Fock States Of Field Research Articles

Evolution of Atomic Entanglement for Different Cavity-Field Statistics in Single-Mode Two-Photon Process

We study the evolution of entanglement for a pair of two-level Rydberg atoms passing one after another into an ideal cavity filled with a single mode radiation field. The atoms interact with the cavity field via two-photon transitions. The initial joint state of two atoms that enter the cavity one after the other is unentangled. Interactions intervened by the single mode cavity photon field brings out the final two-atom mixed entangled type state. We use the well known measure appropriate for the mixed states, i.e. the entanglement of formation to quantify the entanglement. We calculate the entanglement of formation of the joint two-atom state as a function of the Rabi angle, for the Fock state field, coherent field and thermal field respectively inside the cavity. The change in the magnitude of atomic entanglement with cavity photon number has been discussed.

Estimation of temperature in micromaser-type systems

We address the estimation of the number of photons and temperature in a micromaser-type system with Fock state and thermal fields. We analyze the behavior of the quantum Fisher information (QFI) for both fields. In particular, we show that in the Fock state field model, the QFI for non-entangled initial state of the atoms increases monotonously with time, while for entangled initial state of the atoms, it shows oscillatory behavior, leading to non-Markovian dynamics. Moreover, it is observed that the QFI, entropy of entanglement and fidelity have collapse and revival behavior. Focusing on each period that the collapses and revivals occur, we see that the optimal points of the QFI and entanglement coincide. In addition, when one of the subsystems evolved state fidelity becomes maximum, the QFI also achieves its maximum. We also address the evolved fidelity versus the initial state as a good witness of non-Markovianity. Moreover, we interestingly find that the entropy of the composite system can be used as a witness of non-Markovian evolution of the subsystems. For the thermal field model, we similarly investigate the relation among the QFI associated with the temperature, von Neumann entropy, and fidelity. In particular, it is found that at the instants when the maximum values of the QFI are achieved, the entanglement between the two-qubit system and the environment is maximized while the entanglement between the probe and its environment is minimized. Moreover, we show that the thermometry may lead to optimal estimation of practical temperatures. Besides, extending our computation to the two-qubit system, we find that using a two-qubit probe generally leads to more effective estimation than the one-qubit scenario. Finally, we show that initial state entanglement plays a key role in the advent of non-Markovianity and determination of its strength in the composite system and its subsystems.

Effects of Cavity-Field Statistics on Atomic Entanglement in Two-Mode Jaynes-Cummings Model

We study the entanglement properties of a pair of two-level Rydberg atoms passing one after another into a lossless cavity with two modes. The initial joint state of two successive atoms that enter the cavity is unentangled. Interactions mediated by the cavity field results in the final two-atom mixed entangled type state. The entanglement of formation of the joint two-atom state as a function of the Rabi angle gt is calculated for Fock state field, coherent field and thermal field respectively inside the cavity. We present a comparative study of two-atom entanglement corresponding to the different field statistics.

Effects of cavity-field statistics on atomic entanglement in a two-mode Jaynes–Cummings model with intensity-dependent coupling

We study the entanglement properties of a pair of two-level Rydberg atoms passing one after another into a lossless cavity with two modes. The atoms interact with the cavity field via an intensity-dependent, non-degenerate two-photon transition. The initial joint state of two successive atoms that enter the cavity is unentangled. Interactions mediated by the two-mode cavity photon field result in the final two-atom mixed entangled type state. The entanglement of formation of the joint two-atom state as a function of the Rabi angle, gt, is calculated for the two-mode Fock state field, coherent field, and thermal field, respectively, inside the cavity. The change in the magnitude of atomic entanglement with cavity photon number in two modes has been studied.

两原子与数态场相互作用系统中纠缠的调控

两原子与数态场相互作用系统中纠缠的调控

三个两能级原子与数态场相互作用的纠缠特性

The dynamics of entanglement of three two-level atoms initially in GHZ state system interacting with a Fock state field are investigated by means of concurrence and linear entropy.The effect of photon number on the time evolution of concurrence and linear entropy is analyzed.The results show that the phenomenon of sudden birth of entanglement between two atoms trapped in a cavity occurs and the threshold time and maximum for the creation of the entanglement can be controlled by the photon number.The measurement of the atom outside the cavity leads to the periodic evolution of the concurrence and an increase of the photon number results in decreasing in the maximum of concurrence and shortening of the evolution period of the time behavior of concurrence.

Entanglement dynamics of two atoms successively passing a cavity

By means of concurrence, we investigate the dynamics of entanglement between two initially separate atoms in succession passing through a cavity and their interaction with a Fock state field. We then analyze the effects of the atomic coherence, photon number, and atomic motion on the time evolution of atom-atom entanglement. The results show that there can be entanglement between two separate atoms, and that the threshold time for the creation of the entanglement is controllable by the photon number, atomic motion, and field-mode structure.

