腔场初始态对两量子比特空间退相干的影响

研究了两个二能级原子与一个单模腔场的相互作用中,腔场的不同初始态对原子间相对位置退相干的影响。从描述原子间相对位置状态的约化密度矩阵出发,假设原子间相对位置为两个高斯波包的叠加态,讨论了当腔场初始态分别为热态、Fock态和压缩态情况下,原子与光场的相互作用对两原子间相对位置相干性的影响。发现腔场的初始态不同,原子间相对位置的退相干情况有所不同。当腔场初始态为热态或Fock态时,原子间相对位置的相干性会周期性的衰减和回复,而当腔场初始态为压缩态时,原子间相对位置会出现部分退相干,且退相干程度与原子间相对位置的大小成余弦变化关系。

Spatial Decoherence Dynamics of Two Qubits Induced by Initial States of Cavity field

We study the spatial decoherence dynamics for the relative position of two atoms interacting with a single-mode cavity which are assumed initially in three different states. It is assumed that the atomic relative position is in the state of a superposition of two Gaussian wave packets and that the cavity field is initially in thermal state, Fock state and squeezed state respectively. Based on the reduced density matrix for the atomic relative position, we study the influence of the atom-field interaction on the quantum coherence of atomic relative position. We find that for different initial states of the cavity field, the quantum decoherence dynamics of the atomic relative position is different. When the cavity field is initially in a thermal state or Fock state, the spatial coherence oscillates with decay and revival periodically, while when the cavity field is initially in a squeezed state, the spatial coherence of the two-atom relative position is partially destroyed, and the decay degree is connected with the value of the atomic relative position in a cosine law.