Observation of quantum Zeno effect in a superconducting flux qubit

Kakuyanagi, Kosuke; Baba, T.; Matsuzaki, Yuichiro; Nakano, Hideyuki; Saito, Shiro; Semba, Kouichi

doi:10.1088/1367-2630/17/6/063035

Cited by 43 publications

(29 citation statements)

References 48 publications

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“…Moreover, the QAZE is predicted to be an even more ubiquitous phenomenon [14,15]. Both the QZE and the QAZE have been experimentally observed in many physical systems, such as trapped ions [16] and trapped atoms [17], superconducting qubits [18][19][20][21], Bose-Einstein condensates [22], nanomechanical oscillators [23], cavity quan- * Email address: jingjun@zju.edu.cn tum electrodynamics systems [24], and nuclear spin systems [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Criterion for quantum Zeno and anti-Zeno effects

et al. 2018

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In this work, we study the decay behavior of a two-level system under the competing influence of a dissipative environment and repetitive measurements. The sign of the second derivative of the environmental spectral density function with respect to the system transition frequency is found to be a sufficient condition to distinguish between the quantum Zeno (negative) and the anti-Zeno (positive) effects raised by the measurements. We check our criterion for practical measurement intervals, which are larger than the conceptual Zeno time, in various environments. In particular, with the Lorentzian spectrum, the quantum Zeno and anti-Zeno phenomena are found to emerge respectively in the near-resonant and off-resonant cases. For the interacting spectra of hydrogenlike atoms, the quantum Zeno effect usually occurs and the anti-Zeno effect can rarely occur unless the transition frequency is close to the cut-off frequency. With a power-law spectrum, we find that sub-Ohmic and super-Ohmic environments lead to the quantum Zeno and anti-Zeno effects, respectively.

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Section: Introductionmentioning

confidence: 99%

Criterion for quantum Zeno and anti-Zeno effects

et al. 2018

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“…The QZE was first observed experimentally in an ensemble of trapped ions [7], and has since been seen in a variety of other systems, including the electronic, nuclear, or motional states of atoms and molecules [8][9][10][11], optical photons [12][13][14], microwave photons [15], and NV centers [16]. In driven superconducting qubits, the QZE has been indirectly inferred from the transition between coherent Rabi oscillations and incoherent exponential population decay with increasing measurement strength [17], and by studying the dependence of this exponential decay on the time between discrete qubit projection pulses [18]. However, theoretical proposals also exist to observe the QZE in the quantum trajectory of a continuously monitored superconducting qubit [19] or in the suppression by measurement of low-frequency superconducting flux qubit dephasing [20].…”

Section: Introductionmentioning

confidence: 99%

Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics

et al. 2016

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We observe the quantum Zeno effect-where the act of measurement slows the rate of quantum state transitions-in a superconducting qubit using linear circuit quantum electrodynamics readout and a near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals.

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“…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.…”

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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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Observation of quantum Zeno effect in a superconducting flux qubit

Cited by 43 publications

References 48 publications

Criterion for quantum Zeno and anti-Zeno effects

Criterion for quantum Zeno and anti-Zeno effects

Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics

Incoherent Qubit Control Using the Quantum Zeno Effect

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