A quantum engine in the BEC-BCS crossover.

Heat engines convert thermal energy into mechanical work both in the classical and quantum regimes1. However, quantum theory offers genuine non-classical forms of energy, different from heat, which so far have not been exploited in cyclic engines. Here we experimentally realize a quantum many-body engine fuelled by the energy difference between fermionic and bosonic ensembles of ultracold particles that follows from the Pauli exclusion principle2. We employ a harmonically trapped superfluid gas of 6Li atoms close to a magnetic Feshbach resonance3 that allows us to effectively change the quantum statistics from Bose-Einstein to Fermi-Dirac, by tuning the gas between a Bose-Einstein condensate of bosonic molecules and a unitary Fermi gas (and back) through a magnetic field4-10. The quantum nature of such a Pauli engine is revealed by contrasting it with an engine in the classical thermal regime and with a purely interaction-driven device. We obtain a work output of several 106 vibrational quanta per cycle with an efficiency of up to 25%. Our findings establish quantum statistics as a useful thermodynamic resource for work production.

Measurement-Induced Quantum Synchronization and Multiplexing.

Measurements are able to fundamentally affect quantum dynamics. We here show that a continuously measured quantum many-body system can undergo a spontaneous transition from asynchronous stochastic dynamics to noise-free stable synchronization at the level of single trajectories. We formulate general criteria for this quantum phenomenon to occur and demonstrate that the number of synchronized realizations can be controlled from none to all. We additionally find that ergodicity is typically broken, since time and ensemble averages may exhibit radically different synchronization behavior. We further introduce a quantum type of multiplexing that involves individual trajectories with distinct synchronization frequencies. Measurement-induced synchronization appears as a genuine nonclassical form of synchrony that exploits quantum superpositions.

Efficiency at Maximum Power of a Carnot Quantum Information Engine.

Optimizing the performance of thermal machines is an essential task of thermodynamics. We here consider the optimization of information engines that convert information about the state of a system into work. We concretely introduce a generalized finite-time Carnot cycle for a quantum information engine and optimize its power output in the regime of low dissipation. We derive a general formula for its efficiency at maximum power valid for arbitrary working media. We further investigate the optimal performance of a qubit information engine subjected to weak energy measurements.

Noise-Induced Quantum Synchronization.

Synchronization is a widespread phenomenon in science and technology. Here, we study noise-induced synchronization in a quantum spin chain subjected to local Gaussian white noise. We demonstrate stable (anti)synchronization between the endpoint magnetizations of a quantum XY model with transverse field of arbitrary length. Remarkably, we show that noise applied to a single spin suffices to reach stable (anti)synchronization, and find that the two synchronized end spins are entangled. We additionally determine the optimal noise amplitude that leads to the fastest synchronization along the chain, and further compare the optimal synchronization speed to the fundamental Lieb-Robinson bound for information propagation.

Non-Markovian Feedback Control and Acausality: An Experimental Study.

Causality is an important assumption underlying nonequilibrium generalizations of the second law of thermodynamics known as fluctuation relations. We here experimentally study the nonequilibrium statistical properties of the work and of the entropy production for an optically trapped, underdamped nanoparticle continuously subjected to a time-delayed feedback control. Whereas the non-Markovian feedback depends on the past position of the particle for a forward trajectory, it depends on its future position for a time-reversed path, and is therefore acausal. In the steady-state regime, we show that the corresponding fluctuation relations in the long-time limit exhibit a clear signature of this acausality, even though the time-reversed dynamics is not physically realizable.

Nonequilibrium Control of Thermal and Mechanical Changes in a Levitated System.

Fluctuation theorems are fundamental extensions of the second law of thermodynamics for small nonequilibrium systems. While work and heat are equally important forms of energy exchange, fluctuation relations have not been experimentally assessed for the generic situation of simultaneous mechanical and thermal changes. Thermal driving is indeed generally slow and more difficult to realize than mechanical driving. Here, we use feedback cooling techniques to implement fast and controlled temperature variations of an underdamped levitated microparticle that are 1 order of magnitude faster than the equilibration time. Combining mechanical and thermal control, we verify the validity of a fluctuation theorem that accounts for both contributions, well beyond the range of linear response theory. Our results allow the investigation of general far-from-equilibrium processes in microscopic systems that involve fast mechanical and thermal changes at the same time.

Thermodynamics of a Minimal Algorithmic Cooling Refrigerator.

