Measuring the quality factor of a microwave cavity using superconducting qubit devices

Liu, Yu-xi; Wei, L. F.; Nori, Franco

doi:10.1103/physreva.72.033818

Cited by 39 publications

(9 citation statements)

References 43 publications

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“…Such treatment was used in Ref. [44]and can be equivalently done by using the adiabatic elimination approach [57,58]. Up to the order of χ 2 , one can find…”

Section: Appendix B: the Effective Hamiltonianmentioning

confidence: 99%

Criticality-enhanced quantum sensor at finite temperature

Wu,

Shi

2021

Preprint

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Conventional criticality-based quantum metrological schemes work only at zero or very low temperature because the quantum uncertainty around the quantum phase transition point is generally erased by thermal fluctuations with the increase of temperature. Such an ultra-low temperature requirement severely restricts the development of quantum critical metrology. In this paper, we propose a thermodynamic-criticality-enhanced quantum sensing scenario at finite temperature. In our scheme, a qubit is employed as a quantum sensor to estimate parameters of interest in the Dicke model which experiences a thermodynamic phase transition. It is revealed that the thermodynamic criticality of the Dicke model can significantly improve the sensing precision. Enriching the scope of quantum critical metrology, our finding provides a possibility to realize highly sensitive quantum sensing without cooling.

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“…Such treatment was used in Ref. [44]and can be equivalently done by using the adiabatic elimination approach [57,58]. Up to the order of χ 2 , one can find…”

Section: Appendix B: the Effective Hamiltonianmentioning

confidence: 99%

Criticality-enhanced quantum sensor at finite temperature

Wu,

Shi

2021

Preprint

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“…Here, we consider two coupled qubits that are resonantly interacting with a microwave cavity field via two atomic transitions. Such qubit systems were proposed in superconducting circuits [5,6], where the both 2-photon processes and two-qubit coupling have been realized [5][6][7]. In the rotating-wave approximation, the total Hamiltonian iŝ…”

Section: Physical Model and Density Matrixmentioning

confidence: 99%

“…Two-level system (qubit) is not only the key element in various fields of the modern physics, such as quantum optics and collision physics [1,2], but also the fundamental building block of modern applications ranging from quantum control [3] to quantum processing [4]. Such qubit systems were proposed for superconducting circuits [5,6], where both the 2-photon processes and two-qubit coupling have been realized [5][6][7]. Due to the rapid development of experiments in macroscopic solid-state physics, the artificial two-level atoms qubits, based on the superconducting (SC) circuits [8,9] and quantum dots (QDs) [10], have been recognized as possible candidate for the quantum processing.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Coupling between Two Qubits in an Open Coherent Cavity: Nonclassical Information via Quasi-Probability Distributions

Mohamed

Eleuch

Obada

2019

Entropy

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In this paper, we investigate the dynamics of two coupled two-level systems (or qubits) that are resonantly interacting with a microwave cavity. We examine the effects of the intrinsic decoherence rate and the coupling between the two qubits on the non-classicality of different system partitions via quasi-probability functions. New definitions for the partial Q-function and its Wehrl entropy are used to investigate the information and the quantum coherence of the phase space. The amount of the quantum coherence and non-classicality can be appropriately tuned by suitably adopting the rates of the intrinsic-decoherence and the coupling between the two qubits. The intrinsic decoherence has a pronounced effect on the negativity and the positivity of the Wigner function. The coupling between the two qubits can control the negativity and positivity of the quasi-probability functions.The Q-function is one of the simplest QPDs in phase space, and it is always a positive distribution [19]. Q-function and its Wehrl entropy can be used to quantify the quantum correlations and phase space information [20,21]. The Q-function was studied only for representations of the cavity fields, two-level systems [19][20][21], and three-level systems [22,23].There are other information entropies, including von Neumann entropy [24], linear entropy, and Shannon information entropy [25], that are used as a measure for the entanglement in closed systems [10]. For open systems, they are used as a measure of the coherence loss, where there are two quantum coherence sources in a quantum system: The first is due to its unitary interaction, this coherence can be called entanglement between two subsystems and "coherence loss" for one of them. The second is in open systems, it leads to losing the quantum coherence. Wehrl entropy is an additional entropic quantity that has been successfully applied in measuring the entanglement. It gives quantitative and qualitative information on the entanglement of the bipartite system. It is a useful tool to investigate the dynamical properties that contain all the information about the system dynamics. It is proved that the Wehrl entropy exhibits a temporal evolution similar to the von Neumann entropy.Loss of coherence in open quantum systems is as familiar as decoherence [26,27]. An important type of decoherence in open quantum systems is that described by the intrinsic decoherence (ID) model, in which Milburn [28] considers that the system does not evolve continuously, where the quantum coherence is automatically destroyed as the system evolves. The Milburn model is only used to investigate analytically decoherence effects on the dynamics of the non-classicality of the QPDs in two qubits when they are interacting with a coherent cavity field [29]; however, the effect of the coupling constant between the two qubits is neglected.In the current work, (i) the physical model of two coupled two-level systems resonantly interacting with an open cavity initially in a superposition of coherent states is analytically des...

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“…Treating the environment as a cavity of harmonic oscillator modes, this loss is directly proportional to the cavity quality factor Q c = 2πω c /γ for cavity frequency ω c . This quality factor can range from Q c ∼ 10 2 to Q c ∼ 10 6 or higher 49,50 . The cutoff frequency, Ω, defines the peak frequency of the bath's spectral density which has a similar form to the impedance in Josephson circuits 51,52 .…”

Section: First Order Master Equationmentioning

confidence: 99%

Some implications of superconducting quantum interference to the application of master equations in engineering quantum technologies

et al. 2016

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In this paper we consider the modelling and simulation of open quantum systems from a device engineering perspective. We derive master equations at different levels of approximation for a Superconducting Quantum Interference Device (SQUID) ring coupled to an ohmic bath. We demonstrate that the master equations we consider produce decoherences that are qualitatively and quantitativly dependent on both the level of approximation and the ring's external flux bias. We discuss the issues raised when seeking to obtain Lindbladian dissipation and show, in this case, that the external flux (which may be considered to be a control variable in some applications) is not confined to the Hamiltonian, as often assumed in quantum control, but also appears in the Lindblad terms.

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Measuring the quality factor of a microwave cavity using superconducting qubit devices

Cited by 39 publications

References 43 publications

Criticality-enhanced quantum sensor at finite temperature

Criticality-enhanced quantum sensor at finite temperature

Influence of the Coupling between Two Qubits in an Open Coherent Cavity: Nonclassical Information via Quasi-Probability Distributions

Some implications of superconducting quantum interference to the application of master equations in engineering quantum technologies

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