Two-atom Dicke Model Research Articles

Non-equilibrium dynamical phases of the two-atom Dicke model

In this paper, we investigate the non-equilibrium quantum phases of the two-atom Dicke model, which can be realized in a two species Bose-Einstein condensate interacting with a single light mode in an optical cavity. Apart from the usual non-equilibrium normal and inverted phases, a non-equilibrium mixed phase is possible which is a combination of normal and inverted phase. A new kind of quantum phase transition is predicted from non-superradiant mixed phase to the superradiant phase which can be achieved by tuning the two different atom-photon couplings. We also show that a quantum phase transition from the non-superradiant mixed phase to the superradiant phase is forbidden for certain values of the two atom-photon coupling strengths.

Interference of composite bosons

We investigate multi-boson interference. A Hamiltonian is presented that treats pairs of bosons as a single composite boson. This Hamiltonian allows two pairs of bosons to interact as if they were two single composite bosons. We show that this leads to the composite bosons exhibiting novel interference effects, such as Hong–Ou–Mandel interference. We then investigate generalisations of the formalism to the case of interference between two general composite bosons. Finally, we show how one can realise interference between composite bosons in the two-atom Dicke model.

Entanglement and spin squeezing in the two-atom Dicke model

We analyze the relation between the entanglement and spin-squeezing parameter in the two-atom Dicke model and identify the source of the discrepancy recently reported by Banerjee and Zhou et al that one can observe entanglement without spin squeezing. Our calculations demonstrate that there are two criteria for entanglement, one associated with the two-photon coherences that create two-photon entangled states, and the other associated with populations of the collective states. We find that the spin-squeezing parameter correctly predicts entanglement in the two-atom Dicke system only if it is associated with two-photon entangled states, but fails to predict entanglement when it is associated with the entangled symmetric state. This explicitly identifies the source of the discrepancy and explains why the system can be entangled without spin-squeezing. We illustrate these findings in three examples of the interaction of the system with thermal, classical squeezed vacuum and quantum squeezed vacuum fields.

Detailed balance and entropy for atoms in squeezed vacuum

It is shown that the principle of detailed balance is not obeyed in both systems of a single 2-level atom and the two-atom Dicke model interacting with a broad band squeezed vacuum field. Examination of the Boltzmann-Gibbs entropy shows that the stability of either system depends on the initial conditions. In particular, the two-atom system is unstable even for initially ground state condition, unlike the thermal field driven case.

INFORMATION-THEORETIC APPROACH TO THE DYNAMICAL EVOLUTION OF TWO-ATOM DICKE MODEL

The two-atom Dicke model driven by a coherent field and interacting with a thermal reservoir is considered here. The evolution of density operator for this system is explicitly calculated using the maximum entropy principle.

Effect of dispersion forces on the dynamical evolution of the two-atom Dicke model in a broadband squeezed bath

We show that the two-atom Dicke model, including dipole-dipole interaction (dispersion forces) and interaction with a broadband squeezed bath, exhibits a periodic modulation phenomenon in its population decay. For this purpose we have calculated explicitly the analytic expression for the time evolution of the density matrix elements under the intense field limit. The phase sensitive nature of the modulation phenomenon has been clearly brought out in these calculations.

The transient fluorescence spectrum of a strongly driven two-atom Dicke model including dipole interaction in a squeezed vacuum

The time-dependent spectrum of the fluorescence radiation from a strongly driven system of two identical two-level atoms interacting with each other via the dipole-dipole interaction in a squeezed vacuum is studied applying the counting rate definition of Eberly-Wodkiewicz [J. Opt. Soc. Am. 67 (1977) 1252]. Analytic results are obtained in the intense field approximation. The spectrum is found to be sensitive to the relative phase between the squeezed vacuum and the coherent driving field. Also, for a particular choice of squeezed bath parameters one of the Rabi sidebands disappears from the spectrum and the population decays non-exponentially. The features observed here may be useful in the detection of squeezed fields.

Comment on "Phase-sensitive population decay: The two-atom Dicke model in a broadband squeezed vacuum"

A recent paper [G. M. Palma and P. L. Knight, Phys. Rev. A 39, 1962 (1989)] has stated that the two-atom Dicke model exhibits phase-dependent population decay. In this Comment we show that population decay is invariant with respect to the input phase angle of squeezing in the two-atom Dicke model.

Reply to "Comment on 'Phase-sensitive population decay: The two-atom Dicke model in a broadband squeezed vacuum' "

Reply to "Comment on 'Phase-sensitive population decay: The two-atom Dicke model in a broadband squeezed vacuum' "

Phase-sensitive population decay: The two-atom Dicke model in a broadband squeezed vacuum.

Phase-sensitive population decay: The two-atom Dicke model in a broadband squeezed vacuum.