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:quant-ph/0004025 · Conference on the Foundations of Quantum Mechanics: Historical Analysis and Open Questions

QUANTUM FEEDBACK FOR PROTECTION OF SCHRÖDINGER CAT STATES

Mauro Fortunato, P. Tombesi, David Vitali, J. M. Raimond

Published May 1, 2000• 0 citations
arXivHTMLPDF

Abstract

We review the use of quantum feedback for combatting the decoherence of Schroedinger-cat-like states in electromagnetic cavities, with special emphasys on our recent proposal of an automatic mechanism based on the injection of appropriately prepared ``probe'' and ``feedback'' Rydberg atoms. In the latter scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the linear superposition state can be significantly increased using presently available technology.

DOI
10.1142/9789812793560_0014

Related papers

Autofeedback Scheme for Schrödinger Cat Preservation in Microwave Cavities

Mauro Fortunato, P. Tombesi, David Vitali +1 more

We propose a feedback scheme for limiting in a significant way the decoherence of a linear superposition of two coherent states with opposite phases in a high-Q microwave cavity. It is based on the injection of appropriately prepared “probe” and “feedback” Rydberg atoms, and greatly improves the model presented in [D. Vitali et al., Phys. Rev. Lett. 79, 2442 (1997)]. In the present scheme, the information transmission between the probe and the feedback atom is directly mediated by a second auxiliary cavity, making the detection efficiency for the probe atom no longer a critical parameter. The decoherence time of the superposition state can be significantly increased using presently available technology.

Fortschritte der Physik•May 1, 2000•2 citations

Autofeedback scheme for preservation of macroscopic coherence in microwave cavities

Mauro Fortunato, J. M. Raimond, P. Tombesi +1 more

We present a scheme for controlling the decoherence of a linear superposition of two coherent states with opposite phases in a high-$Q$ microwave cavity, based on the injection of appropriately prepared ``probe'' and ``feedback'' Rydberg atoms, improving the one presented by D. Vitali et al. [Phys. Rev. Lett. $79$, 2442 (1997)]. In the present scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the superposition state can be significantly increased using presently available technology.

arXiv:quant-ph/9902071•Physical Review A•Aug 1, 1999•29 citations

Quantum-state protection in cavities

David Vitali, P. Tombesi, Gerard J Milburn

We show how an initially prepared quantum state of a radiation mode in a cavity can be preserved for a long time using a feedback scheme based on the injection of appropriately prepared atoms. We present a feedback scheme both for optical cavities, which can be continuously monitored by a photodetector, and for microwave cavities, which can be monitored only indirectly via the detection of atoms that have interacted with the cavity field. We also discuss the possibility of applying these methods for decoherence control in quantum information processing.

arXiv:quant-ph/9803045•Physical Review A•Jun 1, 1998•69 citations

Decoherence control in optical cavities

David Vitali, P. Tombesi, Gerard J Milburn

Summary form only given.Decoherence, i.e., the rapid destruction of the phase relation between two quantum states of a system caused by the entanglement of these two states with two different states of the environment, is the main limiting factor for quantum information processing. For this reason, decoherence control is now becoming a rapidly expanding field of investigation. Decoherence control would be particularly useful in high-Q electromagnetic cavities. In fact, one of the few experimental realizations of a quantum gate is the Caltech's quantum phase gate, demonstrating conditional quantum dynamics between polarized modes in a high-finesse optical cavity. Moreover, the progressive decoherence of a mesoscopic Schrodinger cat state has been observed for the first time in the experiment of Brune et al. (1996) where the linear superposition of two coherent states of a field in a microwave cavity, with classically distinct phases, has been generated and detected. Here we propose a photodetection-mediated feedback scheme based on a very simple idea: whenever a photon leaks out from the cavity and is detected by a photodetector, a feedback loop supplies the cavity mode with another photon, using a single ion trapped in the cavity and appropriately shaped laser pulses.

Conference on Lasers and Electro-Optics•Nov 27, 2002•1 citation

Quantum feedback experiments stabilizing Fock states of light in a cavity

Bruno Peaudecerf, C. Sayrin, X. Zhou +6 more

The ubiquitous decoherence phenomenon is responsible for the lack of quantum superpositions at the macroscopic scale. It is increasingly difficult to isolate a quantum system from its environment when its size increases. Making use of the weird quantum properties of mesoscopic quantum states thus requires efficient means to combat decoherence. One option is real-time quantum feedback. It features the components of a conventional feedback: measurement of the system's state (sensor), analysis (controller), and feedback action (actuator) aiming to the target state. The random back-action of the measurements by the sensor makes quantum feedback much more difficult than its classical counterpart. Mesoscopic photon number (Fock) states feature a decoherence rate proportional to the photon number. They are thus a simple example of a fragile quantum resource. We demonstrated recently two quantum feedback schemes continuously stabilizing Fock state of a microwave field in a high-quality cavity. Sensitive atoms, crossing the field one at a time, are used as quantum nondemolition (QND) probes of its photon number. The feedback actuator is either a classical source [Sayrin et al., Nature (London) 477, 73 (2011)] or individual resonant atoms emitting or absorbing one photon each [Zhou et al., Phys. Rev. Lett. 108, 243602 (2012)]. Both schemes detect the quantum jumps of the photon number and efficiently correct their adverse effects, preparing and preserving a fragile quantum resource. We present an in-depth analysis of our methods, which sheds light onto the fundamental difficulties encountered in quantum feedback, in particular concerning the state estimation algorithm, and onto the ways to circumvent them. These results open the way to informationally optimal QND measurements or to the stabilization of mesoscopic field state superpositions. More generally, they can be cast in a variety of contexts to loosen the tight constraints set by decoherence in quantum metrology and quantum information processing.

