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

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)

Quantum Nondemolition Detection for Strontium Optical Lattice Clock

Haosen Shang, Miguel A. Cifuentes Marin, Yannick Foucault, Rodolphe Le Targat, Jérôme Lodewyck

Published Apr 24, 2022• 1 citation
Publisher

Abstract

SummaryThe short-term frequency instability of the best optical atomic clock lies in the mid 10−17. However, the Dick effect is still an obstacle for a single operational clock closely followed by the quantum projection noise. To improve the frequency stability of the strontium optical lattice clock, we present a quantum non-demolition detection scheme based on the cavity mediated interaction between the atoms and a probe light that has a large-frequency detuning to the atomic resonance, aiming to bring the detection scheme proposed in [1] to the quantum regime. We obtained a rather small photon scattering rate, measured to be less than 0.1 photon/μs/atom, which allows us to not only preserve the atoms in the lattice but also the atomic wave function as long as the total probe time is on the order of a few microseconds. The detection noise for the number of atoms is 48/√photons atoms, implying that the frequency stability can surpass the standard quantum limit when the number of trapped atoms is larger than 2.3×104with spin squeezing protocols.

DOI
10.1109/eftf/ifcs54560.2022.9850517

Related papers

A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime

Grégoire Vallet, Eva Bookjans, Ulrich Eismann +3 more

We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the dispersive properties of lattice-trapped atoms enhanced by a high finesse cavity. By design, this scheme offers a 1st order rejection of the technical noise sources, an enhanced signal-to-noise ratio, and an homogeneous atom-cavity coupling. We theoretically show that this scheme is optimal with respect to the photon shot noise limit. We experimentally realise this detection scheme in an operational strontium optical lattice clock. The resolution is on the order of a few atoms with a photon scattering rate low enough to keep the atoms trapped after detection. This scheme opens the door to various different interrogations protocols, which reduce the frequency instability, including atom recycling, zero-dead time clocks with a fast repetition rate, and sub quantum projection noise frequency stability.

arXiv:1703.04609•New Journal of Physics•Aug 7, 2017•51 citations

Détection non destructive en cavité pour des horloges à réseau optique au strontium

Grégoire Vallet

The work achieved in the frame of this PhD training consisted in the implementation of a cavity enhanced non destructive detection system of atoms trapped in an optical lattice aiming at improving the stability of an optical strontium clock.The characterization of the system in its classical regime, for which a sufficiently low number of photons are scattered per atom to avoid expelling them off the trap, highlighted significant improvements in term of signal to noise ratio, with gain factor around 100 compared with the previously used fluorescence scheme. Yet, gains in terms of stability via Dick effect reduction still have to be demonstrated.Regarding the quantum regime, for which less than one photon is scattered per atom over the detection, new ideas and significant changes have been carried out on the system and a theoretical study was has been undertaken to determine the strategy for the improvement of the clock stability by quantum projection noise reduction via quantum non demolition measurement.It was as well the opportunity to study the effect of the hot collisions between the trapped strontium atoms and the residual vacuum background gas particles, allowing for the improvement of the clock uncertainty. This work reports in particular on the first measurement of strontium clock hot collisions shifts as well as its theoretical study.

•Dec 13, 2018•0 citations

Spin squeezing in optical lattice clocks via lattice-based QND measurements

D. Meiser, Jun Ye, Murray Holland

Quantum projection noise will soon limit the best achievable precision of optical atomic clocks based on lattice-confined neutral atoms. Squeezing the collective atomic pseudo-spin via measurement of the clock state populations during Ramsey interrogation suppresses the projection noise. We show here that the lattice laser field can be used to perform ideal quantum non-demolition measurements without clock shifts or decoherence and explore the feasibility of such an approach in theory with the lattice field confined in a ring-resonator. Detection of the motional sideband due to the atomic vibration in the lattice wells can yield signal sizes a hundredfold above the projection noise limit.

