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Abstract Solar‐blind ultraviolet (UV) photodetectors based on p‐organic/n‐Ga2O3 hybrid heterojunctions have attracted extensive attention recently. Herein, the multifunctional solar‐blind photodetector based on p‐type poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT)/n‐type amorphous Ga2O3 (a‐Ga2O3) is fabricated and investigated, which can work in the phototransistor mode coupling with self‐powered mode. With the introduction of PCDTBT, the dark current of such the a‐Ga2O3‐based photodetector is decreased to 0.48 pA. Meanwhile, the photoresponse parameters of the a‐Ga2O3‐based photodetector in the phototransistor mode to solar‐blind UV light are further increased, that is, responsivity (R), photo‐detectivity (D*), and external quantum efficiency (EQE) enhanced to 187 A W–1, 1.3 × 1016 Jones and 9.1 × 104 % under the weak light intensity of 11 μW cm–2, respectively. Thanks to the formation of the built‐in field in the p‐PCDTBT/n‐Ga2O3 type‐II heterojunction, the PCDTBT/Ga2O3 multifunctional photodetector shows self‐powered behavior. The responsivity of p‐PCDTBT/n‐Ga2O3 multifunctional photodetector is 57.5 mA W–1 at zero bias. Such multifunctional p‐n hybrid heterojunction‐based photodetectors set the stage for realizing high‐performance amorphous Ga2O3 heterojunction‐based photodetectors.

Precise control of hyperfine matterwaves via Raman excitations is instrumental to a class of atom-based quantum technology. We investigate the Raman matterwave control technique for alkaline-like atoms in an intermediate regime characterized by the single-photon detuning where a choice can be made to balance the Raman excitation power efficiency with the control speed, excited-state adiabatic elimination, and spontaneous-emission suppression requirements. Within the regime, rotations of atomic spinors by the Raman coupling are biased by substantial light shifts. Taking advantage of the fixed bias angle, we show that composite biased rotations can be optimized to enable precise ensemble spinor matterwave control within nanoseconds, even for multiple Zeeman pseudospins defined on the hyperfine ground states and when the laser illumination is strongly inhomogeneous. Our scheme fills a technical gap in light pulse atom interferometry for achieving high-speed Raman spinor matterwave control with moderate laser power.

Abstract Critical quantum metrology, which exploits quantum critical systems as probes to estimate a physical parameter, has gained increasing attention recently. However, the critical quantum metrology with a continuous quantum phase transition (QPT) is experimentally challenging since a continuous QPT only occurs at the thermodynamic limit. Here, we propose an adiabatic scheme on a perturbed Ising spin model with a first-order QPT. By introducing a small transverse magnetic field, we can not only encode an unknown parameter in the ground state but also tune the energy gap to control the evolution time of the adiabatic passage. Moreover, we experimentally implement the critical quantum metrology scheme using nuclear magnetic resonance techniques and show that at the critical point the precision achieves the Heisenberg scaling as 1/T. As a theoretical proposal and experimental implementation of the adiabatic scheme of critical quantum metrology and its advantages of easy implementation, inherent robustness against decays and tunable energy gap, our adiabatic scheme is promising for exploring potential applications of critical quantum metrology on various physical systems.

Summary: Although perovskite/two-dimensional (2D) materials heterojunctions have been employed to improve the optoelectronic performance of perovskite photodetectors and solar cells, effects of the intrinsic potential difference (ΔVin) of asymmetrical 2D materials, like Janus TMDs (J-TMDs), were not revealed yet. Herein, by investigating the optoelectronic properties of CsPbI3/J-TMDs heterojunctions, we find a reversible type-II band alignment related to the intensity and direction of ΔVin, suggesting that carrier transport paths can be reversed by modulating the contact configuration of J-TMDs in the heterojunctions. Meanwhile, the band offset, carrier transfer efficiency and optical properties of those heterojunctions are directly determined by the intensity and direction of ΔVin. Overall, CsPbI3/MoSSe heterojunction is suggested in this work with a tunneling probability of 79.65%. Our work unveils the role of ΔVin in asymmetrical 2D materials on the optoelectronic performances of lead halide perovskite devices, and provides a guideline to design high performance perovskite optoelectronic devices.

