imperial college london institute for mathematical sciences & quantum optics and laser science...

Imperial College London

Institute for Mathematical Sciences&

Quantum Optics and Laser Science GroupBlackett Laboratory

Imperial College London

http://www.imperial.ac.uk/quantuminformation

Principles of Noise Assisted Transport in Networks

Martin B Plenio

In collaboration with: Animesh Datta & Filippo Caruso (Imperial College London, UK) Alex Chin and Susana Huelga (Univ. Hertfordshire, UK)

Lisbon, 8th July 2009


Noise seems a problem here as it destroys quantum coherence


Weak coherent driving

Weak response


Weak coherent driving + weak noise give a strong coherent response.

Stochastic resonance

Noise


Biological systems can use noise to improve their sensitivity to weak coherent signals

Can we use this in quantum mechanics ?

Noise can be good for you in quantum mechanics too for entanglement generation and preservation !

Huelga & Plenio, PRA 1999, PRA 2000 & PRL 2002 & PRL 2007

See also overview talk by Susana Huelga Friday


Clicks

Time

Clicks

Time

A Fundamental Experiment


Clicks

Time

Clicks

Time



Green sulphur Bacteria

Photosynthesis

A black smoker in the Atlantic Ocean ~ 2000m deep

Y.C. Cheng and G.R. Fleming, Annu. Rev. Phys. Chem. 60, 241 (2009)



Exciton Transport in Photosynthesis

Reaction Centre

CO2+ 2 H S

2

+ energy

CH O2

+ 2 S + H O2



Reaction Centre


CO2+ 2 H S

2

+ energy

CH O2

+ 2 S + H O2


Transfer to reaction centre


Reaction Centre


CO2+ 2 H S

2

+ energy

CH O2

+ 2 S + H O2


Loss of excitation

Transfer to reaction centre

Reaction Centre

CO2+ 2 H S

2

+ energy

CH O2

+ 2 S + H O2

M.B. Plenio and S.F. Huelga, New J. Phys. 10, 113019 (2008)

Exchange of excitation

Dephasing


Noise Assisted Transport and Photosynthesis

No dephasing

Some dephasing

Plenio & Huelga, New J. Phys. 2008 Mohseni, Rebentrost, Lloyd, Aspuru-Guzik, J. Phys. Chem. 2008

More dephasing


Physical Origin of Noise Assisted Transport



Show Movie 1: No dephasing Initial excitation in site 1


Two differenttime scales !



Clicks

Time

Clicks

Time

Destructive Interference and Invariant States



J J

Reactioncenter

=



Tra

nsfe

r ef

fici

ency

J J

=

Reactioncenter


Noise Inhibits Destructive Interference

Decoherence inhibits destructive interference !

Tra

nsfe

r ef

fici

ency

Reduction ofdestructive interference

J J

Reactionscenter

Reactioncenter

=



Invariant state:

Two atoms in the same location:


Dephasing on site 1 only

Show Movie1a: Small dephasing on site 1 only


Dephasing on site 1 only



not invariant under Hamiltonian evolution !

Different energy splitting:


Static disorder inhibits destructive interference !

Disorder Inhibits Destructive Interference

J J

J JDestructiveinterference

Reactioncenter

Reduction ofdestructive interference

Reactioncenter


Disorder Inhibits Destructive Interference


The Hamiltonian of the FMO complex

Quite strong static disorder compared to coupling strengths !


Bridging the gap: Enhanced transport via line broadening


Dephasing Noise on Site 3 only

Play Movie1b: Dephasing noise only on site 3

Play Movie1ab: Same amount of dephasing noise now only on site 3


Dephasing Noise on Site 3 only


No line broadening, No transfer!Line broadening does enhance transfer!


J J

destructive interference

-J -J

Spatially Correlated Noise

effect ofnoise reduced

J J


+J -J

effect ofnoise enhanced


local dephasing without correlations

dephasing with non-local correlations

T=5 ps

Therefore, correlated noise does not lead to decisive improvements in this setting!

Spatially Correlated Noise


J J


J J

Loss Enhanced Transport


reduced

J J

excitationlost


Noise Assisted Transport and Photosynthesis

No dephasing

Some dephasing

More dephasing


Reduction of destructive interference

Inhibition of coupling through dephasing

Dependence on Noise Strength


Two differenttime scales !

Robustness against strong static disorder compared to coupling strengths (i.e. 20%)!

optimal dephasing

no dephasing

Robustness of Noise Assisted Transport


F.Caruso., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, to be submitted

Entanglement Dynamics


F.C., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, arxiv:0901.4454 (2009)

|01>-|10>

J J

reduced destructive interferencedestructive interference

J

Each process open additional pathways for propagation


The Fundamental Mechanisms

Dephasing can reduce destructive interference

Energy mismatch can reduce destructive interference

Dephasing noise increases overlap of energy levels

Each process open additional pathways for propagation

Plenio & Huelga, New J. Phys. 10, 113019 (2008)Caruso, Chin, Datta, Huelga, Plenio, arxiv:0901.4454 [quant-ph]


Can we improve solar cellsbased on this idea ?

More generally: Adding the right kind of noise, to the right kind of nano-structure can improve its performance.

Engineer system to generate constructive interplay between quantum dynamics and noise


This talk was based on

Plenio & Huelga, New J. Phys. 10, 113019 (2008)

Caruso, Chin, Datta, Huelga, Plenio, E-Print arXiv:0901.4454

Caruso, Chin, Datta, Huelga, Plenio, to be submitted


We move to Ulm to establish Center for Quantum Engineering

Explain VideoAbstracts

imperial college london institute for mathematical sciences & quantum optics and laser science...

Documents