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Understanding nonequilibrium transport is crucial for controlling energy flow in nanoscale systems. We study thermal energy transfer in a generalized nonequilibrium spin-boson model (NESB) with noncommutative system-bath coupling operators and discover its unusual transport properties. Compared to the conventional NESB, the energy current is greatly enhanced by rotating the system-bath coupling operators. Constructive contribution to thermal rectification can be optimized when two sources of asymmetry, system-bath coupling strength and coupling operators, coexist. At the weak coupling and the adiabatic limit, the scaling dependence of energy current on the coupling strength and the system energy gap changes drastically when the coupling operators become noncommutative. These scaling relations can further be explained analytically by the nonequilibrium polaron-transformed Redfield equation (NE-PTRE). These novel transport properties, arising from the pure quantum effect of noncommutative coupling operators, suggest an unvisited dimension of controlling transport in nanoscale systems and should generally appear in other nonequilibrium set-ups and driven systems.

Objective: The objective of this study is to compare the characteristics of suicide attempts registered in general hospitals in urban and rural areas in China.Methods: From January 2007 to December 2011, suicide attempts registered in hospitals in five rural counties and in the Beijing Municipality were included. Univariate and multivariate analysis were used to compare the characteristics of rural and urban suicide attempts in China.Results: A total of 5,515 episodes of suicide attempts were included, 1,966 (35.6%) of them were from rural counties and 3,549 (64.4%) were from Beijing. Compared with urban counterparts, the rural suicide attempters had lower proportion of females (61.9% vs. 72.3%), more likely reporting previous suicide attempt history (56.9% vs. 16.4%), and staying in hospital for more than 1 day (81.5% vs. 44.6%). The most common methods of suicide attempts were pesticide ingestion in rural areas (52.1%) and taking medications in urban area (39.2%). Results of multivariate analysis indicated that suicide attempt registered in rural areas, pesticide ingestion, and previous suicide attempts history were associated with longer treatment in hospitals.Conclusions: Suicide attempts registered in rural areas were different from those in urban areas in China. It is essential to improve the equipment and ability of medical resuscitation for pesticide ingestion in rural hospitals in China.

The experimental optimization of a two-qubit controlled-Z (CZ) gate is realized following two different data-driven gradient ascent pulse engineering (GRAPE) protocols in the aim of optimizing the gate operator and the output quantum state, respectively. For both GRAPE protocols, the key computation of gradients utilizes mixed information of the input Z-control pulse and the experimental measurement. With an imperfect initial pulse in a flattop waveform, our experimental implementation shows that the CZ gate is quickly improved and the gate fidelities subject to the two optimized pulses are around 99%. Our experimental study confirms the applicability of the data-driven GRAPE protocols in the problem of the gate optimization.

A combination of digitized shortcut to adiabaticity (STA) and sequential digitized adiabaticity is implemented in a superconducting quantum device to determine the electronic states in two example systems, the ${\mathrm{H}}_{2}$ molecule and the topological Bernevig-Hughes-Zhang (BHZ) model. For ${\mathrm{H}}_{2}$, a short internuclear distance is chosen as a starting point, at which the ground and excited states are obtained via digitized STA. From this starting point, a sequence of internuclear distances is built. The eigenstates at each distance are sequentially determined from those at the previous distance via the digitized adiabaticity, leading to the potential energy landscapes of ${\mathrm{H}}_{2}$. The same approach is applied to the BHZ model and the valence and conduction bands are obtained with a high degree of accuracy along the $X$-$\mathrm{\ensuremath{\Gamma}}$-$X$ line cut of the first Brillouin zone. Furthermore, a numerical simulation of this method is performed to successfully extract the ground states of hydrogen chains with lengths of between three and six atoms.

