Enhancing quantum entanglement for continuous variables by a coherent superposition of photon subtraction and addition

Abstract

We investigate how the entanglement properties of a two-mode state can be improved by performing a coherent superposition operation tâ + râ † of photon subtraction and addition, proposed by Lee and Nha [Phys. Rev. A 82, 053812 (2010)], on each mode. We show that the degree of entanglement, the EPR-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 additionâ † particularly in the small squeezing regime, whereas the optimal operation becomes the photon subtraction (case of r = 0) in the large-squeezing regime.

Nonclassical properties of nonlocal coherent photon-added two-mode squeezed thermal states

“…(10a), (11), (19), and (20), we can compute numerically the ab SV criteria as shown in Fig.6 and Fig.7. Fig.6 gives relation curve between the SV criteria of the two-mode optical fields and the squeezed parameter r with 0.01 n  …”

“…On the other hand, one extensively investigated the statistical properties of TMSVstate. Lee et al analyzed a coherent superposition of photon subtraction and addition to TMSVstate and found quantum entanglement of TMSVstate is enhanced [19].…”

Quantum Properties of Single-Mode Squeezing and Two-Mode Squeezing Repeated Role Two-Mode Vacuum State

“…On the other hand, photon subtraction and addition represented by bosonic annihilation operator a and creation operator a + can be employed to transform a field state to a desired one [5]. There are a large number of reports describing operator acting on light field state to generate new quantum state [6][7][8][9][10][11][12][13]. For example, Xu et al have constructed a generalization squeezed Fock state by squeezed operator with three real parameters acting on three-mode Fock state [6], and studied its nonclassical property and decoherence.…”

Nonclassicality generated by repeatedly operating photon annihilation-then-creation and creation-then-annihilation on squeezed vacuum

“…It is shown that these operations enable us to generate highly nonclassical quantum states [8], such as photon-addition coherent state, photon-added thermal states [9][10][11], photon-subtracted squeezed states [12,13], and so on. In addition, single photon operations such as photon subtraction and addition can enhance quantum linear amplifier [14], continuousvariable quantum key distribution [15], entanglement [16][17][18][19], nonlocality [21][22][23], multipartite quantum correlation [20], and the fidelity of continuous variable teleportation [24][25][26]. The entanglement distillation can also be achieved by performing photon subtraction or addition combined with coherent displacement or local squeezing [27][28][29].…”