We investigate, theoretically and experimentally, the thermodynamic performance of a minimal three-qubit heat-bath algorithmic cooling refrigerator. We analytically compute the coefficient of performance, the cooling power, and the polarization of the target qubit for an arbitrary number of cycles, taking realistic experimental imperfections into account. We determine their fundamental upper bounds in the ideal reversible limit and show that these values may be experimentally approached using a system of three qubits in a nitrogen-vacancy center in diamond.

One-Year Outcome of Postoperative Stroke and Nerve Injury After Supraclavicular Revascularization of The Left Subclavian Artery for Proximal Landing Zone Extension in Thoracic Endovascular Aortic Repair.

OBJECTIVE: To assess the outcome of stroke and nerve injury after supraclavicular revascularization of the left subclavian artery for proximal landing zone extension in thoracic endovascular aortic repair (TEVAR). METHODS: Retrospective analysis of all patients undergoing left-sided carotid-subclavian bypass (CSB) and subclavian-carotid transposition (SCT) with simultaneous or staged TEVAR between January 2010 and June 2019. Endpoints were perioperative cerebrovascular events and nerve injuries, patency and re-intervention due to the debranching, and mortality at 30 days and during follow-up. RESULTS: Forty-eight patients (median age 66 years, 81 % male) had 25 (52%) CSB and 23 (48%) SCT. TEVAR was performed simultaneously in 39 (81%) patients, 11 (23%) of them in an emergent setting. There were 7 (15%) re-interventions within 30 days: 3 due to local hematoma, one for bypass occlusion, 2 for stenosis (of which one was not confirmed intraoperatively), and one after initially abandoned SCT with subsequent CSB on the next day. 30-day mortality was 2%; 1 patient died on the first postoperative day after emergency coronary artery bypass surgery and multiorgan failure. 4 (8%) patients suffered postoperative strokes; 3 occurred after simultaneous emergency procedures and none was fatal. There were 9 (19%) left neck nerve injuries in 8 patients, 5 patients had SCT and 3 CSB. During a median follow-up of 37.5 months (IQR 23-83) with a Follow-up Index of 0.77, there were no reinterventions or occlusions, and no graft infections. Primary patency was 90% and primary assisted patency 98% during follow-up. 8 patients died during follow-up, all of them with patent cervical debranching. CONCLUSION: Supraclavicular LSA revascularization for proximal landing zone extension in TEVAR is safe with an acceptable rate of early re-interventions. There is higher risk for perioperative stroke during concomitant emergency LSA revascularization and TEVAR. Left neck nerve injuries are common complications but resolve completely in vast majority of the cases during first postoperative year. During follow-up, excellent patency could be expected.

Use of electronic cigarettes among U.S. Military service members - prevalence and associated risk factors.

BACKGROUND: Decreased physical fitness, loss of vision and hearing, and increased risk of chronic diseases are significant primary and secondary implications associated with the health of U.S. Military Service members who use tobacco, including electronic cigarettes. Despite the medical and non-medical costs to the U.S. Department of Defense and potential adverse health effects to Service members, electronic cigarette use is on the rise. METHODS: U.S. Military Service members who completed their Periodic Health Assessment, a standardized, electronic, logic-based tool, from July 2018 to July 2019 were eligible. This exploratory study examines the prevalence and significant risk factors associated with self-reported use of electronic cigarettes, as well as determines if tobacco use varies by sex and Service branch, through use of Chi-square analysis and logistic regression. RESULTS: U.S. Military Service members 17-70 years old were included in this study (N = 1.12 M), with 80% of study participants being male and 20% female. Exposure to secondhand smoke (OR: 2.12, 95% CI: 2.15-2.22) and screening positive for hazardous drinking (OR: 2.70, 95% CI: 2.64-2.76) were found to show the greatest increase in odds of using electronic cigarettes, with similar findings after stratification by sex and Service branch. Stratification by Service branch revealed further differences in the association between electronic cigarette use and various demographic, military, lifestyle, and health characteristics. CONCLUSION: Electronic cigarette use is increasing across the United States. U.S. Service members have unique risk factors and patterns of tobacco use. Despite tobacco use having potential adverse effects on military readiness, its use remains prevalent in this population. Our findings identify opportunities for the U.S. Department of Defense to review tobacco policy and availability and accessibility of cessation services to promote quitting tobacco, especially electronic cigarettes.

Testing Higher-Order Quantum Interference with Many-Particle States.

