Calculation Of Entanglement Entropy For Bipartite Continuous-Variable Entangled State

Quantum entanglement plays a key role in quantum mechanics as well as quantum information theory, and entangled states are useful resources for various kinds of quantum information processing, including teleportation, cryptographic key distribution, quantum error correction and quantum computation. Thus, it is interested to measure the entanglement of the entangled states.This paper is concentrated on the calculating the entanglement entropy of bipartite continuous-variable entangled states in Fock space. By virtue of the linear quantum transformation theory (LQTT), We obtain a general form of any bipartite pure Gaussian state in Fock space. To calculate the entanglement entropy of the entangled state with the general form, an explicit formula is derived and analyzed in detail. The simplicity and generality of the formula are shown by some continuous-variable systems.Our works are useful in practice for providing a simple method to calculating the entanglement entropy of any bipartite pure Gaussian state.