CAREER: Quantum Cryptography With Entangled Photons

这项研究涉及开发一个使用双光子纠缠态的量子密码保护通信系统的实验原型，并对强调这项技术最终安全的物理原理进行详细的理论研究。通过电信渠道传输的私人和机密数据呈指数级增长，因此需要对其进行保护，以确保敏感信息的安全。基于大数因式分解的数学复杂性的传统加密仍然容易受到掌握大计算能力的不友好方的入侵。量子密码学旨在通过运用量子力学基本定律的力量来解决这个问题。在量子密码学中有两种主要的方法，它们在历史上几乎同时出现。一种是利用从相干态光导出的近单光子态。另一种依赖于自发参量下转换的非线性光学过程中产生的双光子纠缠态的非局域特性。设计了一种新的量子密码学方案，它克服了迄今为止困扰后一种系统在密码学中使用的限制，特别是需要同步操作在空间上完全分开的两个马赫-曾德尔干涉仪。该方法基于一种特殊的偏振量子强度干涉仪，并利用第二类自发参数下转换产生的双纠缠态。

This research involves the development of an experimental prototype of a quantum cryptographically protected communication system using two-photon entangled states of light, and a detailed theoretical study of the physical principles underlining the ultimate security of this technique. The exponentially growing flow of private and confidential data transmitted over telecommunication channels has brought with it the need for its protection to insure the security of sensitive information. Conventional encryption based on the mathematical complexity of factoring large numbers is still vulnerable to the intrusion of an unfriendly party in command of large computational power. Quantum cryptography was designed to address this issue by bringing to bear the power of the fundamental laws of quantum mechanics. There are two major approaches in quantum crytography which, historically, appeared nearly simultaneously. One makes use of near single-photon states derived from coherent-state light. The other relies on the nonlocal character of two-photon entangled states generated in the nonlinear optical process of spontaneous parametric down conversion. A new scheme for quantum cryptography has been designed which overcome the limitations that have heretofore plagued the latter systems for use in cryptography, particularly the requirement for synchronous manipulation of two Mach-Zehnder interferometers that are well separated in space. This new approach is based on the use of a special polarization quantum intensity interferometer and utilized doubly entangled states generated by type-II spontaneous parametric down conversion.