760 research outputs found
Quantum information processing with space-division multiplexing optical fibres
The optical fibre is an essential tool for our communication infrastructure
since it is the main transmission channel for optical communications. The
latest major advance in optical fibre technology is spatial division
multiplexing (SDM), where new fibre designs and components establish multiple
co-existing data channels based on light propagation over distinct transverse
optical modes. Simultaneously, there have been many recent developments in the
field of quantum information processing (QIP), with novel protocols and devices
in areas such as computing, communication and metrology. Here, we review recent
works implementing QIP protocols with SDM optical fibres, and discuss new
possibilities for manipulating quantum systems based on this technology.Comment: Originally submitted version. Please see published version for
improved layout, new tables and updated references following review proces
Certifying an irreducible 1024-dimensional photonic state using refined dimension witnesses
We report on a new class of dimension witnesses, based on quantum random
access codes, which are a function of the recorded statistics and that have
different bounds for all possible decompositions of a high-dimensional physical
system. Thus, it certifies the dimension of the system and has the new distinct
feature of identifying whether the high-dimensional system is decomposable in
terms of lower dimensional subsystems. To demonstrate the practicability of
this technique we used it to experimentally certify the generation of an
irreducible 1024-dimensional photonic quantum state. Therefore, certifying that
the state is not multipartite or encoded using non-coupled different degrees of
freedom of a single photon. Our protocol should find applications in a broad
class of modern quantum information experiments addressing the generation of
high-dimensional quantum systems, where quantum tomography may become
intractable.Comment: Journal version (except for small editorial modifications), 4+12
pages, 7 figure
Postselection-Loophole-Free Bell Test Over an Installed Optical Fiber Network
Device-independent (DI) quantum communication will require a loophole-free
violation of Bell inequalities. In typical scenarios where line-of-sight
between the communicating parties is not available, it is convenient to use
energy-time entangled photons due to intrinsic robustness while propagating
over optical fibers. Here we show an energy-time Clauser-Horne-Shimony-Holt
Bell inequality violation with two parties separated by 3.7 km over the
deployed optical fiber network belonging to the University of Concepci\'on in
Chile. Remarkably, this is the first Bell violation with spatially separated
parties that is free of the post-selection loophole, which affected all
previous in-field long-distance energy-time experiments. Our work takes a
further step towards a fiber-based loophole-free Bell test, which is highly
desired for secure quantum communication due to the widespread existing
telecommunication infrastructure.Comment: 5 pages, 3 figures. Matches published versio
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