We propose an optical cavity-QED scheme for the deterministic generation of polarization-entangled photon pairs that operates with high fidelity even in the bad cavity limit. The scheme is based on the interaction of an excited four-level atom with two empty optical cavity modes via an adiabatic passage process. Monte Carlo wavefunction simulations are used to evaluate the fidelity of the cavity-QED source and its entanglement capability in the presence of decoherence. In the bad cavity limit, fidelities close to one are predicted for state-of-the-art experimental parameter values.

}, url = {http://stacks.iop.org/0953-4075/41/i=4/a=045505}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {1742-6596-84-1-012008, title = {Cavity-QED-based entangled photon pair gun}, journal = {Journal of Physics: Conference Series}, volume = {84}, number = {1}, year = {2007}, pages = {012008}, abstract = {We describe a cavity-QED scheme to deterministically generate polarization entangled photon pairs by using a single atom successively coupled to two single longitudinal mode cavities presenting polarization degeneracy. The cavities are initially prepared either in the vacuum state or in a single photon Fock state for each orthogonal polarization. Sharing the same basic elements, the source can operate on different physical processes. For a V -type three-level atom initially prepared in the ground state two implementations of the source are possible using either: i) two truncated Rabi Oscillations, or ii) a counterintuitive Stimulated Raman Adiabatic Passage process. Although slower than the former implementation, this second one is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost insensitive to atomic decay. For a four-level atom in a diamond configuration initially prepared in the upper state, the source can produce entangled photon pairs even in the bad cavity limit via an adiabatic passage process. We have performed Monte Carlo wave function simulations to characterize these sources by means of: i) the success probability P of producing the desired entangled state, ii) the fidelity F in the reduced space of two emitted cavity photons, and iii) the S parameter of the Clauser-Horne-Shimony-Holt (CHSH) inequality to quantify the entanglement capability.

}, url = {http://stacks.iop.org/1742-6596/84/i=1/a=012008}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {Garcia-Maraver:07, title = {Cavity-quantum-electrodynamics entangled photon source based on two truncated Rabi oscillations}, journal = {J. Opt. Soc. Am. B}, volume = {24}, number = {2}, year = {2007}, month = {Feb}, pages = {257{\textendash}265}, publisher = {OSA}, abstract = {We discuss a cavity-QED scheme to deterministically generate entangled photons pairs by using a three-level atom successively coupled to two single longitudinal mode high-Q cavities presenting polarization degeneracy. The first cavity is prepared in a well-defined Fock state with two photons with opposite circular polarizations while the second cavity remains in the vacuum state. Half of a resonant Rabi oscillation in each cavity transfers one photon from the first to the second cavity, leaving the photons entangled in their polarization degree of freedom. The feasibility of this implementation and some practical considerations are discussed for both microwave and optical regimes. In particular, Monte Carlo wave-function simulations have been performed with state-of-the-art parameter values to evaluate the success probability of the cavity-QED source in producing entangled photon pairs as well as its entanglement capability.

}, keywords = {Photon statistics, Quantum electrodynamics}, doi = {10.1364/JOSAB.24.000257}, url = {http://josab.osa.org/abstract.cfm?URI=josab-24-2-257}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {PhysRevA.74.031801, title = {Deterministic cavity-QED source of polarization-entangled photon pairs}, journal = {Phys. Rev. A}, volume = {74}, year = {2006}, month = {Sep}, pages = {031801}, publisher = {American Physical Society}, abstract = {We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photon pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a polarization-entangled photon pair via two truncated Rabi oscillations, whereas in the adiabatic proposal, a counterintuitive stimulated Raman adiabatic passage process is considered. Although slower than the former process, this second method is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost completely insensitive to atomic decay.

}, doi = {10.1103/PhysRevA.74.031801}, url = {http://link.aps.org/doi/10.1103/PhysRevA.74.031801}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {PhysRevA.70.062324, title = {Cavity QED quantum phase gates for a single longitudinal mode of the intracavity field}, journal = {Phys. Rev. A}, volume = {70}, year = {2004}, month = {Dec}, pages = {062324}, publisher = {American Physical Society}, abstract = {A single three-level atom driven by a longitudinal mode of a high-Q cavity is used to implement two-qubit quantum phase gates for the intracavity field. The two qubits are associated with the zero- and one-photon Fock states of each of the two opposite circular polarization states of the field. The three-level atom mediates the conditional phase gate provided the two polarization states and the atom interact in a V-type configuration and the two-photon resonance condition is satisfied. Microwave and optical implementations are discussed with gate fidelities being evaluated against several decoherence mechanisms such as atomic velocity fluctuations or the presence of a weak magnetic field. The use of coherent states for both polarization states is investigated to assess the entanglement capability of the proposed quantum gates.

}, doi = {10.1103/PhysRevA.70.062324}, url = {http://link.aps.org/doi/10.1103/PhysRevA.70.062324}, author = {R. Garc{\'\i}a-Maraver and R. Corbal{\'a}n and K. Eckert and S. Rebic and M. Artoni and J. Mompart} } @booklet {doi:10.1117/12.589360, title = {Single three-level atoms for quantum information}, howpublished = {Proc. SPIE}, volume = {5622}, year = {2004}, pages = {430-434}, abstract = {A single three-level atom in interaction with a single longitudinal mode of a high-Q cavity is used to quantum engineer the intracavity field. In our proposal the quantum bit states correspond to the vacuum and single photon Fock states of each of two circular polarization states of the longitudinal mode. We show that for particular velocities of the three-level atom crossing the cavity it is possible to implement in one single step a two-qubit quantum phase gate between the two circular polarization states. Fidelity against several decoherence mechanisms such as atomc velocity fluctuations or the presence of a weak magnetic field along the cavity axis is analyzed.

}, doi = {10.1117/12.589360}, url = {http://dx.doi.org/10.1117/12.589360}, author = {J. Mompart and R. Garc{\'\i}a-Maraver and R. Corbal{\'a}n} }