Improvement of the entanglement properties for entangled states using a superposition of number-conserving operations

Abstract

The non-Gaussian operation, which can be easily implemented by current techniques, is an effective way for the improvement of the continuous-variable entanglement. Here, we theoretically propose a scheme for generating a number-conserving two-mode generalized superposition of products (TM-GSP) state by performing the (m, n)-order GSP operations i.e.Then, the entanglement properties of the TM-GSP state are analyzed detailedly by means of logarithmic negative, Einstein-Podolsky-Rosen (EPR) correlation and two-mode squeezing property. It is shown that, in contrast to the TMSV case, for the optimal choices of s 1 and s 2 , the entanglement properties of the TM-GSP state can be improved by using symmetric GSP operations (m, n) and single-side GSP operations (0, n). Furthermore, the fidelity effect is also considered when the TM-GSP state is used as the entangled resource under the Braunstein and Kimble scheme. In terms of the optimal teleportation fidelity, it is found that the effect of the single GSP operation (0, 2) is equivalent to that of the case (1,1). This phenomenon also exists in logarithmic negative, EPR correlation and two-mode squeezing property. These results show that the prepared TM-GSP state may provide a well application in the fields of quantum information processing.

Nonclassicality and entanglement properties of non-Gaussian entangled states via a superposition of number-conserving operations

“…First, we pay attention to the EPR correlation, which can be described as the total variance of a pair of EPR-type operator [12,20,21,23,24]…”

“…Fortunately, most of the theoretical [12][13][14][15][16][17][18][19][20][21][22][23][24] and experimental [25][26][27][28] investigations show that the non-Gaussian operations, including photon subtraction a, photon addition a † and their coherent superposition, are used for effectively improving the nonclassicality and entanglement degrees of quantum states, thereby making these operations more potential in quantum information processing [29][30][31]. For example, Agarwal and Taral showed that the higher nonclassical quantum state can be prepared by performing the photon addition on a coherent state [17], and then Zavatta et al experimentally demonstrated the existence of the nonclassicality of single photonadded thermal states [26].…”

Representation of the coherent state for a beam splitter operator and its applications

“…On the other hand, quantum entanglement is an important resource for realizing quantum information tasks. Facing the real situation where the entanglement degree of the prepared entanglement source is low, lots of researchers have proposed methods that use non-Gaussian operations [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], such as photon addition, photon subtraction, photon catalysis, etc, to further increase the degree of entanglement. Using these proposed states as entangled sources, quantum tasks can be better implemented, such as quantum teleportation.…”

“…the derivation of equations(30),(8) and(10) are used. The completeness of equation(31) is just the reason that the entangled state yñ out | is called the quantum mechanical representation.On the other hand, using the representation equation (14) under the coherent state representation of the BS operator, the Schmidt decomposition of yñ , is just an entangled state representation and equation(31) is the Schmidt decomposition showing the entanglement.…”

Improving phase estimation using the number-conserving operations

“…In particular, the first two have been used to improve entanglement and fidelity of quantum teleportation, but none of them are used to improve phase measurement accuracy. Not only can this GSP operation be implemented experimentally, proposed by Kim [37], but also the GSP operation on the TMSV is able to generate a strongly entangled non-Gaussian state as well [38,39].…”