We show that squeezed states can be generated by the interaction of coherent electromagnetic radiation with a plasma. Inside the plasma the electromagnetic field is represented by quasiphotons. The conditions for obtaining squeezed states in this system are related to dispersion relations of the quasiphotons in the plasma.
A theory is developed for the interaction of coherent electromagnetic (EM) radiation with a free electron gas and for the influence of the plasma on the photon statistics of the radiation field. Two important possibilities for generating squeezed states are shown: Squeezed states can be generated by the interaction of a one-mode laser with a plasma in a cavity; squeezed states can be generated by transmitting coherent radiation through the plasma. The maximal squeezing of the radiation obtained in the latter case is equal to the reciprocal of the dielectric constant of the plasma. Inside the plasma the EM field is represented by quasiphotons. Their dispersion relations are derived by using Bogoliubov transformations together with a self-consistency requirement for the motion of the electrons interacting with these quasiphotons. The squeezing processes are found to be strong when the frequency of the radiation is a little above the plasma frequency. By adding a constant magnetic field in the direction of propagation of the EM wave different amounts of squeezing are obtained for right- and left-circularly polarized EM waves.
We propose a conditional generation of quantum squeezing from realistic single-photon states. The proposed method does not require any coherent measurement projecting on a superposition of internal levels inside single-photon emitters. Interestingly, the squeezing can be generated despite a low single-photon efficiency of the emitters. The method can therefore substantially enlarge the set of existing sources of the squeezed states of electromagnetic radiation. For example, it can be used to produce squeezed ultraviolet radiation based on already available ultraviolet single-photon emitters.
We show by explicit calculations that non-classical states of the radiation field can be produced by allowing short term interaction between a coherent state of the radiation field with plasma. Whereas, long term interaction, which thermalizes the radiation field, can produce non-classical states of the radiation field only at sufficiently small temperatures. A measure of k-th order squeezing, stricter than the one proposed by Zhang et al, is used to check the emergence of squeezing. It is also shown that photons in the considered thermalized field would follow super-Poissonian statistics.
The effects of the Stark interaction in the collective radiation of an ensemble of atoms in the field of a broadband electromagnetic field in a squeezed quantum state have been considered. It has been shown that the inclusion of the conditions for the formation of the squeezed field allows one to describe the dynamics of atoms in terms of random quantum creating, annihilating, and counting processes. The latter process is the Stark interaction of atoms and the field and manifests itself in the form of a trigger superradiance pulse generated by an ensemble of identical atoms excited by a quantized resonant squeezed electromagnetic field. The description is based on the kinetic equation derived for an open localized quantum system in a broadband squeezed quantized electromagnetic field. The resulting equation differs from the known ones, but agrees with them in particular and limiting cases.
This paper develops a method of manipulating the squeezed atom state to generate a few-photon state whose phase or photon-number fluctuations are prescribed at our disposal. The squeezed-atom state is a collective atomic state whose quantum fluctuations in population difference or collective dipole are smaller than those of the coherent atom state. It is shown that the squeezed-atom state can be generated by the interaction of atoms with a coherent state of the electromagnetic field, and that it can be used as a tunable source of squeezed radiation. A variety of squeezed states, including the photon-number squeezed state and the phase squeezed state, can be produced by manipulating the atomic state. This is owing to the fact that quantum-statistical information of the atomic state is faithfully transferred to that of the photon state. Possible experimental situations to implement our theory are discussed.