23 research outputs found
Violation of Bell's inequality for phase singular beams
We have considered optical beams with phase singularity and experimentally
verified that these beams, although being classical, have properties of two
mode entanglement in quantum states. We have observed the violation of Bell's
inequality for continuous variables using the Wigner distribution function
(WDF) proposed by Chowdhury et al. [Phys. Rev. A \textbf{88}, 013830 (2013)].
Our experiment establishes a new form of Bell's inequality in terms of the WDF
which can be used for classical as well as quantum systems.Comment: 7 pages, 9 figures and 1 tabl
Towards Fully Passive Time-Bin Quantum Key Distribution over Multi-Mode Channels
Phase stabilization of distant quantum time-bin interferometers is a major
challenge for quantum communication networks, and is typically achieved by
exchanging optical reference signals, which can be particularly challenging
over free-space channels. We demonstrate a novel approach using reference frame
independent time-bin quantum key distribution that completely avoids the need
for active relative phase stabilization while simultaneously overcoming a
highly multi-mode channel without any active mode filtering. We realized a
proof-of-concept demonstration using hybrid polarization and time-bin entangled
photons, that achieved a sustained asymptotic secure key rate of greater than
0.06 bits/coincidence over a 15m multi-mode fiber optical channel. This is
achieved without any mode filtering, mode sorting, adaptive optics, active
basis selection, or active phase alignment. This scheme enables passive
self-compensating time-bin quantum communication which can be readily applied
to long-distance links and various wavelengths, and could be useful for a
variety of spatially multi-mode and fluctuating channels involving rapidly
moving platforms, including airborne and satellite systems.Comment: 12 pages, 4 Figures, 1 Tabl
Entanglement demonstration on board a nano-satellite
Global quantum networks for secure communication can be realized using large fleets of satellites distributing entangled photon pairs between ground-based nodes. Because the cost of a satellite depends on its size, the smallest satellites will be most cost-effective. This Letter describes a miniaturized, polarization entangled, photon-pair source operating on board a nano-satellite. The source violates Bell’s inequality with a Clauser–Horne–Shimony–Holt parameter of 2.60±0.06. This source can be combined with optical link technologies to enable future quantum communication nano-satellite missions
SpooQy-1: The First Nano-Satellite to Demonstrate Quantum Entanglement in Space
SpooQy-1 is a 3-unit nanosatellite that was launched into a Low Earth Orbit from the International Space Station on the 17th of June 2019. The spacecraft hosts a scientific payload capable of producing entangled photon-pairs and measuring their polarization in orthogonal bases to perform a Bell test. Since launch, SpooQy-1 has routinely demonstrated the generation and detection of polarization entangled photon-pairs in Space, something that has previously only been demonstrated by the 630kg Micius mission by the Chinese Academy of Sciences. The measured entanglement correlations can violate Bell\u27s inequality with a CHSH parameter value of 2.60±0.06, over operating temperatures of 16 °C to 21.5 °C. These results demonstrate that quantum entanglement can be generated in space on highly resource-constrained platforms. A follow-on 12U mission, developed in partnership with RAL space,will build on this to demonstrate space-to-ground entanglement distribution, which is required for space-based nodes to support global quantum communication networks
Observing sub-Poissonian statistics of twisted single photons using oscilloscope
by Nijil Lal, Biveen Shajilal, Ali Anwar, Chithrabhanu Perumangatt and R. P. Sing