2,787 research outputs found
Near-infrared Hong-Ou-Mandel interference on a silicon quantum photonic circuit
Near-infrared Hong-Ou-Mandel quantum interference is observed in silicon
nanophotonic directional couplers with raw visibilities on-chip at 90.5%.
Spectrally-bright 1557-nm two-photon states are generated in a
periodically-poled KTiOPO4 waveguide chip, serving as the entangled photon
source and pumped with a self-injection locked laser, for the photon
statistical measurements. Efficient four-port coupling in the communications
C-band and in the high-index-contrast silicon photonics platform is
demonstrated, with matching theoretical predictions of the quantum interference
visibility. Constituents for the residual quantum visibility imperfection are
examined, supported with theoretical analysis of the sequentially-triggered
multipair biphoton contribution and techniques for visibility compensation,
towards scalable high-bitrate quantum information processing and
communications.Comment: 15 pages, 6 figure
Coherent controllers for optical-feedback cooling of quantum oscillators
We study the cooling performance of optical-feedback controllers for open
optical and mechanical resonators in the Linear Quadratic Gaussian setting of
stochastic control theory. We utilize analysis and numerical optimization of
closed-loop models based on quantum stochastic differential equations to show
that coherent control schemes, where we embed the resonator in an
interferometer to achieve all-optical feedback, can outperform optimal
measurement-based feedback control schemes in the quantum regime of low
steady-state excitation number. These performance gains are attributed to the
coherent controller's ability to simultaneously process both quadratures of an
optical probe field without measurement or loss of fidelity, and may guide the
design of coherent feedback schemes for more general problems of robust
nonlinear and robust control.Comment: 15 pages, 20 figures. Submitted to Physical Review X. Follow-up paper
to arXiv:1206.082
Experimental Long-Distance Decoy-State Quantum Key Distribution Based On Polarization Encoding
We demonstrate the decoy-state quantum key distribution (QKD) with one-way
quantum communication in polarization space over 102km. Further, we simplify
the experimental setup and use only one detector to implement the one-way
decoy-state QKD over 75km, with the advantage to overcome the security
loopholes due to the efficiency mismatch of detectors. Our experimental
implementation can really offer the unconditionally secure final keys. We use 3
different intensities of 0, 0.2 and 0.6 for the pulses of source in our
experiment. In order to eliminate the influences of polarization mode
dispersion in the long-distance single-mode optical fiber, an automatic
polarization compensation system is utilized to implement the active
compensation.Comment: 4 pages,3 figure
Sub-picotesla widely tunable atomic magnetometer operating at room-temperature in unshielded environments
We report on a single-channel rubidium radio-frequency atomic magnetometer
operating in un-shielded environments and near room temperature with a measured
sensitivity of 130 fT/\sqrt{Hz}. We demonstrate consistent, narrow-bandwidth
operation across the kHz - MHz band, corresponding to three orders of magnitude
of magnetic field amplitude. A compensation coil system controlled by a
feedback loop actively and automatically stabilizes the magnetic field around
the sensor. We measure a reduction of the 50 Hz noise contribution by an order
of magnitude. The small effective sensor volume, 57 mm^3, increases the spatial
resolution of the measurements. Low temperature operation, without any magnetic
shielding, coupled with the broad tunability, and low beam power, dramatically
extends the range of potential field applications for our device.Comment: Main text: 6 pages, 9 figures. Supplementary material: 3 pages, 3
figures. Published version can be found at
https://aip.scitation.org/doi/full/10.1063/1.5026769 . V2: Added journal
layout, minor typos fixed. Content unchange
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