Abstract In recent decades, there has been a persistent pursuit of applications for surface/edge states in topological systems, driven by their dissipationless transport effects. This work demonstrates the remarkable properties of the topological material Ta2Pd3Te5, as a thermometer. At low temperatures, it shows a power-law correlation in temperature-dependent resistance, while behaving like a semiconductor at high temperatures. This dual behavior effectively mitigates the issue of infinite resistance in semiconductor thermometers at ultra-low temperatures, making it ideal for millikelvin-range refrigerators. Through chemical doping, thickness adjustment, and gate voltage control, its performance can be finely tuned, and can also enable micron-scale local temperature measurement from millikelvin to room temperature. Furthermore, this thermometer exhibits excellent temperature sensitivity and resolution, and can be fine-tuned to show small magnetoresistance. In summary, the Ta2Pd3Te5-based thermometer, also referred to as a topological thermometer, demonstrates considerable potential for broad-temperature-range detection and merits further investigation and optimization.
Materials of engineering and construction. Mechanics of materials, Atomic physics. Constitution and properties of matter
The unveiling of two-dimensional (2D) van der Waals magnetism ignited a surge of interest in low-dimensional magnetism. With dimensions reduced, research has delved into facile electric control of 2D magnetism, high-quality heterostructure design, and new device functionality. These atomically thin magnetic materials have spawned a burgeoning field known as 2D spintronics, holding immense promise for future quantum technologies. In this review, we comprehensively survey the current advancements in 2D magnet-based quantum devices, accentuating their role in manifesting exotic properties and enabling novel functionalities. Topological states, spin torques, voltage control of magnetic anisotropy, strain engineering, twistronics, and designer interface will be discussed. Furthermore, we offer an outlook for their development in future CMOS and quantum hardware paradigms.
Atomic physics. Constitution and properties of matter, Materials of engineering and construction. Mechanics of materials
Naina Kushwaha, Olivia Armitage, Brendan Edwards
et al.
Abstract Chromium ditelluride, CrTe2, is an attractive candidate van der Waals material for hosting 2D magnetism. However, how the room-temperature ferromagnetism of the bulk evolves as the sample is thinned to the single-layer limit has proved controversial. This, in part, reflects its metastable nature, vs. a series of more stable self-intercalation compounds with higher relative Cr:Te stoichiometry. Here, exploiting a recently developed method for enhancing nucleation in molecular-beam epitaxy growth of transition-metal chalcogenides, we demonstrate the selective stabilisation of high-coverage CrTe2 and Cr2+ε Te3 epitaxial monolayers. Combining X-ray magnetic circular dichroism, scanning tunnelling microscopy, and temperature-dependent angle-resolved photoemission, we demonstrate that both compounds order magnetically with a similar T C. We find, however, that monolayer CrTe2 forms as an antiferromagnetic metal, while monolayer Cr2+ε Te3 hosts an intrinsic ferromagnetic semiconducting state. This work thus demonstrates that control over the self-intercalation of metastable Cr-based chalcogenides provides a powerful route for tuning both their metallicity and magnetic structure, establishing the CrxTey system as a flexible materials class for future 2D spintronics.
Materials of engineering and construction. Mechanics of materials, Atomic physics. Constitution and properties of matter
Manipulations with open quantum systems (such as qubits) are fundamental for any quantum technology. They are the focus of studies involving optimal control theory. Usually, control is achieved through the use of time-dependent external fields when driven system evolution is simulated employing the Davies construction (second-order Markov quantum master equation formulation). As a weak (second order) coupling scheme, the Davies construction is limited in its ability to account for bath-induced coherences. To overcome the limitation, we utilize the nonequilibrium Green’s function method and demonstrate that accounting for the coherences makes a qualitative impact on quantum control studies. We find that accounting for the coherences is especially important when dealing with system evolution involving mixed states.
