Micromaser Cavity Research Articles

Work and heat value of bound entanglement

Entanglement has recently been recognized as an energy resource which can outperform classical resources if decoherence is relatively low. Multi-atom entangled states can mutate irreversibly to so called bound entangled (BE) states under noise. Resource value of BE states in information applications has been under critical study and a few cases where they can be useful have been identified. We explore the energetic value of typical BE states. Maximal work extraction is determined in terms of ergotropy. Since the BE states are non-thermal, extracting heat from them is less obvious. We compare single and repeated interaction schemes to operationally define and harvest heat from BE states. BE and free entangled (FE) states are compared in terms of their ergotropy and maximal heat values. Distinct roles of distillability in work and heat values of FE and BE states are pointed out. Decoherence effects in dynamics of ergotropy and mutation of FE states into BE states are examined to clarify significance of the work value of BE states. Thermometry of distillability of entanglement using micromaser cavity is proposed.

A photonic Carnot engine powered by a spin-star network

We propose a spin-star network, where a central spin-(1/2), acting as a quantum fuel, is coupled to N outer spin-(1/2) particles. If the network is in thermal equilibrium with a heat bath, the central spin can have an effective temperature, higher than that of the bath, scaling nonlinearly with N. Such temperature can be tuned with the anisotropy parameter of the coupling. Using a beam of such central spins to pump a micromaser cavity, we determine the dynamics of the cavity field using a coarse-grained master equation. We find that the central-spin beam effectively acts as a hot reservoir to the cavity field and brings it to a thermal steady state whose temperature benefits from the same nonlinear enhancement with N and results in a highly efficient photonic Carnot engine. The validity of our conclusions is tested against the presence of atomic and cavity damping using a microscopic master equation method for typical microwave cavity-QED parameters. The role played by quantum coherence and correlations on the scaling effect is pointed out. An alternative scheme where the spin-(1/2) is coupled to a macroscopic spin- particle is also discussed.

Effects of mode profile on tunneling and traversal of ultracold atoms through vacuum-induced potentials

We consider the resonant interaction of an ultracold two-level atom with an electromagnetic field inside a high-Q micromaser cavity. In particular, we study the tunneling and traversal of ultracold atoms through vacuum-induced potentials for secant hyperbolic square and sinusoidal cavity mode functions. The phase time which may be considered as an appropriate measure of the time required for the atoms to cross the cavity, significantly modifies with the change of cavity mode profile. For example, switching between the sub and superclassical behaviors in phase time can occur due to the mode function. Similarly, negative phase time appears for the transmission of the two-level atoms in both excited and ground states for secant hyperbolic square mode function which is in contrast to the mesa mode case.

COLLAPSE AND REVIVAL OF ATOMIC ENTANGLEMENT IN AN INTENSITY DEPENDENT JAYNES–CUMMINGS INTERACTION

The evolution of entanglement of a bipartite spin-1/2 system coupled to a micromaser cavity field in an intensity-dependent Jaynes–Cummings model is studied in this paper. The dynamical process of the entanglement is investigated for different cavity fields. We find that the interactions lead to a phenomenon of periodic entanglement and disentanglement between the qubits. Effects such as the growth of the magnitude of atomic entanglement with the increase of the cavity photon number, arising out of the intensity-dependent atom-cavity coupling lead to interesting dissimilarities from the case of entanglement generated by the standard Jaynes–Cummings interaction.

Simultaneous values of non-commuting properties inferred by revealing photons in microwave cavities

A theoretical investigation is performed to show that ideal double slit experiments for atoms can be designed such that the values of non-commuting quantum properties can be inferred simultaneously by revealing photons emitted by single atoms within micro-maser cavities.

Analysis of a teleportation scheme involving cavity field states in a linear superposition of Fock states

We analyse a teleportation scheme of cavity field states. The experimental sketch discussed makes use of cavity quantum electrodynamics involving the interaction of Rydberg atoms with superconducting (micromaser) cavities as well as with classical microwave (Ramsey) cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport a field state, which is formed by a linear superposition of vacuum |∅〉 and the one-photon state |1〉, from a micromaser cavity to another.

Nonprobabilistic teleportation of a field state via cavity QED

In this paper, we discuss a teleportation scheme of coherent states of a cavity field. The experimental realization proposed makes use of cavity quantum electrodynamics, involving the interaction of Rydberg atoms with micromaser and Ramsey cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport the state from one micromaser cavity to another. We show that, even if the correct atomic detection fails in the first trials, one can succeed in teleportating the cavity field state if proper measurement occurs in a later atom.

