nitzan akerman trapped ions group (roee ozeri) weizmann
TRANSCRIPT
Nitzan Akerman
Trapped ions group (Roee Ozeri)
Weizmann Institute of Science
Optical atomic clock with trapped ions
QTC Workshop 28/10/2020
Optical Ion Clock
𝑄 =𝜔0
∆𝜔
+
𝜔0: 1010 → 1015 𝐻𝑧
Principle of optical atomic clock :
Counter Oscillator Reference
The quality factor
Optical clock outperform microwave due to the much higher frequency
Height resolution due to gravitational red shift
1 m
10 cm
1 cm
The Ion Clock Setup
Stable laser @ 1560 nm with ~1Hz linewidth
Ion reference
Optical frequency comb (modelock laser)
+
Trapped Ions as Reference
Trap RF
• Are atoms and identical by their nature
• The charge allows trapping to be decouple from
the internal electronic state
• Deep trapping and strong confinement
• Can be well isolated from the environment
Advantages of trapped ions and clock reference
Disadvantages of trapped ions
• Micromotion needs to be controlled
• Trapping many ions is challenging due to the
strong Coulomb repulsion
The Strontium Ion Setup
Lasers breadboard
Compact vacuum system
5 2P1/2
5 2P3/2
5 2S1/2
4 2D3/2
4 2D5/2
422 nm
1092 nm
1033 nm
674 nm
t ≈ 8 ns
t ≈ 0.4 s
The Strontium Ion Setup
Lasers breadboardSr+ energy levels
Comparison to GPS
Optical frequency comb) locked to stable laserGPS receiver
• Comparing the stable laser to GPS clock through the frequency comb
• At short time scale stability is limited by GPS
• At times > 1 hour the cavity (linear) drift become apparent
The Ion Clock Setup
Ion reference
Optical frequency comb) locked to stable laser
+
GPS receiver• Comparing the stable laser to GPS clock through the frequency comb
• At short time scale stability is limited by GPS
• At times > 1 hour the cavity (linear) drift become apparent
• With calibration of the drift using the ion (3 measurements) the Allen div. keeps improving
Clock interrogation schemes
Two ions Rabi spectroscopy (60ms)
Magnetic field gradient(~60 μG)• Cancelling the DC magnetic field with a single
“magnetic Echo” in a Ramsey sequence Two ions Ramsey spectroscopy (100ms)
• 88Sr+ ions have first order sensitivity to magnetic field.
• For single ion solved by averaging opposite Zeeman states
• For many ions homogeneity matters
• There is advantage in coherent averaging
𝛿f
𝑓= 5 × 10−15 ൗ1 𝜏 (estimation for single ion)
Two entangled ions clock
Another solution is using two ions in entangled state:
• The 𝛿B drops out because of the opposite Zeeman states in each part of the superposition
• The signal is acquired twice faster (however also the dephasing)• Required single ion addressing capability
ȁ ൿ𝑆+1/2 ȁ ൿ𝑆−1/2 + 𝑒𝑖 2𝛿𝑙𝑎𝑠𝑒𝑟 𝑡ȁ ൿ𝐷+3/2 ȁ ൿ𝐷−3/2
+
Δ𝜈𝑆1/2,𝐷5/288,86 = 570,264,063.435(5)(8) (stat)(sys) [Hz]
T. Manovitz et al, Phys. Rev. Lett. 123, 203001 (2019).
88Sr+ 86Sr+
ȁ ൿ𝑆+1/2 ȁ ൿ𝑆−1/2 ȁ ۧ0 ↔ ȁ ൿ𝐷+3/2 ȁ ൿ𝑆−1/2 ȁ ۧ1
ൿห𝐷88
ൿห𝑆86
Τ𝜋 2BSB
𝜋RSB
Τ𝜋 2
ൿห0𝜈 ൿห0𝜈
Τ𝜋 2
Initializing Entangling Interrogating Detecting
Two Isotope entangled clock
Time [us]
ȁ ൿ𝑆+1/2 ȁ ൿ𝑆−1/2 + 𝑒𝑖 2𝛿𝑙𝑎𝑠𝑒𝑟 𝑡ȁ ൿ𝐷+3/2 ȁ ൿ𝐷−3/2
Time [us]
ȁ ൿ𝐷+3/2 ȁ ൿ𝑆−1/2 ȁ ۧ1 ↔ ȁ ൿ𝐷+3/2 ȁ ൿ𝑆−1/2 ȁ ۧ0
Parity=P ȁ ۧ𝑆𝑆 ȁ + P ȁ𝐷 ۧ𝐷− P ȁ ۧ𝑆𝐷 − P ȁ ۧ𝐷𝑆
Two Isotope entangled clock
ȁ ൿ𝑆+1/2 ȁ ൿ𝑆+1/2 + 𝑒𝑖 2𝛿𝑙𝑎𝑠𝑒𝑟+2𝛿B 𝑡ȁ ൿ𝐷+3/2 ȁ ൿ𝐷+3/2
ȁ ൿ𝑆+1/2 ȁ ൿ𝑆−1/2 + 𝑒𝑖 2𝛿𝑙𝑎𝑠𝑒𝑟 𝑡ȁ ൿ𝐷+3/2 ȁ ൿ𝐷−3/2
GHZ :
DFS :
• Here the 50Hz feedforward compensation was off in order to emphasize the difference
Roee Ozeri (PI) Tom ManovitzYotam ShapiraMeirav PinkasOr KatzLee Peleg
Weizmann Institute Trapped-ions group
David SchwerdtHaim NakavSapir CohenAbraham Gross Vidyut Kaushal
Michal GoldenshteinBen Yamin