arXiv:0707.3834•New Journal of Physics•Jul 8, 2008•58 citations

Clock Precision beyond the Standard Quantum Limit at 10 − 18 Level

Yutong Yang, Maya Miklos, Yee Ming Tso +3 more

Optical atomic clocks with unrivaled precision and accuracy have advanced the frontier of precision measurement science and opened new avenues for exploring fundamental physics. A fundamental limitation on clock precision is the standard quantum limit (SQL), which stems from the uncorrelated projection noise of each atom. State-of-the-art optical lattice clocks interrogate large ensembles to minimize the SQL, but density-dependent frequency shifts pose challenges to scaling the atom number. The SQL can be surpassed, however, by leveraging entanglement, though it remains an open problem to achieve quantum advantage from spin squeezing at state-of-the-art stability levels. Here, we demonstrate clock performance beyond the SQL, achieving a fractional frequency precision of 1.1×10^{-18} for a single spin-squeezed clock. With cavity-based quantum nondemolition measurements, we prepare two spin-squeezed ensembles of ∼30 000 strontium atoms confined in a two-dimensional optical lattice. A synchronous clock comparison with an interrogation time of 61 ms achieves a metrological improvement of 2.0(2) dB beyond the SQL, after correcting for state preparation and measurement errors. These results establish the most precise entanglement-enhanced clock to date and offer a powerful platform for exploring the interplay of gravity and quantum entanglement.

arXiv:2505.04538•Physical Review Letters•Nov 7, 2025•12 citations

Zero-Dead-Time Strontium Lattice Clock with a Stability at 10 − 19 Level

Xiao-Yong Liu, Peng Liu, Jie Li +20 more

Optical atomic clocks play a crucial role in fundamental physics, relativistic geodesy, and the future redefinition of the Systeme International second. Standard operation relies on cyclic interrogation sequences, which alternate between atomic interrogation and dead time used for state preparation and readout. This approach introduces the Dick effect, where laser frequency noise aliases onto the atomic transition frequency. Although reducing laser noise improves clock stability, the Dick effect remains a key limitation. In this Letter, we demonstrate a zero-dead-time optical clock based on two interleaved ensembles of cold ^{87}Sr atoms. Our system significantly suppresses this noise and achieves a fractional frequency instability at the 10^{-19} level between 10 000 and 20 000 s over repeated measurements, with a best value of 2.9×10^{-19} at τ=20000 s. The estimated long-term stability based on the combined data of these measurements reaches 2.5×10^{-19} at 1 day. These results represent a more than ninefold improvement over a conventional single-ensemble clock, highlighting its potential for next-generation timekeeping applications.

Physical Review Letters•Nov 26, 2025•9 citations

Prospects for frequency stabilization using collective effects of strontium atoms in an optical cavity

