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:0806.1392 · SIAM Journal on Control and Optimization

Real-Time Synchronization Feedbacks for Single-Atom Frequency Standards

Mazyar Mirrahimi, Pierre Rouchon

Published Jan 1, 2009• 7 citations
arXivHTMLPDF

Abstract

Simple feedback loops, inspired from extremum seeking, are proposed to lock a probe frequency to the transition frequency of a single quantum system following quantum Monte-Carlo trajectories. Two specific quantum systems are addressed: a 2-level one, and a 3-level one that appears in coherence population trapping and optical pumping. For both systems, the feedback algorithm is shown to be convergent in the following sense: the probe frequency converges on average towards the system-transition one and its standard deviation can be made arbitrarily small. Closed-loop simulations illustrate robustness versus jump-detection efficiency and modeling errors.

DOI
10.1137/080726355

Related papers

Real-time synchronization feedbacks for single-atom frequency standards: V - and Λ-structure systems

Mazyar Mirrahimi, Alain Sarlette, Pierre Rouchon

This paper proposes simple feedback loops, inspired from extremum-seeking, that use the photon emission times of a single quantum system following quantum Monte-Carlo trajectories in order to lock in real time a probe frequency to the system's transition frequency. Two specific settings are addressed: a 3-level system coupling one ground to two excited states (one highly unstable and one metastable) and a 3-level system coupling one excited to two ground states (both metastable). Analytical proofs and simulations show the accurate and robust convergence of probe frequency to system-transition frequency in the two cases.

IEEE Conference on Decision and Control (CDC)•Dec 1, 2010•1 citation

Deterministic Equations for Feedback Control of Open Quantum Systems

Alberto J. B. Rosal, Patrick P. Potts, Gabriel Teixeira Landi

Feedback control in open quantum dynamics is crucial for the advancement of various coherent platforms. However, currently only a handful of feedback master equations exist in the literature, which are restricted to specific types of feedback. In this letter we first introduce a unifying framework, based on a single general equation, that describes all possible feedback schemes in sequentially (and continuously) measured systems, and from which all previous results follow. Next, we specialize it to the case of quantum jumps and introduce a new type of feedback based on the channel of the last detected jump, as well as the time elapsed since it occurred. Our description is experimentally grounded, and naturally allows for the introduction of realistic effects, such as time-delays in the feedback loop. We illustrate our results with two time-dependent feedback protocols conditioned on quantum-jump detections: one achieving population inversion of a two-level system against a thermal bath, and another enabling real-time reversal of quantum transitions, both admitting steady-state solutions.

arXiv:2507.01934•Physical Review Letters•Jun 25, 2026•3 citations

Strategies for Real-Time Position Control of a Single Atom in Cavity QED

T. W. Lynn, Kevin M. Birnbaum, Harry J. Kimble

Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favorably to open-loop "switching" analogs, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics.

•Jul 7, 2005•8 citations

Strategies for real-time position control of a single atom in cavity QED

T W Lynn, K Birnbaum, H J Kimble

Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favorably to open-loop "switching" analogs, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics.

arXiv:quant-ph/0507064•Journal of Optics B Quantum and Semiclassical Optics•Sep 14, 2005•8 citations

Rapid and robust control of single quantum dots

Nicolò Accanto, Pablo M. de Roque, Marcial Galvan-Sosa +3 more

The combination of single particle detection and ultrafast laser pulses is an instrumental method to track dynamics at the femtosecond time scale in single molecules, quantum dots and plasmonic nanoparticles. Optimal control of the extremely short-lived coherences of these individual systems has so far remained elusive, yet its successful implementation would enable arbitrary external manipulation of otherwise inaccessible nanoscale dynamics. In ensemble measurements, such control is often achieved by resorting to a closed-loop optimization strategy, where the spectral phase of a broadband laser field is iteratively optimized. This scheme needs long measurement times and strong signals to converge to the optimal solution. This requirement is in conflict with the nature of single emitters whose signals are weak and unstable. Here we demonstrate an effective closed-loop optimization strategy capable of addressing single quantum dots at room temperature, using as feedback observable the two-photon photoluminescence induced by a phase-controlled broadband femtosecond laser. Crucial to the optimization loop is the use of a deterministic and robust-against-noise search algorithm converging to the theoretically predicted solution in a reduced amount of steps, even when operating at the few-photon level. Full optimization of the single dot luminescence is obtained within ~100 trials, with a typical integration time of 100 ms per trial. These times are faster than the typical photobleaching times in single molecules at room temperature. Our results show the suitability of the novel approach to perform closed-loop optimizations on single molecules, thus extending the available experimental toolbox to the active control of nanoscale coherences. Femtosecond laser control allows to harness short-lived coherences and study molecular ultrafast dynamics. Translating such coherent-control schemes from the ensemble to single molecules is challenging due to signal fluctuation and photo-dissociation. Now, Nicolò Accanto and Pablo de Roque from ICFO - the Institute of Photonic Sciences in Barcelona, and colleagues, have reduced the time needed to perform closed-loop optimisations. By employing a new simple deterministic algorithm, and assuming simple optimisation landscapes, they accomplished a phase-only optimisation of the two-photon photoluminescence of a single quantum dot. Combining this rapid feedback process within the search algorithm with a sensitive microscopy technique, they were able to optimise on signals even at the few-photon level, enabling the coherent control of individual quantum-dots at room temperature in a matter of seconds - a speedup critical for capturing details of biomolecular interactions, for instance.

