Work measurement as a generalized quantum measurement

We present a new method to measure the work $w$ performed on a driven quantum system and to sample its probability distribution $P(w)$. The method is based on a simple fact that remained unnoticed until now: Work on a quantum system can be measured by performing a generalized quantum measurement at a single time. Such measurement, which technically speaking is denoted as a POVM (positive operator valued measure) reduces to an ordinary projective measurement on an enlarged system. This observation not only demystifies work measurement but also suggests a new quantum algorithm to efficiently sample the distribution $P(w)$. This can be used, in combination with fluctuation theorems, to estimate free energies of quantum states on a quantum computer.Comment: 4 page

A Wigner quasiprobability distribution of work

In this article we introduce a quasiprobability distribution of work that is based on the Wigner function. This construction rests on the idea that the work done on an isolated system can be coherently measured by coupling the system to a quantum measurement apparatus. In this way, a quasiprobability distribution of work can be defined in terms of the Wigner function of the apparatus. This quasidistribution contains the information of the work statistics and also holds a clear operational definition. Moreover, it is shown that the presence of quantum coherence in the energy eigenbasis is related with the appearance of characteristics related to non-classicality in the Wigner function such as negativity and interference fringes. On the other hand, from this quasiprobability distribution it is straightforward to obtain the standard two-point measurement probability distribution of work and also the difference in average energy for initial states with coherences.Comment: 11 pages, 3 figure

A new group of Archaic Greek Pottery (“Group H”) manufactured in Tartessos (Huelva, SW of Spain)

A la producción por griegos residentes en Huelva de vasos cerámicos caracterizados por una pasta verdosa amarillenta puede sumarse un segundo grupo, convencionalmente denominado “Grupo H”, caracterizado por pastas amarillentas, anaranjadas o rojizas y frecuentes engobes rojos. El estudio preliminar de dos especímenes había ya apuntado una producción local de este nuevo grupo. Una ampliación de los análisis mediante activación neutrónica de otros 10 ejemplares establece de forma concluyente una estrecha semejanza con la composición química de los depósitos de arcillas próximos al hábitat. Asimismo, como en el grupo de pasta verdosa amarillenta, fue detectada una llamativa contaminación de algunos fragmentos cerámicos por metales preciosos, oro y especialmente plata. La representación de ambos grupos sugiere que un significativo porcentaje de los vasos cerámicos griegos arcaicosTo the production by Greek residents in Huelva of pottery characterised by yellowish-green clay, a second ceramic group distinguished by yellowish, orange or reddish clay, and frequently red slipped, conventionally nominated “Group H” can now be added. The preliminary study of two pieces had already aimed at a local production of the new group. This fact is supported by the results of an additional study based on the Neutron Activation Analyses of 10 ceramic specimens conclusively indicating a close resemblance to the chemical composition of clays from local deposits near the habitat. Likewise, as in the group of the yellowish-green clay, a striking contamination with precious metals, gold and especially silver, was detected in some of the fragments. The representation of both groups suggests that a significant percentage of the Archaic Greek vessels found in Huelva was manufactured in sit

Optimal finite-time heat engines under constrained control

This is the final version. Available on open access from the American Physical Society via the DOI in this recordWe optimize finite-time stochastic heat engines with a periodically scaled Hamiltonian under experimentally motivated constraints on the bath temperature T and the scaling parameter λ. We present a general geometric proof that maximum-efficiency protocols for T and λ are piecewise constant, alternating between the maximum and minimum allowed values. When λ is restricted to a small range and the system is close to equilibrium at the ends of the isotherms, a similar argument shows that this protocol also maximizes output power. These results are valid for arbitrary dynamics. We illustrate them for an overdamped Brownian heat engine, which can experimentally be realized using optical tweezers with stiffness λ.China Scholarship CouncilFundational Questions InstituteCaixa FoundationGovernment of SpainFundacio CellexFundacio Mir-PuigGeneralitat de Catalunya (CERCA)Engineering and Physical Sciences Research Council (EPSRC)Royal SocietySwiss National Science FoundationHumboldt foundationCzech Science Foundatio

Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems

This is the final version. Available on open access from IOP Publishing via the DOI in this recordData availability statement; All data that support the findings of this study are included within the article (and any supplementary files).We characterize finite-time thermodynamic processes of multidimensional quadratic overdamped systems. Analytic expressions are provided for heat, work, and dissipation for any evolution of the system covariance matrix. The Bures-Wasserstein metric between covariance matrices naturally emerges as the local quantifier of dissipation. General principles of how to apply these geometric tools to identify optimal protocols are discussed. Focusing on the relevant slow-driving limit, we show how these results can be used to analyze cases in which the experimental control over the system is partial.Humboldt FoundationCzech Science Foundation'la Caixa' FoundationGovernment of SpainSevero OchoaFundacio CellexFundacio Mir-PuigGeneralitat de CatalunyaFundational Questions Institute FundEngineering and Physical Sciences Research Council (EPSRC)China Scholarship CouncilSwiss National Science Foundatio

Adaptive Developmental Delay in Chagas Disease Vectors: An Evolutionary Ecology Approach

The developmental time of vector insects is important to their population dynamics, evolutionary biology, epidemiology of the diseases they transmit, and to their responses to global climatic change. In various triatomine species vectors of Chagas disease (Triatominae, Reduviidae), a delay in the molt of a small proportion of individuals has been observed, and from an evolutionary ecology approach, we propose the hypothesis that the developmental delay is an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) diapause strategy. We confirmed, by means of a survey among specialists, the existence of the developmental delay in triatomines. Statistical descriptions of the developmental time of 11 species of triatomines showed some degree of bi-modality in nine of them. We predicted by means of an optimization model which genotype, coding for a given frequency of developmental diapause, is expected to evolve. We identified a series of parameters that can be measured in the field and in the laboratory to test the hypothesis of an optimal diapause frequency. We also discuss the importance of these findings for triatomines in terms of global climatic change and epidemiological consequences such as their resistance to insecticides