Spectral effects of strong χ(2) nonlinearity for quantum processing

作     者：Patrick M. Leung William J. Munro Kae Nemoto Timothy C. Ralph 

作者机构：Department of Physics Centre for Quantum Computer Technology University of Queensland Brisbane 4072 Australia Hewlett-Packard Laboratories Filton Road Stoke Giord Bristol BS34 8QZ United Kingdom National Institute of Informatics 2-1-2 Hitotsubashi Chiyoda-ku Tokyo 101-8430 Japan 

出 版 物：《Physical Review A》 (物理学评论A辑：原子、分子和光学物理学)

年 卷 期：2009年第79卷第4期

页      面：042307-042307页

核心收录：

学科分类：070207[理学-光学] 07[理学] 08[工学] 0803[工学-光学工程] 0702[理学-物理学] 

基　　金：Australian Research Council IARPA-funded (U.S.) Army Research Office [W911NF-05-0397] EU Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan 

主　　题：Technology transfer 

摘      要：Optical χ(2) nonlinearity can be used for parametric amplification and producing down-converted entangled photon pairs that have broad applications. It is known that weak nonlinear media exhibit dispersion and produce a frequency response. It is therefore of interest to know how spectral effects of a strong χ(2) crystal affect the performance. Here we model the spectral effects of the dispersion of a strong χ(2) crystal and illustrate how this affects its ability to perform Bell measurements and influence the performance of a quantum gates that employ such a Bell measurement. We show that a Dyson series expansion of the unitary operator is necessary in general, leading to unwanted spectral entanglement. We identify a limiting situation employing periodic poling, in which a Taylor series expansion is a good approximation and this entanglement can be removed.