基于低Q腔光子Faraday旋转的远程态制备

基于低Q腔中单光子的输入与输出关系,提出了利用偏振光Faraday旋转分别遥远制备单原子态和两原子纠缠态的可行方案.研究结果表明,当初始原子态的系数为实数时,通过选择合适的偏振光、腔场与原子相互作用系统的参数,单原子态与两原子纠缠态的远程制备均可确定性地得以实现.与以前的原子态远程制备方案相比,本文方案采用光子作为飞行比特来传递量子信息,故原则上可实现原子态的真正长距离制备.由于原子态的信息编码在耗散单边腔囚禁的Λ型三能级原子的两个基态能级,且原子仅虚激发,因此本文方案对腔衰减和原子自发辐射不敏感.此外,本文所提出的两种方案不需要两体或多体正交测量,仅涉及单体直积态测量,而且两种方案都工作在低Q腔,不需要原子与光腔的强耦合,从而有效降低了实验难度.

Remote state preparation via photonic Faraday rotation in low-Q cavities

Based on the input-output relation in low-Q cavities, we propose a feasible scheme to prepare remotely a single-atom state via photonic Faraday rotation, and then the scheme is generalized to the case of remote preparation of a two-atom entangled state. Our results show that when the coefficients of the initial atomic state to be prepared are real, both remote preparation of the single-atom state and that of the two-atom entangled state can be achieved deterministically by selecting appropriate parameters of the systems for the interactions among the atom, polarized single-photon pulse, and cavity field. Compared with the existing schemes for remote preparation of atomic states, in our scheme photons are used as flying qubits to transmit quantum information, which is suitable indeed to achieve a long-distance atomic state preparation in principle. Due to the fact that the information of atomic state is encoded in two degenerate ground-state levels of a Λ-type three-level atom confined in a unilateral dissipative cavity, and that the atoms are only virtually excited, our schemes are insensitive to both cavity decay and atomic spontaneous emission. Besides, the two schemes we proposed do not need two- or multi-particle orthogonal measurements, only product-state measurements are involved, as well as they work in low-Q regime and do not require a strong coupling condition between the atoms and the optical cavities, which greatly reduce the experimental difficulty.