An open question of fundamental importance in thermodynamics is howto describe the fluctuations of work for quantum coherent processes. In the standard approach, based on a projective energy measurement both at the beginning and at the end of the process, the first measurement destroys any initial coherence in the energy basis. Here we seek extensions of this approach which can possibly account for initially coherent states. We consider all measurement schemes to estimate work and require that (i) the difference of average energy corresponds to average work for closed quantum systems and that (ii) the work statistics agree with the standard two-measurement scheme for states with no coherence in the energy basis. We first show that such a scheme cannot exist. Next, we consider the possibility of performing collective measurements on several copies of the state and prove that it is still impossible to simultaneously satisfy requirements (i) and (ii). Nevertheless, improvements do appear, and in particular, we develop a measurement scheme that acts simultaneously on two copies of the state and allows us to describe a whole class of coherent transformations.

VL - 118 ER - TY - JOUR T1 - Extractable Work from Correlations JF - Physical Review X Y1 - 2015 A1 - Martí Perarnau-Llobet A1 - Karen V. Hovhannisyan A1 - Huber, Marcus A1 - Paul Skrzypczyk A1 - Nicolas Brunner A1 - Acín, Antonio VL - 5 UR - http://link.aps.org/doi/10.1103/PhysRevX.5.041011 ER - TY - JOUR T1 - Most energetic passive states JF - Physical Review E Y1 - 2015 A1 - Martí Perarnau-Llobet A1 - Karen V. Hovhannisyan A1 - Huber, Marcus A1 - Paul Skrzypczyk A1 - Tura, Jordi A1 - Acín, Antonio VL - 92 UR - http://link.aps.org/doi/10.1103/PhysRevE.92.042147 ER - TY - JOUR T1 - Thermodynamic cost of creating correlations JF - New Journal of Physics Y1 - 2015 A1 - Huber, Marcus A1 - Martí Perarnau-Llobet A1 - Karen V. Hovhannisyan A1 - Paul Skrzypczyk A1 - Klöckl, Claude A1 - Nicolas Brunner A1 - Acín, Antonio VL - 17 UR - http://stacks.iop.org/1367-2630/17/i=6/a=065008?key=crossref.b9c20f4bb628b09efcb912347c01851e ER - TY - JOUR T1 - Entanglement Generation is Not Necessary for Optimal Work Extraction JF - Physical Review Letters Y1 - 2013 A1 - Hovhannisyan, Karen A1 - Martí Perarnau-Llobet A1 - Huber, Marcus A1 - Acín, Antonio AB - We consider reversible work extraction from identical quantum batteries. From an ensemble of individually passive states, work can be produced only via global unitary (and thus entangling) operations. However, we show here that there always exists a method to extract all possible work without creating any entanglement, at the price of generically requiring more operations (i.e. additional time). We then study faster methods to extract work and provide a quantitative relation between the amount of generated multipartite entanglement and extractable work. Our results suggest a general relation between entanglement generation and the power of work extraction. VL - 111 IS - 24 JO - Phys. Rev. Lett. ER - TY - JOUR T1 - Bell Inequalities with No Quantum Violation and Unextendable Product Bases JF - Phys. Rev. Lett. Y1 - 2011 A1 - Remigiusz Augusiak A1 - Julia Stasińska A1 - Hadley, Christopher A1 - Korbicz, Jarosław K. A1 - Lewenstein, Maciej A1 - Acín, Antonio AB - The strength of classical correlations is subject to certain constraints, commonly known as Bell inequalities. Violation of these inequalities is the manifestation of nonlocality—displayed, in particular, by quantum mechanics, meaning that quantum mechanics can outperform classical physics at tasks associated with such Bell inequalities. Interestingly, however, there exist situations in which this is not the case. We associate an intriguing class of bound entangled states, constructed from unextendable product bases with a wide family of tasks, for which (i) quantum correlations do not outperform the classical ones but (ii) there exist supraquantum nonsignaling correlations that do provide an advantage. PB - American Physical Society VL - 107 ER - TY - JOUR T1 - Quantum Chernoff bound as a measure of distinguishability between density matrices: Application to qubit and Gaussian states JF - Physical Review A (Atomic, Molecular, and Optical Physics) Y1 - 2008 A1 - Calsamiglia, John A1 - Muñoz-Tapia, Ramon A1 - Masanes, Lluís A1 - Acín, Antonio A1 - Bagan, Emili KW - Bayes methods KW - error statistics KW - quantum chernoff bound KW - quantum statistical mechanics KW - quantum theory VL - 77 UR - http://link.aps.org/abstract/PRA/v77/e032311 ER - TY - JOUR T1 - Discriminating States: The Quantum Chernoff Bound JF - Physical Review Letters Y1 - 2007 A1 - K. M. R. Audenaert A1 - Calsamiglia, John A1 - Muñoz-Tapia, Ramon A1 - Bagan, Emili A1 - Masanes, Lluís A1 - Acín, Antonio A1 - Verstraete, Frank KW - quantum chernoff bound KW - state discrimination VL - 98 UR - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000098000016160501000001&idtype=cvips&gifs=yes ER - 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 - 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 - Quantum Key Distillation from Gaussian States by Gaussian Operations JF - Physical Review Letters Y1 - 2005 A1 - Navascués, M. A1 - Bae, J. A1 - Cirac, J. Ignacio A1 - Lewenstein, Maciej A1 - Sanpera, Anna A1 - Acín, Antonio AB - We study the secrecy properties of Gaussian states under Gaussian operations. Although such operations are useless for quantum distillation, we prove that it is possible to distill a secret key secure against any attack from sufficiently entangled Gaussian states with nonpositive partial transposition. Moreover, all such states allow for key distillation, when Eve is assumed to perform finite-size coherent attacks before the reconciliation process. PB - American Physical Society VL - 94 UR - http://link.aps.org/doi/10.1103/PhysRevLett.94.010502 ER -