Quantum computing with superconducting devices: A three-level SQUID qubit

Zhou, Zhóngyuan; Chu, Shih‐I; Han, Siyuan

doi:10.1103/physrevb.66.054527

Cited by 91 publications

(111 citation statements)

References 26 publications

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“…The Hamiltonian of a flux-biased rf SQUID with total magnetic flux Φ enclosed in the loop can be written as [22,67] …”

Section: Microwave-driven Squid Flux Qubits: Analytical Versus Nummentioning

confidence: 99%

“…If φ (t) is the normalized flux coupled to the SQUID from the microwave then H F (x, t) is given by [67] …”

Section: Microwave-driven Squid Flux Qubits: Analytical Versus Nummentioning

confidence: 99%

“…where, ω mn = (E m − E n ) / is the transition frequency, R mn,m ′ n ′ is the matrix element of damping rate superoperator describing the effect of environment on the TLS, [56,61] and H F mn = m |H F | n / is the matrix element of interaction Hamiltonian H F between the TLS and resonant ac driving field. For simplicity and without loss of generality, henceforward, unless otherwise specified, we assume H F 12 = ε cos (ω µ t) and H F 11 − H F 22 = δ cos (ω µ t), where ε and δ are the constants associated with transition matrix elements and field strength.…”

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

“…The effect of the thermal bath on the system can equivalently be characterized by a spectral density J (ω). [62,63] In this case, the matrix elements of the damping rate superoperator can be calculated by [56,61] …”

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

“…After dropping the terms related to the Lamb shifts, the Markovian master equation for the reduced density matrix of a driven multilevel qubit is cast into the generalized Bloch-Redfield equation. [56,60,61] For a driven dissipative TLS with conserved population, the reduced density matrix elements satisfy ρ 21 = ρ * 12 and ρ 11 + ρ 22 = 1 and are governed by [56,61] …”

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

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Relaxation and decoherence in a resonantly driven qubit

Zhou

Chu

Han

2008

J. Phys. B: At. Mol. Opt. Phys.

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Relaxation and decoherence of a qubit coupled to environment and driven by a resonant ac field are investigated by analytically solving Bloch equation of the qubit. It is found that the decoherence of a driven qubit can be decomposed into intrinsic and field-dependent ones. The intrinsic decoherence time equals to the decoherence time of the qubit in free decay while the fielddependent 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 by 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.

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“…The Hamiltonian of a flux-biased rf SQUID with total magnetic flux Φ enclosed in the loop can be written as [22,67] …”

Section: Microwave-driven Squid Flux Qubits: Analytical Versus Nummentioning

confidence: 99%

“…If φ (t) is the normalized flux coupled to the SQUID from the microwave then H F (x, t) is given by [67] …”

Section: Microwave-driven Squid Flux Qubits: Analytical Versus Nummentioning

confidence: 99%

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

Section: Bloch Equation Of a General Driven Dissipative Two-levelmentioning

confidence: 99%

See 3 more Smart Citations

Relaxation and decoherence in a resonantly driven qubit

Zhou

Chu

Han

2008

J. Phys. B: At. Mol. Opt. Phys.

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Controlling Decoherence from Fluctuating Magnetic Field

et al. 2009

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A different strategy is proposed to control decoherence from fluctuating magnetic field by adjusting external controllable parameters. The results show that the output states in terms of the fidelity are pure states, which correspond to the state vectors that are given by a renormalized Hamiltonian. Thus, the output states may perfectly preserve memory of initial single-qubit states at some critical magnetic field parameters.Keywords Decoherence · Controllable parameter · Fluctuating magnetic field In a really physical word, the interaction between a quantum system with its surrounding environment may lead to an irreversible loss of information on the system. Because the interacting effect is that quantum superpositions decay into statistical mixtures so as to result in a relatively short coherence time, the decoherent process limits the ability to maintain pure quantum states in quantum information processing [1-3]. Thus, noise and decoherence are a major challenge how to preserve quantum coherent state in practical applications [4][5][6][7][8][9].Several schemes have been proposed to solve the problem, which included quantum error correction strategies [10][11][12][13], feedback implementations [14][15][16], the realization of qubits in symmetric subspaces decoupled from the environment [17][18][19], dynamical decoupling techniques [20,21], and engineering of pointer states [22]. Though the engineering of pointer states and feedback implementations were proposed to maintain a single-qubit

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Overcoming Decoherent Effects from Squeezed Vacuum Reservoir

Huang-yun

Liu

et al. 2010

Int J Theor Phys

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A strategy is investigated to overcome the decoherence for open quantum system by controlling external parameters. The results show that output state may be a pure state in some critical magnetic field parameters which depend on the decay rates so that one may perfectly preserve memory of initial single-qubit states at the finial state under some conditions. The way is applied to two-level atomic systems interacting with squeezed vacuum reservoir.Keywords Decoherence · Controlling external parameters · Squeezed vacuum reservoir It is important to understand the interaction between a quantum system with its surrounding environment in both the fundamental theory and application. The decoherence is, on the one hand, a possible explanation of the famous Schrödinger cat paradox [1-4], where a macroscopic superposition is shown how to emerge from a microscopic superposition. For the macroscopic systems, the interaction with environment can never be escaped because the decay rate is proportional to the macroscopic separation between two classical states [5,6]. Therefore, a linear superposition of macroscopically distinguishable states is immediately changed into a correspondingly statistical mixture, without leaving any space of quantum coherence. The progressive decoherence of a mesoscopic Schrödinger cat was firstly observed in the experiment [7], where the linear superposition of two coherent states under

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Quantum computing with superconducting devices: A three-level SQUID qubit

Cited by 91 publications

References 26 publications

Relaxation and decoherence in a resonantly driven qubit

Relaxation and decoherence in a resonantly driven qubit

Controlling Decoherence from Fluctuating Magnetic Field

Overcoming Decoherent Effects from Squeezed Vacuum Reservoir

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