Reconstruction of bipartite states via unambiguous state discrimination and mutually unbiased measurement
We propose a scheme for reconstructing an unknown two-particle mixed state by means of unambiguous state discrimination. In this protocol, an ancillary particle is introduced for distinguishing four nonorthogonal states. The discrimination process is performed by a bipartite unitary operation on the two-particle system and the ancilla followed by a von Neumann measurement on the ancilla. Then the original two-particle system is measured in mutually unbiased bases. Consequently, the two-particle mixed state can be reconstructed. Furthermore, the total number of measurements in this protocol is less than that of the standard quantum tomography, thus the quantum resources is saved. Additionally, the nonorthogonal states discrimination and mutually unbiased measurement can be experimentally achieved, therefore our protocol may be realized with the current technology.
unambiguous state discrimination mutually unbiased measurement von neumann measurement quantum state tomography