Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0909.1465 · Physical Review A

Low-velocity limits of cold-atom clocks

J. Muñoz, Ion Lizuain, Juan Gonzalo Muga

Published Aug 19, 2009• 1 citation
arXivHTMLPDF

Abstract

Fundamental low-energy limits to the accuracy of quantum clock and stopwatch models in which the clock hand motion is activated by the presence of a particle in a region of space have been studied in the past, but their relevance for actual atomic clocks had not been assessed. In this work we address the effect of slow atomic quantum motion on Rabi and Ramsey resonance fringe patterns, as a perturbation of the results based on classical atomic motion. We find the dependence of the fractional error of the corresponding atomic clocks on the atomic velocity and interaction parameters.

DOI
10.1103/physreva.80.022116

Related papers

Time-Energy Uncertainty Relation for Noisy Quantum Metrology

Philippe Faist, Mischa P. Woods, Victor V. Albert +3 more

The impact of noise on the accuracy of a quantum clock is investigated, unveiling a necessary and sufficient requirement for accuracy that extends standard error-correcting conditions to quantum metrology.

arXiv:2207.13707•PRX Quantum•Dec 5, 2023•9 citations

Quantum Motion Effects in Atom Interferometry

Dirk Seidel, Juan Gonzalo Muga

Abstract We study the Ramsey interference pattern of ultracold atoms crossing two electromagnetic fields, taking into account quantum motion effects. It is shown that quantum reflection and transmission at the fields lead to a modification of the standard fringes. The implications on present frequency standards are discussed. For weak coupling, the difference between the exact quantum result and the semiclassical result is small but results in a central peak shift that may become important for future accuracies of atomic clocks. In the strong coupling regime, a resonance structure with respect to the detuning is observed and the Ramsey setup acts as a matter‐wave Fabry‐Perot device. Our results question the advantage of using increasingly lower velocities in frequency standards because the peak shift and the resonance positions depend sensitively on very minor variations of the atomic velocity and are difficult to control.

Israel Journal of Chemistry•Dec 1, 2007•1 citation

Tests of Cold Atom Clock in Orbit

Liang Liu, Desheng Lü, Weibiao Chen +23 more

Since the atomic clock was invented, its performance has been improved for one digit every decade until 90s of last century when the traditional atomic clock almost reached its limit. With laser cooled atoms, the performance can be further improved, and nowadays the cold atom based clocks are widely used as primary frequency standards. Such a kind of cold atom clocks has great applications in space. This paper presents the design and tests of a cold atom clock (CAC) operating in space. In microgravity, the atoms are cooled, trapped, launched and finally detected after being interrogated by microwave field with Ramsey method. The results of laser cooling of atoms in microgravity in orbit are presented and compared with that on ground for the first time. That the full width at half maximum (FWHM) of obtained central Ramsey fringes varies linearly with launching velocity of cold atoms shows the effects of microgravity. With appropriate parameters, a closed-loop locking of the CAC is realized in orbit and the estimated short term frequency stability of $3.0\times 10 ^{-13}/\sqrt{τ}$ has been reached.

arXiv:1709.03256•Sep 11, 2017•4 citations

Scattering of cold atom coherences by hot atoms: Background gas collision shifts of primary fountain clocks

Kurt Gibble

We theoretically analyze frequency shifts of cold-atom clocks due to background gas collisions. Because nearly all collisions with room-temperature background gases that transfer momentum eject cold atoms from a clock, the frequency shifts for cold atoms are significantly different than those of room-temperature clocks. From general arguments, measurements of the loss of Ramsey fringe amplitude can usefully bound this source of systematic error.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jul 1, 2013•2 citations

Scattering of Cold-Atom Coherences by Hot Atoms: Frequency Shifts from Background-Gas Collisions

Kurt Gibble

Frequency shifts from background-gas collisions currently contribute significantly to the inaccuracy of atomic clocks. Because nearly all collisions with room-temperature background gases that transfer momentum eject the cold atoms from the clock, the interference between the scattered and unscattered waves in the forward direction dominates these frequency shifts. We show they are ≈ 10 times smaller than in room-temperature clocks and that van der Waals interactions produce the cold-atom background-gas shift. General considerations allow the loss of the Ramsey fringe amplitude to bound this frequency shift.