Light Science & Applications•Sep 28, 2016•23 citations

Laser frequency locking method for Rydberg atomic sensing

Kai Yang, Ruiqi Mao, Qiang An +2 more

Based on the Rydberg cascade electromagnetically induced transparency, we propose a simultaneous dual-wavelength locking method for Rydberg atomic sensing at room temperature.The simplified frequency-locking configuration uses only one signal generator and one electro-optic modulator, realizing real-time feedback for both lasers.We studied the effect of the different probe and coupling laser powers on the error signal.In addition, the Allan variance and a 10 kHz amplitudemodulated signal are introduced to evaluate the performance of the laser frequency stabilization.In principle, the laser frequency stabilization method presented here can be extended to any cascade Rydberg atomic system.

Chinese Optics Letters•Nov 16, 2022•22 citations
Simple feedback loops, inspired from extremum seeking, are proposed to lock a probe frequency to the transition frequency of a single quantum system following quantum Monte-Carlo trajectories. Two specific quantum systems are addressed: a 2-level one, and a 3-level one that appears in coherence population trapping and optical pumping. For both systems, the feedback algorithm is shown to be convergent in the following sense: the probe frequency converges on average towards the system-transition one and its standard deviation can be made arbitrarily small. Closed-loop simulations illustrate robustness versus jump-detection efficiency and modeling errors.
This paper proposes simple feedback loops, inspired from extremum-seeking, that use the photon emission times of a single quantum system following quantum Monte-Carlo trajectories in order to lock in real time a probe frequency to the system's transition frequency. Two specific settings are addressed: a 3-level system coupling one ground to two excited states (one highly unstable and one metastable) and a 3-level system coupling one excited to two ground states (both metastable). Analytical proofs and simulations show the accurate and robust convergence of probe frequency to system-transition frequency in the two cases.
Feedback control in open quantum dynamics is crucial for the advancement of various coherent platforms. However, currently only a handful of feedback master equations exist in the literature, which are restricted to specific types of feedback. In this letter we first introduce a unifying framework, based on a single general equation, that describes all possible feedback schemes in sequentially (and continuously) measured systems, and from which all previous results follow. Next, we specialize it to the case of quantum jumps and introduce a new type of feedback based on the channel of the last detected jump, as well as the time elapsed since it occurred. Our description is experimentally grounded, and naturally allows for the introduction of realistic effects, such as time-delays in the feedback loop. We illustrate our results with two time-dependent feedback protocols conditioned on quantum-jump detections: one achieving population inversion of a two-level system against a thermal bath, and another enabling real-time reversal of quantum transitions, both admitting steady-state solutions.
Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favorably to open-loop "switching" analogs, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics.
Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favorably to open-loop "switching" analogs, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics.
The combination of single particle detection and ultrafast laser pulses is an instrumental method to track dynamics at the femtosecond time scale in single molecules, quantum dots and plasmonic nanoparticles. Optimal control of the extremely short-lived coherences of these individual systems has so far remained elusive, yet its successful implementation would enable arbitrary external manipulation of otherwise inaccessible nanoscale dynamics. In ensemble measurements, such control is often achieved by resorting to a closed-loop optimization strategy, where the spectral phase of a broadband laser field is iteratively optimized. This scheme needs long measurement times and strong signals to converge to the optimal solution. This requirement is in conflict with the nature of single emitters whose signals are weak and unstable. Here we demonstrate an effective closed-loop optimization strategy capable of addressing single quantum dots at room temperature, using as feedback observable the two-photon photoluminescence induced by a phase-controlled broadband femtosecond laser. Crucial to the optimization loop is the use of a deterministic and robust-against-noise search algorithm converging to the theoretically predicted solution in a reduced amount of steps, even when operating at the few-photon level. Full optimization of the single dot luminescence is obtained within ~100 trials, with a typical integration time of 100 ms per trial. These times are faster than the typical photobleaching times in single molecules at room temperature. Our results show the suitability of the novel approach to perform closed-loop optimizations on single molecules, thus extending the available experimental toolbox to the active control of nanoscale coherences. Femtosecond laser control allows to harness short-lived coherences and study molecular ultrafast dynamics. Translating such coherent-control schemes from the ensemble to single molecules is challenging due to signal fluctuation and photo-dissociation. Now, Nicolò Accanto and Pablo de Roque from ICFO - the Institute of Photonic Sciences in Barcelona, and colleagues, have reduced the time needed to perform closed-loop optimisations. By employing a new simple deterministic algorithm, and assuming simple optimisation landscapes, they accomplished a phase-only optimisation of the two-photon photoluminescence of a single quantum dot. Combining this rapid feedback process within the search algorithm with a sensitive microscopy technique, they were able to optimise on signals even at the few-photon level, enabling the coherent control of individual quantum-dots at room temperature in a matter of seconds - a speedup critical for capturing details of biomolecular interactions, for instance.
Based on the Rydberg cascade electromagnetically induced transparency, we propose a simultaneous dual-wavelength locking method for Rydberg atomic sensing at room temperature.The simplified frequency-locking configuration uses only one signal generator and one electro-optic modulator, realizing real-time feedback for both lasers.We studied the effect of the different probe and coupling laser powers on the error signal.In addition, the Allan variance and a 10 kHz amplitudemodulated signal are introduced to evaluate the performance of the laser frequency stabilization.In principle, the laser frequency stabilization method presented here can be extended to any cascade Rydberg atomic system.