Decoherence measurement of two coupled micromasers

We present a setup of two coupled micromaser cavities for studying decoherence. The system is prepared in a state where, initially, one photon is contained in one of the two cavities. The coupling of the two resonators allows the photon to tunnel into the other cavity with a certain probability. The system thus oscillates between the two states vertical bar 1>{sub L} vertical bar 0>{sub R} and vertical bar 0>{sub L} vertical bar 1>{sub R}. It is shown how to map these states onto the states vertical bar g> and vertical bar e> of probe atoms used to investigate the status of the cavity system. It is an important result that the symmetry of our special setup allows decoherence to be monitored by measuring just the diagonal elements of the atomic density matrix. This property relies on the fact that only vertical bar 0> and vertical bar 1> states are relevant. To our knowledge, this is the first proposal that tries to exploit this particular property.

Micromaser cavity field spectrum by atomic beam measurements

It is shown that complete information on the micromaser cavity field correlation function and hence the spectrum for the cavity field at absolute zero is encoded on the atomic beam exiting from the cavity. A possible means of measuring the atomic beam correlation function is discussed.

Teleportation of atomic states via cavity QED for a cavity prepared in a superposition of zero and one Fock states

In this article we discuss two schemes for the teleportation of atomic states. In the first scheme we consider atoms in a three-level cascade configuration and in the second scheme we consider atoms in a three-level lambda configuration. The proposed experimental realization makes use of cavity quantum electrodynamics involving the interaction of Rydberg atoms with a micromaser cavity prepared in a state .

Entanglement swapping: entangling atoms that never interacted

In this paper we discuss four different proposals of entangling atomic states of particles which have never interacted. The experimental realization proposed makes use of the interaction of Rydberg atoms with a micromaser cavity prepared in either a coherent state or in a superposition of the field Fock states |0⟩ and |1⟩. We consider atoms in either a three-level cascade or lambda configuration.

Higher-order parity states of the quantum electromagnetic field

We construct higher-order parity observables for a single mode of the quantum electromagnetic field from harmonics of the ordinary parity observable cos ( π n ˆ ) . Higher-order parity states arise when the quantum-optical Hilbert space is projected into specific groupings of photon number. Optical systems with cross-Kerr nonlinearities can produce such parity states. Here, we generalize the dispersive micromaser cavity QED formalism of C.C. Gerry [Phys. Rev. A 53 (1996) 3818] to demonstrate that these states are also produced in systems governed by atom–field interactions.

A theoretical scheme for generation of nonlinear coherent states in a micromaser under intensity-dependent Jaynes-Cummings model

In this paper we propose a theoretical scheme to show the possibility of generating various families of nonlinear (f-deformed) coherent states of the radiation field in a micromaser. We show that these states can be provided in a lossless micromaser cavity under the weak Jaynes-Cummings interaction with intensity–dependent coupling of large number of individually injected two-level atoms in a coherent superposition of the upper and lower states. In particular, we show that the so-called nonlinear squeezed vacuum and nonlinear squeezed first excited states, as well as the even and odd nonlinear coherent states can be generated in a two-photon micromaser.

How to Measure the Decoherence of a Micromaser Field under Well Controlled Conditions

We discuss a possible realization of a quantum register with controllable decoherence in terms of /0> and /1> photon number states of a micromaser field. It is shown how to create in the Jaynes-Cummings model a superposition state of /0> and /1> photon number states inside a closed micromaser cavity. The loss of phase coherence between these two states can subsequently be measured by a second probe atom monitoring the decoherence of the field. A technique is proposed for forming the superposition of number states /0> and /1> using the time structure of the Rabi oscillation. The proposed method avoids problems with stray fields at the cavity holes, which disturb the coherence of the atomic superposition, and offers a way to study how the coupling strength to the environment influences the decoherence rate, displaying the robustness of physical qubits and the fidelity of quantum computations.

Teleportation of atomic states via cavity quantum electrodynamics

In this paper, we discuss a scheme of teleportation of atomic states. The experimental realization proposed makes use of cavity quatum electrodynamics involving the interaction of Rydberg atoms with a micromaser cavity prepared in a coherent state. We start presenting a scheme to prepare atomic Bell states via the interaction of atoms with a cavity. In our scheme the cavity and some atoms play the role of auxiliary systems used to achieve the teleportation.