Atomic physics. Constitution and properties of matter
Yu. A. Berezhnoy, V. A. Zolotarev, V. P. Mikhailyuk
In the framework of the Born approximation, comparison of the previously used approaches, in which analytical expressions for the scattering amplitudes of particles by nuclei were obtained using the expansion of the potential into the series up to the first significant terms, as well as an approach in which such expansion was not performed, are presented. When obtaining analytical expressions for the amplitudes for elastic scattering of protons by nuclei, the second Born approximation with a potential in the Woods-Saxon form, as well as with the potential with a sharp absorption boundary, which was corrected to take into account the blurring of the nuclear surface, are used. Performed theoretical calculations are compared with the available experimental data for the differential cross sections and polarization observables for proton scattering by 40Ca nuclei at 200 MeV energy.
Atomic physics. Constitution and properties of matter
The current study aims to examine uncertainty relations for quantum measurements assigned to a projective two-design. Complete sets of mutually unbiased bases and symmetric informationally complete measurements are important cases of such measurements. To characterize the amount of uncertainty, we use the Tsallis and Rényi entropies as well as the probabilities of separate outcomes. The obtained results are based on an estimation of the index of coincidence. They improve some uncertainty relations given in the literature.
Atomic physics. Constitution and properties of matter
Patrick Mark, Sebastian Gstir, Julian Münzberg
et al.
We measure the nonlinearity of a telecom-wavelength superconducting nanowire single-photon detector via incoherent beam combination. At typical photon count rates and detector bias current, the observed relative deviation from a perfectly linear response is in the order of 0.1% when the flux is doubled. This arises from a balance between the counteracting nonlinearities of dead time-induced detector saturation and of multi-photon detections. The observed behavior is modeled empirically, which suffices for a correction of measured data. In addition, statistical simulations, taking into account the measured recovery of the detection efficiency (90%-recovery after about 100 ns), provide insight into possible mechanisms of multi-photon detection.
Atomic physics. Constitution and properties of matter
Quantum metaphotonics has emerged as a cutting-edge subfield of meta-optics employing subwavelength resonators and their planar structures, such as metasurfaces, to generate, manipulate, and detect quantum states of light. It holds a great potential for the miniaturization of current bulky quantum optical elements by developing a design of on-chip quantum systems for various applications of quantum technologies. Over the past few years, this field has witnessed a surge of intriguing theoretical ideas, groundbreaking experiments, and novel application proposals. This Perspective aims to summarize the most recent advancements and also provides a perspective on the further progress in this rapidly developing field of research.
Atomic physics. Constitution and properties of matter
S. X. M. Riberolles, Tianxiong Han, Tyler J. Slade
et al.
Abstract Predicting magnetic ordering in kagome compounds offers the possibility of harnessing topological or flat-band physical properties through tuning of the magnetism. Here, we examine the magnetic interactions and phases of ErMn6Sn6 which belongs to a family of RMn6Sn6, R = Sc, Y, Gd–Lu, compounds with magnetic kagome Mn layers, triangular R layers, and signatures of topological properties. Using results from single-crystal neutron diffraction and mean-field analysis, we find that ErMn6Sn6 sits close to the critical boundary separating the spiral-magnetic and ferrimagnetic ordered states typical for non-magnetic versus magnetic R layers, respectively. Finding interlayer magnetic interactions and easy-plane Mn magnetic anisotropy consistent with other members of the family, we predict the existence of a number of temperature and field dependent collinear, noncollinear, and noncoplanar magnetic phases. We show that thermal fluctuations of the Er magnetic moment, which act to weaken the Mn-Er interlayer magnetic interaction and quench the Er magnetic anisotropy, dictate magnetic phase stability. Our results provide a starting point and outline a multitude of possibilities for studying the behavior of Dirac fermions in RMn6Sn6 compounds with control of the Mn spin orientation and real-space spin chirality.
Materials of engineering and construction. Mechanics of materials, Atomic physics. Constitution and properties of matter
Almost a century on from the culmination of the first revolution in quantum physics, we are poised for another. Even as we engage in the creation of impactful quantum technologies, it is imperative for us to face the challenges in understanding the phenomenology of various emergent forms of quantum matter. This will involve building on decades of progress in quantum condensed matter physics, and going beyond the well-established Ginzburg-Landau-Wilson paradigm for quantum matter. We outline and discuss several outstanding challenges, including the need to explore and identify the organisational principles that can guide the development of theories, key experimental phenomenologies that continue to confound, and the formulation of methods that enable progress. These efforts will enable the prediction of new quantum materials whose properties facilitate the creation of next generation technologies.
