Quantum Simulation of single-qubit thermometry using linear optics

Standard thermometry employs the thermalisation of a probe with the system of interest. This approach can be extended by incorporating the possibility of using the non-equilibrium states of the probe, and the presence of coherence. Here, we illustrate how these concepts apply to the single-qubit thermometer introduced by Jevtic et al. by performing a simulation of the qubit-environment interaction in a linear-optical device. We discuss the role of the coherence, and how this affects the usefulness of non-equilibrium conditions. The origin of the observed behaviour is traced back to the propensity to thermalisation, as captured by the Helmholtz free energy.Comment: 6 pages, 6 figure

Monitoring dispersive samples with single photons: the role of frequency correlations

The physics that governs quantum monitoring may involve other degrees of freedom than the ones initialised and controlled for probing. In this context we address the simultaneous estimation of phase and dephasing characterizing a dispersive medium, and we explore the role of frequency correlations within a photon pair generated via parametric down-conversion, when used as a probe for the medium. We derive the ultimate quantum limits on the estimation of the two parameters, by calculating the corresponding quantum Cram\'er-Rao bound; we then consider a feasible estimation scheme, based on the measurement of Stokes operators, and address its absolute performances in terms of the correlation parameters, and, more fundamentally, of the role played by correlations in the simultaneous achievability of the quantum Cram\'er-Rao bounds for each of the two parameters.Comment: to appear in Quantum Measurements and Quantum Metrolog

Assessing frequency correlation through a distinguishability measurement

The simplicity of a question such as wondering if correlations characterize or not a certain system collides with the experimental difficulty of accessing such information. Here we present a low demanding experimental approach which refers to the use of a metrology scheme to obtain a conservative estimate of the strength of frequency correlations. Our testbed is the widespread case of a photon pair produced per downconversion. The theoretical architecture used to put the correlation degree on a quantitative ground is also described

Maxillofacial fractures due to falls: does fall modality determine the pattern of injury?

Objectives: In several epidemiological studies of maxillofacial trauma, falls were one of the most frequent causes of facial injury. The aim of this study is to analyse the patterns of fall-related maxillofacial injuries based on the height of the fall. Material and Methods: Using a systematic computer-assisted database of patients hospitalised with maxillofacial fractures, only those with fall-related injuries were considered. The falls were divided into four groups: falls from slipping, tripping or stumbling (STSF), loss of consciousness (LOCF), stairs (SAF), and height (HF). Data on the age, gender, fracture site, Facial Injury Severity Scale (FISS), facial lacerations, associated lesions, type of treatment, and length of hospital stay were also analysed. Results: This study included 557 patients (338 males, 219 females; average age 51.5 years [range 4 - 99 years]). In the over 60 age group, females were more prevalent in STSF than males. According to aetiology, STSF was the most frequent cause of maxillofacial fractures (315 patients; 56.5%) followed by LOCF (157; 28.2%), HF (55; 9.9%), and SAF (30; 5.4%). The middle third of the face was affected most frequently. After LOCF, however, the inferior third was prevalently involved. The majority of associated fractures, as well as the most severe injuries and greatest rate of facial lacerations, occurred secondary to HF. Conclusions: This study showed that fracture severity and site are influenced not only by patient age, but also by the nature of the fall

Geometrical bounds on irreversibility in open quantum systems

Clausius inequality has deep implications for reversibility and the arrow of time. Quantum theory is able to extend this result for closed systems by inspecting the trajectory of the density matrix on its manifold. Here we show that this approach can provide an upper and lower bound to the irreversible entropy production for open quantum systems as well. These provide insights on the thermodynamics of the information erasure. Limits of the applicability of our bounds are discussed, and demonstrated in a quantum photonic simulator

Multiparameter quantum estimation of noisy phase shifts

Phase estimation is the most investigated protocol in quantum metrology, but its performance is affected by the presence of noise, also in the form of imperfect state preparation. Here we discuss how to address this scenario by using a multiparameter approach, in which noise is associated to a parameter to be measured at the same time as the phase. We present an experiment using two-photon states, and apply our setup to investigating optical activity of fructose solutions. Finally, we illustrate the scaling laws of the attainable precisions with the number of photons in the probe state

Quantum sensors for dynamical tracking of chemical processes

Quantum photonics has demonstrated its potential for enhanced sensing. Current sources of quantum light states tailored to measuring, allow to monitor phenomena evolving on time scales of the order of the second. These are characteristic of product accumulation in chemical reactions of technologically interest, in particular those involving chiral compounds. Here we adopt a quantum multiparameter approach to investigate the dynamic process of sucrose acid hydrolysis as a test bed for such applications. The estimation is made robust by monitoring different parameters at once

Bridging thermodynamics and metrology in non-equilibrium Quantum Thermometry

Single-qubit thermometry presents the simplest tool to measure the temperature of thermal baths with reduced invasivity. At thermal equilibrium, the temperature uncertainty is linked to the heat capacity of the qubit, however the best precision is achieved outside equilibrium condition. Here, we discuss a way to generalize this relation in a non-equilibrium regime, taking into account purely quantum effects such as coherence. We support our findings with an experimental photonic simulation.Comment: 7 pages, 4 figure

Realism-information complementarity in photonic weak measurements

The emergence of realistic properties is a key problem in understanding the quantum-to-classical transition. In this respect, measurements represent a way to interface quantum systems with the macroscopic world: these can be driven in the weak regime, where a reduced back-action can be imparted by choosing meter states able to extract different amounts of information. Here we explore the implications of such weak measurement for the variation of realistic properties of two-level quantum systems pre- and post-measurement, and extend our investigations to the case of open systems implementing the measurements

Low-Enthalpy Geothermal Systems

Energy consumption has increased as a result of two main factors: the economical recovering of industrialized countries after a decrease in energy demand and the economical emergence of countries such as China and India. Geothermal energy is one of the alternatives to ensure sustainable development, representing a clean, free, renewable energy available everywhere. The use of subsoil as a thermal energy reservoir has always been an opportunity. When the heat pump became a consolidated method, geothermal energy became cost-effective. In this method, the subsoil is used to take heat during winter and to release heat during summer, with a sustainable cost. The growing awareness and popularity of geothermal (ground-source) heat pumps have had the most significant impact on direct-use of geothermal energy. The annual energy use for these units grew 2.45 times at a compound annual rate of 19.7%. The installed capacity grew 2.29 times at a compound annual rate of 18.0%. This is due to better reporting and to the ability of geothermal heat pumps to utilize groundwater or ground-coupled temperatures anywhere in the world. This chapter will present a summarized description of the different ground source heat pump systems and a discussion on the efficiency of this equipments and its environmental impact, showing that ground source heat pumps can be an effective, ecological and low cost alternative for heating and cooling application