Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:cond-mat/0604191 · Journal of Physics B Atomic Molecular and Optical Physics

Relaxation and decoherence in a resonantly driven qubit

Zhongyuan Zhou, Shih‐I Chu, Siyuan Han

Published Feb 12, 2008• 15 citations
arXivHTMLPDF

Abstract

Relaxation and decoherence of a qubit coupled to the environment and driven by a resonant ac field are investigated by analytically solving the Bloch equation of the qubit. We found that the decoherence of a driven qubit can be decomposed into intrinsic and field-dependent decoherence. The intrinsic decoherence time equals the decoherence time of the qubit in a free decay while the field-dependent decoherence time is identical with the relaxation time of the qubit in driven oscillation. Analytical expressions of the relaxation and decoherence times are derived and applied to study a microwave-driven SQUID flux qubit. The results are in excellent agreement with those obtained from directly numerically solving the master equation. The relations between the relaxation and decoherence times of a qubit in free decay and driven oscillation can be used to extract the decoherence and thus dephasing times of the qubit by measuring its population evolution in free decay and resonantly driven oscillation.

DOI
10.1088/0953-4075/41/4/045506

Related papers

Relaxation and Decoherence Induced by an External Circuit of a Driven SQUID Flux Qubit

Zhongyuan Zhou, Shih‐I Chu, Siyuan Han

A theory on the dynamics of a driven dissipative multilevel quantum system is applied to investigate relaxation and decoherence induced by an external circuit of a resonantly driven SQUID flux qubit. It is shown that in the case of weak field and weak damping the numerical and analytical results are in excellent agreement. It is also shown that the SQUID qubit can be optimized by varying external circuit parameters.

IEEE Transactions on Applied Superconductivity•Jun 1, 2007•2 citations

Non-Markovian qubit decoherence during dispersive readout

Georg M. Reuther, Peter Hänggi A, Sigmund Kohler

We study qubit decoherence under generalized dispersive readout, i.e., we investigate a qubit coupled to a resonantly driven dissipative harmonic oscillator. We provide a complete picture by allowing for arbitrarily large qubit-oscillator detuning and by considering also a coupling to the square of the oscillator coordinate, which is relevant for flux qubits. Analytical results for the decoherence time are obtained by a transformation of the qubit-oscillator Hamiltonian to the dispersive frame and a subsequent master equation treatment beyond the Markov limit. We predict a crossover from Markovian decay to a decay with Gaussian shape. Our results are corroborated by the numerical solution of the full qubit-oscillator master equation in the original frame.

arXiv:1205.2315•Physical Review A•Jun 28, 2012•6 citations

Decoherence and relaxation of a quantum bit in the presence of Rabi oscillations

Anatoly Yu. Smirnov

The dissipative dynamics of a quantum bit driven by a strong resonant field and interacting with a heat bath is investigated. We derive generalized Bloch equations and find modifications of the qubit's damping rates caused by Rabi oscillations. The nonequilibrium decoherence and relaxation of a phase qubit inductively coupled to a resonant tank circuit is considered as an illustration of the general results.

arXiv:cond-mat/0209217•Physical review. B, Condensed matter•Apr 11, 2003•34 citations

Relaxation and Dephasing in a Flux-qubit

Patrice Bertet, I. Chiorescu, Guido Burkard +4 more

We report detailed measurements of the relaxation and dephasing time in a flux-qubit measured by a switching DC SQUID. We studied their dependence on the two important circuit bias parameters: the externally applied magnetic flux and the bias current through the SQUID in two samples. We demonstrate two complementary strategies to protect the qubit from these decoherence sources. One consists in biasing the qubit so that its resonance frequency is stationary with respect to the control parameters ({\it optimal point}) ; the second consists in {\it decoupling} the qubit from current noise by chosing a proper bias current through the SQUID. At the decoupled optimal point, we measured long spin-echo decay times of up to $4 μs$.

arXiv:cond-mat/0412485•Dec 17, 2004•14 citations

Characterizing decoherence rates of a superconducting qubit by direct microwave scattering

Yong Lu, Andreas Bengtsson, Jonathan Burnett +8 more

Abstract We experimentally investigate a superconducting qubit coupled to the end of an open transmission line, in a regime where the qubit decay rates to the transmission line and to its own environment are comparable. We perform measurements of coherent and incoherent scattering, on- and off-resonant fluorescence, and time-resolved dynamics to determine the decay and decoherence rates of the qubit. In particular, these measurements let us discriminate between non-radiative decay and pure dephasing. We combine and contrast results across all methods and find consistent values for the extracted rates. The results show that the pure dephasing rate is one order of magnitude smaller than the non-radiative decay rate for our qubit. Our results indicate a pathway to benchmark decoherence rates of superconducting qubits in a resonator-free setting.

