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Journal of Sichuan Normal University

Squeezing and Entanglement of the Output Field from the Closed-loop Atomic System

Jin Chen

Published Jan 1, 2014• 0 citations
OpenAlex

Abstract

The two-mode squeezing and entanglement of the output fields are generated by a three-level closed-loop atom interacting with two mode of the cavity.From the squeezing spectrum,we find that the width of squeezing(entanglement) spectrum is sensitive to the cavity decay rate.The depth of the the squeezing or entanglement spectrum is dependent on the microwave field.The results can be useful in realizing the controllable quantum communication.

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The two-mode squeezing and entanglement of the output fields are generated by a three-level closed-loop atom interacting with two mode of the cavity.From the squeezing spectrum,we find that the width of squeezing(entanglement) spectrum is sensitive to the cavity decay rate.The depth of the the squeezing or entanglement spectrum is dependent on the microwave field.The results can be useful in realizing the controllable quantum communication.
The dynamics behavior of output squeezing and entanglement is investigated, based on the off-resonant interaction of a four-level atom with a low-QQQ cavity and two classical fields. By means of the input-output theory, we show that the two-mode squeezing and entanglement of the output fields can always exist. It is found that the maximum entanglement is insensitive to the cavity decay rate, but can be optimized by adjusting the ratio between the effective coupling constants.
The generation and evolution of entanglement and squeezing for the two-mode fields are discussed in a cascade three-level atomic system. Two photons of a strong external pump field induce atomic coherence between the top and bottom levels. The dynamics of this system in the presence of cavity losses is studied. It is shown that entanglement and squeezing between the two modes increase initially, then decrease and eventually disappear. The periods of them are extended with the increasing of the pump field intensity. The effects of the cavity losses on squeezing and entanglement are also discussed.
We consider a three-level cascade laser in which a coherently driven non-degenerate three-level atom available in a closed cavity coupled to a twomode vacuum reservoir.Applying the interaction Hamiltonian and Heisenberg equation of motion, we analyze the mean photon number, quadrature squeezing, and entanglement properties of the light produced by this quantum optical system inside the cavity.We find that the light generated by this system is in a two-mode squeezed state under certain conditions and the state of the system is weakly entangled at steady state due to the presence of the two-mode vacuum reservoir noise.
We study the squeezing of output quadratures of an electro-magnetic field escaping from a resonator coupled to a general quantum system with arbitrary interaction strengths. The generalized theoretical analysis of output squeezing proposed here is valid for all the interaction regimes of cavity-quantum electrodynamics: from the weak to the strong, ultrastrong, and deep coupling regimes. For coupling rates comparable or larger then the cavity resonance frequency, the standard input–output theory for optical cavities fails to calculate the variance of output field-quadratures and predicts a non-negligible amount of output squeezing, even if the system is in its ground state. Here we show that, for arbitrary interaction strength and for general cavity-embedded quantum systems, no squeezing can be found in the output-field quadratures if the system is in its ground state. We also apply the proposed theoretical approach to study the output squeezing produced by: (i) an artificial two-level atom embedded in a coherently-excited cavity; and (ii) a cascade-type three-level system interacting with a cavity field mode. In the latter case the output squeezing arises from the virtual photons of the atom-cavity dressed states. This work extends the possibility of predicting and analyzing the results of continuous-variable optical quantum-state tomography when optical resonators interact very strongly with other quantum systems.
We consider two modes of the electromagnetic field interacting via a three-level atom in a ladder configuration. We calculate the squeezing spectra of the sum and difference of the two output beams. The usefulness of this system as a quantum-nondemolition-measurement scheme is analyzed and a prediction is made using the parameters of a recent experiment by Grangier et al. [Phys. Rev. Lett. 66, 1418 (1991)]. We use a full three-level model in the most general case and in particular the influence of both the one-photon and the two-photon detunings are investigated.