Usually, a lot of manpower was consumed by companies, schools and other institutions on gathering and managing the data of taxi receipts. Due to the bad painting and the irregular arrangement of text, the automatic taxi receipt character recognition task have not been solved yet. This paper proposes an end-to-end taxi receipt automatic recognition method based on two different types of neural network without traditional image processing technology and ordinary optical character recognition(OCR) technology. The Single Shot Multi-Box Detector(SSD) neural network is used to determine the data region, and a CNN (convolution neural network) -GRU (gated recurrent unit) combined neural network is designed for character recognition. The two neural network enhance the method's robustness. Our data set contains 1800 images of taxi receipts, and the cross validation result shows that the accuracy reaches 94.36%.

For an energy transfer network, the irreversible depletion of excited electron energy occurs through either an efficient flow into an outer energy sink or an inefficient decay. With a small decay rate, the energy transfer efficiency is quantitatively reflected by the average life time of excitation energy before being trapped in the sink where the decay process is omitted. In the weak dissipation regime, the trapping time is analyzed within the exciton population subspace based on the secular Redfield equation. The requirement of the noise-enhanced energy transfer is obtained, where the trapping time follows an exact or approximate 1/Γ-scaling of the dissipation strength Γ. On the opposite side, optimal initial system states are conceptually constructed to suppress the 1/Γ-scaling of the trapping time and maximize the coherent transfer efficiency. Our theory is numerically testified in four models, including a biased two-site system, a symmetric three-site branching system, a homogeneous onedimensional chain, and an 8-chromophore FMO protein complex.

In a conformational nonequilibrium steady state (cNESS), enzyme turnover is modulated by the underlying conformational dynamics. On the basis of a discrete kinetic network model, we use an integrated probability flux balance method to derive the cNESS turnover rate for a conformation-modulated enzymatic reaction. The traditional Michaelis-Menten (MM) rate equation is extended to a generalized form, which includes non-MM corrections induced by conformational population currents within combined cyclic kinetic loops. When conformational detailed balance is satisfied, the turnover rate reduces to the MM functional form, explaining its general validity. For the first time, a one-to-one correspondence is established between non-MM terms and combined cyclic loops with unbalanced conformational currents. Cooperativity resulting from nonequilibrium conformational dynamics can be achieved in enzymatic reactions, and we provide a novel, rigorous means of predicting and characterizing such behavior. Our generalized MM equation affords a systematic approach for exploring cNESS enzyme kinetics.

The water meter is a device for measuring the amount of water used by each household. Remote meter reading is one of the main ways to solve the waste of human resources caused by regular manual door-to-door access to mechanical water meter readings. The current use of image acquisition and then accurate reading of the water meter image is one of the ways of remote meter reading. In this paper, the convolutional neural network is used to predict the reading area, and then the non-maximum suppression algorithm (NMS) is used to remove highly overlapping results from prediction region results to obtain the position of the reading area. The experimental results show that with using the method proposed in this paper in the actual application scenario, the IoU of the images of 1000 test sets are all above 0.8 and then combined with the three-layer BP neural network for character recognition, the accuracy rate reaches 98.0%.

Measurement-based feedback control is central in quantum computing and precise quantum control. Here we realize a fast and flexible field-programmable-gate-array-based feedback control in a superconducting Xmon qubit system. The latency of room-temperature electronics is custom optimized to be as short as 140 ns. Projective measurement of a signal qubit produces a feedback tag to actuate a conditional pulse gate to the qubit. In a feed-forward process, the measurement-based feedback tag is brought to a different target qubit for a conditional control. In a two-qubit experiment, the feedback and feed-forward controls are simultaneously actuated in consecutive steps. A quantum number is then generated by the signal qubit, and a random walk of the target qubit is correspondingly triggered and realized on the Bloch sphere. Our experiment provides a conceptually simple and intuitive benchmark for the feedback control in a multi-qubit system. The feedback system can be further scaled up for more complex feedback control experiments.

