Activation of multipartite quantum non-locality (2009)
Almeida, Mafalda L., Cavalcanti, Daniel, Scarani, Valerio, Acin, Antonio
We consider an Elitzur-Popescu-Rohrlich decomposition for correlations obtained by local measurements performed in multipartite quantum systems. Sufficient conditions for a quantum state to be fully...
Perfect Quantum Privacy Implies Nonlocality (2009)
Augusiak, Remigiusz, Cavalcanti, Daniel, Prettico, Giuseppe, Acin, Antonio
Private states are those quantum states from which a perfectly secure cryptographic key can be extracted. They represent the basic unit of quantum privacy. In this work we show that all states...
Open-system dynamics of graph-state entanglement (2009)
Cavalcanti, Daniel, Chaves, Rafael, Aolita, Leandro, Davidovich, Luiz, Acin, Antonio
We consider graph states of arbitrary number of particles undergoing generic decoherence. We present methods to obtain lower and upper bounds for the system's entanglement in terms of that of...
Convergent relaxations of polynomial optimization problems with non-commuting variables (2009)
Pironio, Stefano, Navascues, Miguel, Acin, Antonio
We consider optimization problems with polynomial inequality constraints in non-commuting variables. These non-commuting variables are viewed as operators acting on a Hilbert space whose dimension is...
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...
Area laws and entanglement distillability of thermal states (2008)
Cavalcanti, Daniel, Ferraro, Alessandro, Garcia-Saez, Artur, Acin, Antonio
We study the entanglement distillability properties of thermal states of many-body systems. Following the ideas presented in [D.Cavalcanti et al., arxiv:0705.3762], we first discuss the appearance of...
Non-secret correlations can be used to distribute secrecy (2008)
Bae, Joonwoo, Cubitt, Toby, Acin, Antonio
A counter-intuitive result in entanglement theory was shown in [PRL 91 037902 (2003)], namely that entanglement can be distributed by sending a separable state through a quantum channel. In this...
Space-QUEST: Experiments with quantum entanglement in space (2008)
Ursin, Rupert, Jennewein, Thomas, Kofler, Johannes, Perdigues, Josep M., Cacciapuoti, Luigi, De Matos, Clovis J., ...
The European Space Agency (ESA) has supported a range of studies in the field of quantum physics and quantum information science in space for several years, and consequently we have submitted the...
Navascues, Miguel, Pironio, Stefano, Acin, Antonio
We are interested in the problem of characterizing the correlations that arise when performing local measurements on separate quantum systems. In a previous work [Phys. Rev. Lett. 98, 010401 (2007)],...
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...
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...
Monogamy and ground-state entanglement in highly connected systems (2007)
Ferraro, Alessandro, Garcia-Saez, Artur, Acin, Antonio
We consider the ground-state entanglement in highly connected many-body systems, consisting of harmonic oscillators and spin-1/2 systems. Varying their degree of connectivity, we investigate the...
Bounding the set of quantum correlations (2006)
Navascues, Miguel, Pironio, Stefano, Acin, Antonio
We introduce a hierarchy of conditions necessarily satisfied by any distribution P(ab) representing the probabilities for two separate observers to obtain outcomes a and b when making local...
Efficient quantum key distribution secure against no-signalling eavesdroppers (2006)
Acin, Antonio, Massar, Serge, Pironio, Stefano
By carrying out measurements on entangled states, two parties can generate a secret key which is secure not only against an eavesdropper bound by the laws of quantum mechanics, but also against a...