Dynamics and quantum Zeno effect for a qubit in either a low- or high-frequency bath beyond the rotating-wave approximation

Journal Article · Sun Aug 15 04:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.82.022119· OSTI ID:21448445

Xiufeng, Cao ^[1]; You, J Q ^[1]; Zheng, H ^[2]; Kofman, A G; Nori, Franco ^[1]

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1. Advanced Science Institute, RIKEN, Wako-shi 351-0198 (Japan)
2. Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China)

We use a non-Markovian approach to study the decoherence dynamics of a qubit in either a low- or high-frequency bath modeling the qubit environment. This is done for two separate cases: either with measurements or without them. This approach is based on a unitary transformation and does not require the rotating-wave approximation. In the case without measurement, we show that, for low-frequency noise, the bath shifts the qubit energy toward higher energies (blue shift), while the ordinary high-frequency cutoff Ohmic bath shifts the qubit energy toward lower energies (red shift). In order to preserve the coherence of the qubit, we also investigate the dynamics of the qubit subject to measurements (quantum Zeno regime) in two cases: low- and high-frequency baths. For very frequent projective measurements, the low-frequency bath gives rise to the quantum anti-Zeno effect on the qubit. The quantum Zeno effect only occurs in the high-frequency-cutoff Ohmic bath, after counterrotating terms are considered. In the condition that the decay rate due to the two kinds of baths are equal under the Wigner-Weisskopf approximation, we find that without the approximation, for a high-frequency environment, the decay rate should be faster (without measurements) or slower (with frequent measurements, in the Zeno regime), compared to the low-frequency bath case. The experimental implementation of our results here could distinguish the type of bath (either a low- or high-frequency one) and protect the coherence of the qubit by modulating the dominant frequency of its environment.

• OSTI ID: 21448445
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 2 Vol. 82; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
APPROXIMATIONS
CALCULATION METHODS
COMPUTERIZED SIMULATION
IMPLEMENTATION
INFORMATION
MARKOV PROCESS
MECHANICS
NOISE
QUANTUM DECOHERENCE
QUANTUM INFORMATION
QUANTUM MECHANICS
QUANTUM STATES
QUBITS
RED SHIFT
SIMULATION
STOCHASTIC PROCESSES
TRANSFORMATIONS