160 research outputs found
Photon-Photon Interactions in Dynamically Coupled Cavities
We study theoretically the interaction between two photons in a nonlinear
cavity. The photons are loaded into the cavity via a method we propose here, in
which the input/output coupling of the cavity is effectively controlled via a
tunable coupling to a second cavity mode that is itself strongly
output-coupled. Incoming photon wave packets can be loaded into the cavity with
high fidelity when the timescale of the control is smaller than the duration of
the wave packets. Dynamically coupled cavities can be used to avoid limitations
in the photon-photon interaction time set by the delay-bandwidth product of
passive cavities. Additionally, they enable the elimination of wave packet
distortions caused by dispersive cavity transmission and reflection. We
consider three kinds of nonlinearities, those arising from
and materials and
that due to an interaction with a two-level emitter. To analyze the input and
output of few-photon wave packets we use a Schr\"odinger-picture formalism in
which travelling-wave fields are discretized into infinitesimal time-bins. We
suggest that dynamically coupled cavities provide a very useful tool for
improving the performance of quantum devices relying on cavity-enhanced
light-matter interactions such as single-photon sources and atom-like quantum
memories with photon interfaces. As an example, we present simulation results
showing that high fidelity two-qubit entangling gates may be constructed using
any of the considered nonlinear interactions
Practical high-dimensional quantum key distribution with decoy states
High-dimensional quantum key distribution (HD-QKD) allows two parties to
generate multiple secure bits of information per detected photon. In this work,
we show that decoy state protocols can be practically implemented for HD-QKD
using only one or two decoy states. HD-QKD with two decoy states, under
realistic experimental constraints, can generate multiple secure bits per
coincidence at distances over 200 km and at rates similar to those achieved by
a protocol with infinite decoy states. Furthermore, HD-QKD with only one decoy
state is practical at short distances, where it is almost as secure as a
protocol with two decoy states. HD-QKD with only one or two decoy states can
therefore be implemented to optimize the rate of secure quantum communications.Comment: 11 pages, 3 figure
Wide-field strain imaging with preferentially aligned nitrogen-vacancy centers in polycrystalline diamond
We report on wide-field optically detected magnetic resonance imaging of nitrogen-vacancy centers (NVs) in type IIa polycrystalline diamond. These studies reveal a heterogeneous crystalline environment that produces a varied density of NV centers, including preferential orientation within some individual crystal grains, but preserves long spin coherence times. Using the native NVs as nanoscale sensors, we introduce a three-dimensional strain imaging technique with high sensitivity (<10â»â”Hzâ»Âœ) and diffraction-limited resolution across a wide field of view.United States. Office of Naval Research (N00014-13-1-0316)United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative I(FA9550-14-1-0052)United States. Air Force Office of Scientific Research (Presidential Early Career Award
Self-Similar Nanocavity Design with Ultrasmall Mode Volume for Single-Photon Nonlinearities
United States. Air Force Office of Scientific Research (FA8750-13-2-0120
High-dimensional unitary transformations and boson sampling on temporal modes using dispersive optics
A major challenge for postclassical boson sampling experiments is the need for a large number of coupled optical modes, detectors, and single-photon sources. Here we show that these requirements can be greatly eased by time-bin encoding and dispersive optics-based unitary transformations. Detecting consecutively heralded photons after time-independent dispersion performs boson sampling from unitaries for which an efficient classical algorithm is lacking. We also show that time-dependent dispersion can implement general single-particle unitary operations. More generally, this scheme promises an efficient architecture for a range of other linear optics experiments.United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Grant FA9550-14-1-0052
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