15 research outputs found
Experimental Satellite Quantum Communications
Quantum Communications on planetary scale require complementary channels
including ground and satellite links. The former have progressed up to
commercial stage using fiber-cables, while for satellite links, the absence of
terminals in orbit has impaired theirs development. However, the demonstration
of the feasibility of such links is crucial for designing space payloads and to
eventually enable the realization of protocols such as quantum-key-distribution
(QKD) and quantum teleportation along satellite-to-ground or intersatellite
links. We demonstrated the faithful transmission of qubits from space to ground
by exploiting satellite corner cube retroreflectors acting as transmitter in
orbit, obtaining a low error rate suitable for QKD. We also propose a two-way
QKD protocol exploiting modulated retroreflectors that necessitates a minimal
payload on satellite, thus facilitating the expansion of Space Quantum
Communications
Experimental single photon exchange along a space link of 7000 km
Extending the single photon transmission distance is a basic requirement for
the implementation of quantum communication on a global scale. In this work we
report the single photon exchange from a medium Earth orbit satellite (MEO) at
more than 7000 km of slanted distance to the ground station at the Matera Laser
Ranging Observatory. The single photon transmitter was realized by exploiting
the corner cube retro-reflectors mounted on the LAGEOS-2 satellite. Long
duration of data collection is possible with such altitude, up to 43 minutes in
a single passage. The mean number of photons per pulse ({\mu}sat) has been
limited to 1 for 200 seconds, resulting in an average detection rate of 3.0 cps
and a signal to noise ratio of 1.5. The feasibility of single photon exchange
from MEO satellites paves the way to tests of Quantum Mechanics in moving
frames and to global Quantum Information.Comment: 5 pages, updated versio
Interference at the Single Photon Level Along Satellite-Ground Channels
Quantum interference arising from superposition of states is a striking
evidence of the validity of Quantum Mechanics, confirmed in many experiments
and also exploited in applications. However, as for any scientific theory,
Quantum Mechanics is valid within the limits in which it has been
experimentally verified. In order to extend such limits, it is necessary to
observe quantum interference in unexplored conditions such as moving terminals
at large distance in Space. Here we experimentally demonstrate single photon
interference at a ground station due to the coherent superposition of two
temporal modes reflected by a rapidly moving satellite thousand kilometers
away. The relative speed of the satellite induces a varying modulation in the
interference pattern. The measurement of the satellite distance in real time by
laser ranging allowed us to precisely predict the instantaneous value of the
interference phase. We then observed the interference patterns with visibility
up to with three different satellites and with path length up to 5000
km. Our results attest the viability of photon temporal modes for fundamental
tests of Physics and Quantum Communications in Space.Comment: Version accepted for publication in Phys. Rev. Let
Towards Quantum Communication from Global Navigation Satellite System
Satellite-based quantum communication is an invaluable resource for the
realization of a quantum network at the global scale. In this regard, the use
of satellites well beyond the low Earth orbits gives the advantage of long
communication time with a ground station. However, high-orbit satellites pose a
great technological challenge due to the high diffraction losses of the optical
channel, and the experimental investigation of such quantum channels is still
lacking. Here, we report on the first experimental exchange of single photons
from Global Navigation Satellite System at a slant distance of 20000
kilometers, by exploiting the retroreflector array mounted on GLONASS
satellites. We also observed the predicted temporal spread of the reflected
pulses due to the geometrical shape of array. Finally, we estimated the
requirements needed for an active source on a satellite, aiming towards quantum
communication from GNSS with state-of-the-art technology.Comment: Revte
Extending Wheeler's delayed-choice experiment to Space
Gedankenexperiments have consistently played a major role in the development
of quantum theory. A paradigmatic example is Wheeler's delayed-choice
experiment, a wave-particle duality test that cannot be fully understood using
only classical concepts. Here, we implement Wheeler's idea along a
satellite-ground interferometer which extends for thousands of kilometers in
Space. We exploit temporal and polarization degrees of freedom of photons
reflected by a fast moving satellite equipped with retro-reflecting mirrors. We
observed the complementary wave-like or particle-like behaviors at the ground
station by choosing the measurement apparatus while the photons are propagating
from the satellite to the ground. Our results confirm quantum mechanical
predictions, demonstrating the need of the dual wave-particle interpretation,
at this unprecedented scale. Our work paves the way for novel applications of
quantum mechanics in Space links involving multiple photon degrees of freedom.Comment: 4 figure
Sub-ns timing accuracy for satellite quantum communications
Satellite quantum communications have rapidly evolved in the past few years,
culminating in the proposal, development, and deployment of satellite missions
dedicated to quantum key distribution and the realization of fundamental tests
of quantum mechanics in space. However, in comparison with the more mature
technology based on fiber optics, several challenges are still open, such as
the capability of detecting, with high temporal accuracy, single photons coming
from orbiting terminals. Satellite laser ranging, commonly used to estimate
satellite distance, could also be exploited to overcome this challenge. For
example, high repetition rates and a low background noise can be obtained by
determining the time-of-flight of faint laser pulses that are retro-reflected
by geodynamics satellites and then detected on Earth at the single-photon
level. Here we report an experiment with regard to achieving a temporal
accuracy of approximately 230 ps in the detection of an optical signal of few
photons per pulse reflected by satellites in medium Earth orbit, at a distance
exceeding 7500 km, by using commercially available detectors. Lastly, the
performance of the Matera Laser Ranging Observatory is evaluated in terms of
the detection rate and the signal-to-noise ratio for satellite quantum
communications.Comment: 7 pages, 4 figures, part of the "QUANTUM KEY DISTRIBUTION AND BEYOND"
featured issue of the Journal of the Optical Society of America