利用非局域控制非门操作纯化三粒子纠缠态

提出了两套三粒子纠缠态的纯化方案.第一个方案选择部分纠缠GHZ态作为量子通道,利用具有一个控制位和一个靶位的非局域控制非门操作和采用集体么正操作及适当地制备三粒子A,B和C的初始态,可以以最佳几率2|β|2获得最大三粒子纠缠态.第二个方案选择EPR对作为量子通道,通过利用具有一个控制位和两个靶位的非局域控制非门操作和采用集体么正操作及适当地制备三粒子A,B和C的初始态,可以以与第一个方案相同的几率获得最大三粒子纠缠态.两个方案都可以推广到N粒子纠缠态的纯化.

Tripartite entanglement purification by non-local CNOT operation

Two schemes for tripartite entanglement purification are proposed.In the first scheme,a partially entangled GHZ state is chosen as quantum channel.By using nonlocal controlled-NOT(CNOT)operation,which has one control qubit and one target qubit,collection unitary transformation,and preparing the initial states of qubits A,B and C appropriately,the maximally tripartite entangled state can be obtained with the optimal probability 2|β|2.In the second scheme,an EPR pair is chosen as quantum channel.It is shown that the maximally tripartite entangled state can also be obtained with the same probability as the first scheme,by using another kind of nonlocal CNOT operation,which has one control qubit and two target qubits,collection unitary transformation,and preparing the initial states of qubits A,B and C appropriately. These two schemes can be generalized to purify N particles entangled state,respectively.