Entanglement Manipulation for a Two-Mode Squeezed Vacuum State

By numerically analysing the entropy of entanglement of the output state from a Mach--Zehnder interferometer for the two-mode squeezed vacuum state input, it is found that if the internal phase shift of the interferometer is adjusted to the value of 0 or π, the entangling characteristic of the input state is efficiently preserved at the output. If the internal phase shift is tuned to the value of π, the two-mode squeezed vacuum state is completely disentangled at the output of the setup. If the internal phase shift deviates from the above values, the input state is degraded into a partially entangled output state. Based on these results, a method for optically realizing the entanglement preservation, entanglement degradation, and disentanglement via the interferometer is obtained.