Quantum Entanglement in Nanocavity Arrays

We show theoretically how quantum interference between linearly coupled modes with weak local nonlinearity allows the generation of continuous variable entanglement. By solving the quantum master equation for the density matrix, we show how the entanglement survives realistic levels of pure dephasing. The generation mechanism forms a new paradigm for entanglement generation in arrays of coupled quantum modes.Comment: 5 pages, 3 figure

Artificial Life in an Exciton-Polariton Lattice

We show theoretically that a lattice of exciton-polaritons can behave as a life-like cellular automaton when simultaneously excited by a continuous wave coherent field and a time-periodic sequence of non-resonant pulses. This provides a mechanism of realizing a range of highly sought spatiotemporal structures under the same conditions, including: discrete solitons, oscillating solitons, rotating solitons, breathers, soliton trains, guns, and choatic behaviour. These structures can survive in the system indefinitely, despite the presence of dissipation, and allow universal computation.Comment: 14 pages, 14 figure

Exciton-Polariton Quantum Gates Based on Continuous Variables

We propose a continuous variable analog of quantum controlled-NOT gates based on a system of exciton-polaritons in semiconductor microcavities. This can be realized by the engineering of parametric interaction between control and target polariton modes, which can be varied in time. As an explicit setup we use a system of dipolaritons, which allows for enhancement of parametric interaction by auxiliary classical fields and scalable multigate system realization. The calculated fidelity is shown to exceed 99% for realistic system parameters.Comment: 6 pages, 3 figures + 6 pages, 2 figures supplemental materia

Optically erasing disorder in semiconductor microcavities with dynamic nuclear polarization

The mean squared value of the photonic disorder is found to be reduced by a factor of 100 in a typical GaAs based microcavity, when exposed to a circularly polarized continuous wave optical pump without any special spatial patterning. Resonant excitation of the cavity mode excites a spatially non-uniform distribution of spin-polarized electrons, which depends on the photonic disorder profile. Electrons transfer spin to nuclei via the hyperfine contact interaction, inducing a long-living Overhauser magnetic field able to modify the potential of exciton-polaritons.Comment: 4 pages, 3 figure

Quantum Exciton-Polariton Networks through Inverse Four-Wave Mixing

We demonstrate the potential of quantum operation using lattices of exciton-polaritons in patterned semiconductor microcavities. By introducing an inverse four-wave mixing scheme acting on localized modes, we show that it is possible to develop non-classical correlations between individual condensates. This allows a concept of quantum exciton-polariton networks, characterized by the appearance of multimode entanglement even in the presence of realistic levels of dissipation.Comment: 5 pages, 4 figures, pre-review version of manuscrip

Multimode entanglement in coupled cavity arrays

We study a driven-dissipative array of coupled nonlinear optical resonators by numerically solving the Von Neumann equation for the density matrix. We demonstrate that quantum correlated states of many photons can be generated also in the limit where the nonlinearity is much smaller than the losses, contrarily to common expectations. Quantum correlations in this case arise from interference between different pathways that the system can follow in the Hilbert space to reach its steady state under the effect of coherent driving fields. We characterize in particular two systems: a linear chain of three coupled cavities and an array of eight coupled cavities. We demonstrate the existence of a parameter range where the system emits photons with continuous-variable bipartite and quadripartite entanglement, in the case of the first and the second system respectively. This entanglement is shown to survive realistic rates of pure dephasing and opens a new perspective for the realization of quantum simulators or entangled photon sources without the challenging requirement of strong optical nonlinearities.Comment: 20 pages, 7 figure

Optically induced transparency in bosonic cascade lasers

Bosonic cascade lasers are terahertz (THz) lasers based on stimulated radiative transitions between bosonic condensates of excitons or exciton-polaritons confined in a trap. We study the interaction of an incoming THz pulse resonant in frequency with the transitions between neighboring energy levels of the cascade. We show that at certain optical pump conditions the cascade becomes transparent to the incident pulse: it neither absorbs nor amplifies it, in the mean field approximation. The populations of intermediate levels of the bosonic cascade change as the THz pulse passes, nevertheless. In comparison, a fermionic cascade laser does not reveal any of these properties.Comment: 4 pages, 5 figure