利用双通道级联型原子库实现辐射场双模压缩真空态

The Generation of Two-mode Squeezed Vacuum of Radiation Field from Two-channel Atomic Reservoir

本文研究了利用双级联型四能级原子实现高纯度、强的双模腔场压缩纠缠态。考虑将四能级联型原子注入至一个双模腔中,腔场与原子能级形成共振的相互作用。在原子-腔场弱相互作用下,若原子自发辐射速率远大于腔场的衰减速率,在腔场相干时间内将原子视为腔场的外部环境库,我们推导出腔场所满足的主方程。通过分析主方程并发现：在不考虑腔场真空耗散的情况下,腔场等效地与一个双模压缩真空库耦合,因此在稳态区域处于纯的双模压缩真空态,并且压缩程度只依赖于原子初始上能级的布居;在考虑腔场耗散的情况下,耗散对其纯度的影响大于对纠缠的影响;与单通道原子库情况比较,利用双通道的原子库可以有效地提高腔场的纠缠和纯度。

In this paper,we investigate the generation of stationary entangled state of a two-mode cavity field via injecting into the cavity a beam of four-level atoms with two channels of two-photon cascaded transition.By treating the atomic beam as the external reservoir for the cavity field in weak cavity-atom interactions,we find that a two-mode squeezed vacuum reservoir of the cavity field can be achieved by using the atomic system.Therefore,in the steady-state regime,the cavity field can be driven into the two-mode squeezed vacuum when neglecting the cavity dissipation.The squeezing degree only depends on the initial population of the atomic upper level and thus strong squeezing can be generated in principle.We also reveal that the entanglement between the two cavity fields is less affected by the cavity damping than the purity of the entangled cavity field state.In addition,our two-channel scheme can effectively improve the entanglement and purity of the entangled cavity field,compared to the previous single-channel proposals.