arXiv:1912.02124•npj Quantum Information•Feb 16, 2021•48 citations

Investigation on Decoherence of Superconducting Flux Qubit with Mutual Inductance Coupling

Lihua Wang

In Born-Markov approximation,according to Bloch-Redfield equation,the method to calculate the relaxation time T1 and decoherence time T2 of superconducting qubit is given.Based on this,the decoherence phenomenon of superconducting flux qubit with mutual inductance coupling is investigated.The energy relaxation time T1 and decoherence time T2 of this superconducting qubit is also obtained.The results show that for the flux qubit under investigation,the dephasing time T,the energy relaxation time T1 from high level |j〉 to low level |i〉,and the decoherence time T2 of the quantum system are all proportional to dissipation when other conditions are invariant and the environment thermal bath is equivalent to a pure resistance.

Jiangxi kexue•Jan 1, 2008•0 citations
Relaxation and decoherence of a qubit coupled to the environment and driven by a resonant ac field are investigated by analytically solving the Bloch equation of the qubit. We found that the decoherence of a driven qubit can be decomposed into intrinsic and field-dependent decoherence. The intrinsic decoherence time equals the decoherence time of the qubit in a free decay while the field-dependent decoherence time is identical with the relaxation time of the qubit in driven oscillation. Analytical expressions of the relaxation and decoherence times are derived and applied to study a microwave-driven SQUID flux qubit. The results are in excellent agreement with those obtained from directly numerically solving the master equation. The relations between the relaxation and decoherence times of a qubit in free decay and driven oscillation can be used to extract the decoherence and thus dephasing times of the qubit by measuring its population evolution in free decay and resonantly driven oscillation.
We study qubit decoherence under generalized dispersive readout, i.e., we investigate a qubit coupled to a resonantly driven dissipative harmonic oscillator. We provide a complete picture by allowing for arbitrarily large qubit-oscillator detuning and by considering also a coupling to the square of the oscillator coordinate, which is relevant for flux qubits. Analytical results for the decoherence time are obtained by a transformation of the qubit-oscillator Hamiltonian to the dispersive frame and a subsequent master equation treatment beyond the Markov limit. We predict a crossover from Markovian decay to a decay with Gaussian shape. Our results are corroborated by the numerical solution of the full qubit-oscillator master equation in the original frame.
We report detailed measurements of the relaxation and dephasing time in a flux-qubit measured by a switching DC SQUID. We studied their dependence on the two important circuit bias parameters: the externally applied magnetic flux and the bias current through the SQUID in two samples. We demonstrate two complementary strategies to protect the qubit from these decoherence sources. One consists in biasing the qubit so that its resonance frequency is stationary with respect to the control parameters ({\it optimal point}) ; the second consists in {\it decoupling} the qubit from current noise by chosing a proper bias current through the SQUID. At the decoupled optimal point, we measured long spin-echo decay times of up to 4μs4 μs4μs.
Abstract We experimentally investigate a superconducting qubit coupled to the end of an open transmission line, in a regime where the qubit decay rates to the transmission line and to its own environment are comparable. We perform measurements of coherent and incoherent scattering, on- and off-resonant fluorescence, and time-resolved dynamics to determine the decay and decoherence rates of the qubit. In particular, these measurements let us discriminate between non-radiative decay and pure dephasing. We combine and contrast results across all methods and find consistent values for the extracted rates. The results show that the pure dephasing rate is one order of magnitude smaller than the non-radiative decay rate for our qubit. Our results indicate a pathway to benchmark decoherence rates of superconducting qubits in a resonator-free setting.
In Born-Markov approximation,according to Bloch-Redfield equation,the method to calculate the relaxation time T1 and decoherence time T2 of superconducting qubit is given.Based on this,the decoherence phenomenon of superconducting flux qubit with mutual inductance coupling is investigated.The energy relaxation time T1 and decoherence time T2 of this superconducting qubit is also obtained.The results show that for the flux qubit under investigation,the dephasing time T,the energy relaxation time T1 from high level |j〉 to low level |i〉,and the decoherence time T2 of the quantum system are all proportional to dissipation when other conditions are invariant and the environment thermal bath is equivalent to a pure resistance.