Information preservation of two qubits in a structured environment

The environment-induced decoherence of a quantum open system makes it fundamentally import to preserve the initial quantum information of the system in its steady state. Here we study information preservation of two maximally entangled qubits lying inside a photonic-crystal waveguide with semi-infinite cavity-array structure. We generalize our study to arbitrary position and arbitrary frequency detuning of the qubits. We find that for weak qubits-waveguide couplings, the information preservation greatly depends on the position and the frequency detuning of the qubits, while for strong couplings, both of these dependence is significantly weakened. Interestingly, by suitably choosing the position and the frequency of the qubits, high information preservation could be achieved for both weak and strong couplings, irrespective to Markovian or non-Markovian dynamics. Physically, we analytically verify that the ability of information preservation is indeed determined by the existence of the bound states of the entire system, but the probability of information preservation is closely related to the probability of the initial state of the qubits in the bound states. Our results provide an alternative route getting high information preservation without any external controls of the system.

Automated summary

In this study, we investigate the preservation of quantum information in two maximally entangled qubits inside a photonic-crystal waveguide. We find that the preservation of information is weakened by the position and frequency detuning of the qubits in strong couplings. However, high information preservation can be achieved by choosing suitable positions and frequencies, regardless of weak or strong couplings.