Bjarke T. R. Christensen, Martin R. Henriksen, Philip G. Westergaard +2 more

The stability of current state-of-the-art optical atomic clocks [1]-[5] is mostly limited by the frequency noise of the interrogation oscillator through the Dick effect. To achieve the heralded ultimate stability, future optical frequency standards will need to produce light sources with frequency stability at the 10−17fractional level or below at one second of integration time. Recently, a new frontier in cavity stabilized laser sources has pushed the fractional instability to the lower 10−16level at one second of integration time [6]-[8]. However, this instability is limited by thermal noise in the reference cavity elements and may be difficult to reduce further. These state-of-the-art reference cavities are technically challenging to construct and their stability is still at least an order of magnitude too large for lattice clocks to achieve their ultimate performance.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•May 1, 2014•0 citations
SummaryThe short-term frequency instability of the best optical atomic clock lies in the mid 10−17. However, the Dick effect is still an obstacle for a single operational clock closely followed by the quantum projection noise. To improve the frequency stability of the strontium optical lattice clock, we present a quantum non-demolition detection scheme based on the cavity mediated interaction between the atoms and a probe light that has a large-frequency detuning to the atomic resonance, aiming to bring the detection scheme proposed in [1] to the quantum regime. We obtained a rather small photon scattering rate, measured to be less than 0.1 photon/μs/atom, which allows us to not only preserve the atoms in the lattice but also the atomic wave function as long as the total probe time is on the order of a few microseconds. The detection noise for the number of atoms is 48/√photons atoms, implying that the frequency stability can surpass the standard quantum limit when the number of trapped atoms is larger than 2.3×104with spin squeezing protocols.
We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the dispersive properties of lattice-trapped atoms enhanced by a high finesse cavity. By design, this scheme offers a 1st order rejection of the technical noise sources, an enhanced signal-to-noise ratio, and an homogeneous atom-cavity coupling. We theoretically show that this scheme is optimal with respect to the photon shot noise limit. We experimentally realise this detection scheme in an operational strontium optical lattice clock. The resolution is on the order of a few atoms with a photon scattering rate low enough to keep the atoms trapped after detection. This scheme opens the door to various different interrogations protocols, which reduce the frequency instability, including atom recycling, zero-dead time clocks with a fast repetition rate, and sub quantum projection noise frequency stability.
The work achieved in the frame of this PhD training consisted in the implementation of a cavity enhanced non destructive detection system of atoms trapped in an optical lattice aiming at improving the stability of an optical strontium clock.The characterization of the system in its classical regime, for which a sufficiently low number of photons are scattered per atom to avoid expelling them off the trap, highlighted significant improvements in term of signal to noise ratio, with gain factor around 100 compared with the previously used fluorescence scheme. Yet, gains in terms of stability via Dick effect reduction still have to be demonstrated.Regarding the quantum regime, for which less than one photon is scattered per atom over the detection, new ideas and significant changes have been carried out on the system and a theoretical study was has been undertaken to determine the strategy for the improvement of the clock stability by quantum projection noise reduction via quantum non demolition measurement.It was as well the opportunity to study the effect of the hot collisions between the trapped strontium atoms and the residual vacuum background gas particles, allowing for the improvement of the clock uncertainty. This work reports in particular on the first measurement of strontium clock hot collisions shifts as well as its theoretical study.
Quantum projection noise will soon limit the best achievable precision of optical atomic clocks based on lattice-confined neutral atoms. Squeezing the collective atomic pseudo-spin via measurement of the clock state populations during Ramsey interrogation suppresses the projection noise. We show here that the lattice laser field can be used to perform ideal quantum non-demolition measurements without clock shifts or decoherence and explore the feasibility of such an approach in theory with the lattice field confined in a ring-resonator. Detection of the motional sideband due to the atomic vibration in the lattice wells can yield signal sizes a hundredfold above the projection noise limit.
Optical atomic clocks with unrivaled precision and accuracy have advanced the frontier of precision measurement science and opened new avenues for exploring fundamental physics. A fundamental limitation on clock precision is the standard quantum limit (SQL), which stems from the uncorrelated projection noise of each atom. State-of-the-art optical lattice clocks interrogate large ensembles to minimize the SQL, but density-dependent frequency shifts pose challenges to scaling the atom number. The SQL can be surpassed, however, by leveraging entanglement, though it remains an open problem to achieve quantum advantage from spin squeezing at state-of-the-art stability levels. Here, we demonstrate clock performance beyond the SQL, achieving a fractional frequency precision of 1.1×10^{-18} for a single spin-squeezed clock. With cavity-based quantum nondemolition measurements, we prepare two spin-squeezed ensembles of ∼30 000 strontium atoms confined in a two-dimensional optical lattice. A synchronous clock comparison with an interrogation time of 61 ms achieves a metrological improvement of 2.0(2) dB beyond the SQL, after correcting for state preparation and measurement errors. These results establish the most precise entanglement-enhanced clock to date and offer a powerful platform for exploring the interplay of gravity and quantum entanglement.
Optical atomic clocks play a crucial role in fundamental physics, relativistic geodesy, and the future redefinition of the Systeme International second. Standard operation relies on cyclic interrogation sequences, which alternate between atomic interrogation and dead time used for state preparation and readout. This approach introduces the Dick effect, where laser frequency noise aliases onto the atomic transition frequency. Although reducing laser noise improves clock stability, the Dick effect remains a key limitation. In this Letter, we demonstrate a zero-dead-time optical clock based on two interleaved ensembles of cold ^{87}Sr atoms. Our system significantly suppresses this noise and achieves a fractional frequency instability at the 10^{-19} level between 10 000 and 20 000 s over repeated measurements, with a best value of 2.9×10^{-19} at τ=20000 s. The estimated long-term stability based on the combined data of these measurements reaches 2.5×10^{-19} at 1 day. These results represent a more than ninefold improvement over a conventional single-ensemble clock, highlighting its potential for next-generation timekeeping applications.
The stability of current state-of-the-art optical atomic clocks [1]-[5] is mostly limited by the frequency noise of the interrogation oscillator through the Dick effect. To achieve the heralded ultimate stability, future optical frequency standards will need to produce light sources with frequency stability at the 10−17fractional level or below at one second of integration time. Recently, a new frontier in cavity stabilized laser sources has pushed the fractional instability to the lower 10−16level at one second of integration time [6]-[8]. However, this instability is limited by thermal noise in the reference cavity elements and may be difficult to reduce further. These state-of-the-art reference cavities are technically challenging to construct and their stability is still at least an order of magnitude too large for lattice clocks to achieve their ultimate performance.