Entanglement sudden death of two atoms successive passing a cavity

We investigate the dynamics of entanglement of two initial entangled atoms passing through a cavity one after another. By considering the field statistics of the Fock state field and the thermal field, respectively, inside the cavity, we show that initial entanglement of two atoms has interesting subsequent time evolution, including the so-called entanglement sudden death effect.

EFFECTS OF CAVITY-FIELD STATISTICS ON ATOMIC ENTANGLEMENT IN THE JAYNES–CUMMINGS MODEL

We study the entanglement properties of a pair of two-level atoms going through a cavity one after another. The initial joint state of two successive atoms that enter the cavity is unentangled. Interactions mediated by the cavity photon field result in the final two-atom state being of a mixed entangled type. We consider the field statistics of the Fock state field, and the thermal field, respectively, inside the cavity. The entanglement of formation of the joint two-atom state is calculated for both these cases as a function of the Rabi angle gt. We present a comparitive study of two-atom entanglement for low and high mean photon number cases corresponding to the different fields statistics.

INFLUENCE OF THE COUNTER-ROTATING TERMS ON THE RABI OSCILLATIONS IN THE POLYATOMIC JAYNES-CUMMINGS MODEL WITH CAVITY LOSSES FOR INITIAL FOCK-STATE FIELDS

The significance of the counter-rotating terms in the polyatomic Jaynes-Cummings model with cavity losses is demonstrated. Numerical results for the time evolution of the atomic population inversion and dipole moment for an initial Fock-state field with different photon numbers are presented for various cavity dampings. The appearance of new steady states for the population inversion and the mean-photon number under the influence of the counter-rotating terms is pointed out. Namely, as is shown, the presence of “virtual photons”, produced by the counter-rotating terms, leads to these effects.

The effect of the counter-rotating terms in the Dicke model

The significance of the counter-rotating terms in the Dicke model (a sample of N identical two-level atoms inside a single-mode cavity) is demonstrated. Numerical results for the time evolution of the atomic population inversion and the mean photon number for various numbers of atoms and different cavity dampings (low- and high-Q cavities) and different photon numbers of the Fock-state field (being present initially in the cavity) are presented. An initial coherent field is also treated. The appearance of new steady states under the influence of the counter-rotating terms is pointed out. Finally, by applying a modified Robertson projection-operator method, developed previously by the author, an analytic solution in the case of strongly damped (low-Q) cavities is derived.

Atoms in fock state fields: I. Exact analytical results

A theoretical analysis of the fundamental problem of two-level atomic systems radiatively decaying and coupled to Fock state radiation fields is presented. First, for a broad-band Fock state field and for a single two-level atom the Einstein radiation rate equation is derived within a scheme of matter-field statistical decorrelation. This holds too for N > 1 “independent” two-level atoms. Second, for a single-mode Fock state field exact analytical solution for the atomic inversion, in the single-atom case, is derived within the rotating wave approximation. For N > 1 cooperative two-level atoms exact results are also derived in the steady state regime. In a thermodynamic limit where N→ ∞, the scaled atomic inversion is expressed as Poisson-Charlier polynomials. Connection with earlier results for coherent and incoherent (chaotic) state fields is made. Of mathematical interest: a formal expression for the cofactor elements in terms of the original elements of a triangular matrix is derived in appendix B.

Influence of the Fock-state field on the many-atom radiation processes in a damped cavity.

Radiation effects from two-level atoms caused by the presence of a Fock-state field in a damped single-mode cavity are examined. An exact recurrence differential equation for density-matrix elements valid for any number of atoms or photons is derived. Numerical solutions for different cavity dampings (low- and high-Q cavities) and different photon numbers of the Fock-state field being present initially in the cavity are presented. Collective effects caused by the presence of many atoms are investigated. It is shown that new quasistationary states as well as collective radiation inhibition appear in the time behavior of the atomic energy expectation value. These effects arise from averaging over an ensemble of which each member consists of N identical two-level atoms placed into a resonant single-mode cavity. A comparison of the obtained results with those for an initial coherent or thermal field is also given.

Single-atom radiation effects in the presence of a damped fock-state field

In this paper an exact analytic solution for the Jaynes-Cummings model in the presence of a damped Fock-state field is derived. In addition simpler approximate solutions are given for large and small cavity damping. Moreover, numerical results for atomic population inversion, atomic radiation rate and atom-field correlation are presented for different cavity dampings and initial photon numbers. In the case of small cavity damping damped periodic revivals as well as the existence of a new quasistationary state are pointed out.