Photon correlation spectroscopy as a witness for quantum coherence

The development of spectroscopic techniques able to detect and verify quantum coherence is a goal of increasing importance given the rapid progress of new quantum technologies, the advances in the field of quantum thermodynamics, and the emergence of new questions in chemistry and biology regarding the possible relevance of quantum coherence in biochemical processes. Ideally, these tools should be able to detect and verify the presence of quantum coherence in both the transient dynamics and the steady state of driven-dissipative systems, such as light-harvesting complexes driven by thermal photons in natural conditions. This requirement poses a challenge for standard laser spectroscopy methods. Here, we propose photon correlation measurements as a new tool to analyse quantum dynamics in molecular aggregates in driven-dissipative situations. We show that the photon correlation statistics on the light emitted by a molecular dimer model can signal the presence of coherent dynamics. Deviations from the counting statistics of independent emitters constitute a direct fingerprint of quantum coherence in the steady state. Furthermore, the analysis of frequency resolved photon correlations can signal the presence of coherent dynamics even in the absence of steady state coherence, providing direct spectroscopic access to the much sought-after site energies in molecular aggregates

Degenerate parametric oscillation in quantum membrane optomechanics

The promise of innovative applications has triggered the development of many modern technologies capable of exploiting quantum effects. But in addition to future applications, such quantum technologies have already provided us with the possibility of accessing quantum-mechanical scenarios that seemed unreachable just a few decades ago. With this spirit, in this work we show that modern optomechanical setups are mature enough to implement one of the most elusive models in the field of open system dynamics: degenerate parametric oscillation. The possibility of implementing it in nonlinear optical resonators was the main motivation for introducing such model in the eighties, which rapidly became a paradigm for the study of dissipative phase transitions whose corresponding spontaneously broken symmetry is discrete. However, it was found that the intrinsic multimode nature of optical cavities makes it impossible to experimentally study the model all the way through its phase transition. In contrast, here we show that this long-awaited model can be implemented in the motion of a mechanical object dispersively coupled to the light contained in a cavity, when the latter is properly driven with multi-chromatic laser light. We focus on membranes as the mechanical element, showing that the main signatures of the degenerate parametric oscillation model can be studied in state-of-the-art setups, thus opening the possibility of studying spontaneous symmetry breaking and enhanced metrology in one of the cleanest dissipative phase transitions.Comment: We welcome comments, suggestions, and (constructive) criticis

Enhanced two-photon emission from a dressed biexciton

Radiative two-photon cascades from biexcitons in semiconductor quantum dots under resonant two-photon excitation are promising candidates for the generation of photon pairs. In this work, we propose a scheme to obtain two-photon emission that allows to operate under very intense driving fields. This approach relies on the Purcell enhancement of two-photon virtual transitions between states of the biexciton dressed by the laser. The richness provided by the biexcitonic level structure allows to reach a variety of regimes, from antibunched and bunched photon pairs with polarization orthogonal to the driving field, to polarization entangled two-photon emission. This evidences that the general paradigm of two-photon emission from a ladder of dressed states can find interesting, particular implementations in a variety of systems

Recursive linear estimation for discrete time systems in the presence of different multiplicative observation noises

This paper describes a design for a least mean square error estimator in discrete time systems where the components of the state vector, in measurement equation, are corrupted by different multiplicative noises in addition to observation noise. We show how known results can be considered a particular case of the algorithm stated in this paperState estimation, multiplicative noise, uncertain observations

Detection Limits and Planet Occurrence Rate in the CARMENES Sample

Màster Oficial d'Astrofísica, Física de Partícules i Cosmologia, Facultat de Física, Universitat de Barcelona, Curs: 2019-2020, Tutors: Juan Carlos Morales, Carme JordiThe CARMENES survey is monitoring more than 300 M-dwarf stars looking for exoplanets. Besides planet discoveries, the data it produces can also be used to estimate the statistics of planets around late-type stars. In this work, we aim at estimating the detection limits of the CARMENES survey, and the occurrence rate of Jupiter- and Neptune-like planets around M-dwarf stars. For this purpose, we use a sample with 324 stars for which values for the radial velocity as a function of time have been measured. We remove the signals produced by planets or intrinsic stellar variability to analyse the instrumental noise. In this noise we look for the minimum planetary mass that could be discovered, obtaining a lower detection limit. With this result we estimate the occurrence rate of M-dwarf planets at different minimum mass and orbital period ranges. For Jupiter- and Neptune-like planets we obtained an occurrence rate of ~ 1%

Flame propagation along the interface between a gas and a reacting medium

Flame propagation process over the surface of a solid or liquid fuel (or oxidizer) in contact with a gaseous oxidizer (or fuel) is studied. Flame propagation velocity is calculated by assuming that flame reaches a certain location when temperature at the fuel surface at that location reaches an ignition temperature. This assumption is correct when the time consumed for the heating process is large as compared with the time required for vaporization of the fuel, mixing, and combustion of the oxidizer-fuel vapors mixture. Heating of the fuel ahead of the flame is studied by considering radiation and convection heat-transfer mechanisms flame to fuel, and bidimensional heat conduction within the fuel. The problem lies in solving a heat-balance partial-differential equation in the solid or liquid fuel for which heat fluxes from the flame are the fundamental boundary conditions. An analytical solution is obtained by means of a boundary-layer approximation, and general results are given. An experimental and theoretical application of the general study is performed for the case of liquid hydrocarbon fuels burning in ai

Propagación de una llama sobre la superficie de separación de un gas y un medio reactante.

Hay muchos problemas relacionados con el proceso general de propagación de la llama a lo largo de la superficie de separación de un oxidante gaseóseo (ó combustible gaseoso) y un combustible líquido o sólido (u oxidante)