Quantum hypothesis testing plays a pivotal role in quantum technologies, making decisions or drawing conclusions about quantum systems based on observed data. Recently, quantum control techniques have been successfully applied to quantum hypothesis testing, enabling the reduction of error probabilities in the task of distinguishing magnetic fields in presence of environmental noise. In real-world physical systems, such control is prone to various channels of inaccuracies. Therefore improving the robustness of quantum control in the context of quantum hypothesis testing is crucial. In this work, we utilize optimal control methods to compare scenarios with and without accounting for the effects of signal frequency inaccuracies. For parallel dephasing and spontaneous emission, the optimal control inherently demonstrates a certain level of robustness, while in the case of transverse dephasing with an imperfect signal, it may result in a higher error probability compared to the uncontrolled scheme. To overcome these limitations, we introduce a robust control approach optimized for a range of signal noise, demonstrating superior robustness beyond the predefined tolerance window. On average, both the optimal control and robust control show improvements over the uncontrolled schemes for various dephasing or decay rates, with the robust control yielding the lowest error probability.

Abstract Generally, growing phase pure CsPbBr3 single crystals is challenging, and CsPb2Br5 or Cs4PbBr6 by‐products are usually formed due to the different solubilities of CsBr and PbBr2 in the single solvent. Herein, the growth of high‐quality phase pure CsPbBr3 perovskite single crystals at room temperature by a humidity controlled solvent evaporation method is reported first. Meanwhile, the room temperature phase transition process from three dimensional (3D) cubic CsPbBr3 to two dimensional (2D) layered tetragonal CsPb2Br5 and the detailed mechanism induced by humidity are revealed. Moreover, compared with the organic–inorganic perovskite, the prepared CsPbBr3 single crystals are much more stable under high humidity, which satisfies the long‐term working conditions of X‐ray detectors. The X‐ray detectors based on CsPbBr3 single crystals show a high sensitivity and a low detection limit of 1.89 μGyair s–1, all of which meet the needs of medical diagnosis.

Quantum parameter estimation promises a high-precision measurement in theory; however, how to design the optimal scheme in a specific scenario, especially under a practical condition, is still a serious problem that needs to be solved case by case due to the existence of multiple mathematical bounds and optimization methods. Depending on the scenario considered, different bounds may be more or less suitable, both in terms of computational complexity and the tightness of the bound itself. At the same time, the metrological schemes provided by different optimization methods need to be tested against realization complexity, robustness, etc. Hence, a comprehensive toolkit containing various bounds and optimization methods is essential for the scheme design in quantum metrology. To fill this vacancy, here we present a Python-Julia-based open-source toolkit for quantum parameter estimation, which includes many well-used mathematical bounds and optimization methods. Utilizing this toolkit, all procedures in the scheme design, such as the optimizations of the probe state, control and measurement, can be readily and efficiently performed.

New tools for quantum parameter estimation: more general and more efficient Measuring the parameters of interest with high precision is essential for science and technology, where the main quest is to find the ultimate precision limit and the optimal schemes to attain it. For a general noisy dynamics, the identification of the ultimate precision limit usually requires certain assumptions. In this work, Haidong Yuan from the Chinese University of Hong Kong and Chi-Hang Fred Fung from Munich Research Center, Huawei Technologies provided a systematic method to obtain the ultimate precision limit for general dynamics which does not make any assumptions and is more efficient than existing methods. Their method is based on an extension of a popular tool, the Bures angle, from quantum states to quantum channels, which is expected to have wide applications not only in quantum metrology but in many other fields of quantum information science.

Quantum discrimination and estimation are pivotal for many quantum technologies, and their performance depends on the optimal choice of probe state and measurement. Here we show that their performance can be further improved by suitably tailoring the pulses that make up the interferometer. Developing an optimal control framework and applying it to the discrimination and estimation of a magnetic field in the presence of noise, we find an increase in the overall achievable state distinguishability. Moreover, the maximum distinguishability can be stabilized for times that are more than an order of magnitude longer than the decoherence time.

The quantum speed limit is a fundamental concept in quantum mechanics, which aims at finding the minimum time scale or the maximum dynamical speed for some fixed targets. In a large number of studies in this field, the construction of valid bounds for the evolution time is always the core mission, yet the physics behind it and some fundamental questions like which states can really fulfill the target are ignored. Understanding the physics behind the bounds is at least as important as constructing attainable bounds. Here we provide an operational approach for the definition of the quantum speed limit, which utilizes the set of states that can fulfill the target to define the speed limit. Its performances in various scenarios have been investigated. For time-independent Hamiltonians, it is inverse proportional to the difference between the highest and lowest energies. The fact that its attainability does not require a zero ground-state energy suggests it can be used as an indicator of quantum phase transitions. For time-dependent Hamiltonians, it is shown that, contrary to the results given by existing bounds, the true speed limit should be independent of the time. Moreover, in the case of spontaneous emission, we find a counterintuitive phenomenon that a lousy purity can benefit the reduction of the quantum speed limit.

