Experimental bath engineering for quantitative studies of quantum control

Soare, Alexander; Ball, Harrison; Hayes, David; Zhen, Xing-Long; Jarratt, Marie Claire; Sastrawan, Jarrah; Uys, Hermann

doi:10.1103/physreva.89.042329

Cited by 37 publications

(48 citation statements)

References 52 publications

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“…More precisely if our experimenter makes measurements in the instantaneous eigenbasis ofˆ( ) H t at times dictated by a Poisson process with rate γ, then the density operator resulting from averaging over all measurement realizations obeys equation (4), with g g = ij . Yet another interpretation of the dephasing master equation arises when (b) one averages over noise that is introduced by adding an appropriately designed, randomly fluctuating term to the bare system Hamiltonianˆ( ) H t [48,49]. The validity of equation (1) in case (a) has been noted explicitly by Campisi et al [55,56], and in case (b) by Campisi, Pekola and Fazio [57].…”

Section: Multiple Interpretationsmentioning

confidence: 99%

Verification of the quantum nonequilibrium work relation in the presence of decoherence

Smith

et al. 2018

New J. Phys.

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Although nonequilibrium work and fluctuation relations have been studied in detail within classical statistical physics, extending these results to open quantum systems has proven to be conceptually difficult. For systems that undergo decoherence but not dissipation, we argue that it is natural to define quantum work exactly as for isolated quantum systems, using the two-point measurement protocol. Complementing previous theoretical analysis using quantum channels, we show that the nonequilibrium work relation remains valid in this situation, and we test this assertion experimentally using a system engineered from a trapped ion, adding external noise to produce the effects of decoherence. Our experimental results reveal the work relationʼs validity over a variety of driving speeds, decoherence rates, and effective temperatures and represent the first confirmation of the work relation for evolution described by a non-unitary master equation.

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Section: Multiple Interpretationsmentioning

confidence: 99%

Verification of the quantum nonequilibrium work relation in the presence of decoherence

Smith

et al. 2018

New J. Phys.

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“…Addressable AC-Stark shifts have been shown to enable the generation of programmable disorder [39] and have been proposed for the simulation of dephasing in adiabatic quantum optimization [52]. Amplitude and phase modulations have also been used to simulate a qubit in a dephasing environment [53]. These ingredients render trapped ions a highly versatile platform for investigating the excitation transfer in open quantum networks.…”

Section: Introductionmentioning

confidence: 99%

Trapped-ion quantum simulation of excitation transport: Disordered, noisy, and long-range connected quantum networks

Trautmann

Hauke

2018

Phys. Rev. A

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The transport of excitations governs fundamental properties of matter. Particularly rich physics emerges in the interplay between disorder and environmental noise, even in small systems such as photosynthetic biomolecules. Counterintuitively, noise can enhance coherent quantum transport, which has been proposed as a mechanism behind the high transport efficiencies observed in photosynthetic complexes. This effect has been called "environment-assisted quantum transport" (ENAQT). Here, we propose a quantum simulation of the excitation transport in an open quantum network, taking advantage of the high controllability of current trapped-ion experiments. Our scheme allows for the controlled study of various different aspects of the excitation transfer, ranging from the influence of static disorder and interaction range, over the effect of Markovian and non-Markovian dephasing, to the impact of a continuous insertion of excitations. Our proposal discusses experimental error sources and realistic parameters, showing that it can be implemented in state-of-the-art ion-chain experiments.

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“…A key tool in our studies is bath engineering 16 , in which we add noise with userdefined spectral characteristics to the control system, producing well-controlled unitary dephasing or depolarization.…”

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confidence: 99%

Experimental noise filtering by quantum control

et al. 2014

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Extrinsic interference is routinely faced in systems engineering, and a common solution is to rely on a broad class of filtering techniques to a ord stability to intrinsically unstable systems or isolate particular signals from a noisy background. Experimentalists leading the development of a new generation of quantum-enabled technologies similarly encounter time-varying noise in realistic laboratory settings. They face substantial challenges in either suppressing such noise for high-fidelity quantum operations 1 or controllably exploiting it in quantum-enhanced sensing [2][3][4] or system identification tasks 5,6 , due to a lack of e cient, validated approaches to understanding and predicting quantum dynamics in the presence of realistic time-varying noise. In this work we use the theory of quantum control engineering . We demonstrate the utility of these constructs for directly predicting the evolution of a quantum state in a realistic noisy environment as well as for developing novel robust control and sensing protocols. These experiments provide a significant advance in our understanding of the physics underlying controlled quantum dynamics, and unlock new capabilities for the emerging field of quantum systems engineering.Time-varying noise coupled to quantum systems-typically qubits-generically results in decoherence, or a loss of 'quantumness' of the system. Broadly, one may think of the state of the quantum system becoming randomized through uncontrolled (and often uncontrollable) interactions with the environment during both idle periods and active control operations (Fig. 1a). Despite the ubiquity of this phenomenon, it is a challenging problem to predict the average evolution of a qubit state undergoing a specific, but arbitrary operation in the presence of realistic time-dependent noise-how much randomization does one expect and how well can one perform the target operation? Making such predictions accurately is precisely the capability that experimentalists require in realistic laboratory settings. Moreover, this capability is fundamental to the development of novel control techniques designed to modify or suppress decoherence as researchers attempt to build quantum-enabled technologies for applications such as quantum information and quantum sensing.These considerations motivate the development of novel engineering-inspired analytic tools enabling a user to accurately predict the behaviour of a controlled quantum system in realistic laboratory environments. Recent work has demonstrated that the average dynamics of a controlled qubit state evolution may be captured using filter-transfer functions (FFs) characterizing the control. The fidelity of an arbitrary operation over duration τ ,, is degraded owing to frequency-domain spectral overlap between noise in the environment given by a power spectrum S(ω), and the filter-transfer functions denoted F(ω) (Methods) [11][12][13][14] . The FF description of ensemble-average quantum dynamics tremendously simplifies the task of analysing the expected performa...

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Experimental bath engineering for quantitative studies of quantum control

Cited by 37 publications

References 52 publications

Verification of the quantum nonequilibrium work relation in the presence of decoherence

Verification of the quantum nonequilibrium work relation in the presence of decoherence

Trapped-ion quantum simulation of excitation transport: Disordered, noisy, and long-range connected quantum networks

Experimental noise filtering by quantum control

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