Confined quantum Zeno dynamics of a watched atomic arrow

Signoles, Adrien; Facon, Adrien; Grosso, Dorian; Dotsenko, Igor; Haroche, S.; Raimond, Jean‐Michel; Brune, M.; Gleyzes, Sébastien

doi:10.1038/nphys3076

Cited by 132 publications

(134 citation statements)

References 31 publications

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“…This measurement scheme also generalizes to multi-level systems. In such multi-level settings, fast measurement rates of certain operators restrict the system to evolve within a particular subspace of the total Hilbert space, which is known as Quantum Zeno Dynamics [43][44][45]. Such restriction has been recently shown to enable uni-versal quantum computation within that subspace [46].…”

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confidence: 99%

Incoherent Qubit Control Using the Quantum Zeno Effect

et al. 2018

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The quantum Zeno effect is the suppression of Hamiltonian evolution by repeated observation, resulting in the pinning of the state to an eigenstate of the measurement observable. Using measurement only, control of the state can be achieved if the observable is slowly varied such that the state tracks the now time-dependent eigenstate. We demonstrate this using a circuit-QED readout technique that couples to a dynamically controllable observable of a qubit. Continuous monitoring of the measurement record allows us to detect an escape from the eigenstate, thus serving as a built-in form of error detection. We show this by post-selecting on realizations with arbitrarily high fidelity with respect to the target state. Our dynamical measurement operator technique offers a new tool for numerous forms of quantum feedback protocols, including adaptive measurements and rapid state purification.In the field of quantum control, two essentially distinct resources are available for state manipulation. Application of a time-dependent Hamiltonian via external driving enables state preparation given a known initial state. In contrast, measurement and dissipation provide a uniquely quantum resource, owing to the stochastic back-action that necessarily accompanies acquisition of information. In addition, measurement-based, or incoherent control [1] also extracts entropy from a system, this information can be used to detect and correct for errors and imperfections. While incoherent and Hamiltonian control are often used in conjunction [2-7], full control is also possible using measurement alone [8][9][10][11][12][13][14]. Measurement-only manipulation has been demonstrated using a fixed measurement basis [15], but unlike Hamiltonian-based methods, implementation of a timedependent measurement basis is lacking. Such a capability is a versatile additional degree of freedom for measurement based protocols, such as rapid state purification [5] and state manipulation [9,10,16], for control by projection into a subspace referred to as quantum Zeno dynamics [17], and for measurement-based quantum computation [18].In this Letter, we present a method to dynamically tune the measurement operator in a circuit-QED system, and use this capability to deterministically and incoherently manipulate the state of an effective qubit. Our method relies on the suppression of coherent evolution via strong measurement, known as the quantum Zeno effect (QZE), which has been observed in many systems [19][20][21][22][23][24][25][26][27][28][29][30]. Essentially it pins a quantum state to an eigenstate of the measurement operator. Changing the operator at a rate slow compared to the rate of measurement-induced dephasing Γ D , we effectively 'drag' the state using measurement alone [11][12][13][14]. This method does not require the measurement record or feedback to achieve control. However by monitoring the record with a quantum-limited Josephson parametric amplifier (JPA), we characterize the dynamics and arXiv:1706.08577v1 [quant-ph]

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confidence: 99%

Incoherent Qubit Control Using the Quantum Zeno Effect

et al. 2018

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“…In our case we have an additional factor depending on p(µ) as given by Eq. (13). We can saturate the bound for product states with |ψ 0 = |00...0 and α n = (1, 0, 0), as well as the bound for entangled states is with the GHZ state (|0..00 − i|1..1 )/ √ 2 and α n = (0, 0, 1).…”

Section: Figmentioning

confidence: 85%

Fisher information from stochastic quantum measurements

Müller¹,

Gherardini²,

Smerzi³

et al. 2016

Phys. Rev. A

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The unavoidable interaction between a quantum system and the external noisy environment can be mimicked by a sequence of stochastic measurements whose outcomes are neglected. Here we investigate how this stochasticity is reflected in the survival probability to find the system in a given Hilbert subspace at the end of the dynamical evolution. In particular, we analytically study the distinguishability of two different stochastic measurement sequences in terms of a new Fisher information measure depending on the variation of a function, instead of a finite set of parameters. We find a novel characterization of Zeno phenomena as the physical result of the random observation of the quantum system, linked to the sensitivity of the survival probability with respect to an arbitrary small perturbation of the measurement stochasticity. Finally, the implications on the Cramér-Rao bound are discussed, together with a numerical example. These results are expected to provide promising applications in quantum metrology towards future, more robust, noise-based quantum sensing devices.Introduction.-Interaction with an external environment lies at the heart of the dynamical characterization of an open quantum system. No quantum system, indeed, is completely isolated, and it is always characterized by a non-unitary evolution of its state [1,2]. Local coupling effects of the system with the outside can be described as projection events due to the action of one (or more) measurement operators [3], along the lines of formalism of the quantum jump trajectories [4] for open quantum systems. Moreover, as one may expect, these trajectories resulting by the dissipative action of the environment are intrinsically stochastic processes, since any interaction shall occur at irregular time intervals, in general without any a-priori predictability. In this context, it becomes important to investigate the distinguishability of quantum states [5,6] of a randomly perturbed quantum system when also the characterization of the stochasticity rate affecting the system is taken into account.

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“…Moreover, the fact that disputable quantum features play no role is clearly illustrated by the numerous demonstrations of Zeno-like dynamics in classical physics [4,5]. The interest in the research in quantum Zeno dynamics is evidenced by several proposals (e.g., [6]) as well as recent experiments [7][8][9], with application to the control of quantum states and to quantum information processing.…”

Section: Introductionmentioning

confidence: 99%

Potential barrier mimicking frequent location measurements in quantum Zeno dynamics

2016

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We show that quantum Zeno dynamics can be mimicked by the isolated evolution of an unobserved system in an effective potential. Monitoring frequently whether a particle remains in a region of space leads to the same wave-packet dynamics as placing the region on top of a potential barrier and letting the particle evolve on its own, without external couplings. We focus on very frequent but not continuous observation so that the particle abandons the initial region with some finite probability. The height of the barrier relative to the surroundings for a high frequency ν of the observations being mimicked is found numerically to be hν/2, where h is Planck's constant.

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Confined quantum Zeno dynamics of a watched atomic arrow

Cited by 132 publications

References 31 publications

Incoherent Qubit Control Using the Quantum Zeno Effect

Incoherent Qubit Control Using the Quantum Zeno Effect

Fisher information from stochastic quantum measurements

Potential barrier mimicking frequent location measurements in quantum Zeno dynamics

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