[Show abstract][Hide abstract] ABSTRACT: We report on the performance of a compact photon pair source that was
recovered intact from a failed space launch. The source had been embedded in a
nanosatellite and was designed to perform pathfi?nder experiments leading to
global quantum communication networks using spacecraft. Despite the launch
vehicle explosion soon after takeoff?, the nanosatellite was successfully
retrieved from the accident site and the source within it was found to be fully
operational. We describe the assembly technique for the rugged source.
Post-recovery data is compared to baseline measurements collected before the
launch attempt and no degradation in brightness or polarization correlation was
observed. The survival of the source through an extreme environment provides
strong evidence that it is possible to engineer rugged quantum optical systems.
[Show abstract][Hide abstract] ABSTRACT: We present comprehensive measurement data on the pump and collection beam
parameters necessary to achieve high collection efficiency ($89.0 \pm 1.7 \%$)
together with high brightness when a single $\beta$-Barium Borate crystal is
operated in the thick-crystal regime and pumped with a narrow linewidth laser
source. Spectral analysis of the collinear, non-degenerate photons suggest that
the effective interaction length within the crystal is dominated by the
collection beam mode and the use of longer crystals with increased spatial
walk-off does not necessarily lead to a reduced collection efficiency. This
result is an important consideration for optical designers who seek to develop
practical photon pair sources.
[Show abstract][Hide abstract] ABSTRACT: Quantum Key Distribution (QKD) using entangled photon pairs enables highly-secure communications but requires that individual photons be exchanged between the two communicating parties. Practical limitations prevent the distance over which this is performed being more than a few hundred kilometres on the ground, but from space much longer distances can be achieved. A first step towards enabling space-to-ground QKD is to develop and demonstrate a space-compatible entangled photon source. To pursue this goal CQT are developing miniaturised ruggedised sources that are compatible with the CubeSat nanosatellite platform. Although CubeSats impose significant size, weight and power restrictions, their large developer base and widespread adoption enables low-cost raising of technology readiness level with rapid development cycles. This paper gives an overview of the SPEQS-1 devices that are being built to prove the new principles of our miniaturised entangled photon sources, SPEQS-2 which is being developed to be powerful enough for space-to-ground QKD and SpooQySats, the CubeSat platforms we are developing to test SPEQS-2 prior to full space-to-ground QKD demonstrations. This abstract has been modified from the one originally submitted to the IAC conference proceedings, for original see appendix.
[Show abstract][Hide abstract] ABSTRACT: In this paper we present a high-level numerical model for estimating rates of
accidental correlations between a pair of passively quenched Geiger mode
avalanche photodiodes operating in the saturated regime. By considering the
recovery time of both the diodes and the detection circuit we introduce the
concept of an "effective duty cycle" and show that it may be estimated by
numeric simulation. The impact of effective duty cycle on the observed
accidental rate is examined and we demonstrate that the updated model leads to
an improved correction factor in actual experiments. This will improve the
signal-to-noise ratio in applications depending on correlation measurements.
[Show abstract][Hide abstract] ABSTRACT: To enable space-based quantum key distribution proposals the Centre for
Quantum Technologies is developing a source of entangled photons ruggedized to
survive deployment in space and greatly miniaturised so that it conforms to the
strict form factor and power requirements of a 1U CubeSat. The Small Photon
Entangling Quantum System is an integrated instrument where the pump, photon
pair source and detectors are combined within a single optical tray and
electronics package that is no larger than 10 cm x 10 cm x 3 cm. This footprint
enables the instrument to be placed onboard nanosatellites or the CubeLab
structure aboard the International Space Station. We will discuss the
challenges and future prospects of CubeSat-based missions.
[Show abstract][Hide abstract] ABSTRACT: The Small Photon Entangling Quantum System is an integrated instrument where
the pump, photon pair source and detectors are combined within a single optical
tray and electronics package that is no larger than 10cm x 10cm x 3cm. This
footprint enables the instrument to be placed onboard nanosatellites or the
CubeLab facility within the International Space Station. The first mission is
to understand the different environmental conditions that may affect the
operation of an entangled photon source in low Earth orbit. This understanding
is crucial for the construction of cost-effective entanglement based
experiments that utilize nanosatellite architecture. We will discuss the
challenges and lessons we have learned over three years of development and
testing of the integrated optical platform and review the perspectives for
future advanced experiments.
[Show abstract][Hide abstract] ABSTRACT: We report the design and implementation of a complete electronics platform
for conducting a quantum optics experiment that will be operated on board a 1U
CubeSat (a 10 x 10 x 10 cm satellite). The quantum optics experiment is
designed to produce polarization-entangled photon pairs using non-linear
optical crystals and requires opto-electronic components such as a pump laser,
single photon detectors and liquid crystal based polarization rotators in
addition to passive optical elements. The platform provides mechanical support
for the optical assembly. It also communicates autonomously with the host
satellite to provide experiment data for transmission to a ground station. A
limited number of commands can be transmitted from ground to the platform
enabling it to switch experimental modes. This platform requires less than 1.5W
for all operations, and is space qualified. The implementation of this
electronics platform is a major step on the road to operating quantum
communication experiments using nanosatellites.