arXiv:1304.3486•Physical Review Letters•May 3, 2013•71 citations

Quantum Variational Optimization of Ramsey Interferometry and Atomic Clocks

Raphael Kaubruegger, Denis V. Vasilyev, Marius Schulte +2 more

We discuss quantum variational optimization of Ramsey interferometry with ensembles of N entangled atoms, and its application to atomic clocks based on a Bayesian approach to phase estimation.We identify best input states and generalized measurements within a variational approximation for the corresponding entangling and decoding quantum circuits.These circuits are built from basic quantum operations available for the particular sensor platform, such as one-axis twisting, or finite range interactions.Optimization is defined relative to a cost function, which in the present study is the Bayesian mean squared error of the estimated phase for a given prior distribution; i.e., we optimize for a finite dynamic range of the interferometer.In analogous variational optimizations of optical atomic clocks, we use the Allan deviation for a given Ramsey interrogation time as the relevant cost function for the long-term instability.Remarkably, even low-depth quantum circuits yield excellent results that closely approach the fundamental quantum limits for optimal Ramsey interferometry and atomic clocks.The quantum metrological schemes identified here are readily applicable to atomic clocks based on optical lattices, tweezer arrays, or trapped ions.While in the present work variationally optimized circuits are found with classical simulations, optimization can also be performed "on" the (physical) quantum sensor, also in regimes not accessible to classical computations and in the presence of imperfections.

arXiv:2102.05593•Physical Review X•Dec 6, 2021•87 citations
Fundamental low-energy limits to the accuracy of quantum clock and stopwatch models in which the clock hand motion is activated by the presence of a particle in a region of space have been studied in the past, but their relevance for actual atomic clocks had not been assessed. In this work we address the effect of slow atomic quantum motion on Rabi and Ramsey resonance fringe patterns, as a perturbation of the results based on classical atomic motion. We find the dependence of the fractional error of the corresponding atomic clocks on the atomic velocity and interaction parameters.
Abstract We study the Ramsey interference pattern of ultracold atoms crossing two electromagnetic fields, taking into account quantum motion effects. It is shown that quantum reflection and transmission at the fields lead to a modification of the standard fringes. The implications on present frequency standards are discussed. For weak coupling, the difference between the exact quantum result and the semiclassical result is small but results in a central peak shift that may become important for future accuracies of atomic clocks. In the strong coupling regime, a resonance structure with respect to the detuning is observed and the Ramsey setup acts as a matter‐wave Fabry‐Perot device. Our results question the advantage of using increasingly lower velocities in frequency standards because the peak shift and the resonance positions depend sensitively on very minor variations of the atomic velocity and are difficult to control.
Since the atomic clock was invented, its performance has been improved for one digit every decade until 90s of last century when the traditional atomic clock almost reached its limit. With laser cooled atoms, the performance can be further improved, and nowadays the cold atom based clocks are widely used as primary frequency standards. Such a kind of cold atom clocks has great applications in space. This paper presents the design and tests of a cold atom clock (CAC) operating in space. In microgravity, the atoms are cooled, trapped, launched and finally detected after being interrogated by microwave field with Ramsey method. The results of laser cooling of atoms in microgravity in orbit are presented and compared with that on ground for the first time. That the full width at half maximum (FWHM) of obtained central Ramsey fringes varies linearly with launching velocity of cold atoms shows the effects of microgravity. With appropriate parameters, a closed-loop locking of the CAC is realized in orbit and the estimated short term frequency stability of 3.0×10−13/τ3.0\times 10 ^{-13}/\sqrt{τ}3.0×10−13/τ​ has been reached.
Frequency shifts from background-gas collisions currently contribute significantly to the inaccuracy of atomic clocks. Because nearly all collisions with room-temperature background gases that transfer momentum eject the cold atoms from the clock, the interference between the scattered and unscattered waves in the forward direction dominates these frequency shifts. We show they are ≈ 10 times smaller than in room-temperature clocks and that van der Waals interactions produce the cold-atom background-gas shift. General considerations allow the loss of the Ramsey fringe amplitude to bound this frequency shift.
We discuss quantum variational optimization of Ramsey interferometry with ensembles of N entangled atoms, and its application to atomic clocks based on a Bayesian approach to phase estimation.We identify best input states and generalized measurements within a variational approximation for the corresponding entangling and decoding quantum circuits.These circuits are built from basic quantum operations available for the particular sensor platform, such as one-axis twisting, or finite range interactions.Optimization is defined relative to a cost function, which in the present study is the Bayesian mean squared error of the estimated phase for a given prior distribution; i.e., we optimize for a finite dynamic range of the interferometer.In analogous variational optimizations of optical atomic clocks, we use the Allan deviation for a given Ramsey interrogation time as the relevant cost function for the long-term instability.Remarkably, even low-depth quantum circuits yield excellent results that closely approach the fundamental quantum limits for optimal Ramsey interferometry and atomic clocks.The quantum metrological schemes identified here are readily applicable to atomic clocks based on optical lattices, tweezer arrays, or trapped ions.While in the present work variationally optimized circuits are found with classical simulations, optimization can also be performed "on" the (physical) quantum sensor, also in regimes not accessible to classical computations and in the presence of imperfections.