Closing the detection loophole in Bell experiments using qudits (2009)
Vertesi, Tamas, Pironio, Stefano, Brunner, Nicolas
We show that the detection efficiencies required for closing the detection loophole in Bell tests can be significantly lowered using quantum systems of dimension larger than two. We introduce a...
Closed sets of non-local correlations (2009)
Allcock, Jonathan, Brunner, Nicolas, Linden, Noah, Popescu, Sandu, Skrzypczyk, Paul, Vertesi, Tamas
We introduce a fundamental concept -- closed sets of correlations -- for studying non-local correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more...
Recovering part of the quantum boundary from information causality (2009)
Allcock, Jonathan, Brunner, Nicolas, Pawlowski, Marcin, Scarani, Valerio
Recently, the principle of information causality has appeared as a good candidate for an information-theoretic principle that would single out quantum correlations among more general non-signalling...
Device-independent quantum key distribution secure against collective attacks (2009)
Pironio, Stefano, Acin, Antonio, Brunner, Nicolas, Gisin, Nicolas, Massar, Serge, Scarani, Valerio
Device-independent quantum key distribution (DIQKD) represents a relaxation of the security assumptions made in usual quantum key distribution (QKD). As in usual QKD, the security of DIQKD follows...
Quantum experiments with human eyes as detectors based on cloning via stimulated emission (2009)
Sekatski, Pavel, Brunner, Nicolas, Branciard, Cyril, Gisin, Nicolas, Simon, Christoph
We show theoretically that the multi-photon states obtained by cloning single-photon qubits via stimulated emission can be distinguished with the naked human eye with high efficiency and fidelity....
Non-locality distillation and post-quantum theories with trivial communication complexity (2009)
Brunner, Nicolas, Skrzypczyk, Paul
We first present a protocol for deterministically distilling non-locality, building upon a recent result of Forster et al. [Phys. Rev. Lett. 102, 120401 (2009)]. Our protocol, which is optimal for...
Couplers for Non-Locality Swapping (2008)
Skrzypczyk, Paul, Brunner, Nicolas
Studying generalized non-local theories brings insight to the foundations of quantum mechanics. Here we focus on non-locality swapping, the analogue of quantum entanglement swapping. In order to...
Emergence of Quantum Correlations from Non-Locality Swapping (2008)
Skrzypczyk, Paul, Brunner, Nicolas, Popescu, Sandu
By studying generalized non-signalling theories, the hope is to find out what makes quantum mechanics so special. In the present paper, we revisit the paradigmatic model of non-signalling boxes and...
Testing a Bell inequality in multi-pair scenarios (2008)
Bancal, Jean-Daniel, Branciard, Cyril, Brunner, Nicolas, Gisin, Nicolas, Popescu, Sandu, Simon, Christoph
To date, most efforts to demonstrate quantum nonlocality have concentrated on systems of two (or very few) particles. It is however difficult in many experiments to address individual particles,...
Simulation of partial entanglement with nonsignaling resources (2008)
Brunner, Nicolas, Gisin, Nicolas, Popescu, Sandu, Scarani, Valerio
With the goal of gaining a deeper understanding of quantum non-locality, we decompose quantum correlations into more elementary non-local correlations. We show that the correlations of all pure...
Testing the Hilbert space dimension (2008)
Brunner, Nicolas, Pironio, Stefano, Acin, Antonio, Gisin, Nicolas, Methot, Andre Allan, Scarani, Valerio
Given a set of correlations originating from measurements on a quantum state of unknown Hilbert space dimension, what is the minimal dimension d necessary to describes such correlations? We introduce...
Can one see entanglement ? (2008)
Brunner, Nicolas, Branciard, Cyril, Gisin, Nicolas
The human eye can detect optical signals containing only a few photons. We investigate the possibility to demonstrate entanglement with such biological detectors. While one person could not detect...
A simple approach to test Leggett's model of nonlocal quantum correlations (2008)
Branciard, Cyril, Brunner, Nicolas, Gisin, Nicolas, Kurtsiefer, Christian, Lamas-Linares, Antia, Ling, Alexander, ...