Quantum theory permits interference between indistinguishable paths but, at the same time, restricts its order. Single-particle interference, for instance, is limited to the second order, that is, to pairs of single-particle paths. To date, all experimental efforts to search for higher-order interferences beyond those compatible with quantum mechanics have been based on such single-particle schemes. However, quantum physics is not bound to single-particle interference. We here experimentally study many-particle higher-order interference using a two-photon-five-slit setup. We observe nonzero two-particle interference up to fourth order, corresponding to the interference of two distinct two-particle paths. We further show that fifth-order interference is restricted to 10^{-3} in the intensity-correlation regime and to 10^{-2} in the photon-correlation regime, thus providing novel bounds on higher-order quantum interference.

Experimental Validation of Fully Quantum Fluctuation Theorems Using Dynamic Bayesian Networks.

Fluctuation theorems are fundamental extensions of the second law of thermodynamics for small systems. Their general validity arbitrarily far from equilibrium makes them invaluable in nonequilibrium physics. So far, experimental studies of quantum fluctuation relations do not account for quantum correlations and quantum coherence, two essential quantum properties. We here apply a novel dynamic Bayesian network approach to experimentally test detailed and integral fully quantum fluctuation theorems for heat exchange between two quantum-correlated thermal spins-1/2 in a nuclear magnetic resonance setup. We concretely verify individual integral fluctuation relations for quantum correlations and quantum coherence, as well as for the sum of all quantum contributions. We further investigate the thermodynamic cost of creating correlations and coherence.

Design of Stimuli-Responsive Dynamic Covalent Delivery Systems for Volatile Compounds (Part†1): Controlled Hydrolysis of Micellar Amphiphilic Imines in Water.

Despite their intrinsic hydrolysable character, imine bonds can become remarkably stable in water when self-assembled in amphiphilic micellar structures. In this work, we systematically studied some of these structures and the influence of various parameters that can be used to take control of their hydrolysis, including pH, concentration, the position of the imine function in the amphiphilic structure, relative lengths of the linked hydrophilic and hydrophobic moieties. Thermodynamic and kinetic data led us to the rational design of stable imines in water, partly based on the location of the imine function within the hydrophobic part of the amphiphile and on a predictable quantitative term that we define as the total hydrophilic-lipophilic balance (HLB). In addition, we show that such stable systems are also stimuli-responsive and therefore, of potential interest in trapping and releasing micellar components on demand.

Design of Stimuli-Responsive Dynamic Covalent Delivery Systems for Volatile Compounds (Part†2): Fragrance-Releasing Cleavable Surfactants in Functional Perfumery Applications.

Amphiphilic imines prepared by condensation of a hydrophobic fragrance aldehyde with a hydrophilic amine derived from a poly(propylene oxide) and poly(ethylene oxide) diblock copolymer were investigated as cleavable surfactant profragrances in applications of functional perfumery. In water, the cleavable surfactants assemble into micelles that allow solubilization of perfume molecules that are not covalently attached to the surfactant. Dynamic headspace analysis on a glass surface showed that solubilized perfume molecules evaporated in a similar manner in the presence of the cleavable surfactant as compared with a non-cleavable reference surfactant. Under application conditions, the cleavable surfactant imine hydrolysed to release the covalently linked fragrance aldehyde. The profragrances were stable during storage in aqueous media, and upon dilution showed a blooming effect for the hydrolytical fragrance release and a more balanced performance of a solubilized perfume by retaining the more volatile fragrances and boosting the evaporation of the less volatile fragrances.

Quantum Fluctuation Theorems beyond Two-Point Measurements.

We derive detailed and integral quantum fluctuation theorems for heat exchange in a quantum correlated bipartite thermal system using the framework of dynamic Bayesian networks. Contrary to the usual two-projective-measurement scheme that is known to destroy quantum features, these fluctuation relations fully capture quantum correlations and quantum coherence at arbitrary times. We further obtain individual integral fluctuation theorems for classical and quantum correlations, as well as for local and global quantum coherences.

Continuous-Time Random Walk for a Particle in a Periodic Potential.

Continuous-time random walks offer powerful coarse-grained descriptions of transport processes. We here microscopically derive such a model for a Brownian particle diffusing in a deep periodic potential. We determine both the waiting-time and the jump-length distributions in terms of the parameters of the system, from which we analytically deduce the non-Gaussian characteristic function. We apply this continuous-time random walk model to characterize the underdamped diffusion of single cesium atoms in a one-dimensional optical lattice. We observe excellent agreement between experimental and theoretical characteristic functions, without any free parameter.

