Tools for quantum information: work at INRIM on characterization of quantum optical states, communication channels, and photo-detectors

2007 ◽  
Author(s):  
N. Antonietti ◽  
G. Brida ◽  
M. Genovese ◽  
M. Gramegna ◽  
L. Krivitsky ◽  
...  
Keyword(s):  
Quantum Information ◽  
Communication Channels ◽  
Photo Detectors ◽  
Information Work ◽  
Quantum Optical

scholarly journals Topological protection of biphoton states

Science ◽  
2018 ◽  
Vol 362 (6414) ◽  
pp. 568-571 ◽  
Author(s):  
Andrea Blanco-Redondo ◽  
Bryn Bell ◽  
Dikla Oren ◽  
Benjamin J. Eggleton ◽  
Mordechai Segev
Keyword(s):  
Quantum Information ◽  
Thermal Environment ◽  
Propagation Constant ◽  
Quantum Systems ◽  
Quantum Gates ◽  
Scattering Loss ◽  
Spatial Features ◽  
Quantum Optical ◽  
Nontrivial Topology ◽  
Large Quantum

The robust generation and propagation of multiphoton quantum states are crucial for applications in quantum information, computing, and communications. Although photons are intrinsically well isolated from the thermal environment, scaling to large quantum optical devices is still limited by scattering loss and other errors arising from random fabrication imperfections. The recent discoveries regarding topological phases have introduced avenues to construct quantum systems that are protected against scattering and imperfections. We experimentally demonstrate topological protection of biphoton states, the building block for quantum information systems. We provide clear evidence of the robustness of the spatial features and the propagation constant of biphoton states generated within a nanophotonics lattice with nontrivial topology and propose a concrete path to build robust entangled states for quantum gates.

scholarly journals Characterization of linear maps onMnwhose multiplicity maps have maximal norm, with an application in quantum information

Quantum ◽  
2018 ◽  
Vol 2 ◽  
pp. 51
Author(s):  
Daniel Puzzuoli
Keyword(s):  
Quantum Information ◽  
Quantum Channel ◽  
Operator Algebras ◽  
Optimal Performance ◽  
Single Shot ◽  
Trace Norm ◽  
Linear Maps ◽  
The Family ◽  
Matrix Transposition

Given a linear mapΦ:Mn→Mm, its multiplicity maps are defined as the family of linear mapsΦ⊗idk:Mn⊗Mk→Mm⊗Mk, whereidkdenotes the identity onMk. Let‖⋅‖1denote the trace-norm on matrices, as well as the induced trace-norm on linear maps of matrices, i.e.‖Φ‖1=max{‖Φ(X)‖1:X∈Mn,‖X‖1=1}. A fact of fundamental importance in both operator algebras and quantum information is that‖Φ⊗idk‖1can grow withk. In general, the rate of growth is bounded by‖Φ⊗idk‖1≤k‖Φ‖1, and matrix transposition is the canonical example of a map achieving this bound. We prove that, up to an equivalence, the transpose is the unique map achieving this bound. The equivalence is given in terms of complete trace-norm isometries, and the proof relies on a particular characterization of complete trace-norm isometries regarding preservation of certain multiplication relations.We use this result to characterize the set of single-shot quantum channel discrimination games satisfying a norm relation that, operationally, implies that the game can be won with certainty using entanglement, but is hard to win without entanglement. Specifically, we show that the well-known example of such a game, involving the Werner-Holevo channels, is essentially the unique game satisfying this norm relation. This constitutes a step towards a characterization of single-shot quantum channel discrimination games with maximal gap between optimal performance of entangled and unentangled strategies.

scholarly journals Quantum optical frequency up-conversion for polarisation entangled qubits: towards interconnected quantum information devices

2019 ◽  
Vol 27 (18) ◽  
pp. 25603 ◽  
Author(s):  
Florian Kaiser ◽  
Panagiotis Vergyris ◽  
Anthony Martin ◽  
Djeylan Aktas ◽  
Marc P. De Micheli ◽  
...  
Keyword(s):  
Quantum Information ◽  
Optical Frequency ◽  
Quantum Optical

scholarly journals Optical Chirality and Single-Photon Isolation

2020 ◽  
Author(s):  
Lei Tang ◽  
Keyu Xia
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Information Processing ◽  
Single Photon ◽  
Kerr Nonlinearity ◽  
Single Photons ◽  
Optical Isolation ◽  
Optical Chirality ◽  
Magneto Optical Effect ◽  
Quantum Optical

Optical isolation is important for protecting a laser from damage due to the detrimental back reflection of light. It typically relies on breaking Lorentz reciprocity and normally is achieved via the Faraday magneto-optical effect, requiring a strong external magnetic field. Single-photon isolation, the quantum counterpart of optical isolation, is the key functional component in quantum information processing, but its realization is challenging. In this chapter, we present all-optical schemes for isolating the backscattering from single photons. In the first scheme, we show the single-photon isolation can be realized by using a chiral quantum optical system, in which a quantum emitter asymmetrically couples to nanowaveguide modes or whispering-gallery modes with high optical chirality. Secondly, we propose a chiral optical Kerr nonlinearity to bypass the so-called dynamical reciprocity in nonlinear optics and then achieve room-temperature photon isolation with low insertion loss. The concepts we present may pave the way for quantum information processing in an unconventional way.

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