基于交叉克尔非线性的超纠缠纯化

Hyper-Entanglement Purification Via Cross-Kerr Nonlinearity

量子信息处理中许多任务都要求量子通道必须是最大纠缠态,但最大纠缠态不可避免地要受到环境噪声等因素的影响,变成部分纠缠态或混合态,因此纠缠纯化至关重要。早期人们基于交叉克尔非线性主要针对单个自由度进行纯化,或者用超纠缠的一个自由度去纯化另一个自由度,很少有方案涉及到超纠缠纯化。提出了一种基于交叉克尔非线性的超纠缠纯化方案,几乎确定性地实现了空间自由度和偏振自由度两个自由度的纯化。该方案只需要线性光学元件、弱的克尔非线性、强的相干光场和零差探测。

For many tasks in quantum information processing,the quantum channels should be preferred in maximally entangled states.However,noise will degrade the entanglement of a photon pair or even turn it into a mixed state.So entanglement purification is a very important element for long-distance quantum communication.The purification has been studied by some groups.But,few schemes are proposed to purify the hyperentangled states.We present a scheme for hyper-entanglement purification via cross-Kerr nonlinearity.The advantage of this scheme is the achievement of the entanglement purification in polarization modes and spatial modes.The scheme is based on linear optical elements,weak cross-Kerr nonlinearity,and homodyne detection.