Guidance and control in a Josephson charge qubit

Ralph, Jason F.; Griffith, Elias J.; Clark, T. D.; Everitt, Mark J.

doi:10.1103/physrevb.70.214521

Cited by 17 publications

(16 citation statements)

References 26 publications

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“…By direct computation [29] it is possible to show that the variance of the observable σ z , V t (ρ t ) = tr(σ 2 z ρ t ) − tr 2 (σ z ρ t ) ≥ 0, represents a stochastic Lyapunov function for the system in the sense of [81], and that all the trajectories converge in probability to the equilibrium states. From a physics viewpoint, the free dynamics of a system like (38) asymptotically replicate the effect of a projective measurement, with the correct probabilities of "collapsing" on the eigenstates of σ z induced by the initial state [82], [29].…”

Section: E Quantum Stochastic Modelsmentioning

confidence: 99%

Modeling and Control of Quantum Systems: An Introduction

Altafini

Ticozzi²

2012

IEEE Trans. Automat. Contr.

246

214

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Abstract-The scope of this work is to provide a self-contained introduction to a selection of basic theoretical aspects in the modeling and control of quantum mechanical systems, as well as a brief survey on the main approaches to control synthesis. While part of the existing theory, especially in the open-loop setting, stems directly from classical control theory (most notably geometric control and optimal control), a number of tools specifically tailored for quantum systems have been developed since the 1980s, in order to take into account their distinctive features: the probabilistic nature of atomic-scale physical systems, the effect of dissipation and the irreversible character of the measurements have all proved to be critical in feedbackdesign problems. The relevant dynamical models for both closed and open quantum systems are presented, along with the main results on their controllability and stability. A brief review of several currently available control design methods is meant to provide the interested reader with a roadmap for further studies.

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Section: E Quantum Stochastic Modelsmentioning

confidence: 99%

Modeling and Control of Quantum Systems: An Introduction

Altafini

Ticozzi²

2012

IEEE Trans. Automat. Contr.

246

214

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“…Generally speaking, entanglement degradation through uncontrolled coupling with the environment remains a major obstacle in practice [5][6][7], which would limit the lifetime of entangled states and demand efficient schemes to protect them. In this context, * guolingzhen@mail.bnu.edu.cn † lixinqi@bnu.edu.cn we note that owing to the remarkable progress in theory and particularly in experiments on the real-time monitoring and manipulation of individual quantum systems [8][9][10][11], the quantum-feedback-control technique may emerge as a possible route to develop strategies to prepare entangled states and prevent their deterioration.…”

Section: Introductionmentioning

confidence: 99%

Deterministic creation and stabilization of entanglement in circuit QED by homodyne-mediated feedback control

Liu

Kuang

et al. 2010

Phys. Rev. A

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In a solid-state circuit QED system, we demonstrate that a homodyne-current-based feedback can create and stabilize highly entangled two-qubit states in the presence of a moderate noisy environment. Particularly, we present an extended analysis for the current-based Markovian feedback, which leads to an improved feedback scheme. We show that this is essential to achieve a desirable control effect by the use of dispersive measurement.

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“…For instance, it enhances the concurrence to values higher than 0.9, by noting the 0.31 obtained in Ref. [11]; and also it avoids the experimental difficulty in the jump-based feedback [12] or the complexity for a state-estimation feedback [2,13,14].…”

Section: Introductionmentioning

confidence: 85%

Generating and stabilizing the Greenberger-Horne-Zeilinger state in circuit QED: Joint measurement, Zeno effect, and feedback

et al. 2011

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In a solid-state circuit QED system, we extend the previous study of generating and stabilizing a two-qubit Bell state [Phys. Rev. A 82, 032335 (2010)] to a three-qubit GHZ state. In a dispersive regime, we employ the homodyne joint readout for multiple qubits to infer the state for further processing, and in particular we use it to stabilize the state directly by means of an alternate-flip-interrupted Zeno (AFIZ) scheme. Moreover, the stateof-the-art feedback action based on the filtered current enables not only a deterministic generation of the pre-GHZ state in the initial stage, but also a fast recovery from occasional error in the later stabilization process. We show that the proposed scheme can maintain the state with high fidelity if the efficient quantum measurement and rapid single-qubit rotations are available.

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Guidance and control in a Josephson charge qubit

Abstract: In this paper we propose a control strategy based on a classical guidance law and consider its use for an example system: a Josephson charge qubit. We demonstrate how the guidance law can be used to attain a desired qubit state using the standard qubit control fields.

Cited by 17 publications

References 26 publications

Modeling and Control of Quantum Systems: An Introduction

Modeling and Control of Quantum Systems: An Introduction

Deterministic creation and stabilization of entanglement in circuit QED by homodyne-mediated feedback control

Generating and stabilizing the Greenberger-Horne-Zeilinger state in circuit QED: Joint measurement, Zeno effect, and feedback

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