The characteristics of ferroelectric capacitors with poly(vinylidene fluoride-trifluoroethlene) (P(VDF-TrFE)) films have been studied at different structures of cell electrodes. It is suggested that the effect of electrode structures could induce changes of performance. Remarkably, cells with line electrodes display a better polarization and fatigue resistance than those with flat electrodes. For P(VDF-TrFE) ultrathin films with different electrode structures, the models of charge compensation mechanism for depolarization field and domain fatigue decomposition are used to explain the effect of electrode structure. Furthermore, the driving voltage based on normal speed-functionality is designed, and the testing results show that the line electrode structure could induce a robust switching, which is determined by the free charges concentration in active layer. These findings provide an effective route to design the optimum structure for a ferroelectric capacitor based on P(VDF-TrFE) copolymer ultrathin film.

We study the existence of the maximal quantum Fisher information matrix in the multi-parameter quantum estimation, which bounds the ultimate precision limit. We show that when the maximal quantum Fisher information matrix exists, it can be directly obtained from the underlying dynamics. Examples are then provided to demonstrate the usefulness of the maximal quantum Fisher information matrix by deriving various trade-off relations in multi-parameter quantum estimation and obtaining the bounds for the scalings of the precision limit.

The fidelity function for quantum states has been widely used in quantum information science and frequently arises in the quantification of optimal performances for the estimation and distinguishing of quantum states. A fidelity function for quantum channels is expected to have the same wide applications in quantum information science. In this paper we propose a fidelity function for quantum channels and show that various distance measures on quantum channels can be obtained from this fidelity function; for example, the Bures angle and the Bures distance can be extended to quantum channels via this fidelity function. We then show that the distances between quantum channels lead naturally to a quantum channel Fisher information which quantifies the ultimate precision limit in quantum metrology; the ultimate precision limit can thus be seen as a manifestation of the distances between quantum channels. We also show that the fidelity of quantum channels provides a unified framework for perfect quantum channel discrimination and quantum metrology. In particular, we show that the minimum number of uses needed for perfect channel discrimination is exactly the counterpart of the precision limit in quantum metrology, and various useful lower bounds for the minimum number of uses needed for perfect channel discrimination can be obtained via this connection.

The widely used quantum Cramér–Rao bound (QCRB) sets a lower bound for the mean square error of unbiased estimators in quantum parameter estimation, however, in general QCRB is only tight in the asymptotical limit. With a limited number of measurements biased estimators can have a far better performance for which QCRB cannot calibrate. Here we introduce a valid lower bound for all estimators, either biased or unbiased, which can serve as standard of merit for all quantum parameter estimations.

Quantum correlation provides a promising measure beyond entanglement. Here, we propose a necessary and sufficient condition for nonzero quantum correlation in continuous variable systems, which is simple and easy to perform in terms of a marker Q _r . In order to get this condition, we introduce continuous-variable local orthogonal bases of the operator space, which are generalized from the orthogonal basis sets in local operator space for discrete variables. Based on this, we obtain the marker Q _r for all bipartite continuous variable states, and provide several examples including two-mode Gaussian and non-Gaussian states. Our result may provide a candidate for quantum correlation measures, and can be measured by designed quantum circuits.

Decoupling is an important tool used to prolong the coherence time of quantum systems. However, most decoupling schemes have assumed selective controls on the system, and it is believed that with global pulses one can only decouple systems with certain coupling terms like secular dipole-dipole coupling. In this article, we show that with global pulses it is possible to reduce the coupling strength of other types of coupling, which we demonstrate with Ising coupling. The complexity of such pulses is independent of the size of the system.

The non-uniform stiffness distribution of irregular large thin-walled structures leads to warping deformation in the process of machining and assembly. The structure modeling and accurate calculation of the large deformation is the key to predict and control the deviation. A novel irregular higher-order composite shell element based on the absolute nodal coordinate formulation (ANCF) was proposed to accurately calculate the deformation of irregular large thin-walled structures with higher-order slope coordinates and improved shape function, considering the continuity of elements at the contact interface. A discrete method of irregular large thin-walled structures was proposed to solve the problem of node connection and deformation coupling between elements with different thicknesses, and to describe the large deformation of irregular large thin-walled structures effectively by using the combination of irregular higher-order elements and composite elements. An assembly deformation calculation model of irregular large thin-walled structures was proposed based on continuum mechanics. The influence of the thickened area on assembly deviation and stiffness of scalloped segment structures of heavy rocket tank bottom was studied with the new elements and calculation model, so as to provide guidance for structure design.