Nitzan Akerman Trapped ions group (Roee Ozeri) Weizmann ...
Transcript of Nitzan Akerman Trapped ions group (Roee Ozeri) Weizmann ...
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