As emerging topological nodal-line semimetals, the family of ZrSiX (X = O, S, Se, Te) has attracted broad interests in condensed matter physics due to their future applications in spintonics. Here, we apply a scanning tunneling microscopy (STM) to study the structural symmetry and electronic topology of ZrSiSe. The glide mirror symmetry is verified by quantifying the lattice structure of the ZrSe bilayer based on bias selective topographies. The quasiparticle interference analysis is used to identify the band structure of ZrSiSe. The nodal line is experimentally determined at $\sim$ 250 meV above the Fermi level. An extra surface state Dirac point at $\sim$ 400 meV below the Fermi level is also determined. Our STM measurement provides a direct experimental evidence of the nodal-line state in the family of ZrSiX., Comment: 14 pages, 6 figures

In a `shortcut-to-adiabaticity' (STA) protocol, the counter-diabatic Hamiltonian, which suppresses the non-adiabatic transition of a reference `adiabatic' trajectory, induces a quantum uncertainty of the work cost in the framework of quantum thermodynamics. Following a theory derived recently [Funo et al 2017 Phys. Rev. Lett. 118 100602], we perform an experimental measurement of the STA work statistics in a high-quality superconducting Xmon qubit. Through the frozen-Hamiltonian and frozen-population techniques, we experimentally realize the two-point measurement of the work distribution for given initial eigenstates. Our experimental statistics verify (i) the conservation of the average STA work and (ii) the equality between the STA excess of work fluctuations and the quantum geometric tensor., 21 pages, 5 figures

Based on a `shortcut-to-adiabaticity' (STA) scheme, we theoretically design and experimentally realize a set of high-fidelity single-qubit quantum gates in a superconducting Xmon qubit system. Through a precise microwave control, the qubit is driven to follow a fast `adiabatic' trajectory with the assistance of a counter-diabatic field and the correction of derivative removal by adiabatic gates. The experimental measurements of quantum process tomography and interleaved randomized benchmarking show that the process fidelities of our STA quantum gates are higher than 94.9% and the gate fidelities are higher than 99.8%, very close to the state-of-art gate fidelity of 99.9%. An alternate of high-fidelity quantum gates is successfully achieved under the STA protocol., 18 pages, 6 figures

A small-size reconfigurable loop antenna for mobile phone applications with a compact volume of $55 \times 5 \times 3$ mm3 is proposed. In addition to the traditional three loop antenna modes, namely, 0.5- $\lambda $ , 1- $\lambda $ , and 1.5- $\lambda $ modes, the proposed loop antenna also generates another 2- $\lambda $ mode. To cover more operating bands with such compact antenna volume, the reconfigurable technique is therefore applied by inserting an RF switch at the end of the proposed antenna to improve bandwidth at the low band. By combining the four working states of RF switch, the proposed antenna can cover GSM850/900, DCS1800, PCS1900, UMTS2100, and LTE2300/2500 bands with low specific absorption rate and high efficiencies.

The energy absorbed in a light-harvesting protein complex is often transferred collectively through aggregated chromophore clusters. For population evolution of chromophores, the time-integrated effective rate matrix allows us to construct quantum kinetic clusters quantitatively and determine the reduced cluster-cluster transfer rates systematically, thus defining a minimal model of energy-transfer kinetics. For Fenna-Matthews-Olson (FMO) and light-havrvesting complex II (LCHII) monomers, quantum Markovian kinetics of clusters can accurately reproduce the overall energy-transfer process in the long-time scale. The dominant energy-transfer pathways are identified in the picture of aggregated clusters. The chromophores distributed extensively in various clusters can assist a fast and long-range energy transfer.

The significance of topological phases has been widely recognized in the community of condensed matter physics. The well controllable quantum systems provide an artificial platform to probe and engineer various topological phases. The adiabatic trajectory of a quantum state describes the change of the bulk Bloch eigenstates with the momentum, and this adiabatic simulation method is however practically limited due to quantum dissipation. Here we apply the `shortcut to adiabaticity' (STA) protocol to realize fast adiabatic evolutions in the system of a superconducting phase qubit. The resulting fast adiabatic trajectories illustrate the change of the bulk Bloch eigenstates in the Su-Schrieffer-Heeger (SSH) model. A sharp transition is experimentally determined for the topological invariant of a winding number. Our experiment helps identify the topological Chern number of a two-dimensional toy model, suggesting the applicability of the fast adiabatic simulation method for topological systems., Comment: 37 pages, 8 figures including Supplementary

