Frequency standards and frequency measurement

Bauch, A.; Telle, H.R.

doi:10.1088/0034-4885/65/5/203

Cited by 40 publications

(38 citation statements)

References 218 publications

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“…Advances in trapping and laser control of a single ion [1][2][3] began a new era for the frequency standards in the optical range, which are aimed to achieve a fractional accuracy of 10 [11,12], 40 Ca + [13,14], 27 Al + [15] etc. have been undertaken in the experiments to attain such promising optical frequency standards.…”

Section: Introductionmentioning

confidence: 99%

An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks

Batra

Sahoo

2016

Chinese Phys. B

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We propose a new ion-trap geometry to carry out accurate measurements of the quadrupole shifts in the 171 Yb-ion. This trap will produce nearly ideal harmonic potential where the quadrupole shifts due to the anharmonic components can be reduced by four orders of magnitude. This will be useful to reduce the uncertainties in the clock frequency measurements of the 6s 2 S 1/2 → 4f 13 6s 2 2 F 7/2 and 6s 2 S 1/2 → 5d 2 D 3/2 transitions, from which we can deduce precise values of the quadrupole moments (Θs) of the 4f 13 6s 2 2 F 7/2 and 5d 2 D 3/2 states. Moreover, it may be able to affirm validity of the measured Θ value of the 4f 13 6s 2 2 F 7/2 state where three independent theoretical studies defer almost by one order in magnitude from the measurement. We also perform calculations of Θs using the relativistic coupled-cluster (RCC) method. We use these Θ values to estimate quadrupole shift that can be measured in our proposed ion trap experiment.

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Section: Introductionmentioning

confidence: 99%

An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks

Batra

Sahoo

2016

Chinese Phys. B

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“…Yz, 03.65.Ta, 42.50.Ct Superpositions of hyperfine states of atoms have been the subject of considerable experimental interest. A good example is the role they have played in the development of atomic clocks over the last five decades [1]. More recently, hyperfine coherences of quantum-degenerate gases have been used to reveal their intrinsic properties [2,3].…”

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confidence: 99%

Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

Ozeri¹,

Langer²,

Jost³

et al. 2005

Phys. Rev. Lett.

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The coherence of a hyperfine-state superposition of a trapped 9 Be + ion in the presence of offresonant light is experimentally studied. It is shown that Rayleigh elastic scattering of photons that does not change state populations also does not affect coherence. Coherence times exceeding the average scattering time of 19 photons are observed. This result implies that, with sufficient control over its parameters, laser light can be used to manipulate hyperfine-state superpositions with very little decoherence.PACS numbers: 03.65. Yz, 03.65.Ta, 42.50.Ct Superpositions of hyperfine states of atoms have been the subject of considerable experimental interest. A good example is the role they have played in the development of atomic clocks over the last five decades [1]. More recently, hyperfine coherences of quantum-degenerate gases have been used to reveal their intrinsic properties [2,3]. Atomic hyperfine-state superpositions are also being investigated as possible information carriers for quantum information processing [4].In many such experiments, laser light is used to coherently manipulate the hyperfine superpositions with stimulated Raman transitions. In addition, laser light can be used to trap atoms as in the case of optical-dipole traps. Since light perturbs the energies of hyperfine levels, imperfect control of laser-beam parameters can lead to dephasing of the superpositions and loss of coherence [5,6,7].Past experiments with neutral-atoms in dipole traps investigated the coherence of hyperfine superpositions in the presence of light [6,7]. In these experiments the dominant source of dephasing was noise in experimental parameters such as fluctuations in the laser intensity or the ambient magnetic field.A more fundamental source of decoherence arises from spontaneous scattering of photons [8]. Spontaneous scattering is typically suppressed by detuning the laser frequency from allowed optical transitions, but it cannot be eliminated completely. Generally, if a spontaneously scattered photon carries information about which hyperfine state scattered the light, the event effectively measures the atomic state and the superposition collapses. In contrast, if the scattered photon does not contain this information then coherence is preserved. In this letter, we verify this effect by means of an experimental study of the hyperfine decoherence of a trapped 9 Be + ion caused by spontaneous scattering of photons from a non-resonant laser beam. Our results show that coherence can be preserved in the presence of spontaneous photon scattering.Off-resonant spontaneous scattering is a two-photon process in which the atom scatters a laser photon into an electromagnetic vacuum mode. Following such a scattering event the atom can be found in the same or a different internal state, corresponding to elastic Rayleigh or inelastic Raman scattering, respectively. The polarization and frequency of a Raman scattered photon depend on the angular momentum and energy imparted to the atom and are therefore entangled with the atomic i...

