TY - JOUR
T1 - Secrecy properties of quantum channels
JF - Physical Review A (Atomic, Molecular, and Optical Physics)
Y1 - 2006
A1 - Acín, Antonio
A1 - Bae, J.
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Masanes, Lluís
A1 - Muñoz-Tapia, Ramon
KW - information theory
KW - protocols
KW - quantum cryptography
VL - 73
UR - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLRAAN000073000001012327000001&idtype=cvips&gifs=yes
ER -
TY - JOUR
T1 - Cold Atoms in Non-Abelian Gauge Potentials: From the Hofstadter "Moth" to Lattice Gauge Theory
JF - Physical Review Letters
Y1 - 2005
A1 - Osterloh, K.
A1 - Baig, Marià
A1 - Santos, L.
A1 - Zoller, P.
A1 - Lewenstein, Maciej
AB - We demonstrate how to create artificial external non-Abelian gauge potentials acting on cold atoms in optical lattices. The method employs atoms with k internal states, and laser assisted state sensitive tunneling, described by unitary k×k matrices. The single-particle dynamics in the case of intense U(2) vector potentials lead to a generalized Hofstadter butterfly spectrum which shows a complex mothlike structure. We discuss the possibility to realize non-Abelian interferometry (Aharonov-Bohm effect) and to study many-body dynamics of ultracold matter in external lattice gauge fields.
PB - American Physical Society
VL - 95
UR - http://link.aps.org/doi/10.1103/PhysRevLett.95.010403
ER -
TY - JOUR
T1 - Multiple-copy two-state discrimination with individual measurements
JF - Physical Review A (Atomic, Molecular, and Optical Physics)
Y1 - 2005
A1 - Acín, Antonio
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Masanes, Lluís
A1 - Muñoz-Tapia, Ramon
KW - state discrimination
VL - 71
UR - http://link.aps.org/abstract/PRA/v71/e032338
ER -
TY - JOUR
T1 - Collective versus local measurements in a qubit mixed-state estimation
JF - Physical Review A (Atomic, Molecular, and Optical Physics)
Y1 - 2004
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Muñoz-Tapia, Ramon
A1 - Rodriguez, A.
AB - We discuss the problem of estimating a qubit mixed state. We give the optimal estimation that can be inferred from any given set of measurements. For collective measurements and for a large number N of copies, we show that the error in the estimation varies as 1/N. For local measurements, we focus on the simpler case of states lying on the equatorial plane of the Bloch sphere. We show that the error using plain tomography varies as 1/N1/4, while our approach leads to an error proportional to 1/N3/4.
PB - American Physical Society
VL - 69
UR - http://link.aps.org/doi/10.1103/PhysRevA.69.010304
ER -
TY - JOUR
T1 - Entanglement-assisted alignment of reference frames using a dense covariant coding
JF - Physical Review A (Atomic, Molecular, and Optical Physics)
Y1 - 2004
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Muñoz-Tapia, Ramon
AB - We present a procedure inspired by dense coding, which enables a highly efficient transmission of information of a continuous nature. The procedure requires the sender and the recipient to share a maximally entangled state. We deal with the concrete problem of aligning reference frames or trihedra by means of a quantum system. We find the optimal covariant measurement and compute the corresponding average error, which has a remarkably simple close form. The connection of this procedure with that of estimating unitary transformations on qubits is briefly discussed.
PB - American Physical Society
VL - 69
UR - http://link.aps.org/doi/10.1103/PhysRevA.69.050303
ER -
TY - JOUR
T1 - Fixed boundary conditions analysis of the 3d gonihedric Ising model with k=0
JF - Physics Letters B
Y1 - 2004
A1 - Baig, Marià
A1 - Clua, J.
A1 - Johnston, D. A.
A1 - Villanova, R.
KW - Author Keywords: Spin systems
KW - Fixed boundary conditions
KW - Gonihedric models
KW - Phase transitions
AB - The gonihedric Ising model is a particular case of the class of models defined by Savvidy and Wegner intended as discrete versions of string theories on cubic lattices. In this Letter we perform a high statistics analysis of the phase transition exhibited by the 3d gonihedric Ising model with k=0 in the light of a set of recently stated scaling laws applicable to first order phase transitions with fixed boundary conditions. Even though qualitative evidence was presented in a previous paper to support the existence of a first order phase transition at k=0, only now are we capable of pinpointing the transition inverse temperature at $\beta$c=0.54757(63) and of checking the scaling of standard observables.
VL - 585
UR - http://www.sciencedirect.com/science?\_ob=ArticleURL&\_udi=B6TVN-4BSN95Y-3&\_user=1517286&\_coverDate=04%2F08%2F2004&\_rdoc=1&\_fmt=high&\_orig=search&\_sort=d&\_docanchor=&view=c&\_acct=C000053449&\_version=1&\_urlVersion=0&\_userid=1517286&md5=b8fb559f9
ER -
TY - JOUR
T1 - Quantum reverse engineering and reference-frame alignment without nonlocal correlations
JF - Physical Review A (Atomic, Molecular, and Optical Physics)
Y1 - 2004
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Muñoz-Tapia, Ramon
AB - The estimation of unknown qubit elementary gates and the alignment of reference frames are formally the same problem. Using quantum states made out of N qubits, we show that the theoretical precision limit for both problems, which behaves as 1∕N2, can be asymptotically attained with a covariant protocol that exploits the quantum correlation of internal degrees of freedom instead of the more fragile entanglement between distant parties. This cuts by half the number of qubits needed to achieve the precision of the dense covariant coding protocol.
PB - American Physical Society
VL - 70
UR - http://link.aps.org/doi/10.1103/PhysRevA.70.030301
ER -
TY - CONF
T1 - Optimal reconstruction of a pure qubit state with local measurements
T2 - Proceedings of the 8th ICSSUR
Y1 - 2003
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Monras, Alex
A1 - Muñoz-Tapia, Ramon
JF - Proceedings of the 8th ICSSUR
PB - Rinton Press (2003)
ER -
TY - JOUR
T1 - Aligning Reference Frames with Quantum States
JF - arXiv
Y1 - 2001
A1 - Bagan, Emili
A1 - Baig, Marià
A1 - Muñoz-Tapia, Ramon
UR - http://arxiv.org/abs/quant-ph/0106155
ER -