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.

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.

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.

Fundamental energy cost of finite-time parallelizable computing.

The fundamental energy cost of irreversible computing is given by the Landauer bound of [Formula: see text]/bit, where k is the Boltzmann constant and T is the temperature in Kelvin. However, this limit is only achievable for infinite-time processes. We here determine the fundamental energy cost of finite-time parallelizable computing within the framework of nonequilibrium thermodynamics. We apply these results to quantify the energetic advantage of parallel computing over serial computing. We find that the energy cost per operation of a parallel computer can be kept close to the Landauer limit even for large problem sizes, whereas that of a serial computer fundamentally diverges. We analyze, in particular, the effects of different degrees of parallelization and amounts of overhead, as well as the influence of non-ideal electronic hardware. We further discuss their implications in the context of current technology. Our findings provide a physical basis for the design of energy-efficient computers.

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.

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.

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.

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.

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.

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.

Recurrent clonazepam withdrawal delirium in a postoperative neurosurgical patient: a case report.

We present a case of benzodiazepine withdrawal delirium in a middle-aged man undergoing spinal surgery. Benzodiazepines were stopped prior to surgery and on postoperative day 4, the patient exhibited significant paranoia, hyperarousal and ideas of reference. Patient's symptoms resolved after reintroduction of his benzodiazepines. It is important to include benzodiazepine withdrawal in the differential diagnosis for acute delirium even in those patients taking low or moderate doses. Benzodiazepine withdrawal delirium typically responds rapidly to restarting benzodiazepines. In patients with known discontinuation issues, early consultation with consult-liaison psychiatry and preoperative planning for early medication re-initiation is paramount.

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.

A quantum heat engine driven by atomic collisions.

Quantum heat engines are subjected to quantum fluctuations related to their discrete energy spectra. Such fluctuations question the reliable operation of thermal machines in the quantum regime. Here, we realize an endoreversible quantum Otto cycle in the large quasi-spin states of Cesium impurities immersed in an ultracold Rubidium bath. Endoreversible machines are internally reversible and irreversible losses only occur via thermal contact. We employ quantum control to regulate the direction of heat transfer that occurs via inelastic spin-exchange collisions. We further use full-counting statistics of individual atoms to monitor quantized heat exchange between engine and bath at the level of single quanta, and additionally evaluate average and variance of the power output. We optimize the performance as well as the stability of the quantum heat engine, achieving high efficiency, large power output and small power output fluctuations.

Evaluation of CBRN Respirator Protection in Simulated Fire Overhaul Settings.

Overhaul is the phase of firefighting after flames have been extinguished but when products of combustion are still being released. While positive pressure self-contained breathing apparatus (SCBA) provide the highest level of respiratory protection during overhaul, use of air-purifying respirators (APRs) with suitable filters could potentially provide a lower weight, longer duration option for first responders. The objective of this study was to assess whether an APR with a chemical, biological, radiological, and nuclear (CBRN) canister could be recommended as substitution for SCBA during overhaul. A total of 15 simulated standard overhaul environments were created by burning household materials. Sampling was conducted using mannequin heads fitted with full facepiece respirators with either a CBRN canister or SCBA. In-mask and personal samples were collected for aldehydes, polynuclear aromatic hydrocarbons, inorganic acids, aromatic hydrocarbons, nitrogen dioxide, and particulate matter. An additional six simulated high-exposure overhaul environments were created in a flashover chamber by continuously adding household materials to a smoldering fire. The sampling train was the same for both the standard and high-exposure environments; however, the facepiece was sealed to the mannequin head in the high-exposure environments. In the standard overhaul environment, the CBRN canister effectively reduced the level of exposure for most contaminants, while in the high-exposure overhaul exposure setting in-mask acetaldehyde and formaldehyde were detected. In both exposure settings, the SCBA prevented almost all exposure, and therefore remains the recommended respiratory protection during overhaul.

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.

Thermodynamics of continuous non-Markovian feedback control.

Feedback control mechanisms are ubiquitous in science and technology, and play an essential role in regulating physical, biological and engineering systems. The standard second law of thermodynamics does not hold in the presence of measurement and feedback. Most studies so far have extended the second law for discrete, Markovian feedback protocols; however, non-Markovian feedback is omnipresent in processes where the control signal is applied with a non-negligible delay. Here, we experimentally investigate the thermodynamics of continuous, time-delayed feedback control using the motion of an optically levitated, underdamped microparticle. We test the validity of a generalized second law which bounds the energy extracted from the system, and study the breakdown of feedback cooling for very large time delays.

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.