Physical Review B

Decoherence by quantum telegraph noise: A numerical evaluation

Benjamin Abel, Florian Marquardt

Published Nov 24, 2008• 75 citations

Abstract

We investigate the time evolution of a charge qubit subject to quantum telegraph noise produced by a single electronic defect level. We obtain results for the time evolution of the coherence that are strikingly different from the usual case of a harmonic-oscillator bath (Gaussian noise). When the coupling strength crosses a certain temperature-dependent threshold, we observe coherence oscillations in the strong-coupling regime. Moreover, we present the time evolution of the echo signal in a spin-echo experiment. Our analysis relies on a numerical evaluation of the exact solution for the density matrix of the qubit.

DOI: 10.1103/physrevb.78.201302

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Physical Review B

Decoherence by quantum telegraph noise: A numerical evaluation

Benjamin Abel, Florian Marquardt

Published Nov 24, 2008• 75 citations

Publisher

Abstract

DOI: 10.1103/physrevb.78.201302

Related papers

Decoherence by Quantum Telegraph Noise

Benjamin Abel, Florian Marquardt

We investigate the time-evolution of a charge qubit subject to quantum telegraph noise produced by a single electronic defect level. We obtain results for the time-evolution of the coherence that are strikingly different from the usual case of a harmonic oscillator bath (Gaussian noise). When the coupling strength crosses a certain temperature-dependent threshold, we observe coherence oscillations in the strong-coupling regime. Moreover, we present the time-evolution of the echo signal in a spin-echo experiment. Our analysis relies on a numerical evaluation of the exact solution for the density matrix of the qubit.We investigate the time-evolution of a charge qubit subject to quantum telegraph noise produced by a single electronic defect level. We obtain results for the time-evolution of the coherence that are strikingly different from the usual case of a harmonic oscillator bath (Gaussian noise). When the coupling strength crosses a certain temperature-dependent threshold, we observe coherence oscillations in the strong-coupling regime. Moreover, we present the time-evolution of the echo signal in a spin-echo experiment. Our analysis relies on a numerical evaluation of the exact solution for the density matrix of the qubit.

arXiv:0805.0962May 7, 20082 citations

Partial decoherence in a qubit coupled to a control register subject to telegraph noise

Amnon Aharony A, Ora Entin-wohlman A, Sushanta Dattagupta

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We analyze local spin-echo procedures for protecting entanglement between two non-interacting qubits, each subject to pure-dephasing random telegraph noise. For superconducting qubits, this simple model captures the characteristic features of the effect of bistable impurities coupled to the device. An analytic expression for the entanglement dynamics is reported. Peculiar features related to the non-Gaussian nature of the noise already observed in the single-qubit dynamics also occur in the entanglement dynamics for proper values of the ratio g = v / γ , between the qubit–impurity coupling strength and the switching rate of the random telegraph process, and of the separation between the pulses Δ t . We found that the echo procedure may delay the disappearance of entanglement, cancel the dynamical structure of entanglement revivals and dark periods and induce peculiar plateau-like behaviors of the concurrence.We analyze local spin-echo procedures for protecting entanglement between two non-interacting qubits, each subject to pure-dephasing random telegraph noise. For superconducting qubits, this simple model captures the characteristic features of the effect of bistable impurities coupled to the device. An analytic expression for the entanglement dynamics is reported. Peculiar features related to the non-Gaussian nature of the noise already observed in the single-qubit dynamics also occur in the entanglement dynamics for proper values of the ratio g = v / γ , between the qubit–impurity coupling strength and the switching rate of the random telegraph process, and of the separation between the pulses Δ t . We found that the echo procedure may delay the disappearance of entanglement, cancel the dynamical structure of entanglement revivals and dark periods and induce peculiar plateau-like behaviors of the concurrence.

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arXiv:0803.3452Physical Review BJul 9, 200843 citations

A qubit (containing two quantum states, 1 and 2), is coupled to a control register (state 3), which is subject to telegraph noise. We study the time evolution of the density matrix

ρ

of an electron which starts in some coherent state on the qubit. At infinite time,

ρ

usually approaches the fully decoherent state, with

ρ^{}_{nm}=δ^{}_{nm}/3

. However, when the Hamiltonian is symmetric under

1\leftrightarrow 2

, the element

ρ^{}_{12}

approaches a non-zero real value, implying a partial coherence of the asymptotic state. The asymptotic density matrix depends only on

{\rm Re}[ρ^{}_{12}(t=0)]

. In several cases, the information stored on the qubit is protected from the noise.

1/f

noise spectrum with a characteristic temperature depedence. We discuss the strategy for suppression of decoherence by the application of higher-order (beyond spin echo) pulse sequences.