Experimental verification of Landauer's principle linking information and thermodynamics.

In 1961, Rolf Landauer argued that the erasure of information is a dissipative process. A minimal quantity of heat, proportional to the thermal energy and called the Landauer bound, is necessarily produced when a classical bit of information is deleted. A direct consequence of this logically irreversible transformation is that the entropy of the environment increases by a finite amount. Despite its fundamental importance for information theory and computer science, the erasure principle has not been verified experimentally so far, the main obstacle being the difficulty of doing single-particle experiments in the low-dissipation regime. Here we experimentally show the existence of the Landauer bound in a generic model of a one-bit memory. Using a system of a single colloidal particle trapped in a modulated double-well potential, we establish that the mean dissipated heat saturates at the Landauer bound in the limit of long erasure cycles. This result demonstrates the intimate link between information theory and thermodynamics. It further highlights the ultimate physical limit of irreversible computation.

Individual Tracer Atoms in an Ultracold Dilute Gas.

We report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the relaxation of the initial nonthermal state and detect the effect of single collisions which has so far eluded observation. We show that, after few collisions, the measured spatial distribution of the tracer atoms is correctly described by a Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers. Our results extend the simple and effective Langevin treatment to the realm of light particles in dilute gases. The experimental technique developed opens up the microscopic exploration of a novel regime of diffusion at the level of individual collisions.

Comparison of personal diesel and biodiesel exhaust exposures in an underground mine.

This study aimed to compare personal exposures to diesel fuel and a biodiesel blend exhaust in an underground mine. Personal exposure monitoring was performed in a non-operational, hard rock underground mine during use of a load-haul-dump vehicle. Eight-hour time-weighted average (TWA8) exposure concentrations of ultra-low sulfur diesel and 75% biodiesel/25% diesel blend (B75) fuels were compared. Compared to diesel, use of B75 was associated with relative percent reductions of 22 and 28% in median respirable (r) diesel particulate matter (DPM) and nitrogen dioxide and 25 and 23% increases in median total DPM and nitric oxide TWA8 exposure concentrations, respectively. Diesel was associated with a slightly greater total geometric mean mass concentration and lower mean surface area concentration. Although further testing is needed, B75 has the potential to reduce rDPM exposures.

Thermodynamics of Weakly Measured Quantum Systems.

We consider continuously monitored quantum systems and introduce definitions of work and heat along individual quantum trajectories that are valid for coherent superposition of energy eigenstates. We use these quantities to extend the first and second laws of stochastic thermodynamics to the quantum domain. We illustrate our results with the case of a weakly measured driven two-level system and show how to distinguish between quantum work and heat contributions. We finally employ quantum feedback control to suppress detector backaction and determine the work statistics.

Evaluation of a fitness intervention for new firefighters: injury reduction and economic benefits.

BACKGROUND: Firefighting is a hazardous profession and firefighters suffer workplace injury at a higher rate than most US workers. Decreased physical fitness is associated with injury in firefighters. A physical fitness intervention was implemented among Tucson Fire Department recruit firefighters with the goals of decreasing injury and compensation claims frequency and costs during the recruit academy, and over the subsequent probationary year. METHODS: Department injury records were analysed and described by body part, injury type and mechanism of injury. Injury and workers' compensation claims outcomes from the recruit academy initiation through the 12-month probationary period for the intervention recruit class were compared with controls from three historical classes. RESULTS: The majority of injuries were sprains and strains (65.4%), the most common mechanism of injury was acute overexertion (67.9%) and the lower extremity was the most commonly affected body region (61.7%). The intervention class experienced significantly fewer injuries overall and during the probationary year (p=0.009), filed fewer claims (p=0.028) and experienced claims cost savings of approximately US$33 000 (2013) from avoided injury and reduced claims costs. The estimated costs for programme implementation were $32 192 leading to a 1-year return on investment of 2.4%. CONCLUSIONS: We observed reductions in injury occurrence and compensation costs among Probationary Firefighter Fitness (PFF-Fit) programme participants compared with historical controls. The initiation of the PFF-Fit programme has demonstrated promise in reducing injury and claims costs; however, continued research is needed to better understand the programme's potential effectiveness with additional recruit classes and carryover effects into the recruit's career injury potential.