A Method for Transferring an Unknown Quantum State andIts Application

Abstract

We suggest a method for transferring an unknown quantum state.In this method the sender Alice first applies a controlled-not operationon the particle in the unknown quantum state and an ancillary particlewhich she wants to send to the receiver Bob. Then she sends the ancillaryparticle to Bob. When Alice is informed by Bob that the ancillary particleis received, she performs a local measurement on her particle and sendsBob the outcome of the local measurement via a classical channel.Depending on the outcome Bob can restore the unknown quantum state,which Alice destroyed, on the ancillary particle successfully. As anapplication of this method we propose a quantum secure directcommunication protocol. By introducing the decoy qubits the securityof the scheme is guaranteed.