We present new inequalities for testing Leggett's model [Found. Phys. 33, 1469 (2003)] of non-local quantum correlations. Remarkably these inequalities can be derived in a very simple way, assuming...
Partial list of bipartite Bell inequalities with four binary settings (2007)
Brunner, Nicolas, Gisin, Nicolas
We give a partial list of 26 tight Bell inequalities for the case where Alice and Bob choose among four two-outcome measurements. All tight Bell inequalities with less settings are reviewed as well....
Device-independent security of quantum cryptography against collective attacks (2007)
Acin, Antonio, Brunner, Nicolas, Gisin, Nicolas, Massar, Serge, Pironio, Stefano, Scarani, Valerio
We present the optimal collective attack on a Quantum Key Distribution (QKD) protocol in the "device-independent" security scenario, where no assumptions are made about the way the QKD devices work...
Detection loophole in asymmetric Bell experiments (2007)
Brunner, Nicolas, Gisin, Nicolas, Scarani, Valerio, Simon, Christoph
The problem of closing the detection loophole with asymmetric systems, such as entangled atom-photon pairs, is addressed. We show that, for the Bell inequality I_3322, a minimal detection efficiency...
Secrecy extraction from no-signalling correlations (2006)
Scarani, Valerio, Gisin, Nicolas, Brunner, Nicolas, Masanes, Lluis, Pino, Sergi, Acin, Antonio
Quantum cryptography shows that one can guarantee the secrecy of correlation on the sole basis of the laws of physics, that is without limiting the computational power of the eavesdropper. The usual...
Bell-type inequalities for non-local resources (2006)
Brunner, Nicolas, Scarani, Valerio, Gisin, Nicolas
We present bipartite Bell-type inequalities which allow the two partners to use some non-local resource. Such inequality can only be violated if the parties use a resource which is more non-local...
Fast and simple one-way Quantum Key Distribution (2005)
Stucki, Damien, Brunner, Nicolas, Gisin, Nicolas, Scarani, Valerio, Zbinden, Hugo
We present and demonstrate a new protocol for practical quantum cryptography, tailored for an implementation with weak coherent pulses to obtain a high key generation rate. The key is obtained by a...
Entanglement and non-locality are different resources (2004)
Brunner, Nicolas, Gisin, Nicolas, Scarani, Valerio
Bell's theorem states that, to simulate the correlations created by measurement on pure entangled quantum states, shared randomness is not enough: some "non-local" resources are required. It has been...
Towards practical and fast Quantum Cryptography (2004)
Gisin, Nicolas, Ribordy, Gregoire, Zbinden, Hugo, Stucki, Damien, Brunner, Nicolas, Scarani, Valerio
We present a new protocol for practical quantum cryptography, tailored for an implementation with weak coherent pulses. The key is obtained by a very simple time-of-arrival measurement on the data...
Direct measurement of superluminal group velocity and of signal velocity in an optical fiber (2004)
Brunner, Nicolas, Scarani, Valerio, Wegmuller, Mark, Legre, Matthieu, Gisin, Nicolas
We present an easy way of observing superluminal group velocities using a birefringent optical fiber and other standard devices. In the theoretical analysis, we show that the optical properties of...
Quantum cryptography with and without entanglement (2003)
Gisin, Nicolas, Brunner, Nicolas
Quantum cryptography is reviewed, first using entanglement both for the intuition and for the experimental realizations. Next, the implementation is simplified in several steps until it becomes...
Optical telecom networks as weak measurements with post-selection (2003)
In this work we establish a link between two apparently unrelated subjects: polarization effects in optical fibers and devices, and the quantum theory of weak measurements. We show that the abstract...
Optical telecom networks as weak quantum measurements with post- selection (2003)
Brunner, Nicolas, Acin, Antonio, Collins, Daniel, Gisin, Nicolas, Scarani, Valerio
We show that weak measurements with post-selection, proposed in the context of the quantum theory of measurement, naturally appear in the everyday physics of fiber optics telecom networks through...