Preview · Article · May 2015 · Journal of Lightwave Technology
[Show abstract][Hide abstract] ABSTRACT: Experiments in long distance quantum key distribution have motivated the
development of ruggedised single photon sources, capable of producing useful
correlations even when removed from the warm, nurturing environment found in
most optics laboratories. As part of an ongoing pro- gramme to place such
devices into low earth orbit (LEO), we have developed and built a number of
rugged single photon sources based on spontaneous parametric downconversion. In
order to evalu- ate device reliability, we have subjected our design to various
thermal, mechanical and atmospheric stresses. Our results show that while such
a device may tolerate launch into orbit, operation in orbit and casual
mishandling by graduate students, it is probably unable to survive the forcible
disassembly of a launch vehicle at the top of a ball of rapidly expanding and
oxidising kerosene and liquid oxygen.
[Show abstract][Hide abstract] ABSTRACT: Plasma in low earth orbit can damage electronic components and potentially
jeopardise the scientific missions in space. Predicting the accumulated damage
and understanding the components' radiation tolerance are important to mission
planning. In this manuscript we report on the observed radiation tolerance of
single photon detectors and a liquid crystal polarization rotator. We conclude
that an uncooled Si APD could continue to operate from more than a month up to
beyond the lifetime of the satellite depending on the orbit. The polarization
rotator was also unaffected by the exposed dosage.
Preview · Article · Jan 2015 · Journal of Modern Optics
[Show abstract][Hide abstract] ABSTRACT: We report the successful test flight of a device for generating and
monitoring correlated photon pairs under near-space conditions up to 35.5km
altitude. Data from ground based qualification tests and the high altitude
experiment demonstrate that the device continues to operate even under harsh
environmental conditions. The design of the rugged, compact and power-efficient
photon pair system is presented. This design enables autonomous photon pair
systems to be deployed on low-resource platforms such as nanosatellites hosting
remote nodes of a quantum key distribution network. These results pave the way
for tests of entangled photon technology in low earth orbit.
[Show abstract][Hide abstract] ABSTRACT: Silicon avalanche photodiodes (APDs) are sensitive to operating temperature
fluctuations and are also susceptible to radiation flux expected in
satellite-based quantum experiments. We introduce a low power voltage adjusting
mechanism to overcome the effects of in-orbit temperature fluctuations. We also
present data on the performance of Si APDs after irradiation (gamma-ray and
proton beam). Combined with an analysis of expected orbital irradiation, we
propose that a Si APD in a 400 km equatorial orbit may operate beyond the
lifetime of the satellite.
[Show abstract][Hide abstract] ABSTRACT: We report on our efforts in integrating a source and detection system of
photon pairs that have a high end-to-end system efficiency. This
requires combining appropriate detectors and photon pair sources.
Preliminary measurements show that an observed heralding efficiency of
65% for single photons is readily achieved.
No preview · Article · Aug 2010 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: We map the transverse profile of light beams using photon-number-resolving detectors, and observe compression of beam profiles for higher detected photon-number, enabling contrast enhancement between two Airy disk beams at the Rayleigh limit.
[Show abstract][Hide abstract] ABSTRACT: We report on an experimental implementation of an interface between quantum dots (QD) and parametric downconversion (PDC). We present a PDC source compatible with QD emission and our efforts to demonstrate such compatibility.
[Show abstract][Hide abstract] ABSTRACT: We use strain to tune into resonance two different, remote quantum dots and show that the emitted photons will produce Hong-Ou-Mandel interference. Pulsed excitation will allow deterministic timing of these indistinguishable photons.
[Show abstract][Hide abstract] ABSTRACT: We show that with simple spectral filtering, the Schmidt number for the transmitted photon-pairs (with 90% transmittance) which are produced via type-II parametric down-conversion in a KTP waveguide equals to unity to within 0.2 %.
[Show abstract][Hide abstract] ABSTRACT: We experimentally map the transverse profile of diffraction-limited beams
using photon-number-resolving detectors. We observe strong compression of
diffracted beam profiles for high detected photon number. This effect leads to
higher contrast than a conventional irradiance profile between two Airy
disk-beams separated by the Rayleigh criterion.
[Show abstract][Hide abstract] ABSTRACT: We report the development of a fiber-based single spatial-mode source of photon-pairs where the efficiency of extracting photon-pairs is increased through the use of fiber-end expansion and Bragg filters. This improvement in efficiency enabled a spectrally bright and pure photon-pair source having a small second-order correlation function (0.03) and a raw spectral brightness of 44,700 pairs s(-1)nm(-1)mW(-1). The source can be configured to generate entangled photon-pairs, characterized via optimal and minimal quantum state tomography, to have a fidelity of 97% and tangle of 92%, without subtracting any background.