Interferometric phase estimation and quantum resource dynamics in Bell coherent-state superpositions generated via a unitary beam splitter

Abstract

Beam splitters are optical elements widely used in modern technological applications to split the initial light beam into a required number of beams, and they play a very promising role for generating entangled optical states. Here, a potential scheme is proposed to generate Bell coherent-state superpositions through the action of a beam splitter when a Glauber coherent state is injected on one input mode and a vacuum state is incident on the other. Different quantifiers are used to measure the quantumness in the output state, such as concurrence entanglement, entropic quantum discord, quantum coherence, geometric measure of quantum discord, local quantum uncertainty (LQU), and local quantum Fisher information. Thereby, we derive their analytical formulas and focus more on the behavior and bounds of each measure. Besides, we have introduced the notion of “weak measurement-induced LQU” captured by weak measurements as the generalization of normal LQU defined for standard projective measurement, and we investigate the effect of the measurement strength on the estimated phase enhancement if the generated Bell cat states are the probe states in quantum metrology. Our results suggest that the sensitivity of the interferometric phase estimation depends on how strongly one perturbs the probe state and that a weak measurement does not necessarily capture more quantumness in the composite system.