Photon emission probability of many ultracold two-level atoms in a micromaser cavity

Photon emission induced by the interaction of many ultracold two-level atoms with a single-mode of the electromagnetic field in a micromaser cavity is studied in the Dicke limit when the center-mass motion of the atoms is treated quantum mechanically. We show that quantum interference between probability amplitudes of either reflection or transmission of the CM motion wave packet incident upon the cavity makes photon emission probabilities essentially different for the atomic clusters with even and odd atoms.

Generation of higher-order atomic dipole squeezing in a high-Q micromaser cavity. (VIII). Multi-photon interaction

In our preceding serial works, we have investigated the generation of higher-order atomic dipole squeezing (HOADS) in a high-Q micromaser cavity, discussing the effects of dynamic Stark shift, atomic damping, atomic coherence and nonlinear one-photon processes and different initial states (for example, correlated and uncorrelated states, superposition states, squeezed vacuum). In this paper, we continue to study HOADS in a high-Q micromaser cavity, but consider that the atom interacts with the optical field via a multi-photon transition process and that the initial atom is arbitrarily prepared. For a vacuum initial field, we demonstrate that HOADS cannot occur if the atom is initially prepared in a chaotic state and that a coherent atomic state generates less efficient and stable HOADS than an arbitrary one. It is found that large detuning may lead to enhanced and strong HOADS.

Quantum-entanglement production in a micromaser

We show that a micromaser can work as an effective source of highly correlated atoms. We consider a one-photon micromaser pumped by a Poissonian beam of atomic pairs. We show that the atoms forming the pairs leave the micromaser's cavity in entangled states and that they can violate the Bell inequality. We consider two aspects of the violation of the Bell inequality: we study the maximal value ${\mathbf{B}}_{\mathrm{max}}$ of an expression appearing in the Bell inequality and we evaluate a vector-dependent $\mathbf{B}(\stackrel{\ensuremath{\rightarrow}}{a},{a}^{\ensuremath{'}},\stackrel{\ensuremath{\rightarrow}}{b},{b}^{\ensuremath{'}})$ depending upon experimental setup. We calculate the entanglement of the formation of states of the atomic pairs. We show that the pairs of atoms, which fly out from the micromaser cavity, are entangled for almost all values of control parameters characterizing the considered two-atom micromaser. This happens even if they do not violate the Bell inequality.

Generation of higher-order atomic dipole squeezing in a high-Q micromaser cavity. (V). A linear superposition of states

In our preceding paper, we investigated the generation of higher-order atomic dipole squeezing (HOADS) in a nondegenerate two-photon Jaynes–Cummings model in the absence of Stark shift. In this paper, we continue to study HOADS in this model but with the inclusion of Stark shift. Based on the linear superposition principle of quantum mechanics, we discuss the cases where the atom or the two-mode fields are initially prepared in a superposition of states. We demonstrate that the essential condition for generating HOADS is that the initial state of the system should include phase information, and HOADS cannot appear in atomic spontaneous radiation processes. The Stark shift brings time-dependent phase information into emitted photons and has a significant effect (constructively and destructively) on HOADS. It is found that weakly coupling of the intermediate virtual state to the ground state of the atom would lead to much more squeezing and collapse-revival phenomena. The relation between HOADS and second-order atomic dipole squeezing is also discussed.

Generation of higher-order atomic dipole squeezing in a high-Q micromaser cavity. (VI). Atomic damping by a squeezed vacuum

In our previous serial works, we investigated the generation of higher-order atomic dipole squeezing (HOADS) in a high-Q micromaser cavity. In this paper, we continue to study HOADS in this system but consider the effect of atomic damping by a squeezed vacuum in the absence of an external field. The corresponding master equation is introduced and its solutions for an initial SU(2) coherent state of the atom are presented. In the absence of the atomic damping, we have shown that stable and permanent HOADS can be generated by properly preparing the atom in certain SU(2) coherent state. We demonstrate the destructive effect of atomic damping on HOADS by changing the initial atomic coherence or the average number of the reservoir photons. The relation between HOADS and second-order atomic dipole squeezing (SOADS) is discussed. It is found that the atomic damping has more destructive effects on SOADS than on HOADS.