任意多体高维偏振纠缠态的有效制备

纠缠态与高维量子态是量子信息科学关注的焦点，在光学领域，如何有效制备高维纠缠态是值得探讨的问题．基于交又相位调制技术，利用单光子高维空间态作为辅助，通过纠缠光子对与单光子之间的相互作用，以及多光子的干涉，可以制备出任意系数的两体高维偏振纠缠态．其成功概率由高维偏振量子态，也就是多光子干涉决定．同时，这一方案可以很容易推广到任意多体高维偏振纠缠态的制备．所制备纠缠态的灵活性，将为研究高维纠缠态的性质、多体相互作用等问题提供一定的便利．

Efficient generation of arbitrary multi-partite, polarized entangled qudits

Quantum entanglement plays a crucial role in the area of quantum information processing, which was widely used in various quantum information tasks. With the development of quantum information, more and more attentions are paid to high dimensional quantum state and entangled state, since higher dimension means stronger nonlocality, which enables securer and more powerful quantum information processing. Thereafter, how to create entangled qudits efficiently is worth discussed, which is the motivation of this paper. Based on the technique of cross phase modulation, we firstly introduce a single-photon qudit （n-dimension） encoded by spatial mode as ancilla, and then let it interact with n pairs of Bell states in the Kerr medias respectively. Finally, the arbitrary two-partite polarized entangled qudits could be generated after the multi-photon interference. This approach could be directly generalized to the generaion of arbitrary multi-partite polarized entangled qudits. The interactions between an ancilla single-photon qudit and n multi-photon GHZ states, associated with multi-photon interference＇,, will yield the desired arbitrary multi-partite polarized entangled qudits. Except of the inevitable multi-photon interference, which is used to generate polarized qudit from single photons, all the generation processes are deterministic, tlherefore the generation efficiency is higher than the former proposals. In addition, using quantum nondemolitioa detection module to preserve two cases that all the single photons appear in the same spatial mode, the success probability of multi-photon interference, i.e., the generation of entangled qudits could be increased. Furthermore, the generated multi-partite polarized entangled qudits are flexible, whose coefficients could be adjusted flexibly by the single-photon unitary operations used in the generation of single-photon qudit. Thanks to this flexibility, it is convertient for the research of the property of entangled qudits and the many-body problem.