For a frequency-tunable two-qubit system, a controlled-Z (CZ) gate can be realized by adiabatically driving the qubit system through an avoided level crossing between an auxiliary state and computational levels. Here, we theoretically propose a fast CZ gate using a shortcut-to-adiabaticity (STA). Experimentally, the STA CZ gate is implemented with a 52 ns control pulse for two coupled superconducting Xmon qubits. Measured fidelity of the STA CZ gate is higher than 96.0%, in both quantum process tomography and randomized benchmarking. The protocol allows a flexible design of the evolution time and control waveform. We suggest that this `fast adiabatic' CZ gate can be directly applied to other multi-qubit quantum systems., Comment: 7 pages, 4 figures

Following a recently proposed decomposition technique [C. R. Duan et al., Phys. Rev. B 95, 214308 (2017)], we inspect the zero-temperature spin-boson model for five different cutoff functions of the spectral density. With oscillatory and non-oscillatory exponentially decaying functions to decompose the bath correlation function, the hierarchy equation of motion is reliably extended to each spectral density under our investigation. The predicted spin dynamics is gradually converged with the increase of the hierarchic expansion order and the number of decomposing basis functions. Our systematic study of different cutoff functions expands previous results of the delocalized-localized phase transition with the exponential and sudden cutoffs in the spectral density.

Fully spin-polarized hole current is theoretically proposed to be generated by photoexcitation in the impurity states of the $\mathrm{Mo}{\mathrm{S}}_{2}$ monolayer with sulfur partially substituted by copper. To understand the dynamics of the photogenerated spin hole current, we perform a time-domain ab initio nonadiabatic molecular dynamics investigation with different initial excitation and temperature. First, the spin hole relaxes in a band-by-band manner. Therefore a longer lifetime can be achieved if the initial hole is generated at the lower edge of the impurity bands. Second, the phonon excitation is found to affect the spin hole dynamics significantly. When the temperature is decreased from 100 to 50 K, the hole relaxation across the band gap is strongly suppressed by the phonon bottleneck, which is due to the reduction of the phonon occupations. Our results show that the initial hole generation and phonon excitation are two key factors determining the dynamics of the photogenerated spin hole, which provide insights into the design of optimal spintronic devices.

With a decomposition scheme for the bath correlation function, the hierarchy equation of motion (HEOM) is extended to the zero-temperature sub-Ohmic spin-boson model, providing a numerically accurate prediction of quantum dynamics. As a dynamic approach, the extended HEOM determines the delocalized-localized (DL) phase transition from the extracted rate kernel and the coherent-incoherent dynamic transition from the short-time oscillation. As the bosonic bath approaches from the strong to weak sub-Ohmic regimes, a crossover behavior is identified for the critical Kondo parameter of the DL transition, accompanied by the transition from the coherent to incoherent dynamics in the localization.

With a counter-diabatic field supplemented to the reference control field, the `shortcut to adiabaticiy' (STA) protocol is implemented in a superconducting phase qubit. The Berry phase measured in a short time scale is in good agreement with the theoretical result acquired from an adiabatic loop. The trajectory of a qubit vector is extracted, verifying the Berry phase alternatively by the integrated solid angle. The classical noise is introduced to the amplitude or phase of the total control field. In the statistics of the Berry phase, the mean with either noise is almost equal to that without noise, while the variation with the amplitude noise can be described by an analytical expression., Comment: 27 pages, 5 figures, and 1 table including Supplementary

The linear absorption spectrum of a multisite system can be written as a weighted accumulation of elements of an absorption matrix. In the framework of the quantum-classical Liouville equation (QCLE), a mean-field approximation is introduced to simplify the calculation of the absorption matrix. The classical bath oscillators are propagated under partially shifted potentials, which reflects an averaged behavior after considering quantum jumps of the system states. For a specified initial condition, the time-dependent shifting possibility of each bath potential is given by the time evolution of site population estimated by the Redfield equation or the noninteracting blip approximation. The two hybrid QCLE approaches are tested in various models, including biased and unbiased two-site models, a subnetwork and the whole monomer of Fenna-Matthews-Olson, and harmonic and anharmonic baths. With numerically excellent results, the numerical studies show reliability and flexibility of the hybrid QCLE in calculating the absorption matrix and spectrum.

