Correlated and collective stochastic dephasing of qubit entanglement

Masashi Ban

XIAO SAN MA, An Min Wang

Masashi Ban, Sachiko Kitajima, Fumiaki Shibata

Masashi Ban

Mazhar Ali

Most studies of collective dephasing for bipartite as well as multipartite quantum systems focus on a very specific orientation of magnetic field, that is, z-orientation. However, in practical situations, there are always small fluctuations in stochastic field and it is necessary that more general orientations of fields should be considered. We extend this problem to qubit-qutrit systems and study correlation dynamics for entanglement and local quantum uncertainty for some specific quantum states. We find that certain quantum states exhibit freezing dynamics both for entanglement and local quantum uncertainty. We analyze the asymptotic states and find the conditions for having non-zero entanglement and local quantum uncertainty. Our results are relevant for ion-trap experiments and can be verified with current experimental setups.

Masashi Ban, Fumiaki Shibata, Sachiko Kitajima

It is shown that the stochastic dephasing of a qubit caused by the random frequency modulation in which the stochastic variable obeys the stationary Gauss–Markov process can be suppressed by applying a sequence of π pulses to the qubit. It is found that the application of around ten π pulses within the correlation time of the stochastic variable is enough to suppress the decoherence of the qubit. The recovery of the entanglement of the Werner state by means of π pulses is also discussed.