26 research outputs found
Single-photon detection timing jitter in a visible light photon counter
Visible light photon counters (VLPCs) offer many attractive features as
photon detectors, such as high quantum efficiency and photon number resolution.
We report measurements of the single-photon timing jitter in a VLPC, a critical
performance factor in a time-correlated single-photon counting measurement, in
a fiber-coupled closed-cycle cryocooler. The measured timing jitter is 240 ps
full-width-at-half-maximum at a wavelength of 550 nm, with a dark count rate of
25 000 counts per second. The timing jitter increases modestly at longer
wavelengths to 300 ps at 1000 nm, and increases substantially at lower bias
voltages as the quantum efficiency is reduced
Analysis of a distributed fiber-optic temperature sensor using single-photon detectors
We demonstrate a high-accuracy distributed fiber-optic temperature sensor using superconducting nanowire single-photon detectors and single-photon counting techniques. Our demonstration uses inexpensive single-mode fiber at standard telecommunications wavelengths as the sensing fiber, which enables extremely low-loss experiments and compatibility with existing fiber networks. We show that the uncertainty of the temperature measurement decreases with longer integration periods, but is ultimately limited by the calibration uncertainty. Temperature uncertainty on the order of 3 K is possible with spatial resolution of the order of 1 cm and integration period as small as 60 seconds. Also, we show that the measurement is subject to systematic uncertainties, such as polarization fading, which can be reduced with a polarization diversity receiver
Distribution of Time-Energy Entanglement over 100 km fiber using superconducting single-photon detectors
In this letter, we report an experimental realization of distributing
entangled photon pairs over 100 km of dispersion-shifted fiber. In the
experiment, we used a periodically poled lithium niobate waveguide to generate
the time-energy entanglement and superconducting single-photon detectors to
detect the photon pairs after 100 km. We also demonstrate that the distributed
photon pairs can still be useful for quantum key distribution and other quantum
communication tasks.Comment: 6 pages, 3 figure
Observation of Transparency of Erbium-doped Silicon nitride in photonic crystal nanobeam cavities
One-dimensional nanobeam photonic crystal cavities are fabricated in an
Er-doped amorphous silicon nitride layer. Photoluminescence from the cavities
around 1.54 um is studied at cryogenic and room temperatures at different
optical pump powers. The resonators demonstrate Purcell enhanced absorption and
emission rates, also confirmed by time-resolved measurements. Resonances
exhibit linewidth narrowing with pump power, signifying absorption bleaching
and the onset of stimulated emission in the material at both 5.5 K and room
temperature. We estimate from the cavity linewidths that Er has been pumped to
transparency at the cavity resonance wavelength.Comment: 10 pages, 7 figure
Higher-order photon correlations in pulsed photonic crystal nanolasers
We report on the higher-order photon correlations of a high- nanolaser
under pulsed excitation at room temperature. Using a multiplexed four-element
superconducting single photon detector we measured g with
=2,3,4. All orders of correlation display partially chaotic statistics, even
at four times the threshold excitation power. We show that this departure from
coherence and Poisson statistics is due to the quantum fluctuations associated
with the small number of dipoles and photons involved in the lasing process
Generation of degenerate, factorizable, pulsed squeezed light at telecom wavelengths
We characterize a periodically poled KTP crystal that produces an entangled,
two-mode, squeezed state with orthogonal polarizations, nearly identical,
factorizable frequency modes, and few photons in unwanted frequency modes. We
focus the pump beam to create a nearly circular joint spectral probability
distribution between the two modes. After disentangling the two modes, we
observe Hong-Ou-Mandel interference with a raw (background corrected)
visibility of 86 % (95 %) when an 8.6 nm bandwidth spectral filter is applied.
We measure second order photon correlations of the entangled and disentangled
squeezed states with both superconducting nanowire single-photon detectors and
photon-number-resolving transition-edge sensors. Both methods agree and verify
that the detected modes contain the desired photon number distributions
Ultra fast quantum key distribution over a 97 km installed telecom fiber with wavelength-division multiplexing clock synchronization
We demonstrated ultra fast BB84 quantum key distribution (QKD) transmission
at 625 MHz clock rate through a 97 km field-installed fiber using practical
clock synchronization based on wavelength-division multiplexing (WDM). We
succeeded in over-one-hour stable key generation at a high sifted key rate of
2.4 kbps and a low quantum bit error rate (QBER) of 2.9%. The asymptotic secure
key rate was estimated to be 0.78-0.82 kbps from the transmission data with the
decoy method of average photon numbers 0, 0.15, and 0.4 photons/pulse.Comment: 7 pages, 3 figures, v2 : We added a comment on the significance of
our work, some minor corrections, and reference