Uncertainty evaluation of the caesium fountain clock PTB-CSF2

Gerginov, Vladislav; Nemitz, Nils; Weyers, S.; Schröder, R.; Griebsch, D.; Wynands, R.

doi:10.1088/0026-1394/47/1/008

Cited by 124 publications

(118 citation statements)

References 42 publications

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“…The Rabi pulling shift depends on residual populations P m F of the m F = 0 Zeeman sub-levels relative to that of the m F = 0 initial clock state (see, for instance, [59]). We measured these populations and found P ±1 ≈ 10 −3 for the leading ones, with a difference less than 10 −4 .…”

Section: G Rabi and Ramsey Pulling Shiftsmentioning

confidence: 99%

Contributing to TAI with a secondary representation of the SI second

et al. 2014

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Abstract-We report the first contribution to the international atomic time (TAI) based on a secondary representation of the SI second. This work is done with the LNE-SYRTE FO2-Rb fountain frequency standard using the 87 Rb ground state hyperfine transition. We describe FO2-Rb and how it is connected to local and international time scales. We report on local measurements of this frequency standard in the SI system, i.e. against primary frequency standards, down to a fractional uncertainty of 4.4 × 10 −16 , and on the establishment of the recommended value for the 87 Rb hyperfine transition by the CIPM. We also report on the process that led to the participation of the FO2-Rb frequency standard to Circular T and to the elaboration of TAI. This participation enables us to demonstrate absolute frequency measurement directly in terms of the SI second realized by the TAI ensemble with a statistical uncertainty of 1.1 × 10 −16 , therefore at the limit allowed by the accuracy of primary frequency standards. This work constitutes a demonstration of how other secondary representations, based on optical transitions, could also be used for TAI, and an investigation of a number of issues relevant to a future redefinition of the SI second.

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Section: G Rabi and Ramsey Pulling Shiftsmentioning

confidence: 99%

Contributing to TAI with a secondary representation of the SI second

et al. 2014

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“…Each data point is the average of 60 s signal integration. The fractional difference includes corrections due to the systematic shifts of the clocks as well as the gravitational red shift of 2.4(1.0) × 10 −16 [16,22,23]. The frequency difference between uplink and downlink causes different delays due to the dispersion of the ionosphere.…”

Section: Fig 1 Schematic Diagram Of the Frequency Comparison Of Twomentioning

confidence: 99%

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km

Hachisu¹,

Fujieda²,

Nagano³

et al. 2014

Opt. Lett.

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We have demonstrated a direct frequency comparison between two 87 Sr lattice clocks operated in intercontinentally separated laboratories in real time. Two-way satellite time and frequency transfer technique based on the carrier phase was employed for a direct comparison with a baseline of 9 000 km between Japan and Germany. A frequency comparison was achieved for 83 640 s resulting in a fractional difference of (1.1 ± 1.6) × 10 −15 , where the statistical part is the biggest contribution to the uncertainty. This measurement directly confirms the agreement of the two optical frequency standards on an intercontinental scale.

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“…Even without improvements to our squeezedstate preparation or 9 s cycle time, this could yield a short-term stability of σ(τ ) ≈ 2 × 10 −13 s 1/2 / √ τ , competitive with the stability of current fountain clocks [25].…”

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confidence: 99%

Orientation-Dependent Entanglement Lifetime in a Squeezed Atomic Clock

2010

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We study experimentally the lifetime of a special class of entangled states in an atomic clock, squeezed spin states. In the presence of anisotropic noise, their lifetime is strongly dependent on squeezing orientation. We measure the Allan deviation spectrum of a clock operated with a phasesqueezed input state. For integration times up to 50 s the squeezed clock achieves a given precision 2.8(3) times faster than a clock operating at the standard quantum limit.Atomic interference provides an exquisitely sensitive tool for measuring gravitation, magnetic fields, acceleration, rotation, and time itself [1,2]. It has long been hoped that quantum-mechanical entanglement might enhance the precision of such measurements: maximallyentangled states can increase the sensitivity of the interference fringe to the parameter of interest [3], while squeezed spin states can redistribute quantum noise away from that quantity [4,5]. In experiments, both approaches have overcome the standard quantum limit (SQL) of phase sensitivity [6][7][8][9][10][11]. However, Huelga et al. pointed out early on that entangled states might provide little gain in real metrological performance because they are more fragile than uncorrelated states, such that the entanglement-induced increase in phase sensitivity comes at the expense of reduced interrogation time [12]. Analyses with specific noise models [13,14], however, found parameter regimes where entanglement could be helpful despite decoherence. It is thus interesting, practically as well as fundamentally, to investigate the fragility of the entangled states relevant to metrology.In this Letter we show that for an atomic clock in which the dominant environmental perturbation is phase noise, the squeezed-state lifetime varies by an order of magnitude depending on whether the squeezed variable is the phase (subject to environmental perturbation) or the (essentially unperturbed) population difference between states. We operate an atomic clock with a phasesqueezed input state whose precision exceeds the SQL, as also recently demonstrated by Louchet-Chauvet et al. [11], and present the first measurement of such a clock's Allan deviation spectrum. The clock reaches a given precision 2.8(3) times faster than the SQL for integration times up to 50 s. The squeezed states used in this work are prepared by cavity feedback squeezing [10,15], a new technique which deterministically produces entangled states of distant atoms using their collective interaction with a driven optical resonator.Given any two-level atom we can define a spin-1/2 s i . For an ensemble of such atoms, we introduce the total spin S = s i whoseẑ component and azimuthal angle φ represent the population difference and relative phase, respectively, between the two atomic levels. Simultaneously preparing the atoms in the same single-particle

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Uncertainty evaluation of the caesium fountain clock PTB-CSF2

Cited by 124 publications

References 42 publications

Contributing to TAI with a secondary representation of the SI second

Contributing to TAI with a secondary representation of the SI second

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km

Orientation-Dependent Entanglement Lifetime in a Squeezed Atomic Clock

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