Scheme for a compact cold-atom clock based on diffuse laser cooling in a cylindrical cavity

Liu, Peng; Meng, Yu; Wan, Jinyin; Wang, Xiumei; Wang, Yaning; Liu, Xiao; Cheng, Huadong; Liu, Liang

doi:10.1103/physreva.92.062101

Cited by 37 publications

(23 citation statements)

References 19 publications

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“…Probe-field-induced shifts also cause instability for microwave atomic clocks based on coherent population trapping (CPT) [15][16][17][18][19][20]. Compact microwave cold-atom clocks [21,22] and hot-cell devices like the pulsed optical pumping (POP) clock [23,24] that are based on direct microwave interrogation can also be affected by probe-induced frequency shifts.…”

Section: Introductionmentioning

confidence: 99%

Combined error signal in Ramsey spectroscopy of clock transitions

et al. 2018

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We have developed a universal method to form the reference signal for the stabilization of arbitrary atomic clocks based on Ramsey spectroscopy. Our approach uses an interrogation scheme of the atomic system with two different Ramsey periods and a specially constructed combined error signal (CES) computed by subtracting two error signals with the appropriate calibration factor. CES spectroscopy allows for perfect elimination of probe-induced light shifts and does not suffer from the effects of relaxation, time-dependent pulse fluctuations and phase-jump modulation errors and other imperfections of the interrogation procedure. The method is simpler than recently developed autobalanced Ramsey spectroscopy techniques (Sanner et al 2018 Phys. Rev. Lett. 120 053602; Yudin et al 2018 Phys. Rev. Appl. 9 054034), because it uses a single error signal that feeds back on the clock frequency. The use of CES is a general technique that can be applied to many applications of precision spectroscopy.clocks were theoretically described in [27], which proposed the use of pulses of differing durations ( 1 2 t t ¹ ) and the use of composite pulses instead of the standard Ramsey sequence with two equal π/2 pulses. This 'hyper-Ramsey' scheme has been successfully realised in an ion clock based on an octupole transition in Yb + [5,28], where a suppression of the light shift by four orders of magnitude and an immunity against its fluctuations were demonstrated. Further developments in Ramsey spectroscopy resulted in additional suppression of probe-fieldinduced frequency shifts. For example, the hyper-Ramsey approach uses new phase variants to construct error signals [29][30][31][32] to significantly suppress the probe-field-induced shifts in atomic clocks. However, as was shown in [33], all previous hyper-Ramsey methods [5, 27-29, 31, 34] are sensitive to decoherence and spontaneous relaxation, which can prevent the achievement of state-of-the-art performance in some systems. To overcome the effect of decoherence, a more complicated construction of the error signal was recently proposed in [35], which requires four measurements for each frequency point (instead of two) combined with the use of the generalized hyper-Ramsey sequences presented in [31]. Nevertheless the method in [35] is not free from other disadvantages related to technical issues such as time-dependent pulse area fluctuations and/or phase-jump modulation errors during the measurements.The above approaches [5, 27-29, 31, 34, 35] are all one-loop methods, since they use one feedback loop and one error signal. However, frequency stabilization can also be realized with two feedback loops combined with Ramsey sequences with different dark periods T 1 and T 2 [33,36,37]. For example, the synthetic frequency protocol [33] in combination with the original hyper-Ramsey sequence [27] allows for substantial reduction in the sensitivity to decoherence and imperfections of the interrogation procedure. Auto-balanced Ramsey spectroscopy (ABRS) is another effective approach that was ...

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Section: Introductionmentioning

confidence: 99%

Combined error signal in Ramsey spectroscopy of clock transitions

et al. 2018

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“…In the first one, the core of the clock apparatus is a sample of lasercooled atoms. These clocks are relatively recent [1][2][3] and can in principle provide the accuracy information not only on ground applications but, taking advantage of the micro-gravity environment, also in space [4].…”

Section: Introductionmentioning

confidence: 99%

Reducing Cavity-Pulling Shift in Ramsey-Operated Compact Clocks

Gozzelino

Micalizio

Levi

et al. 2018

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

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We describe a method to stabilize the amplitude of the interrogating microwave field in compact atomic clocks working in a Ramsey approach. In this technique, we take advantage of the pulsed regime to use the atoms themselves as microwave amplitude discriminators. Specifically, in addition to the dependence on the microwave detuning, the atomic signal after the Ramsey interrogation acquires a dependence on the microwave pulse area (amplitude times duration) that can be exploited to implement an active stabilization of the microwave field amplitude, in a similar way in which the Ramsey clock signal is used to lock the local oscillator frequency to the atomic reference. The stabilization allows us to reduce the microwave field-amplitude fluctuations, which in turn impact the clock frequency through cavity pulling. The proposed technique has shown to be effective to improve our clock frequency stability on medium and long term. We demonstrate the method for a vapor-cell clock working with a hot sample of atoms, but it can be extended to cold-atom compact clocks.

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“…The integrating sphere cold atom clock (ISCAC) [4] is a kind of compact atomic clock that uses diffuse laser cooling [5][6][7] and the POP [8] operating scheme to achieve a good frequency stability with a small volume and weight. Compared with a vapor cell POP atomic clock, the ISCAC has less atomic collision frequency shifts and less sensitivity to the temperature fluctuations making it easier to achieve a better frequency stability for a long operation time.…”

Section: Introductionmentioning

confidence: 99%

“…Compared with a vapor cell POP atomic clock, the ISCAC has less atomic collision frequency shifts and less sensitivity to the temperature fluctuations making it easier to achieve a better frequency stability for a long operation time. Unlike other compact cold atom clocks, ISCAC uses a microwave cavity to diffusely reflect cooling light and cools atoms without a quartz chamber in it [4]. This scheme can eliminate the influence of the quartz chamber on the microwave resonant frequency in the microwave cavity.…”

Section: Introductionmentioning

confidence: 99%

Improvement in medium long-term frequency stability of the integrating sphere cold atom clock

et al. 2016

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The medium-long term frequency stability of the integrating sphere cold atom clock was improved. During the clock operation, Rb atoms were cooled and manipulated using cooling light diffusely reflected by the inner surface of a microwave cavity in the clock. This light heated the cavity and caused a frequency drift from the resonant frequency of the cavity. Power fluctuations of the cooling light led to atomic density variations in the cavity's central area, which increased the clock frequency instability through a cavity pulling effect. We overcame these limitations with appropriate solutions. A frequency stability of 3.5 × 10 −15 was achieved when the integrating time τ increased to 2 × 10 4 s.

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Scheme for a compact cold-atom clock based on diffuse laser cooling in a cylindrical cavity

Cited by 37 publications

References 19 publications

Combined error signal in Ramsey spectroscopy of clock transitions

Combined error signal in Ramsey spectroscopy of clock transitions

Reducing Cavity-Pulling Shift in Ramsey-Operated Compact Clocks

Improvement in medium long-term frequency stability of the integrating sphere cold atom clock

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