1,720,994 research outputs found
Maximum entanglement in a Jaynes-Cummings system with strongly driven atoms
No full textWe describe the entanglement of a Jaynes-Cummings system, where a two-level atom is also strongly driven by an external coherent field while it crosses a resonant cavity prepared in a coherent state. First we consider the atom-cavity field entanglement, described by the Von Neumann entropy. We find that it depends only on the interaction time and the initial atomic state. The entropy vanishes in the case of maximally polarized atom, independent of the interaction time, whereas it reaches its maximum value for atom in the upper or lower state and for long enough interaction times. Then we investigate the entanglement between two consecutive strongly driven atoms interacting with the cavity mode assumed in the vacuum state, showing that they never entangle in spite of the existence of atom-atom correlations
Atomic correlations and cavity field decoherence in a strongly driven micromaser
No full textIn a micromaser where a classical field strongly drives the atoms
while they cross the cavity, remarkable atom-atom correlations show
up at steady-state, which vanish much faster than dissipative decay.
Hence we consider atom pair correlation measurements in which the
detection of the first probe atom prepares a mesoscopic
superposition state of the cavity field, that entangles with a
second probe atom. The conditional probabilities for the latter
atomic detection provide a description of the decoherence of the
superposition state, occurring in an open system in the presence of
pumping, driving, dissipative, and thermal effects. The decoherence
rate scales as the squared interaction time, that sets the
separation in phase space between the superposition components,
whereas the quantum coherence is unaffected by the atomic pumping.
Hence we further investigate the system when the cavity is not
pumped. Starting the correlation measurements from a thermal state,
we can describe the effect of temperature on decoherence. Starting
from a vacuum state, the superposition states are maximally
separated Schrödinger cat states, whose decoherence can be thus
monitored
Generation and decoherence of mesoscopic superposition states in a strongly driven micromaser
No full textWe show that the decoherence of mesoscopic superposition states of a cavity field can be observed when an additional classical field strongly drives the atoms in a micromaser like device. Due to solvable system dynamics, analytical expressions provide phase space descriptions of all stages of atom pair correlation measurements at steady-state in the presence of pumping, driving, and dissipative effects. The detection of the first atom prepares a pure field state, which entangles with the second atom that acts as a meter. The decoherence rate, derived from conditional probabilities for atomic detection, depends on the square of the interaction time, that is the parameter that rules the separation in phase space between the pure state components. The quantum coherence is unaffected by the atomic pumping. Starting instead the correlation measurement from a vacuum state and without pumping the cavity we propose an alternative method to monitor the decoherence of Schrodinger cat states
Generation of maximally entangled atom pairs in driven dissipative cavity QED systems
No full textWe investigate the entanglement of an open tripartite system where a cavity field mode in thermal equilibrium is off-resonantly coupled with two atoms that are simultaneously driven by a resonant coherent field. For moderately detuned atom-field coupling and strong atomic driving we show the generation, at given interaction times and for low enough cavity decay rates, of atomic Bell states and of Bell state superpositions relevant for quantum gates implementation. The system can oscillate between bi-separable and fully separable states. Also we describe the distribution of quantum correlations between the atom-atom and the two atom-field subsystems. In the dispersive coupling regime with strongly driven atoms we show the generation of nearly stationary Bell states which remain protected from cavity dissipation
Atomic Bell states generation in an open driven cavity QED system
No full textWe show that two uncorrelated two-level atoms can become maximally entangled if they are both off-resonantly coupled to a dissipative cavity mode, initially in the vacuum state, and strongly driven by a resonant coherent field. For moderate atom-field detuning we find that the quantum correlations in the tripartite system can alternatively concentrate either in the atom-atom subsystem or in the two atom-field subsystems. In the first case Bell states as well as their superpositions are generated for low enough cavity decay rates. In a dispersive coupling regime the atomic entanglement grows up monotonically to the maximum value where it remains nearly stationary without being affected by cavity dissipation
Entanglement, decoherence and correlations in a strongly driven Jaynes-Cummings system
No full textWe consider the resonant interaction of a cavity mode with a two-level atom that is
driven by a coherent field while it crosses the cavity. Starting from the cavity field in a coherent state, we show that the state of the system can reach the maximum entanglement after a unitary evolution for long enough interaction times. Also we illustrate how the generation of cavity field superposition states can allow, in the open system dynamics, the observation of their decoherence in atomic correlation measurements, for any initial cavity field state, and even under the combined
effects of dissipation, thermal noise, and atomic pumping
Reply to comment on collective effects and trapping states by a quantum-trajectory treatment of micromaser dynamics
No full textIn the preceding Comment [Phys. Rev. A 67, 027801 (2003)] Johnson and Schieve raise doubts on the
validity of a result obtained in our treatment of collective atomic effects in micromaser dynamics [Phys. Rev.
A 60, 1582 (1999)]. We fully confirm the validity of our results, showing that the conclusions derived from
their analysis are not relevant
Tripartite entanglement transfer from flying modes to localized qubits
Full text linkWe investigate the process of entanglement transfer from a three-mode quantized field to a system of three spatially separated qubits, each one made of a two-level atom resonantly coupled to a cavity mode. The optimal conditions for entanglement transfer, evaluated by atomic tripartite negativity, are derived for radiation prepared in qubitlike and Gaussian entangled states in terms of field parameters, atom-cavity interaction time, cavity mirror losses, and atomic preparation. For qubitlike states we find that for negligible cavity losses some states may completely transfer their entanglement to the atoms and/or be exactly mapped to the atomic state, whereas for Gaussian states we find a range of field parameters needed to obtain a large entanglement transfer. The purity of the three-qubit states and the entanglement of two-qubit subsystems are also discussed in some detail
Solvable dynamics of N driven two-level atoms coupled to a dissipative cavity mode
No full textWe solve exactly the dynamics of N strongly driven two-level atoms equally coupled on resonance to a dissipative cavity mode. Analytical results are derived on decoherence, entanglement, purity, atomic correlations and cavity field mean photon number. Decoherence-free subspaces are predicted for the whole system and the N-quibit subsystem. Multi-partite entangled states and cavity cat-like states can be conditionally generated. The decay of quantum coherence and purity can be monitored by joint measurements on atomic populations. Atoms prepared in states invariant under permutation of any two components evolve within the subspace spanned by the completely symmetric Dicke states. Applications to N = 3, 4 are discussed
Decoherence-free multipartite atomic entanglement in a cavity QED system
No full textWe present analytical results on entanglement and decoherence in a system of N strongly driven two-level atoms resonantly coupled to a dissipative cavity mode. In the specific cases of N = 3 and 4 qubits we show the existence of decoherence-free subspaces for the whole system and/or the atomic subsystem and we discuss examples where a multipartite qubit entanglement remains preserved. Also we illustrate the conditional preparation of cat-like states of the cavity field and the generation of atomic correlations
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