Dr. Jean Lautier-Gaud October, 14 th 2016

Transcription

1 New generation of operational atomic clock: what perspectives for radio-astronomy & VLBI? Dr. Jean Lautier-Gaud October, 14 th 2016 Courtesy of Noel Dimarcq, SYRTE

2 Content 1. Why is Muquans here? 2. What is an atomic clock? - Tools to discuss atomic clocks - Cold atoms at a pedagogical level - State-of the art frequency references 3. The Muclock 4. What solutions for VLBI

3 MUQUANS: OFFER THE BEST OF QUANTUM TECHNOLOGIES FOR HIGH-PRECISION MEASUREMENTS Muquans is the world s first company to design, manufacture, and commercialize scientific instruments based on high-precision measurement using laser-cooled atoms. Absolute Quantum Gravimeter Muclock atomic clock Scientific laser systems Time & Frequency dissemination

4 CAPABILITIES: INDUSTRY GRADE QUANTUM TECHNOLOGIES AS OPERATIONAL TURN-KEY DEVICES FOR RESEARCH-GRADE HIGH-PRECISION MEASUREMENTS Technology transfers from Institut d Optique & LNE-SYRTE laboratory (French National Institute of Standards for Time & Frequency) Patented core technology developed for over 15 years Team of 22 engineers and scientists state-of-the-art laboratories & production lines Founded in 2011 Active in more than 20 countries Muquans is a French company located in the Bordeaux area

5 What is an atomic clock?

6 Oscillators, frequency, clocks, time, General view of a clock SI second Counter 1 second Oscillator n 0 11h13, 47 seconds UTC City clock on Market Street, San Francisco, USA

7 What is an atomic clock OSCILLATOR (quartz, laser, ) n frequency n : Unstable unaccurate Inaccurate

8 What is an atomic clock correction OSCILLATOR (quartz, laser, ) n frequency n : = n 0 Stable Unstable SERVO LOOP Accurate Inaccurate ATOM / ION REFERENCE 2 E 2 n 1 n 0 E 1 h n 0 = E 2 E 1

9 Atomic clock for VLBI Frequency standard (L.O. for acquisition) Time standard (Time tagging) Ultra-stable frequency reference as the local oscillator for: - down-conversion (FE) - sampling (BE) Time-stamping of data sets for highresolution correlation Example of objectives: VGOS resolution : 1 mm or 4 ps delay

10 Take-home message 1 Frequency standard # Time standard Accuracy # Stability # Sensitivity # Repeatability

11 Take-home message 2 Characterization of atomic clocks: Allan Deviation Mathematical tool to characterize the stability of time signals Expression of the frequency stability of an output signal Here is a typical ADEV plot for a clock signal Statistical uncertainty σ(τ) Allan deviation Clock short-term Stability Or «stability at 1 s» White frequency noise Slope : 1/ τ Clock long-term stability VGOS Time (τ)

12 The family of atomic clocks «Frequency stability» Medium size clocks : Industry, atomic time scales, GNSS, Laboratory RF/optical clocks : Fundamental metrology / physics cm 3 Miniaturized clocks : Industry, telecoms, 1 dm 3 1 m 3 Size

13 History of timekeeping

14 History of timekeeping

15 Atomic clocks based on cold atoms

16 Atomic clock correction OSCILLATOR (quartz, laser, ) n frequency n : = n 0 Stable Unstable SERVO LOOP Accurate Inaccurate ATOM / ION REFERENCE n 0 CLOCK SIGNAL n 2 n 0 E 2 h n 0 = E 2 E 1 n 1 E 1 Cs : 9,2 GHz Rb : 6,8 GHz The longer the atoms are interrogated as a reference, the sharper the error signal, the higher the resolution of the correction in frequency

17 Benefit of cold atoms Need: increase interrogation time of the atoms + intrinsic linewidth of the frequency reference Cold atoms in a nutshell: Laser beams can have a mechanical effects on atoms. Counter-propagative laser beams (see below) can dissipate thermal energy of room-temperature atoms (recoil) and slow them until almost pure «rest». 2 cm Picture of a cloud of cold atoms Manipulation of cold atoms + «Ramsey interrogation scheme» then allow to reach increased interrogration times in reasonably «small» physics packages

18 Benefit of cold atoms, state of the art Atomic fountains: cold atoms are launched upwards and gravity is used Optical clock: an ultra-stable laser is used as the LO to probe higher resonance frequencies Atomic fountain «quality»: / ~ 700 / 800 k$ Optical clock «quality»: / ~ 1 M$ Schematic of an atomic fountain Picture of an atomic fountain at PTB, Germany Cryogenic Sapphire Osc (no cold atoms) «quality»: (short-term) ~ 200 k$

19 The MuClock

20 1 m Muclock World s first industrial clock based on cold atoms - Frequency stability and accuracy at level - Use of cold atoms - Fully integrated and automated Physical characteristics: Dimensions 120 x 50 x 50 cm 3 Weight < 100 kg Power consumption 200 W typ. Lifetime > 10 years - VGOS compatible : 15 min - Bonus: long-term stability without drift (months) («GPS-free» VLBI and correlation operation) - Bonus: superior robustness to environment

21 Where Muclock stands Short-term stability : < Long-term stability : < Accuracy : few Comparison of Allan deviations VGOS Cs clock H-MASER Muclock + increased robustness to environment (T, P, ) + accuracy (few ) 21

22 The family of atomic clocks «Frequency stability» Medium size clocks : Industry, atomic time scales, GNSS, Muclock 0-14 Area for VLBI Laboratory RF/optical clocks : Fundamental metrology / physics cm 3 Miniaturized clocks : Industry, telecoms, 1 dm 3 1 m 3 Size

23 And VLBI?

24 Take-home message 3 Operational cold-atom clock commercially available (interesting complement of Maser ensembles) Ultra-low phase noise High accuracy of time-stamping Remarkable long-term frequency stability Excellent robustness to the environment (temperature, atmospheric pressure, )

25 A sustainable future for VLBI: Distributed time / frequency references Leverage existing infrastructure: Frequency/time transfer over existing optical telecom links - Optical frequency reference over optical carrier - RF frequency reference over optical carrier Antenna 1 + receiver 1 Master clock (Reference clock) Antenna 2 + receiver 2 Antenna 4 + receiver 4 Antenna 3 + receiver 3 Muquans is a world pioneer for this approach (transfer parallel to existing data traffic) Antenna N + receiver N

26 A future for Geodesy: multi-observable geodesy Couple VLBI geodesy with absolute gravimetry and other geophysical observables To include measurements of terrestrial tides, ocean loading, hydrology in terrestrial reference frames + GRACE terrestrial baseline

27 Thank you for your attention! See you at the next AGU meeting Booth # 1441 VISIT CONTACT jean.lautier@muquans.com FOLLOW US ON LINKEDIN