Uma nova abordagem para experimentos com luz comprimida: explicações sem estados comprimidos e sem emaranhamento em dois modos

Abstract

Although the quantum state of a laser field is generally treated as a coherent state in quantum optics, the unknown absolute phase of the laser allows it to be represented as a statistical mixture of coherent states with random phases, equivalent to a statistical mixture of Fock states. Using this perspective, we show that by employing a Fock state for the laser, we can generate experimental predictions consistent with those obtained by assuming a coherent state, but with different physical explanations. We apply these concepts to single-mode and two-mode squeezed light experiments, demonstrating that typical experimental results can also be predicted by considering the laser field in a Fock state or in a mixture of Fock states, and we conclude that, besides no squeezed state being produced, in the case of two-mode squeezed vacuum experiments, there is no entanglement between the "twin" beam modes of signal and idler. We provide a general physical explanation for the noise reduction in the experiments using the concept of relative phase probability distribution, initially proposed by Luis and Sánchez-Soto [1], and we generalize the two-mode relative phase distribution proposed by Luis and Sánchez-Soto to handle four optical modes: signal, idler, and two local oscillators. The physical explanation is based on a better definition of phase relation, either between the signal field and the field used as the local oscillator in the case of single-mode squeezed vacuum experiments, or the relation among the four optical modes involved in the case of two-mode squeezed vacuum experiments: signal, idler, and two local oscillators.