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.

}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.118.070601}, author = {Perarnau-Llobet, Marti and Baumer, Elisa and Hovhannisyan, Karen V. and Huber, Marcus and Ac{\'\i}n, Antonio} } @article {perarnau-llobet_extractable_2015, title = {Extractable Work from Correlations}, journal = {Physical Review X}, volume = {5}, number = {4}, year = {2015}, month = {oct}, issn = {2160-3308}, doi = {10.1103/PhysRevX.5.041011}, url = {http://link.aps.org/doi/10.1103/PhysRevX.5.041011}, author = {Mart{\'\i} Perarnau-Llobet and Karen V. Hovhannisyan and Huber, Marcus and Paul Skrzypczyk and Nicolas Brunner and Ac{\'\i}n, Antonio} } @article {perarnau-llobet_most_2015, title = {Most energetic passive states}, journal = {Physical Review E}, volume = {92}, number = {4}, year = {2015}, issn = {1539-3755, 1550-2376}, doi = {10.1103/PhysRevE.92.042147}, url = {http://link.aps.org/doi/10.1103/PhysRevE.92.042147}, author = {Mart{\'\i} Perarnau-Llobet and Karen V. Hovhannisyan and Huber, Marcus and Paul Skrzypczyk and Tura, Jordi and Ac{\'\i}n, Antonio} } @article {huber_thermodynamic_2015, title = {Thermodynamic cost of creating correlations}, journal = {New Journal of Physics}, volume = {17}, number = {6}, year = {2015}, pages = {065008}, issn = {1367-2630}, doi = {10.1088/1367-2630/17/6/065008}, url = {http://stacks.iop.org/1367-2630/17/i=6/a=065008?key=crossref.b9c20f4bb628b09efcb912347c01851e}, author = {Huber, Marcus and Mart{\'\i} Perarnau-Llobet and Karen V. Hovhannisyan and Paul Skrzypczyk and Kl{\"o}ckl, Claude and Nicolas Brunner and Ac{\'\i}n, Antonio} } @article {570, title = {Entanglement Generation is Not Necessary for Optimal Work Extraction}, journal = {Physical Review Letters}, volume = {111}, year = {2013}, month = {12/2013}, abstract = {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.}, issn = {1079-7114}, doi = {10.1103/PhysRevLett.111.240401}, author = {Hovhannisyan, Karen and Mart{\'\i} Perarnau-Llobet and Huber, Marcus and Ac{\'\i}n, Antonio} } @article {PhysRevLett.107.070401, title = {Bell Inequalities with No Quantum Violation and Unextendable Product Bases}, journal = {Phys. Rev. Lett.}, volume = {107}, number = {7}, year = {2011}, month = {Aug}, pages = {070401}, publisher = {American Physical Society}, abstract = {The strength of classical correlations is subject to certain constraints, commonly known as Bell inequalities. Violation of these inequalities is the manifestation of nonlocality{\textemdash}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.}, doi = {10.1103/PhysRevLett.107.070401}, author = {Remigiusz Augusiak and Julia Stasi{\'n}ska and Hadley, Christopher and Korbicz, Jaros{\l}aw K. and Lewenstein, Maciej and Ac{\'\i}n, Antonio} } @article {Calsamiglia2008, title = {Quantum Chernoff bound as a measure of distinguishability between density matrices: Application to qubit and Gaussian states}, journal = {Physical Review A (Atomic, Molecular, and Optical Physics)}, volume = {77}, number = {3}, year = {2008}, month = {03/2008}, pages = {032311{\textendash}15}, keywords = {Bayes methods, error statistics, quantum chernoff bound, quantum statistical mechanics, quantum theory}, doi = {10.1103/PhysRevA.77.032311}, url = {http://link.aps.org/abstract/PRA/v77/e032311}, author = {Calsamiglia, John and Mu{\~n}oz-Tapia, Ramon and Masanes, Llu{\'\i}s and Ac{\'\i}n, Antonio and Bagan, Emili} } @article {Audenaert2007, title = {Discriminating States: The Quantum Chernoff Bound}, journal = {Physical Review Letters}, volume = {98}, number = {16}, year = {2007}, month = {04/2007}, pages = {160501{\textendash}4}, keywords = {quantum chernoff bound, state discrimination}, doi = {10.1103/PhysRevLett.98.160501}, url = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal\&id=PRLTAO000098000016160501000001\&idtype=cvips\&gifs=yes}, author = {K. M. R. Audenaert and Calsamiglia, John and Mu{\~n}oz-Tapia, Ramon and Bagan, Emili and Masanes, Llu{\'\i}s and Ac{\'\i}n, Antonio and Verstraete, Frank} } @article {Acin2006, title = {Secrecy properties of quantum channels}, journal = {Physical Review A (Atomic, Molecular, and Optical Physics)}, volume = {73}, number = {1}, year = {2006}, month = {01/2006}, pages = {012327{\textendash}5}, keywords = {information theory, protocols, quantum cryptography}, doi = {10.1103/PhysRevA.73.012327}, url = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal\&id=PLRAAN000073000001012327000001\&idtype=cvips\&gifs=yes}, author = {Ac{\'\i}n, Antonio and Bae, J. and Bagan, Emili and Baig, Mari{\`a} and Masanes, Llu{\'\i}s and Mu{\~n}oz-Tapia, Ramon} } @article {Acin2005, title = {Multiple-copy two-state discrimination with individual measurements}, journal = {Physical Review A (Atomic, Molecular, and Optical Physics)}, volume = {71}, number = {3}, year = {2005}, pages = {032338}, keywords = {state discrimination}, doi = {10.1103/PhysRevA.71.032338}, url = {http://link.aps.org/abstract/PRA/v71/e032338}, author = {Ac{\'\i}n, Antonio and Bagan, Emili and Baig, Mari{\`a} and Masanes, Llu{\'\i}s and Mu{\~n}oz-Tapia, Ramon} } @article {Navascues2005, title = {Quantum Key Distillation from Gaussian States by Gaussian Operations}, journal = {Physical Review Letters}, volume = {94}, number = {1}, year = {2005}, month = {01/2005}, pages = {010502}, publisher = {American Physical Society}, abstract = {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.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.94.010502}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.94.010502}, author = {Navascu{\'e}s, M. and Bae, J. and Cirac, J. Ignacio and Lewenstein, Maciej and Sanpera, Anna and Ac{\'\i}n, Antonio} }