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

Weak measurement based feedback control of atomic ensembles (Orale)

Andréa D Bertoldi, Ralf Kohlhaas, Etienne Cantin, Arnaud Landragin, Philippe Bouyer

Published Sep 23, 2013• 0 citations
OpenAlex

Abstract

Atom interferometry based sensors provide today the most precise measurements of time, inertial forces and magnetic fields. In the common approach, a superposition state is interrogated for a given time interval and finally destructively measured. Conversely, we can repeatedly probe non-destructively the same quantum system and demonstrate efficient measurement schemes using feedback. First, we protect a spin polarized atomic ensemble from the decoherence induced by a synthetic noise. After the noise action, the state of the atomic system is read out with negligible projection using a non-destructive probe, and later corrected with a coherent manipulation to restore the initial state. The efficiency of the feedback scheme is studied versus the strength of the measurement and a maximum is found from the trade-off between information gain and probe destructivity. Our feedback controller is then applied to stabilize a classical local oscillator on a collective quantum state, and this is used in an atomic clock configuration to demonstrate experimentally that in some contexts a hybrid phase and frequency lock can surpass conventional atomic clocks which rely only on a frequency lock.

Related papers

Feedback Control of Atomic Coherent Spin States

Etienne Cantin, Ralf Kohlhaas, Andréa D Bertoldi +4 more

We demonstrate the feedback control of the internal states of atomic ensembles and their protection against collective noise. Weak measurements with negligible back-action and coherent microwave manipulations are used in a feedback controller to protect a superposition state. The efficiency of the feedback is studied for a simple binary noise model and characterized in terms of the trade-off between information retrieval and destructivity from the optical probe. More complex feedback scenarios are implemented which provide a way towards novel atom interferometry schemes using repeated measurements and feedback.

•Jul 23, 2012•0 citations

Protecting atomic coherent spin states with weak measurements and feedback

Thomas Vanderbruggen, Ralf Kohlhaas, Andréa D Bertoldi +4 more

Weak measurements provide new ways to observe and control quantum systems. Here we use weak non-destructive measurements in a feedback scheme to protect an atomic ensemble in a coherent superposition against a simple decoherence model. The feedback efficiency, defined as the ability to recover the coherence of the initial state, is studied versus the number of photons in the probe beam. This allows us to precisely characterize the trade-off between information retrieval and destructivity. The lifetime of the coherent spin state is increased by one order of magnitude when the correction cycle is iterated.

•Jul 13, 2012•0 citations

Feedback Control of Trapped Coherent Atomic Ensembles

Thomas Vanderbruggen, Ralf Kohlhaas, Andréa D Bertoldi +4 more

We demonstrate how to use feedback to control the internal states of trapped coherent ensembles of two-level atoms, and to protect a superposition state against the decoherence induced by a collective noise. Our feedback scheme is based on weak optical measurements with negligible backaction followed by coherent microwave manipulations. The efficiency of the feedback system is studied for a simple binary noise model and characterized in terms of the trade-off between information retrieval and destructivity from the optical probe. We also demonstrate the correction of more general types of collective noise. This technique can be used for the operation of atomic interferometers beyond the standard Ramsey scheme, opening the way towards improved atomic sensors.

arXiv:1207.3203•Physical Review Letters•May 23, 2013•35 citations

Phase locking an atom interferometer

Andréa D Bertoldi, Ralf Kohlhaas, Etienne Cantin +3 more

In atom interferometry the phase evolution of a quantum superposition state is measured with respect to a reference signal. The measurement has a limited unambiguous interval, since not the phase but its projection is measured as a population unbalance on two energetic levels. Resolving phase wrapping brings to a longer interrogation interval and hence instrument sensitivity. We extended the unambiguous probe interval using coherence preserving measurements and phase corrections, and demonstrated the phase lock of the clock oscillator to an atomic superposition state. On this basis we implemented a protocol to improve atomic clocks limited by local oscillator noise, which is the case of optical atomic clocks, nowadays the best frequency standard in terms of both accuracy and precision. The technique could be adopted to enhance the sensitivity of atomic gravimeters.

European Frequency and Time Forum•Apr 1, 2016•0 citations

Feedback control of coherent spin states using weak nondestructive measurements

Thomas Vanderbruggen, Ralf Kohlhaas, Andréa D Bertoldi +3 more

We consider the decoherence of a pseudospin ensemble under collective random rotations and study, both theoretically and experimentally, how a nondestructive measurement combined with real-time feedback correction can protect the state against such a decoherence process. We theoretically characterize the feedback efficiency with different parameters---coherence, entropy, fidelity---and show that a maximum efficiency is reached in the weak measurement regime, when the projection of the state induced by the measurement is negligible. This article presents in detail the experimental results published previously [T. Vanderbruggen et al., Phys. Rev. Lett. 110, 210503 (2013)], where the feedback scheme stabilizes coherent spin states of trapped ultracold atoms and nondestructively probes them with dispersive optical detection. In addition, we study the influence of several parameters, such as atom number and rotation angle, on the performance of the method. We analyze the various decoherence sources limiting the feedback efficiency and propose a way to mitigate their effect. The results demonstrate the potential of the method for the real-time coherent control of atom interferometers.

