A Hybrid Long-Distance Entanglement Distribution Protocol

We propose a hybrid (continuous-discrete variable) quantum repeater protocol for distribution of entanglement over long distances. Starting from entangled states created by means of single-photon detection, we show how entangled coherent state superpositions, also known as `Schr\"odinger cat states', can be generated by means of homodyne detection of light. We show that near-deterministic entanglement swapping with such states is possible using only linear optics and homodyne detectors, and we evaluate the performance of our protocol combining these elements.Comment: 4 pages, 3 figure

Nondiffracting beams for vortex tomography

We propose a reconstruction of vortex beams based on the implementation of quadratic transformations in the orbital angular momentum. The information is encoded in a superposition of Bessel-like nondiffracting beams. The measurement of the angular probability distribution at different positions allows for the reconstruction of the Wigner function.Comment: 3 pages. 2 eps figures. To appear in Optics Letter

Amplification of realistic Schrödinger-cat-state-like states by homodyne heralding

We present a scheme for the amplification of Schrodinger cats that collapses two smaller states onto their constructive interference via a homodyne projection. We analyze the performance of the amplification in terms of fidelity and success rate when the input consists of either exact coherent state superpositions or of photon-subtracted squeezed vacua. The impact of imprecise homodyne detection and of impure squeezing is quantified. We also assess the scalability of iterated amplifications.Comment: 11 pages, 15 figure

Anything but qubits

<p>Poster presented at the Photons Beyond Qubits workshop in Olomouc, April 2013.</p> <p>Three topics are briefly covered: </p> <p> * Cat state amplification by conditional homodyning</p> <p> * Displacement-enhanced entanglement distillation</p> <p> * Towards an efficient single photon source with NV centres in an open microcavity</p> <p>The first two are theoretical schemes for quantum information processing with squeezed and cat states, published in Physical Review A 87, 043826 (2013) and Optics Express 21, 6670-6680 (2013), respectively.</p> <p>The third subject is our current experimental work on creating micron-sized optical resonators with fibres, particularly for the purpose of interfacing with nitrogen-vacancy centres in diamond nanocrystals.</p