Enhancing quantum entanglement for continuous variables by a coherent superposition of photon subtraction and addition
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We investigate how the entanglement properties of a two-mode state can be improved by performing a coherent superposition operation ta+ra of photon subtraction and addition, proposed by Lee and Nha [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.82.053812 82, 053812 (2010)], on each mode. We show that the degree of entanglement, the Einstein-Podolsky-Rosen- type correlation, and the performance of quantum teleportation can be all enhanced for the output state when the coherent operation is applied to a two-mode squeezed state. The effects of the coherent operation are more prominent than those of the mere photon subtraction a and the addition a particularly in the small-squeezing regime, whereas the optimal operation becomes the photon subtraction (case of r=0) in the large-squeezing regime. 2011 American Physical Society.