Off-resonant quantum Zeno and anti-Zeno effects on entanglement

Peng Zhang, Qing Ai, Yong Li +2 more

Qian Wang, Jun-Gang Li & Yuan-Mei Wang

Antonio D’Arrigo, G. Falci, Elisabetta Paladino

艾清, 廖洁桥

Francesco Francica, Sabrina Maniscalco, Francesco Plastina

We examine the appearance of Zeno and anti-Zeno effects (Misra and Sudarshan 1977 J. Math. Phys. 18 756; Kofman and Kurizki 2000 Nature 405 546; Kofman and Kurizki 1996 Phys. Rev. A 54 3750; Facchi et al 2001 Phys. Rev. Lett. 86 2699) in the entanglement dynamics of two qubits off-resonantly coupled to the same lossy cavity when the unitary evolution of the system is interrupted by repeated projective measurements. We describe in detail these quantum effects by comparing the measurement-induced coarse-grained dynamics to the entanglement evolution in the absence of measurements in several scenarios (Francica et al 2009 Phys. Rev. A 79 032310). In particular, we examine the strong and weak coupling regimes, the role of the relative coupling strengths between the two qubits and the reservoir and the effect of the detuning from the main cavity frequency. We show that the anti-Zeno effect can occur in the entanglement dynamics when the qubit frequencies are detuned from the main reservoir frequency. Furthermore, we find that Zeno and anti-Zeno effects can even appear sequentially many times as a function of the interval between the measurements. Finally, we show that, in the off-resonant regime, we can preserve the entanglement using the quantum Zeno effect more efficiently than in the resonant limit (Maniscalco et al 2008 Phys. Rev. Lett. 100 090503), even if, in this case, no sub-radiant state exists.

Alireza Nourmandipour, Mohammad Kazem Tavassoly, M. A. Bolorizadeh

We investigate the quantum Zeno and anti-Zeno effects on pairwise entanglement dynamics of a collective of noninteracting qubits which have been initially prepared in a Werner state and are off-resonantly coupled to a common and non-Markovian environment. We obtain the analytical expression of the concurrence in the absence and presence of the nonselective measurements. In particular, we express our results in the strong and weak coupling regimes and examine the role of the system size and the effect of the detuning from the cavity field frequency on the temporal behavior of the pairwise entanglement. We show that the detuning parameter has a positive role in protection of entanglement in the absence of the measurement for the weak coupling regime. We find that for the values of detuning parameter less than the cavity damping rate, the quantum Zeno effect is always dominant, while for values greater than the cavity damping rate, both Zeno and anti-Zeno effects can occur, depending on the measurement intervals. We also find that the anti-Zeno effect can occur in the pairwise entanglement dynamics in the absence and presence of the detuning in the strong coupling regime.