Quantum-trajectory thermodynamics with discrete feedback control

Gong, Zongping; Ashida, Yuto; Ueda, Masahito

doi:10.1103/physreva.94.012107

Cited by 46 publications

(51 citation statements)

References 110 publications

(216 reference statements)

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“…In conclusion, we have shown quantum trajectories of a superconducting qubit reconstructed from three measurements originating from the simultaneous monitoring of its decoherence channels. It looks promising to test statistical properties of quantum trajectories [27,28], fluctuation relations in quantum thermodynamics [29][30][31][32][33][34][35], quantum smoothing protocols [20,[36][37][38][39][40][41], and to perform parameter estimation [42,43]. perimental setup; All authors wrote the paper.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

et al. 2018

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Decoherence originates from the leakage of quantum information into external degrees of freedom. For a qubit, the two main decoherence channels are relaxation and dephasing. Here, we report an experiment on a superconducting qubit where we retrieve part of the lost information in both of these channels. We demonstrate that raw averaging the corresponding measurement records provides a full quantum tomography of the qubit state where all three components of the effective spin-1/2 are simultaneously measured. From single realizations of the experiment, it is possible to infer the quantum trajectories followed by the qubit state conditioned on relaxation and/or dephasing channels. The incompatibility between these quantum measurements of the qubit leads to observable consequences in the statistics of quantum states. The high level of controllability of superconducting circuits enables us to explore many regimes from the Zeno effect to underdamped Rabi oscillations depending on the relative strengths of driving, dephasing, and relaxation.

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Section: Resultsmentioning

confidence: 99%

Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

et al. 2018

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“…We note that the quantitative difference between the relevant information and the QC-mutual information is discussed in Ref. [71].…”

Section: Detailed Fluctuation Theoremmentioning

confidence: 96%

“…We introduce the protocol of discrete feedback control as schematically illustrated in Fig. 1 [38,71], which is a quantum analog of the protocol of the classical discrete feedback control in Ref. [40].…”

Section: A Protocol Of Feedback Controlmentioning

confidence: 99%

Fluctuation theorems in feedback-controlled open quantum systems: Quantum coherence and absolute irreversibility

et al. 2017

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Thermodynamics of quantum coherence has attracted growing attention recently, where the thermodynamic advantage of quantum superposition is characterized in terms of quantum thermodynamics. We investigate thermodynamic effects of quantum coherent driving in the context of the fluctuation theorem. We adopt a quantum-trajectory approach to investigate open quantum systems under feedback control. In these systems, the measurement backaction in the forward process plays a key role, and therefore the corresponding time-reversed quantum measurement and post-selection must be considered in the backward process in sharp contrast to the classical case. The state reduction associated with quantum measurement, in general, creates a zero-probability region in the space of quantum trajectories of the forward process, which causes singularly strong irreversibility with divergent entropy production (i.e., absolute irreversibility) and hence makes the ordinary fluctuation theorem break down. In the classical case, the error-free measurement ordinarily leads to absolute irreversibility because the measurement restricts classical paths to the region compatible with the measurement outcome. In contrast, in open quantum systems, absolute irreversibility is suppressed even in the presence of the projective measurement due to those quantum rare events that go through the classically forbidden region with the aid of quantum coherent driving. This suppression of absolute irreversibility exemplifies the thermodynamic advantage of quantum coherent driving. Absolute irreversibility is shown to emerge in the absence of coherent driving after the measurement, especially in systems under time-delayed feedback control. We show that absolute irreversibility is mitigated by increasing the duration of quantum coherent driving or decreasing the delay time of feedback control. arXiv:1705.06513v3 [cond-mat.stat-mech]

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“…The monitored system also displays a clear connection between synchronization entailed by phase-locking and entanglement in quantum trajectories. It would be also interesting to explore connections and possible applications to quantum control [58][59][60], quantum information processing [61][62][63] or quantum thermodynamics along trajectories [64][65][66][67]. Finally, we remark possible extensions of this work considering different measurements for quantum trajectories, reactive instead of dissipative couplings as well as other systems amenable to experimental realizations, as optomechanical systems, atomic ones or superconducting qubits.…”

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confidence: 91%

Synchronization along quantum trajectories

Es'haqi-Sani

Manzano

Zambrini

et al. 2020

Phys. Rev. Research

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We employ a quantum trajectory approach to characterize synchronization and phase-locking between open quantum systems in nonequilibrium steady states. We exemplify our proposal for the paradigmatic case of two quantum Van der Pol oscillators interacting through dissipative coupling. We show the deep impact of synchronization on the statistics of phase-locking indicators and other correlation measures defined for single trajectories. Our results shed new light on fundamental issues regarding quantum synchronization providing new methods for its precise quantification. PACS numbers: 05.30.-d 03.67.-a 42.50.DvSynchronization is one of the most universal manifestations of emergent cooperative behavior, observed in a broad range of physical, chemical and biological systems [1,2]. It can be defined as the progressive adjustment of rhythms between oscillatory units due to their weak interaction and despite their different natural frequencies. Appealing examples with interesting applications comprise synchronization between hearth cardiac pacemaker cells [2], chaotic laser signals [3] or micromechanical oscillators [4][5][6].In the last decade, the interest on this paradigmatic phenomenon has been extended to the quantum realm, see e.g. [14][15][16][17][18][19][20][21][22][23]. Quantum mechanics plays a crucial role when exploring this phenomenon beyond the classical regime [24] and in relation to the degree of synchronization that systems can reach [11]. Quantum synchronization can be characterized with different outcomes [25] using local or global indicators in the system observables [24]. It has been shown that the emergence of this phenomenon is often connected to the generation of quantum correlations such as discord [9,10,[26][27][28] or entanglement [7,10,29,[31][32][33]. However, a universal relation between quantum correlations and synchronization is not expected in general, and thus whether quantum synchronization may be used for witnessing quantum correlations is still an open question. In addition, quantum synchronization may also find applications for probing spectral densities in natural or engineered environments [34,35].In classical systems, spontaneous synchronization is usually characterized through the trajectories in phasespace [2]. In contrast, measuring synchronization in open quantum systems becomes more challenging and different avenues have been explored. For instance, temporal correlations in local observables can be quantified by using the Pearson correlation coefficient [9] or global quantum correlations can be addressed through the synchronization error [11]. Quantitative measures of phase-locking based on the expectation values of different non-local correlators [11,16,18,36] have been proposed, but they are often not indicative of the underlying processes [37]. Finally, information measures of correlations like the mutual information [38] or have also been also employed. In all these approaches, synchronization is computed through the expectation values of different (local or global) obse...

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Quantum-trajectory thermodynamics with discrete feedback control

Cited by 46 publications

References 110 publications

Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Fluctuation theorems in feedback-controlled open quantum systems: Quantum coherence and absolute irreversibility

Synchronization along quantum trajectories

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