The Research On The Quantum Clone Of Four-qubit Entangled States

Quantum entanglement is an important information resource of quantum cloning,four-qubit entanglement has more special entanglement structure and properties,thus,its application would generate many special phenomena in quantum cloning.Therefore,the study on four-qubit quantum cloning has been widely spread in recent yearsThis paper introduced the theory of quantum remote 1?2 approximate cloning for the two-qubit and the three-qubit entanglement.The quantum remote cloning scheme was utilized to study the 1?2 approximate cloning of four-qubit entangled state,the mainly research results were as followsFirstly,based on the single quantum channel,the study on three different kinds of unknown four-qubit GHZ state of quantum remote approximate cloning was made and extended to remote cloning of all unknown GHZ states.In the measurement phase,the sender Alice can conduct measurement based on Bell and projection measurement based on Hadamard transformation.After the measurement,the measurement results would be transmitted to the receiver Bob and Charlie through the classical channel.In recovery phase,the corresponding quantum recovery operations was conducted according to the characteristics of the input state by Bob and Charlie.And the fidelity of output state was calculated according to the characteristics of the input state.The result demonstrated the fidelity of output states were 5/6 in all cloning schemes,confirming the developed scheme was generalSencondly,we came up with three kinds of unknown type four-qubit GHZ state of quantum remote approximate cloning,which was extended to remote cloning of all unknown type GHZ states based on two quantum channels.In the quantum measurement phase,Alice performed three times of Bell based joint measurements.In recovery phase,the corresponding quantum recovery operations was conducted according to the characteristics of the input state by Bob and Charlie.By calculating the fidelity of output state,it was found that the fidelity was in the ranges from 21/36 to 25/36.Further,the change curves of the fidelity with the input state parameters was discussed.In summary,the selection rule of additional particle in recovery stage was received about four-qubit GHZ state quantum remote approximate cloning.The advantages and disadvantages of the two schemes were compared.The research provided theoretical guidance for the channel selection of multi-qubit entangement state in quantum cloning.