Target detection through quantum illumination

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2012."February 2012." Cataloged from PDF version of thesis.Includes bibliographical references (p. 69-70).Classical target detection can suffer large error probabilities in noisy and lossy environments when noise photons are mistaken for signal photons reflected from an object. It has been shown theoretically that the correlation between entangled photons can be used to better discriminate between the signal photons reflected by an object and noise photons, thus reducing the probability of error [13, 15, 17, 7, 6]. This thesis presents the first experimental implementation of target detection enhanced by quantum illumination (QI). Nondegenerate, time entangled signal and idler beams are created through Type-O spontaneous parametric downconversion (SPDC). The signal is attenuated and combined with large levels of noise. The signal is phase modulated to improve the observation by shifting it from DC to 16 kHz. The return signal and idler are recombined in an optical parametric amplifier (OPA) which captures the phase correlation between the two beams. It is found that only 10% of the total signal and idler photons interact at the OPA due to the multi-mode nature of the SPDC emission which does not match the pump spatial mode and thus experience lower gains at the OPA. Considering only the power interacting at the OPA, the signal-to-noise ratio (SNR) of QI agrees with the theoretical model.by Sara L. Mouradian.M.Eng

Efficient Photon Coupling from a Diamond Nitrogen Vacancy Centre by Integration with Silica Fibre

A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing. Here, we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit, the nitrogen vacancy (NV) centre in diamond, with a single-mode optical fibre. In this approach, single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibres. Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes. Experimentally, we find an overall collection efficiency between 18-40 % and observe a raw single photon count rate above 700 kHz. This integrated system enables robust, alignment-free, and efficient interfacing of single-mode optical fibres with single photon emitters and quantum memories in solids

Entanglement-Enhanced Sensing in a Lossy and Noisy Environment

Nonclassical states are essential for optics-based quantum information processing, but their fragility limits their utility for practical scenarios in which loss and noise inevitably degrade, if not destroy, nonclassicality. Exploiting nonclassical states in quantum metrology yields sensitivity advantages over all classical schemes delivering the same energy per measurement interval to the sample being probed. These enhancements, almost without exception, are severely diminished by quantum decoherence. Here, we experimentally demonstrate an entanglement-enhanced sensing system that is resilient to quantum decoherence. We employ entanglement to realize a 20% signal-to-noise ratio improvement over the optimum classical scheme in an entanglement-breaking environment plagued by 14 dB of loss and a noise background 75 dB stronger than the returned probe light. Our result suggests that advantageous quantum-sensing technology could be developed for practical situations.United States. Army Research Office (Grant W911NF-10-1-0430)United States. Office of Naval Research (Grant N00014-13-1-0774

Low-jitter single-photon detector arrays integrated with silicon and aluminum nitride photonic chips

We present progress on a scalable scheme for integration of single-photon detectors with silicon and aluminum nitride photonic circuits. We assemble arrays of low-jitter waveguide-integrated single-photon detectors and show up to 24% system detection efficiency

Scalable Integration of Solid State Quantum Memories into a Photonic Network

Single nitrogen vacancy centers in nanostructured diamond form high quality nodes integrated into low-loss photonic circuitry, enabling on-chip detection and signal manipulation. Pre-selection provides near-unity yield. Long coherence times are demonstrated in integrated nodes

Solid state quantum memories coupled to photonic integrated circuits

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 93-107).Quantum computation and communication systems exploit quantum mechanical effects to surpass their classical counterparts in certain applications. However, while proof-of-principle experimental demonstrations have been performed, these are limited to a handful of nodes with limited - and often immutable - connectivity. Here we demonstrate an integrated platform for solid state quantum information processing. Pre-characterized solid state quantum nodes (nitrogen vacancy centers in diamond nanophotonic structures) are placed into a photonic integrated circuit which allows for low-loss and phase-stable collection, routing, and detection of photons as well as on-chip state manipulation and classical control. Moreover, the fabrication of high-quality photonic resonators in diamond allows for the increased emission and collection rates of photons coherent with the spin state. These two advances promise an on-chip entanglement rate much larger than the decoherence rate, allowing the creation and maintenance of cluster states for quantum computation.by Sara Lambert Mouradian.Ph. D