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New generation of operational atomic clock:what perspectives for
radio-astronomy & VLBI ?
Dr. Jean Lautier-Gaud
October, 14th 2016
Courtesy of Noel Dimarcq, SYRTE
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
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
CAPABILITIES: INDUSTRY GRADE QUANTUM TECHNOLOGIESAS OPERATIONAL TURN-KEY DEVICES FORRESEARCH-GRADE HIGH-PRECISION MEASUREMENTS
Technology transfers from Institut d’Optique & LNE-SYRTE laboratory
(French National Institute of Standards for Time & Frequency)
Founded in 2011
Active in more than 20 countries
Team of 22 engineers and scientists
state-of-the-art laboratories & production
lines
Patented core technology developed for over 15 years
Muquans is a French company located in the Bordeaux area
What is an atomicclock ?
Oscillators, frequency, clocks, time,SI second
Oscillatorn0
Counter
11h13, 47 secondsUTC
City clock on Market Street, San Francisco, USA
1 second
General view of a clock
What is an atomic clock
OSCILLATOR
(quartz, laser, …)
frequency n :
Unstable
Inaccurate
nfrequency n
Unstable
unaccurate
What is an atomic clock
OSCILLATOR
(quartz, laser, …)
frequency n :
Unstable
Inaccurate
n
nn0
E2
E1
h n0 = E2 –E1
ATOM / ION
REFERENCE
SERVO LOOP
correctionfrequency n :
Stable
Accurate
= n0
2
1
Atomic clock for VLBI
• Frequency standard
(L.O. for acquisition)
Ultra-stable frequencyreference as the local oscillator for:
- down-conversion (FE)
- sampling (BE)
• Time standard
(Time tagging)
Time-stamping of data sets for high-resolution correlation
Example of objectives: VGOS resolution : 1 mm or 4 ps delay
Take-home message 1
Accuracy # Stability # Sensitivity # Repeatability
Frequency standard # Time standard
Take-home message 2Characterization of atomic clocks: Allan DeviationMathematical 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 uncertaintyσ(τ) Allan deviation
Time (τ)0.1 1 10 103102 104 105
10-11
10-13
10-15
10-17
White frequencynoiseSlope : 1/√ τ
Clock short-termStabilityOr « stability at 1 s »
Clock long-termstability
VGOS
The family of atomic clocks« Frequency
stability »
Size
Laboratory RF/optical clocks : Fundamental metrology / physics
Medium size clocks : Industry, atomic time scales, GNSS, …
Miniaturized clocks : Industry, telecoms, …
1 m31 dm31 cm3
10-12
10-11
10-14
10-13
10-16
10-15
10-18
History of timekeeping
History of timekeeping
201610-18
Atomic clocksbased on
cold atoms
Atomic clock
OSCILLATOR
(quartz, laser, …)
frequency n :
Unstable
Inaccurate
n
nn0
E2
E1
h n0 = E2 –E1
ATOM / ION
REFERENCE
n0 n
SERVO LOOP
correctionfrequency n :
Stable
Accurate
= n0
CLOCK
SIGNAL
2
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
Benefit of cold atoms
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 ».
Need: increase interrogation time of the atoms
+ intrinsic linewidth of the frequency reference
Picture of a cloud of cold atoms
2 cm
Manipulation of cold atoms + « Ramsey interrogation scheme » then allow to reachincreased interrogration times in reasonably « small » physics packages
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 »: 10-15 / 10-16
Optical clock «quality »: 10-17 / 10-18
~ 700 / 800 k$
~ 1 M$
Cryogenic Sapphire Osc(no cold atoms)« quality »: 10-15 (short-term)
~ 200 k$Schematic of anatomic fountain
Picture of an atomic fountainat PTB, Germany
The MuClock
Muclock
Physical characteristics:
Dimensions 120x50x50cm3Weight <100kgPowerconsumption 200Wtyp.Lifetime >10years
- Frequency stability and accuracy at 10-15 level- Use of cold atoms- Fully integrated and automated
1 m
World’s first industrial clock based on cold atoms
- VGOS compatible : 10-14 @ 15 min- Bonus: long-term stability without drift (months)
(« GPS-free » VLBI and correlation operation)- Bonus: superior robustness to environment
Where Muclock stands
21
Muclock
+ increased robustness to environment (T, P, …)
+ accuracy (few 10-15)
Short-term stability : < 3.10-13
Long-term stability : < 2.10-15
Accuracy : few 10-15
VGOS
Comparison of Allan deviations
Cs clock
H-MASER
The family of atomic clocks« Frequency
stability »
Size
Laboratory RF/optical clocks : Fundamental metrology / physics
Medium size clocks : Industry, atomic time scales, GNSS, …
Miniaturized clocks : Industry, telecoms, …
1 m31 dm31 cm3
10-12
10-11
10-14
10-13
10-16
10-15
10-18
Area for VLBI
Muclock
And VLBI ?
Take-home message 3
• Operational cold-atom clock commercially available
(interesting complement of Maser ensembles)
• Ultra-low phase noise
• High accuracy of time-stampingRemarkable long-term frequency stability
• Excellent robustness to the environment
(temperature, atmospheric pressure, …)
A sustainable future for VLBI:Distributed time / frequency references
Antenna 1+ receiver 1
Antenna 2+ receiver 2
Antenna 3+ receiver 3
Antenna N+ receiver N
Master clock(Reference clock)
Antenna 4+ receiver 4
Leverage existing infrastructure: Frequency/time transfer over existing optical telecom links- Optical frequency reference over optical carrier- RF frequency reference over optical carrier
Muquans is a world pioneer for this approach(transfer parallel to existing data traffic)
A future for Geodesy:multi-observable geodesy
Couple VLBI geodesy with absolute gravimetryand other geophysical observables
To include measurements of terrestrial tides, ocean loading, hydrologyin terrestrial reference frames+ GRACE terrestrial baseline
Thank you for your attention!
See you at the next AGU meetingBooth # 1441
VISIT
www.muquans.com
CONTACT
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www.linkedin.com/muquans
