The dynamic response of the inversion in a two-level atom to single-mode squeezed states of the radiation field is examined. Depending on the direction of squeezing, an increase or decrease in the collapse time is demonstrated. A number of additional departures from the response of the atom to a coherent field are noted. In particular, for certain squeezed states the response of the atom is similar to that expected for chaotic radiation.

Interaction of a Two-level Atom with Squeezed Light

We study the spectrum of squeezing in the light transmitted by a system of two-level atoms in an optical cavity driven by a coherent field, as recently observed by Kimble and collaborators. Our analysis does not introduce any restriction on the detuning parameters or on the relative order of magnitude of the atomic and cavity relaxation rates. Using the dressed-mode formalism, we derive explicit analytic expressions for the spectrum of squeezing and for the second-order intensity correlation function. We describe how the spectrum depends on the various parameters of the system; this study provides general indications on how to optimize the conditions to observe squeezing in optical bistability. A special attention is devoted to the changes of the spectrum under variation of the detuning parameters or of the ratio of cavity to atomic-damping rate. In all cases, the changes are continuous and smooth, with quantitative variations in the level of squeezing. This indicates the existence of a single avenue to squeezing in this system. The bad-cavity direction is identified as especially conventient to obtain a significant amount of squeezing.

Squeezing in optical bistability without adiabatic elimination

Second harmonic generation and statistical properties of light

The change in nature of light in propagation through a lossless isotropic nonlinear Kerr medium is studied. Considering a monochromatic unidirectional light beam, we see that coherent light remains coherent but the polarization state changes in general, and completely unpolarized light retains its nature in all respects. For a light beam having a coherent signal and unpolarized noise, a change in polarization state of the signal and depolarization occurs in general. For circular and plane polarized signals, the polarization states of the signal do not change and depolarization is absent for the former and maximum for the latter. Numerical calculations for a practical case indicate that these effects are observable.

https://iopscience.iop.org/article/10.1088/0953-4075/41/4/045401/pdf

Change in coherence properties and degree of polarization of light propagating in a lossless isotropic nonlinear Kerr medium

Statistical behaviour of the Nth subharmonic generated in a resonator well above threshold is examined. By including losses and using adiabatic elimination of pumping together with linearization of Heisenberg equations of motion, the stability of stationary solutions, their statistics and quadrature noises are calculated for any integer N > 1. It is proved that squeezing is maximal near the threshold and photon statistics are super-Poissonian.

Photon Statistics of the Nth Subharmonics

An ultimate limit to the sensitivity achieved by detectors for gravitational radiation is set by quantum fluctuations. All detection systems are subject to this limit, however we shall restrict our attention to the affect of quantum fluctuations on optical detection systems such as the Michelson interferometer. The techniques developed to treat quantum fluctuations in optical systems may prove to be useful in analysing other detection systems. In a Michelson interferometer quantum fluctuations may affect the final measurement in two ways; namely photon counting fluctuations and radiation pressure fluctuations. The effect of these sources of error oil the interferometer detection scheme have been discussed by Caves and by Unruh. Caves suggested that these errors could be reduced by injecting special states of the radiation field with reduced fluctuations into one port of the interferometer. These states called “squeezed states” show reduced fluctuations in one quadrature and enhanced fluctuations in the other4–8. They also play a general role in quantum non demolition (Q.N.D.) measurements9 since the state of a system after certain Q.N.D. measurements (back action evading measurements) resembles a squeezed state.

D. F. Walls

Papers

Quantum Fluctuations in Nonlinear Optics