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Muquans MuClockThis product is the first and only commercially available atomic clock based on cold atoms in the world.  This unique solution is the result of more than 15 years of experience acquired by our academic partner, LNE-SYRTE, the French National Metrological Institute for Time and Frequency, one of the major international experts in the field of time standards.

The approach developed by Muquans relies on laser manipulation of cold atoms. We are able to produce more than 10 times per second a dense atomic cloud showing an exceptional stability over time, quasi-independently of external conditions. This unique atomic medium allows us to perform spectroscopy measurements with an exceptionally high signal-to-noise ratio, over extremely long periods of time. Therefore, this approach enables the MuClock to offer exceptional performances in terms of both short and long-term stability, as well as accuracy.

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Principle of operation

The basic principle of the MuClock is very similar to the one utilized in the atomic fountains for the definition of the Atomic International Time. However, instead of launching a cloud of cold atoms through a microwave cavity where the atoms are interrogated, the preparation of the cold atomic sample is done inside the microwave cavity. This preparation phase is thus quickly followed by the interrogation of the atoms, which allows to perform measurements with a high repetition frequency, higher than 10 Hz. With this approach, we therefore obtain performances close to atomic fountains with a very significant weight reduction and increase in compacity.

A typical measurement sequence is organized as follows:
First, atoms are cooled in the vacuum chamber with lasers down to a temperature of a few µK.
All laser beams are shut down, then the atoms undergo Ramsey interrogation in the microwave cavity.
Characterization of the clock transition signal through a laser absorption measurement. This signal allows us to precisely determine the clock frequency, which for rubidium atoms is close to 6.834 682 612 Ghz. This atomic signal is used to lock the local oscillator of the MuClock in order to guarantee its long-term stability and accuracy.


Frequency stability

1 s ≦ 3.0 10-13
10 s ≦ 9.5 10-14
100 s
≦ 3.0 10-14
1 000 s
≦ 9.5 10-15
10 000 s ≦ 3.0 10-15
1 day ≦ 2.0 10-15
Flicker floor ≦ 2.0 10-15 (@ 10 days)

Phase noise

Offset (Hz)
5MHz Output
1 -121 dBc
10 -151 dBc
-163 dBc
-168 dBc
-176 dBc
100,000 -178 dBc


High predictability: low floor noise and accuracy of a few 10-15

Available outputs

Output frequencies: 5, 10 and 100 MHz      
Synchronization options: PPS input & output


Operating power 200 W
Peak power
250 W


Height 155 cm
55 cm
80 cm
Weight 135 kg


Time and Frequency metrology and calibration
Time-scale operation
Global Navigation Satellite Systems & radionavigation
VLBI and Geodesy
High-performance network synchronization (transportation, power grid, telecommunication…)


- Esnault et al, Advances in Space Research 47, 854-858 (2011)
- Guéna et al, Contributing to TAI with a secondary representation of the SI second. Metrologia 2014, 51, 108-120
- BIPM, Recommended values of standard frequencies for secondary representations of the definition of the second, CIPM (2015)