Multiqubit Nonlocal Operation and Physical Implementation

We propose a scheme of preparing four-atom cluster states in thermal cavity. Four two-level atoms, three thermal cavities and classical field are used in the scheme. Compared with previous schemes, the scheme can be generalized to n-atom cluster states and the successful probability can be 100%, which the system of the photon can never reach. In addition, the system is insensitive to cavity decay and the thermal field. Using the four-atom cluster state, we also propose a simpler scheme for remote controlled not gate （CNOT）, in which we detect the separate states instead of the joint-Bell states measurement.

Multiqubit Nonlocal Operation and Physical Implementation

Two subsystems A and B prepared in the maximally entangled state simultaneously interact with two spatially distant quantum systems, then muhiqubit nonlocal operation on the two quantum systems is directly implemented after measuring the states of subsystems A and B in reasonable bases. In this paper, we have also presented a physical system for realizing the idea above, where certain practical sources of noise simply decreases the success probability but exerts no influence on the fidelity of nonlocal operation.