The Vacuum in Quantum Optics

Nikolay N. Rosanov

Ian S. Osborne

Quantum Optics According to quantum mechanics, a vacuum is not empty space. A consequence of the uncertainly principle is that particles or energy can come into existence for a fleeting moment. Such vacuum or quantum fluctuations are known to exist, but evidence for them has been indirect. Riek et al. present an ultrafast optical based technique that probes the vacuum fluctuation of electromagnetic radiation directly. Science , this issue p. [420][1] [1]: /lookup/doi/10.1126/science.aac9788

Chunguang Du, Shiqun Li

The effect of a squeezed vacuum on the optical bistable and multistable behaviour of a system of N three-level atoms is investigated, where the quantum interference between the atomic transition paths is considered. It is shown that the squeezed vacuum can profoundly affect the output field of this system. A strong squeezed vacuum can lead to multistable behaviour, even in the case where the cooperation parameter C is so small that the input–output relationship curve is monotone in the absence of the squeezed vacuum. The optical multistability is most significant when the quantum interference is perfect. The bistability and multistability can be controlled by the squeezing photon number and the strength of the two-photon correlation.

S. Olivares

Z. Y. Ou, Silvania F. Pereira, Harry J. Kimble

Quantum fluctuations in optical amplification are investigated with a nondegenerate optical parametric amplifier whose internal idler mode is coupled to a squeezed vacuum. Reductions of the inherent quantum noise of the amplifier are observed with a minimum noise level 0.7 dB below the usual noise level of the amplifier with its internal idler mode in a vacuum state. With a small coherent field as the signal input, the amplified output exhibits an improvement in signal-to-noise ratio of 0.5 dB for the case of a squeezed-vacuum as compared to a vacuum state for the amplifier's internal mode.

S. Chua