quantum information and computation protocols. For this purpose, the local NOT

operation in the computational basis on one or both qubits has been proposed. In

this talk, I will discuss the phenomenon of ESD followed by an all-optical

implementation of the NOT operations that can hasten, delay, or completely avert

ESD, all depending on when it is applied during the process of decoherence for

the polarization entangled photonic qubits as the system [1]. The simulation

results of such manipulations of ESD will be presented along with the latest

experimental results.

[1] M. P. Almeida, F. de Melo, M. Hor-Meyll, A. Salles, S.P. Walborn, P. H.

Souto Ribeiro, L. Davidovich, Science 316, 555 (2007).

Name Souradeep Sasmal Affiliation Bose Institute, Kolkata, India Title Necessary and sufficient condition for violation of a steering inequality for

two-qubit states, monogamy and shareability of steering

Abstract Necessary and sufficient condition for violation of Clauser-Horne-Shimony-Holt

like inequality for steering by an arbitrary two qubit state is derived. As a

corollary of this derivation maximal violation of this inequality is obtained. Then

we establish monogamy relation for this steering inequality which states that two

party can’t steer a third party’s system simultaneously through violation of this

inequality. Then we investigate how two observers can demonstrate steering of

third party’s system invoking a scenario where half of an entangled pair shared

between single Alice in one wing and several Bobs on the other wing.

Interestingly we also show three Bobs can steer Alice’s system considering three

settings steering inequality and conjecture when steering is probed through n-

settings steering inequality atmost n Bobs can demonstrate steering of Alice’s

system.

ICQF-17 / 33

Name H. S. Smitha Affiliation University of Mysore, India Title Construction of new observables for spin-1 system and their optimum

measurement

Abstract Any spin-j density matrix is completely characterized by independent

parameters, where . The optimum measurement to obtain all the

independent parameters involves Mutually Unbiased Bases. For spin-1/2 system,

the eigenbasis of Pauli operators turn out to be the MUBs. In the Stern-Gerlach

experiment, all the parameters , and characterizing the spin-1/2 density

matrix are obtained when the measurement is carried out in the diagonal bases of

Pauli operators and the physical interpretation is very clear. To achieve the same

for spin-1 system, with the help of existing MUBs, we first obtain the set of eight

parameters characterizing the density matrix in the Weyl basis. As these

parameters do not have any physical interpretation, we construct a new set of

operators, using the suitable combination of projection operators required to

obtain all the eight parameters. These operators form an orthonormal operator

basis. The new coefficients which are the expectation values of the these operators

now have the physical meaning. In an experiment, measurement for spin-1 system

thus corresponds to the measurement of particular combination of different order

moments of , and .

Name Akhilesh K. S Affiliation University of Mysore, India Title Geometric phase, spin squeezing and Majorana star constellation in pure

symmetric states

Abstract Berry phase plays a foundational role in understanding geometry of quantum

systems. For an arbitrary pure qubit state, Berry phase admits a geometric

representation on the surface of the unit Bloch sphere. As Majorana construction

(E. Majorana, Nuovo Cimento 9, 43 (1932)) enablesnmapping of permutationally

invariant N –qubit pure states with N unit vectors on the surface of the Bloch

sphere, it offers a powerful method to explore Berry phase associated with

multiqubit systems geometrically. To this end, we focus on the Berry phase of

pure symmetric N -qubit states constructed using only two distinct Majorana

spinors. This brings forth the connection between Berry phase, entanglement and

spin squeezing in this specific class of N -qubit symmetric states.

Name Shreekanth S Affiliation Regional Institute of Education, Mysore Title Quantum Fisher Information Matrix for mixed spin-1/2 system.

Abstract Employing the new parametrization of spin-j density matrix we outline the

procedure to compute Quantum Fisher Information Matrix which plays a key role

in parameter estimation. Taking the example of mixed spin-1/2 density matrix we

show that the off diagonal elements of the Fisher Information Matrix are

proportional to the covariance of spin operators σx, σy and σz .

ICQF-17 / 34

Note