Physical Review A•Apr 18, 2013•31 citations

Protecting schrödinger cat states using feedback

David Vitali, P. Tombesi, Gerard J Milburn

A feedback model based on direct photodetection and micromaser-like atomic injection is proposed for the preservation of quantum coherence in a cavity. We show that in this way it is possible to slow down significantly the decoherence of Schrödinger cat states.

Journal of Modern Optics•Nov 1, 1997•6 citations
We review the use of quantum feedback for combatting the decoherence of Schroedinger-cat-like states in electromagnetic cavities, with special emphasys on our recent proposal of an automatic mechanism based on the injection of appropriately prepared probe'' and feedback'' Rydberg atoms. In the latter scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the linear superposition state can be significantly increased using presently available technology.
We propose a feedback scheme for limiting in a significant way the decoherence of a linear superposition of two coherent states with opposite phases in a high-Q microwave cavity. It is based on the injection of appropriately prepared “probe” and “feedback” Rydberg atoms, and greatly improves the model presented in [D. Vitali et al., Phys. Rev. Lett. 79, 2442 (1997)]. In the present scheme, the information transmission between the probe and the feedback atom is directly mediated by a second auxiliary cavity, making the detection efficiency for the probe atom no longer a critical parameter. The decoherence time of the superposition state can be significantly increased using presently available technology.
We present a scheme for controlling the decoherence of a linear superposition of two coherent states with opposite phases in a high-QQQ microwave cavity, based on the injection of appropriately prepared ``probe'' and ``feedback'' Rydberg atoms, improving the one presented by D. Vitali et al. [Phys. Rev. Lett. 797979, 2442 (1997)]. In the present scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the superposition state can be significantly increased using presently available technology.
We show how an initially prepared quantum state of a radiation mode in a cavity can be preserved for a long time using a feedback scheme based on the injection of appropriately prepared atoms. We present a feedback scheme both for optical cavities, which can be continuously monitored by a photodetector, and for microwave cavities, which can be monitored only indirectly via the detection of atoms that have interacted with the cavity field. We also discuss the possibility of applying these methods for decoherence control in quantum information processing.
Summary form only given.Decoherence, i.e., the rapid destruction of the phase relation between two quantum states of a system caused by the entanglement of these two states with two different states of the environment, is the main limiting factor for quantum information processing. For this reason, decoherence control is now becoming a rapidly expanding field of investigation. Decoherence control would be particularly useful in high-Q electromagnetic cavities. In fact, one of the few experimental realizations of a quantum gate is the Caltech's quantum phase gate, demonstrating conditional quantum dynamics between polarized modes in a high-finesse optical cavity. Moreover, the progressive decoherence of a mesoscopic Schrodinger cat state has been observed for the first time in the experiment of Brune et al. (1996) where the linear superposition of two coherent states of a field in a microwave cavity, with classically distinct phases, has been generated and detected. Here we propose a photodetection-mediated feedback scheme based on a very simple idea: whenever a photon leaks out from the cavity and is detected by a photodetector, a feedback loop supplies the cavity mode with another photon, using a single ion trapped in the cavity and appropriately shaped laser pulses.
The ubiquitous decoherence phenomenon is responsible for the lack of quantum superpositions at the macroscopic scale. It is increasingly difficult to isolate a quantum system from its environment when its size increases. Making use of the weird quantum properties of mesoscopic quantum states thus requires efficient means to combat decoherence. One option is real-time quantum feedback. It features the components of a conventional feedback: measurement of the system's state (sensor), analysis (controller), and feedback action (actuator) aiming to the target state. The random back-action of the measurements by the sensor makes quantum feedback much more difficult than its classical counterpart. Mesoscopic photon number (Fock) states feature a decoherence rate proportional to the photon number. They are thus a simple example of a fragile quantum resource. We demonstrated recently two quantum feedback schemes continuously stabilizing Fock state of a microwave field in a high-quality cavity. Sensitive atoms, crossing the field one at a time, are used as quantum nondemolition (QND) probes of its photon number. The feedback actuator is either a classical source [Sayrin et al., Nature (London) 477, 73 (2011)] or individual resonant atoms emitting or absorbing one photon each [Zhou et al., Phys. Rev. Lett. 108, 243602 (2012)]. Both schemes detect the quantum jumps of the photon number and efficiently correct their adverse effects, preparing and preserving a fragile quantum resource. We present an in-depth analysis of our methods, which sheds light onto the fundamental difficulties encountered in quantum feedback, in particular concerning the state estimation algorithm, and onto the ways to circumvent them. These results open the way to informationally optimal QND measurements or to the stabilization of mesoscopic field state superpositions. More generally, they can be cast in a variety of contexts to loosen the tight constraints set by decoherence in quantum metrology and quantum information processing.