The most recent crystal structure of the Fenna–Matthews–Olson (FMO) protein complex indicates the presence of an additional eighth chromophore, which has been proposed to serve as a link between th...

In the framework of the quantum-classical Liouville equation (QCLE), the quantum kinetic expansion (QKE) of the spin-boson model is extended to an arbitrary combination of the bath potential and the system-bath interaction. The mixed quantum-classical estimation of the QKE rate kernels and modification functions are transformed into averages of deterministic classical trajectories over the Wigner initial distribution. For the standard spin-boson model, the QCLE-QKE method produces exactly the same result as that from full quantum dynamics and the numerical applicability of the approximate action-angle initial distribution is verified. For an anharmonic bath with the quartic potential, the QCLE-QKE calculation under the action-angle initial distribution illustrates the influence of this specific anharmonicity. With the increase of the quartic parameter, the fourth order QKE corrections are suppressed and the short-time population transfer is accelerated together with an enhanced quantum oscillation.

An extended hierarchy equation of motion (HEOM) is proposed and applied to study the dynamics of the spin-boson model. In this approach, a complete set of orthonormal functions are used to expand an arbitrary bath correlation function. As a result, a complete dynamic basis set is constructed by including the system reduced density matrix and auxiliary fields composed of these expansion functions, where the extended HEOM is derived for the time derivative of each element. The reliability of the extended HEOM is demonstrated by comparison with the stochastic Hamiltonian approach under room-temperature classical ohmic and sub-ohmic noises and the multilayer multiconfiguration time-dependent Hartree theory under zero-temperature quantum ohmic noise. Upon increasing the order in the hierarchical expansion, the result obtained from the extended HOEM systematically converges to the numerically exact answer.

For a general two-cluster network, a new methodology of the cluster-based generalized quantum kinetic expansion (GQKE) is developed in the matrix formalism under two initial conditions: the local cluster equilibrium and system-bath factorized states. For each initial condition, the site population evolution follows exactly a distinct closed equation, where all the four terms involved are systematically expanded over inter-cluster couplings. For the system-bath factorized initial state, the numerical investigation of the two models, a biased (2, 1)-site system and an unbiased (2, 2)-site system, verifies the reliability of the GQKE and the relevance of higher-order corrections. The time-integrated site-to-site rates and the time evolution of site population reveal the time scale separation between intra-cluster and inter-cluster kinetics. The population evolution of aggregated clusters can be quantitatively described by the approximate cluster Markovian kinetics.

In the spin-boson model, a continued fraction form is proposed to systematically resum high-order quantum kinetic expansion (QKE) rate kernels, accounting for the bath relaxation effect beyond the second-order perturbation. In particular, the analytical expression of the sixth-order QKE rate kernel is derived for resummation. With higher-order correction terms systematically extracted from higher-order rate kernels, the resummed quantum kinetic expansion (RQKE) approach in the continued fraction form extends the Pade approximation and can fully recover the exact quantum dynamics as the expansion order increases., accepted by J. Chem. Phys

A matrix formalism defined in the complete dynamic phase space is developed to analyze spin relaxation in the East model and the dynamic slow-down of dissipative systems in general. The truncated basis set expansion provides a direct route to calculate spin correlation functions systematically and to evaluate the mean relaxation time. Examining the relaxation time scales of linear and nonlinear modes leads to the observation that the full correlation and irreducible correlation functions defined in the complete space describe the slow dynamics of a dissipative system and can be related to their equivalent physical quantities in nondissipative systems, whereas the reduced correlation functions and associated memory kernels defined in the projected space involve faster time scales and cannot be directly reduced through mode coupling approximations. Matrix relations allow us to recover the simple mode coupling and extended mode coupling equations first obtained through an elegant diagrammatic expansion by Pi...