arXiv:1405.4749•Physical Review A•Jun 25, 2014•4 citations

Phase Locking a Clock Oscillator to a Coherent Atomic Ensemble

Ralf Kohlhaas, Andréa D Bertoldi, Etienne Cantin +3 more

Time measurements and navigation rely on atomic interferometers and atomic clocks. A new technique can improve the stability of such clocks by coupling a classical oscillator to an ensemble of atoms in a superposition state using repeated, coherence-preserving measurements.

arXiv:1501.03709•Physical Review X•Apr 27, 2015•57 citations
Atom interferometry based sensors provide today the most precise measurements of time, inertial forces and magnetic fields. In the common approach, a superposition state is interrogated for a given time interval and finally destructively measured. Conversely, we can repeatedly probe non-destructively the same quantum system and demonstrate efficient measurement schemes using feedback. First, we protect a spin polarized atomic ensemble from the decoherence induced by a synthetic noise. After the noise action, the state of the atomic system is read out with negligible projection using a non-destructive probe, and later corrected with a coherent manipulation to restore the initial state. The efficiency of the feedback scheme is studied versus the strength of the measurement and a maximum is found from the trade-off between information gain and probe destructivity. Our feedback controller is then applied to stabilize a classical local oscillator on a collective quantum state, and this is used in an atomic clock configuration to demonstrate experimentally that in some contexts a hybrid phase and frequency lock can surpass conventional atomic clocks which rely only on a frequency lock.
We demonstrate the feedback control of the internal states of atomic ensembles and their protection against collective noise. Weak measurements with negligible back-action and coherent microwave manipulations are used in a feedback controller to protect a superposition state. The efficiency of the feedback is studied for a simple binary noise model and characterized in terms of the trade-off between information retrieval and destructivity from the optical probe. More complex feedback scenarios are implemented which provide a way towards novel atom interferometry schemes using repeated measurements and feedback.
Weak measurements provide new ways to observe and control quantum systems. Here we use weak non-destructive measurements in a feedback scheme to protect an atomic ensemble in a coherent superposition against a simple decoherence model. The feedback efficiency, defined as the ability to recover the coherence of the initial state, is studied versus the number of photons in the probe beam. This allows us to precisely characterize the trade-off between information retrieval and destructivity. The lifetime of the coherent spin state is increased by one order of magnitude when the correction cycle is iterated.
We demonstrate how to use feedback to control the internal states of trapped coherent ensembles of two-level atoms, and to protect a superposition state against the decoherence induced by a collective noise. Our feedback scheme is based on weak optical measurements with negligible backaction followed by coherent microwave manipulations. The efficiency of the feedback system is studied for a simple binary noise model and characterized in terms of the trade-off between information retrieval and destructivity from the optical probe. We also demonstrate the correction of more general types of collective noise. This technique can be used for the operation of atomic interferometers beyond the standard Ramsey scheme, opening the way towards improved atomic sensors.
In atom interferometry the phase evolution of a quantum superposition state is measured with respect to a reference signal. The measurement has a limited unambiguous interval, since not the phase but its projection is measured as a population unbalance on two energetic levels. Resolving phase wrapping brings to a longer interrogation interval and hence instrument sensitivity. We extended the unambiguous probe interval using coherence preserving measurements and phase corrections, and demonstrated the phase lock of the clock oscillator to an atomic superposition state. On this basis we implemented a protocol to improve atomic clocks limited by local oscillator noise, which is the case of optical atomic clocks, nowadays the best frequency standard in terms of both accuracy and precision. The technique could be adopted to enhance the sensitivity of atomic gravimeters.
We consider the decoherence of a pseudospin ensemble under collective random rotations and study, both theoretically and experimentally, how a nondestructive measurement combined with real-time feedback correction can protect the state against such a decoherence process. We theoretically characterize the feedback efficiency with different parameters---coherence, entropy, fidelity---and show that a maximum efficiency is reached in the weak measurement regime, when the projection of the state induced by the measurement is negligible. This article presents in detail the experimental results published previously [T. Vanderbruggen et al., Phys. Rev. Lett. 110, 210503 (2013)], where the feedback scheme stabilizes coherent spin states of trapped ultracold atoms and nondestructively probes them with dispersive optical detection. In addition, we study the influence of several parameters, such as atom number and rotation angle, on the performance of the method. We analyze the various decoherence sources limiting the feedback efficiency and propose a way to mitigate their effect. The results demonstrate the potential of the method for the real-time coherent control of atom interferometers.