14 research outputs found
Coherence measures for heralded single-photon sources
Single-photon sources (SPSs) are mainly characterized by the minimum value of
their second-order coherence function, viz. their function. A precise
measurement of may, however, require high time-resolution devices, in
whose absence, only time-averaged measurements are accessible. These
time-averaged measures, standing alone, do not carry sufficient information for
proper characterization of SPSs. Here, we develop a theory, corroborated by an
experiment, that allows us to scrutinize the coherence properties of heralded
SPSs that rely on continuous-wave parametric down-conversion. Our proposed
measures and analysis enable proper standardization of such SPSs.Comment: 4 pages, 4 figures, corrected Eq. (10
Characterizing heralded single-photon sources with imperfect measurement devices
Any characterization of a single-photon source is not complete without
specifying its second-order degree of coherence, i.e., its function.
An accurate measurement of such coherence functions commonly requires
high-precision single-photon detectors, in whose absence, only time-averaged
measurements are possible. It is not clear, however, how the resulting
time-averaged quantities can be used to properly characterize the source. In
this paper, we investigate this issue for a heralded source of single photons
that relies on continuous-wave parametric down-conversion. By accounting for
major shortcomings of the source and the detectors--i.e., the multiple-photon
emissions of the source, the time resolution of photodetectors, and our chosen
width of coincidence window--our theory enables us to infer the true source
properties from imperfect measurements. Our theoretical results are
corroborated by an experimental demonstration using a PPKTP crystal pumped by a
blue laser, that results in a single-photon generation rate about 1.2 millions
per second per milliwatt of pump power. This work takes an important step
toward the standardization of such heralded single-photon sources.Comment: 18 pages, 9 figures; corrected Eq. (11) and the description follows
Eq. (22
Room temperature triggered single-photon source in the near infrared
We report the realization of a solid-state triggered single-photon source
with narrow emission in the near infrared at room temperature. It is based on
the photoluminescence of a single nickel-nitrogen NE8 colour centre in a
chemical vapour deposited diamond nanocrystal. Stable single-photon emission
has been observed in the photoluminescence under both continuous-wave and
pulsed excitations. The realization of this source represents a step forward in
the application of diamond-based single-photon sources to Quantum Key
Distribution (QKD) under practical operating conditions.Comment: 10 page
Nonclassical 2-photon interference with separate intrinsically narrowband fibre sources
In this paper, we demonstrate a source of photon pairs based on
four-wave-mixing in photonic crystal fibres. Careful engineering of the phase
matching conditions in the fibres enables us to create photon pairs at 597 nm
and 860 nm in an intrinsically factorable state showing no spectral
correlations. This allows for heralding one photon in a pure state and hence
renders narrow band filtering obsolete. The source is narrow band, bright and
achieves an overall detection efficiency of up to 21% per photon. For the first
time, a Hong-Ou-Mandel interference with unfiltered photons from separate fibre
sources is presented.Comment: 10 pages, 6 figure
Optical source of individual pairs of colour-conjugated photons
We theoretically demonstrate that Kerr nonlinearity in optical circuits can lead to both resonant four-wave mixing and photon blockade, which can be used for high-yield generation of high-fidelity individual photon pairs with conjugated frequencies. We propose an optical circuit, which, in the optimal pulsed-drive regime, would produce photon pairs at the rate up to 5âĂâ105â sâ1 (0.5 pairs per pulse) with g(2)(0)<10â2g(2)(0)<10â2 for one of the conjugated frequencies. We show that such a scheme can be utilised to generate colour-entangled photons