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Entanglement can effectively increase communication channel capacity as evidenced by dense coding that predicts a capacity gain of 1 bit when compared to entanglement-free protocols. However, dense coding relies on Bell states and when…

Quantum Physics · Physics 2016-10-13 P. Lougovski , D. B. Uskov

We propose a scheme for optical entanglement distribution in quantum networks based on a quasi-deterministic entangled photon pair source. By combining heralded photonic Bell pair generation with spectral mode conversion to interface with…

Quantum Physics · Physics 2023-06-16 Kevin C. Chen , Prajit Dhara , Mikkel Heuck , Yuan Lee , Wenhan Dai , Saikat Guha , Dirk Englund

We demonstrate an efficient experimental procedure based on entanglement swapping to determine the Bell nonlocality measure of Horodecki et al. [Phys. Lett. A 200, 340 (1995)] and the fully-entangled fraction of Bennett et al. [Phys. Rev. A…

Quantum Physics · Physics 2017-03-22 Karol Bartkiewicz , Karel Lemr , Antonín Černoch , Adam Miranowicz

Quantum correlations may violate the Bell inequalities. Most of the experimental schemes confirming this prediction have been realized in all-optical Bell tests suffering from the detection loophole. Experiment which closes this loophole…

Quantum Physics · Physics 2011-09-23 Magdalena Stobińska , Pavel Sekatski , Adam Buraczewski , Nicolas Gisin , Gerd Leuchs

Many quantum information tasks rely on entanglement, which is used as a resource, for example, to enable efficient and secure communication. Typically, noise, accompanied by loss of entanglement, reduces the efficiency of quantum protocols.…

High-fidelity entanglement shared between distant quantum systems is an essential resource for quantum communication and computation. Entanglement distillation addresses this need by converting multiple noisy Bell pairs into fewer…

Quantum Physics · Physics 2025-03-14 Shoham Jacoby , Rotem Arnon-Friedman , Serge Rosenblum

Quantum state preparation and measurement of photonic and phononic Schr\"odinger cat states have gathered significant interest due to their implications for alternative encoding schemes in quantum computation. These scheme employ coherent…

Quantum Physics · Physics 2024-04-25 Roson Nongthombam , Urmimala Dewan , Amarendra K. Sarma

We report an experimental demonstration of entanglement swapping over two quantum stages. By successful realizations of two cascaded photonic entanglement swapping processes, entanglement is generated and distributed between two photons,…

Distributing entangled states over potentially long distances provides a key resource for many protocols in quantum communication and quantum cryptography. Ideally, this should be implemented in a heralded manner. By starting with four…

Quantum Physics · Physics 2024-06-19 Francis Marcellino , Patrik Caspar , Tiff Brydges , Hugo Zbinden , Rob Thew

We theoretically investigate the joint photodetection probabilities of the biexciton-exciton cascade in single semiconductor quantum dots and analytically derive the density matrix and the Bell's inequalities of the entangled state. Our…

Optics · Physics 2009-11-13 Matthieu Larqué , Isabelle Robert-Philip , Alexios Beveratos

We analyze device-dependent correlation sets generated by fixed local dichotomic measurements for two-qubit systems in the $(2,m,2)$ Bell scenario. We consider three fundamental state spaces for the composite system: the separable state…

Quantum Physics · Physics 2026-04-28 Ryosuke Nogami , Jaeha Lee

Photonic-based qubits and integrated photonic circuits have enabled demonstrations of quantum information processing (QIP) that promises to transform the way in which we compute and communicate. To that end, sources of…

We observe polarization-entanglement between four photons produced from a single down-conversion source. The non-classical correlations between the measurement results violate a generalized Bell inequality for four qubits. The…

Quantum Physics · Physics 2009-11-10 M. Eibl , S. Gaertner , M. Bourennane , Ch. Kurtsiefer , M. Zukowski , H. Weinfurter

We apply the Wigner function formalism to the study of two-photon polarization-momentum hyperentanglement generated in parametric down conversion. It is shown that the consideration of a higher number of degrees of freedom is directly…

Quantum Physics · Physics 2014-07-23 A. Casado , S. Guerra , J. Plácido

Mutually unbiased bases (MUBs) play a key role in many protocols in quantum science, such as quantum key distribution. However, defining MUBs for arbitrary high-dimensional systems is theoretically difficult, and measurements in such bases…

Quantum Physics · Physics 2013-04-03 D. Giovannini , J. Romero , J. Leach , A. Dudley , A. Forbes , M. J. Padgett

Pairs of photons entangled in their time-frequency degree of freedom are of great interest in quantum optics research and applications, due to their relative ease of generation and their high capacity for encoding information. Here we…

Quantum Physics · Physics 2022-02-23 Sofiane Merkouche , Valérian Thiel , Brian J. Smith

A quantum system composed of two or more subsystems can be in an entangled state, i.e. a state in which the properties of the global system are well defined but the properties of each subsystem are not. Entanglement is at the heart of…

The heralded generation of entangled states underpins many photonic quantum technologies. As quantum error correction thresholds are determined by underlying physical noise mechanisms, a detailed and faithful characterization of resource…

Quantum Physics · Physics 2023-05-16 Reece D. Shaw , Alex E. Jones , Patrick Yard , Anthony Laing

Bell state measurements, in which two quantum bits are projected onto a maximally entangled state, are an essential component of quantum information science. We propose and experimentally demonstrate the projection of two quantum systems…

Quantum Physics · Physics 2011-03-31 A. Halevy , E. Megidish , T. Shacham , L. Dovrat , H. S. Eisenberg

Separability and entanglement for n-qubits systems are quantified by using Hilbert-Schmidt (HS) decompositions in which the density matrices are decomposed into various terms representing certain one qubit, two-qubits,and larger qubits…

Quantum Physics · Physics 2016-02-23 Y. Ben-Aryeh