Decoherence and entanglement in quantum systems

Murat Çetinbaş

The interaction of a quantum system with its surrounding environment results in losses of quantum correlations in the state of the system due to a decoherence process. The origin of decoherence is often attributed to the system–environment entanglement, which is not the only source of decoherence, however. Here we show that environment-induced coherent quantum fluctuations, i.e. Lamb or Stark shift-like effects, can also lead to the emergence of decoherence, which we call an incoherence process, even in the absence of the system–environment entanglement. We isolate the incoherence process from a general decoherence dynamics and formulate the exact equation of motion governing the incoherence dynamics in the absence of entanglement-induced decoherence. We exemplify the incoherence dynamics for a number of different situations including chaotic, regular and decoherence-free environments.

A.‐S. F. Obada, Abdel‐Baset A. Mohamed, Hosney A. Hessein

Jamal Anwar, S., Ramzan, M., Usman, M. +1 more

We investigate the quantum Fisher information (QFI) and quantum entanglement (QE) dynamics of moving two three-level atoms interacting with a thermal field. The time evolution of the quantum system is studied numerically under the effect of intrinsic decoherence (ID) in a thermal environment. ID and thermal environment play a critical role during the time evolution of the quantum system. It is found that QE changes drastically when ID increases in the absence of atomic motion. However, a periodic behavior of QE is observed in the case of moving atoms. The thermal environment is seen to have a prominent effect on QFI in the presence of ID. Moreover, the decay of QE is further suppressed at larger time-scales which ensures the enhanced influence of ID on the system’s dynamics in a thermal environment. However, QFI and QE saturate to a lower level at larger time-scales under these environments. The behavior of QFI and QE is opposite to each other under these environments. Furthermore, it is seen that the thermal environment induces a faster decay of QE as compared to the decay induced by ID. Therefore, ID diminishes the degree of QE for higher-dimensional quantum systems. Moreover, the system’s dynamics changes remarkably by increasing the mean number of photons.

Jian Zou

To reveal how the decoherence modifies the time evolution of the entanglement of quantum system, the intrinsic decoherence approach and the entanglement of formation are used, and the time evolution of entanglement for two-qubit 1D quantum Heisenberg model in an external uniform magnetic field is derived. It is shown that the external magnetic field can strengthen the effects of the intrinsic decoherence on the entanglement of the system.