| Abstract: | We present a scheme for quantum privacy amplification (QPA) for a
sequence of single qubits. The QPA procedure uses a unitary
operation with two controlled-not gates and a Hadamard gate. Every
two qubits are performed with the unitary gate operation, and a
measurement is made on one photon and the other one is retained.
The retained qubit carries the state information of the discarded
one. In this way, the information leakage is reduced. The
procedure can be performed repeatedly so that the information
leakage is reduced to any arbitrarily low level. With this QPA
scheme, the quantum secure direct communication with single qubits
can be implemented with arbitrarily high security. We also exploit
this scheme to do privacy amplification on the single qubits in
quantum information sharing for long-distance communication with quantum repeaters. |
