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Indian Journal of Scientific Research

Spin Squeezing and Quantum Entanglement in interaction of two excited two-level atoms with a single mode coherent radiation

Rakesh Kumar

Published Jan 1, 2015• 0 citations
OpenAlex

Abstract

In the present paper, we study the relation between spin squeezing and entanglement in two two-level atoms interacting with a single mode coherent field. We use the negativity criterion for the measurement of entanglement and obtain results considering atoms in excited states initially. We conclude that our recently reported criterion for spin squeezing is suitable for characterizing entanglement of composite systems.

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The ability of parameter recently proposed by Sorensen et al. (Nature, 409, 63 (2001)) to characterize entanglement or inseparability is investigated for a system of two two-level atoms interacting with a single mode of radiation field. For comparison we employ the necessary and sufficient criterion of Peres and Horodecki for inseparability of bipartite states. We show that for diagonal atomic density matrix the parameter of Sorensen et al. fails to show entangled nature of collective atomic state whereas same state is inseparable in accordance with Peres-Horodecki criterion.

arXiv:quant-ph/0110032•Oct 5, 2001•1 citation
In the present paper, we study the relation between spin squeezing and entanglement in two two-level atoms interacting with a single mode coherent field. We use the negativity criterion for the measurement of entanglement and obtain results considering atoms in excited states initially. We conclude that our recently reported criterion for spin squeezing is suitable for characterizing entanglement of composite systems.
This paper investigates the entropy squeezing of a moving two-level atom interacting with the two-mode entangled coherent field via two-photon transition by using an entropic uncertainty relation and the degree of entanglement between the two-mode fields by using quantum relative entropy. The results obtained from numerical calculation indicate that the squeezed period, the duration of entropy squeezing and the maximal squeezing can be controlled by appropriately choosing the intensity of the light field, the atomic motion and the field-mode structure. The atomic motion leads to the periodic recovery of the initial maximal degree of entanglement between the two-mode fields. Moreover, there exists a corresponding relation between the time evolution properties of the atomic entropy squeezing and those of the entanglement between the two-mode fields.
The interaction between two Ξ -type three-level atoms and a single-mode cavity field in the intensity-dependent coupling regime has been studied. The exact analytical solution of the wave function for the considered atom–field system has been obtained by using the Laplace transform technique when the atoms are initially prepared in the excited state and the field is in a coherent state. The presented structure has the potential ability to generate various new classes of entangled states depending on the chosen nonlinearity function. Two forms of intensity-dependent coupling as well as constant coupling are considered. Some important physical properties such as quantum entanglement, quantum statistics and quadrature squeezing of the corresponding states are investigated, numerically, by which the nonclassicality features of the produced entangled state are well-established. In particular, the effect of intensity-dependent coupling on the degree of entanglement between different bipartite partitions of the system (that is, 'atom atom'-field and 'field atom'-atom) using the linear entropy is investigated. At the same time, by paying attention to the negativity as a useful measure, the entanglement between the two atoms is studied in detail.
We consider a system of NNN two-level atoms (spins) interacting with the radiation field in a dispersive but high-QQQ cavity. Under an adiabatic condition, the interaction Hamiltonian reduces to a function of spin operators which is capable of producing spin squeezing. For a bipartite system (N=2)(N=2)(N=2), the expressions for spin squeezing get very simple, giving a clear indication of close to 100% noise reduction. We analyse this squeezing as a measure of bipartite entanglement.
The light squeezing effects in the system of two identical two-level atoms in the Bell state interacting with the two-mode entangled coherent states field are investigated by means of Schrdinger equation solution and numerical calculations.The results show that light squeezing effects not only depends on the mean photon numbers and atomic initial state but also the degree of entanglement of the two-mode entangled coherent state optics field,whereas the coupling between two atoms does not affect the light squeezing effects.The light squeezing effects does not appear for a special kind of Bell state |β11〉,however there can appear the light squeezing effects under some conditions for the other three Bell states.
We investigate the entanglement properties of the two-mode coherent fields interacting with a two-level atom via the two-photon transition. We discuss the quantum entanglement between the two-mode coherent fields and the two-level atom by using the quantum reduced entropy and that between the two-mode coherent fields by using the quantum relative entropy. We also examine the influences of the initial states of the atom and the two-mode coherent fields on the quantum entanglement of the system. Our results show that three types of entangled states can be prepared via the two-mode coherent fields interacting with a two-level atom and choosing appropriately the initial-state parameters of the system.
The ability of parameter recently proposed by Sorensen et al. (Nature, 409, 63 (2001)) to characterize entanglement or inseparability is investigated for a system of two two-level atoms interacting with a single mode of radiation field. For comparison we employ the necessary and sufficient criterion of Peres and Horodecki for inseparability of bipartite states. We show that for diagonal atomic density matrix the parameter of Sorensen et al. fails to show entangled nature of collective atomic state whereas same state is inseparable in accordance with Peres-Horodecki criterion.