We develop a novel approach to Bell inequalities based on constraint that the correlations exhibited by local variable theories must satisfy. This is used construct family of for bipartite quantum systems arbitrarily high dimensionality which are strongly resistant noise. In particular, our work gives an analytic description previous numerical results and generalizes them dimensionality.

We computationally investigate the complete polytope of Bell inequalities for two particles with small numbers possible measurements and outcomes. Our approach is limited by Pitowsky's connection this problem to hard NP problem. Despite this, we find that there are very few relevant inequivalent numbers. For example, in case three 2-outcome on each particle, just one new inequality. describe mixed 2-qubit states which violate inequality but not CHSH. The also illustrates a sharing bi-partite...

We analyze the structure of correlations among more than two quantum systems. introduce a classification based on concept nonseparability, which is different priori from entanglement. Generalizing result Svetlichny [Phys. Rev. D 35, 3066 (1987)] three-particle correlations, we find an inequality for n-particle that holds under most general separability condition and violated by some quantum-mechanical states.

A long distance quantum teleportation experiment with a fiber-delayed Bell state measurement (BSM) is reported. The source creating the qubits to be teleported and necessary entangled are connected beam splitter realizing BSM by two 2 km optical fibers. In addition, analyzed after 2.2 of fiber, in another laboratory separated 55 m. Time-bin carried photons at 1310 nm onto 1550 nm. fidelity 77%, above maximal value obtainable without entanglement. This first realization an elementary relay...

We show that quantum operations on multiparticle systems have a nonlocal content; this mirrors the content of states. introduce general framework for discussing operations, and give number examples. Quantitative relations between actions entanglement classical communication resources needed to implement these are also described. how can catalyze from action.

Quantum Cryptography is on the verge of commercial application. One its greatest limitations over long distance - secret key rates are low and longest fibre which any has been exchanged currently 100 km. We investigate quantum relay, can increase maximum at cryptography possible. The relay splits channel into sections, sends a different photon across each section, increasing signal to noise ratio. photons linked as in teleportation, with entangled pairs Bell measurements. show that such...

In the analysis of experiments designed to reveal violation Bell-type inequalities, it is usually assumed that any hidden variables associated with $n\mathrm{th}$ particle pair would be independent measurement choices and outcomes for first $(n\ensuremath{-}1)$ pairs. Models which violate this assumption exploit what we call memory loophole. We focus on strongest type violation, uses two-sided loophole, in n can depend previous both wings experiment. show loophole allows a systematic...

We show that quantum entanglement has a very close classical analogue, namely secret correlations. The fundamental analogy stems from the behavior of under local operations and communication correlations public communication. A large number derived analogies follow. In particular teleportation is analogous to one-time-pad, concept ``pure state'' exists in domain, concentration dilution are essentially secrecy protocols, single copy manipulations have such analog majorization results...

We show that weak measurements with post-selection, proposed in the context of quantum theory measurement, naturally appear everyday physics fiber optics telecom networks through polarization-mode dispersion (PMD) and polarization-dependent losses (PDL). Specifically, PMD leads to a time-resolved discrimination polarization; post-selection is done most natural way: one post-selects those photons have not been lost because PDL. The formalism shown simplify calculation optical limit PMD.

Transfer of conserved quantities between two remote regions is generally assumed to be a rather trivial process: flux particles carrying the propagates from one region another. However, we demonstrate flow angular momentum another across space in which there vanishingly small probability any (or fields) being present. This shows that usual view how conservation laws work needs revisited. Published by American Physical Society 2024

Communicating a physical quantity cannot be done using information only---i.e., abstract cbits and∕or qubits. Rather one needs appropriate realizations of We illustrate this by considering the problem communicating chirality. discuss in detail resources necessitates and introduce natural concept quantum gloves---i.e., rotationally invariant states that encode as much possible chirality nothing more.

Teleportation allows Alice to send a pre-prepared quantum state Bob using only pre-shared entanglement and classical communication. Here we show that it is possible teleport which also <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mi class="MJX-tex-mathit" mathvariant="italic">p</mml:mi><mml:mi mathvariant="italic">o</mml:mi><mml:mi mathvariant="italic">s</mml:mi><mml:mi mathvariant="italic">t</mml:mi></mml:mrow></mml:math>-selected....

Here we introduce the concept of classical input – quantum output (C-Q) non-signalling boxes, a generalisation (C-C) boxes. We argue that studying such objects leads to better understanding relation between nonlocality and non-locality beyond mechanics. The main issue discussed in paper is whether there exist &amp;apos;genuine&amp;apos; C-Q boxes or all can be built from already known, namely C-C acting on pre-shared entangled particles. show large classes are non-genuine. In particular,...

Abstract A quantum teleportation over long distances is reported. Alice's unknown state carried by a 1300 nm photon teleported onto Bob's 1550 photon. Bob situated in another lab connected with the EPR source 2 km of optical fibres and at physical distance 55 m. The Bell measurement performed between two photons that travelled through each. This simulation transmission 6 using which principle relay protocol. fidelity 77% obtained higher than best protocol not entangled particles.

Results obtained in two recent papers, (Kaszlikowski D, Gnacinski P, Zukowski M, Miklaszewski W and Zeilinger A 2000 Phys. Rev. Lett. 85 4418 Durt T, Kaszlikowski D M 2001 Preprint quant-ph/0101084) seem to indicate that the nonlocal character of correlations between outcomes measurements performed on entangled systems separated space is not robust presence noise. This surprising, since entanglement itself robust. Here we revisit this problem argue class gedanken experiments considered...

"Information is physical", and here we consider the physical directional information of a particle with spin. We ask whether, in presence classical frame reference, such contains any intrinsic information, ie. above that which can be transmitted by bit. show when sending large number spins, answer asymptotically "no". For finite numbers N, do not know answer. also reference to must use some resource exponentially N. This gives quantitative meaning idea objects are big.

Here we introduce the concept of classical input - quantum output (C-Q) non-signalling boxes, a generalisation (C-C) boxes. We argue that studying such objects leads to better understanding relation between nonlocality and non-locality beyond mechanics. The main issue discussed in paper is whether there exist 'genuine' C-Q boxes or all can be built from already known, namely C-C acting on pre-shared entangled particles. show large classes are non-genuine. In particular, bi-partite with...

Transfer of conserved quantities between two remote regions is generally assumed to be a rather trivial process: flux particles carrying the propagates from one region another. We however demonstrate flow angular momentum another across space in which there vanishingly small probability any (or fields) being present. This shows that usual view how conservation laws work needs revisited.