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Acta Sinica Quantum Optica

The Property of Quantum Noise in Quantum Coherent Atomic System

Junxiang Zhang

Published Jan 1, 2006• 0 citations
OpenAlex

Abstract

The coherent superposition of atomic states leads to the change of properties of interaction lights because of the coupling between the lights and atoms.In this paper,the noise spectrum of the quantified light interacting with the atoms is studied;it shows that the squeezing of 1.25 dB can be observed at the detuning of probe light,which then can be used to get the entanglement.

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The quantum entanglement of two entangled atoms interacting with the squeezed coherent state is studied by means of full quantum theory. The influences of coherent amplitude factor, squeezing factor, ratio of two coupling coefficients on the entanglement property are discussed. The results show that two atoms entanglement evolution property is opposed to atom-field entanglement evolution property when the coherent amplitude factor was zero or small. The interaction of the atoms and field weakens the entanglement degree of atom-atom. With increasing coherent amplitude factor or decreasing squeezing factor of light, the time of two atoms staying in the steady entangled state becomes longer. The increase of the coherent amplitude factor or the decrease of squeezing factor of light lead to the increase of atom-atom entanglement degree while the decrease of atoms-field entanglement degree. Moreover, the two-atom quantum state stays in the maximum entangled state when the atomic dipole-dipole coupling coefficient is large enough.

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Bulgarian Journal of Physics•Sep 21, 2025•0 citations

Effect of Squeezing on the Atomic and the Entanglement Dynamics in the Jaynes-Cummings Model

T. Subeesh, Vivishek Sudhir, A.B.M.a d Ahmed +1 more

The dynamics of the Jaynes-Cummings interaction of a two-level atom interacting with a single mode of the radiation field is investigated, as the state of the field is gradually changed from a coherent state to a squeezed coherent state. The effect of mild squeezing on the coherent light is shown to be striking: the photon number distribution gets localized and it peaks maximally for a particular value of squeezing. The atomic inversion retains its structure for a longer time. The mean linear entropy shows that the atom has a tendency to get disentangled from field within the collapse region and also in the revival region, for mild squeezing. These properties are absent for the case of a coherent state or for an excessively squeezed coherent state. We also elucidate a connection between these properties and the photon statistics of the mildly squeezed coherent state; these states have the minimum variance and are also maximally sub-Poissonian.

arXiv:1203.4792•Mar 21, 2012•1 citation
The coherent superposition of atomic states leads to the change of properties of interaction lights because of the coupling between the lights and atoms.In this paper,the noise spectrum of the quantified light interacting with the atoms is studied;it shows that the squeezing of 1.25 dB can be observed at the detuning of probe light,which then can be used to get the entanglement.
The quantum entanglement of two entangled atoms interacting with the squeezed coherent state is studied by means of full quantum theory. The influences of coherent amplitude factor, squeezing factor, ratio of two coupling coefficients on the entanglement property are discussed. The results show that two atoms entanglement evolution property is opposed to atom-field entanglement evolution property when the coherent amplitude factor was zero or small. The interaction of the atoms and field weakens the entanglement degree of atom-atom. With increasing coherent amplitude factor or decreasing squeezing factor of light, the time of two atoms staying in the steady entangled state becomes longer. The increase of the coherent amplitude factor or the decrease of squeezing factor of light lead to the increase of atom-atom entanglement degree while the decrease of atoms-field entanglement degree. Moreover, the two-atom quantum state stays in the maximum entangled state when the atomic dipole-dipole coupling coefficient is large enough.
Light and atoms couple together via the electromagnetic interaction. The simplest form of this interaction is the electric dipole interaction, and in its quantised form it provides a useful starting point for the investigation of quantum effects in optics. Two examples of quantum noise manipulation of the light field due to interaction with atoms will be presented, as well as an analysis of a simple model for laser cooling of trapped atoms. The first example of quantum noise manipulation is the investigation of a quantum non-demolition measurement scheme based on a three-level atomic system in the ladder configuration. An effective two-level model of the atomic system is used, which enables the inclusion of spontaneous emission noise from the upper atomic level. The system is found to perform well, when detuned far from resonance. The second example is the treatment of squeezing in the intensity difference between two modes coupled by a three-level atomic system in the ladder configuration. The noise correlations are similar to those occurring in the optical parametric oscillator, and give rise to good squeezing when the system is well detuned from the intermediate level. The simple model of laser cooling consists of a single two-level atom with quantised centre-of-mass motion constrained to move in a one-dimensional harmonic potential while interacting with a single-mode classical travelling light field. It is shown that there is an analogy between this model and the Jaynes-Cummings model. This gives rise to interesting coherent effects including quantum collapses and revivals in the atomic inversion. Sideband cooling occurs for this model when the light field is tuned to the atom's first lower vibrational sideband. The strong sideband and Lamb-Dicke perturbation regimes are defined. Analytic results have previously been obtained for the latter regime, but we carry out a numerical investigation of the steady state and time evolution behaviour in the former regime. Differences in the behaviour in the two regimes are discussed. Finally the possibility of observing quantum jumps between trap levels is discussed.
Quantum entanglement between a squeezed coherent state and a Λ-type three level atom was studied via quantum entropy theory.The results show that the maximal degree of entanglement depends on the initial state parameters of the atom,squeezing factor,coherent amplitude factor,and the ratio of detuning to coupling constant.The entanglement strengthens with the increasing of squeezing factor of light.The entanglement occurs periodic evolution with the increasing of the ratio of detuning to coupling constant,the system appears disentanglement.When the ratio of detuning to coupling constant becomes larger,the entanglement between the field and atoms shows periodical change.The system appears steady and maximal entanglement state periodically as the ratio of detuning to coupling constant is sufficiently large.
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.
The dynamics of the Jaynes-Cummings interaction of a two-level atom interacting with a single mode of the radiation field is investigated, as the state of the field is gradually changed from a coherent state to a squeezed coherent state. The effect of mild squeezing on the coherent light is shown to be striking: the photon number distribution gets localized and it peaks maximally for a particular value of squeezing. The atomic inversion retains its structure for a longer time. The mean linear entropy shows that the atom has a tendency to get disentangled from field within the collapse region and also in the revival region, for mild squeezing. These properties are absent for the case of a coherent state or for an excessively squeezed coherent state. We also elucidate a connection between these properties and the photon statistics of the mildly squeezed coherent state; these states have the minimum variance and are also maximally sub-Poissonian.