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“…The obvious disadvantage is that the limited duration of the experiments of typically a few years only is not well adapted to search for evolution on a cosmological time scale. Application of the methods of laser cooling and trapping has led to significant improvements in the precision of atomic clocks and frequency standards over the last years [17,18]: Primary cesium clocks based on atomic fountains [19,20] realize the SI second with a relative uncertainty below 1 · 10 −15 and a similar level of accuracy has been achieved for the ground state hyperfine frequency of 87 Rb [20]. Research towards optical clocks with trapped ions and atoms [21,18] has resulted in several systems that approach the accuracy of primary cesium clocks or show an even higher reproducibility.…”

Section: Search For Variations Of Constants In Astrophysics and With mentioning

confidence: 99%

Laboratory Limits for Temporal Variations of Fundamental Constants: An Update

Peik¹,

Lipphardt²,

Schnatz³

et al. 2008

The Eleventh Marcel Grossmann Meeting

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Precision comparisons of different atomic frequency standards over a period of a few years can be used for a sensitive search for temporal variations of fundamental constants. We present recent frequency measurements of the 688 THz transition in the 171 Yb + ion. For this transition frequency a record over six years is now available, showing that a possible frequency drift relative to a cesium clock can be constrained to (−0.54 ± 0.97) Hz/yr, i.e. at the level of 2 · 10 −15 per year. Combined with precision frequency measurements of an optical frequency in 199 Hg + and of the hyperfine ground state splitting in 87 Rb a stringent limit on temporal variations of the fine structure constant α: d ln α/dt = (−0.26 ± 0.39) · 10 −15 yr −1 and a model-dependent limit for variations of the proton-to-electron mass ratio µ in the present epoch can be derived:−15 yr −1 . We discuss these results in the context of astrophysical observations that apparently indicate changes in both of these constants over the last 5-10 billion years. Search for variations of constants in astrophysics and with atomic clocksOver the past few years there has been great interest in the possibility that the fundamental constants of nature might show temporal variations over cosmological time scales [1,2,3,4,5]. Such an effect -as incompatible as it seems with the present foundations of physics -appears quite naturally in the attempt to find a unified theory of the fundamental interactions. An active search for an indication of variable constants is pursued mainly in two areas: observational astrophysics and laboratory experiments with atomic frequency standards. The two most important quantities under test are Sommerfeld's fine structure constant α = e 2 /(4πǫ 0h c) and the proton-to-electron mass ratio µ = m p /m e . While α is the coupling constant of the electromagnetic interaction, µ also depends on the strength of the strong force and on the quark masses via the proton mass. It is important that these quantities are dimensionless numbers so that results can be interpreted independently from the conventions of a specific system of units. Quite conveniently, both constants appear prominently in atomic and molecular transition energies: α in atomic fine structure splittings and other relativistic contributions, and µ in molecular vibration and rotation frequencies as well as in hyperfine structure.A multitude of data on variations of α and µ has been obtained from astrophysical observations but the present picture that is obtained is not completely consistent: Evidence for a variation of α has been derived from a shift of wavelengths of metal ion absorption lines produced by interstellar clouds in the light from distant quasars [6]. These observations suggest that about 10 billion years ago (redshift range 0.5 < z < 3.5), the value of α was 1

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Frequency standards and frequency measurement

Cited by 40 publications

References 218 publications

An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks

An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks

Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

Laboratory Limits for Temporal Variations of Fundamental Constants: An Update

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Frequency standards and frequency measurement

Cited by 40 publications

References 218 publications

An optimized ion trap geometry to measure quadrupole shifts of 171 Yb + clocks

An optimized ion trap geometry to measure quadrupole shifts of 171 Yb + clocks

Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

Laboratory Limits for Temporal Variations of Fundamental Constants: An Update

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An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks

An optimized ion trap geometry to measure quadrupole shifts of ¹⁷¹ Yb ⁺ clocks