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Laser Physics

Coherence and squeezing of a two-level system with a phase jump

K. Berrada, Hichem Eleuch

Published May 23, 2019• 0 citations
Publisher

Abstract

Abstract By using the exact analytical solution and exploring the effect of ultra-short strong pulses in the presence of an external classical field for a two-level atom, we discuss the influence of the phase jump on the behavior of the atomic inversion, coherence and squeezing entropy during the time evolution of various pulse shapes. We show the optimal conditions to attain the phenomenon of coherence trapping. Moreover, we identify the range of physical parameters required for squeezing and its enhancement. The few-cycle pulses present new interesting features for controlling the physical quantities and are a good candidate to perform quantum optics tasks.

DOI
10.1088/1555-6611/ab0a6e

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Abstract By using the exact analytical solution and exploring the effect of ultra-short strong pulses in the presence of an external classical field for a two-level atom, we discuss the influence of the phase jump on the behavior of the atomic inversion, coherence and squeezing entropy during the time evolution of various pulse shapes. We show the optimal conditions to attain the phenomenon of coherence trapping. Moreover, we identify the range of physical parameters required for squeezing and its enhancement. The few-cycle pulses present new interesting features for controlling the physical quantities and are a good candidate to perform quantum optics tasks.
In this paper we consider the influence of phase damping on the Jaynes?Cummings model (JCM) in the presence of the classical laser field. It is shown that for the temporal evolution of the atomic inversion a detuning parameter plays a role in delaying the effect of the damping. Our consideration is also extended to discuss the atomic Wehrl entropy and entropy squeezing. For the case of the marginal distribution, it is noted that the damping factor plays a considerable role in reducing the number of the fluctuations in the function behavior. On the other hand the damping factor removes the phenomenon of squeezing from both quadratures of the entropy squeezing.
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Abstract This paper presents new results on some aspects of the properties of the entropy squeezing in the time development of a degenerate two-photon of a single-mode interacting with a two-level system with a nonlinear medium. A general analytic expression for the density matrix is obtained on the basis of a Hamiltonian generalized in that it includes nonlinear effects and Stark shifts, by means of which we identify and numerically demonstrate the region of parameters where significantly large squeezing can be obtained. The influence of various parameters on the entropy squeezing are explored. It is shown that features of the entropy squeezing were influenced significantly by changing the nonlinear medium, Stark shift and the detuning. The results show that, certain amounts of the nonlinear effect yield the superstructure of atomic Rabi oscillation and changes the quasiperiod of the entropy evolution and atomic inversion.
We consider a double two-level system in which each single two-level system is driven by a strong pulse. The light shifts induced by the strong field are probed by a weak pulse that connects the two sub-system in a crossed manner connecting the ground state of one system with the excited state of the other and vice versa. We are interested in coherent control of medium gain for the weak pulse and we demonstrate the conditions on laser and atomic parameters that render this control possible. Both ultra-short and long pulse regimes are discussed
Entropy squeezing is an important feature in performing different tasks in quantum information processing such as quantum cryptography and superdense coding. These quantum information tasks depend on finding the states in which squeezing can be created. In this article, a new feature on entropy squeezing for a two level system with a class of nonlinear coherent state (NCS) is observed. An interesting result on the comparison between the coherent state (CS) and NCS is explored. The influence of the Lamb-Dick parameter in both absence and presence of the Kerr medium is examined. A rich feature of entropy squeezing in the case of NCS, which is observed to describe the motion of the trapped ion, has been obtained.