Loading a fountain clock with an enhanced low-velocity intense source of atoms

Dobrev, Georgi; Gerginov, Vladislav; Weyers, S.

doi:10.1103/physreva.93.043423

Cited by 8 publications

(19 citation statements)

References 15 publications

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“…At a detuning of −5.9 kHz, ðΔθÞ 2 reaches a minimum value −1.56 þ0. 41 −0.45 dB below the SQL. The two-sample variance, which rejects long term technical drifts and is therefore better suited to estimate the fundamental noise, reaches −2.05 þ0.…”

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confidence: 96%

“…In summary, our experiments present the first proof-ofprinciple implementation of squeezed vacuum in an atomic microwave clock. Microwave fountain clocks, providing the realization of the SI second, are currently limited by the SQL [38][39][40][41]. In combination with the recently developed sources of Bose-Einstein condensed atoms with small densities [42,43] and high repetition rates [44], our results pave the way for the development of a new generation of atomic microwave clocks operating beyond the SQL [20].…”

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confidence: 99%

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Improvement of an Atomic Clock using Squeezed Vacuum

et al. 2016

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Since the pioneering work of Ramsey, atom interferometers are employed for precision metrology, in particular to measure time and to realize the second. In a classical interferometer, an ensemble of atoms is prepared in one of the two input states, whereas the second one is left empty. In this case, the vacuum noise restricts the precision of the interferometer to the standard quantum limit (SQL). Here, we propose and experimentally demonstrate a novel clock configuration that surpasses the SQL by squeezing the vacuum in the empty input state. We create a squeezed vacuum state containing an average of 0.75 atoms to improve the clock sensitivity of 10000 atoms by 2.05_{-0.37}^{+0.34} dB. The SQL poses a significant limitation for today's microwave fountain clocks, which serve as the main time reference. We evaluate the major technical limitations and challenges for devising a next generation of fountain clocks based on atomic squeezed vacuum.

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Improvement of an Atomic Clock using Squeezed Vacuum

et al. 2016

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“…Since the systematic uncertainty of the collisional shift is below 0.5%, much higher atom numbers are compatible with systematic collisional shift uncertainties below the 10 −16 level. Molasses loading from a cold atom beam [3] enables a relatively short loading time of 340 ms (T c = 1.2345 s) for the minimization of the overall uncertainty. Increasing the loading time to 690 ms (T c = 1.5845 s), however, optimizes the statistical uncertainty.…”

Section: B Resulting Frequency Instabilities Of the Fountain Clocks mentioning

confidence: 99%

Optical Stabilization of a Microwave Oscillator for Fountain Clock Interrogation

Lipphardt

Gerginov

Weyers

2017

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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We describe an optical frequency stabilization scheme of a microwave oscillator that is used for the interrogation of primary cesium fountain clocks. Because of its superior phase noise properties, this scheme, which is based on an ultrastable laser and a femtosecond laser frequency comb, overcomes the frequency instability limitations of fountain clocks given by the previously utilized quartz-oscillator-based frequency synthesis. The presented scheme combines the transfer of the short-term frequency instability of an optical cavity and the long-term frequency instability of a hydrogen maser to the microwave oscillator and is designed to provide continuous long-term operation for extended measurement periods of several weeks. The utilization of the twofold stabilization scheme on the one hand ensures the referencing of the fountain frequency to the hydrogen maser frequency and on the other hand results in a phase noise level of the fountain interrogation signal, which enables fountain frequency instabilities at the 2.5 ×10 (τ/s) level that are quantum projection noise limited.

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“…A low-velocity intense source (LVIS) in CSF2 provides a cold atom beam to load atoms in optical molasses (figure 1) [24,25]. The molasses laser beams, with a (1,1,1) geometry, collect atoms for typically 340 ms, again, as a compromise between the frequency instability (see section 4) and the collisional shift uncertainty (see subsection 3.4), and to average out potential microwave phase deviations synchronous with the fountain cycle (see subsection 3.10).…”

Section: Csf2mentioning

confidence: 99%

Advances in the accuracy, stability, and reliability of the PTB primary fountain clocks

Weyers,

Gerginov,

Kazda

et al. 2018

Preprint

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Improvements of the systematic uncertainty, frequency instability, and long-term reliability of the two caesium fountain primary frequency standards CSF1 and CSF2 at PTB (Physikalisch-Technische Bundesanstalt) are described. We have further investigated many of the systematic effects and made a number of modifications of the fountains. With an optically stabilized microwave oscillator, the quantum projection noise limited frequency instabilities are improved to 7.2 × 10 −14 (τ /1 s) −1/2 for CSF1 and 2.5×10 −14 (τ /1 s) −1/2 for CSF2 at high atom density. The systematic uncertainties of CSF1 and CSF2 are reduced to 2.74 × 10 −16 and 1.71 × 10 −16 , respectively. Both fountain clocks regularly calibrate the scale unit of International Atomic Time (TAI) and the local realization of Coordinated Universal Time, UTC(PTB), and serve as references to measure the frequencies of local and remote optical frequency standards.

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Loading a fountain clock with an enhanced low-velocity intense source of atoms

Cited by 8 publications

References 15 publications

Improvement of an Atomic Clock using Squeezed Vacuum

Improvement of an Atomic Clock using Squeezed Vacuum

Optical Stabilization of a Microwave Oscillator for Fountain Clock Interrogation

Advances in the accuracy, stability, and reliability of the PTB primary fountain clocks

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