The isoscalar giant monopole resonance (ISGMR) of even molybdenum isotopes 92,94,96,98,100Mo has been studied within the Skyrme self-consistent Hartree - Fock - Bardeen, Cooper, and Schrieffer and quasi-particle random phase approximation. Ten sets of Skyrme-type interactions of different values of the nuclear matter incompressibility coefficient KNM are used in the calculations. The calculated strength distributions, centroid energies Ecen, scaled energies Es and constrained energies Econ of ISGMR are compared with available experimental data. Due to the appropriate value of the nuclear matter incompressibility KNM, several types of Skyrme interactions were successful in describing the ISGMR strength distribution in the 92,94,96,98,100Mo isotopes. As a result, high correlations between Ecen and KNM were found.
Atomic physics. Constitution and properties of matter
The short-term forecasting of photovoltaic (PV) power generation ensures the scheduling and dispatching of electrical power, helps design a PV-integrated energy management system, and enhances the security of grid operation. However, due to the randomness of solar energy, the output of the PV system will fluctuate, which will affect the safe operation of the grid. To solve this problem, a high-precision hybrid prediction model based on variational quantum circuit (VQC) and long short-term memory (LSTM) network is developed to predict solar irradiance 1 hour in advance. VQC is embedded in LSTM to iteratively optimize the weight parameters of four gates (forgetting gate, input gate, cell state, and output gate) to improve prediction accuracy. To evaluate the prediction performance of this model, five solar radiation observatories located in China are selected, together with widely used models including seasonal autoregressive integrated moving average, convolution neural network, recurrent neural network (RNN), gate recurrent unit, (GRU), and LSTM; comparisons are made under different seasons and months. The experimental results show that the annual average root mean square error of the quantum long short-term memory model is 61.756 <inline-formula><tex-math notation="LaTeX">$\text{W/m}^{2}$</tex-math></inline-formula>, which is reduced by 10.7%, 13.9%, 8.1%, 3.8%, and 3.4%, respectively, compared with other models; the annual average mean absolute error is 24.257 <inline-formula><tex-math notation="LaTeX">$\text{W/m}^{2}$</tex-math></inline-formula>, which is reduced by 28.1%, 28.9%, 24.1%, 12.2%, and 12.8%, respectively, compared with other models; the annual average R-Square (<inline-formula><tex-math notation="LaTeX">$R^{2}$</tex-math></inline-formula>) is 0.946, which is improved by 1.5%, 1.9%, 1.2%, 0.4%, and 0.4%, respectively, compared with other models.
Atomic physics. Constitution and properties of matter, Materials of engineering and construction. Mechanics of materials
Understanding the equation of state of dense QCD matter remains a major challenge in both nuclear physics and astrophysics. Neutron star observations from electromagnetic and gravitational wave spectra provide critical insights into the behavior of dense neutron-rich matter. The next generation of telescopes and gravitational wave observatories will offer even more detailed observations of neutron stars. Utilizing deep learning techniques to map neutron star mass and radius observations to the equation of state allows for its accurate and reliable determination. This work demonstrates the feasibility of using deep learning to extract the equation of state directly from neutron star observational data, and to also obtain related nuclear matter properties such as the slope, curvature, and skewness of the nuclear symmetry energy at saturation density. Most importantly, we show that this deep learning approach is able to reconstruct \textit{realistic} equations of state, and deduce \textit{realistic} nuclear matter properties. This highlights the potential of artificial neural networks in providing a reliable and efficient means to extract crucial information about the equation of state and related properties of dense neutron-rich matter in the era of multi-messenger astrophysics.
Structural equation modeling (SEM) is a statistical method widely used in educational research to investigate relationships between variables. SEM models are typically constructed based on theoretical foundations and assessed through fit indices. However, a well-fitting SEM model alone is not sufficient to verify the causal inferences underlying the proposed model, as there are statistically equivalent models with distinct causal structures that equally well fit the data. Therefore, it is crucial for researchers using SEM to consider statistically equivalent models and to clarify why the proposed model is more accurate than the equivalent ones. However, many SEM studies did not explicitly address this important step, and no prior study in physics education research has delved into potential methods for distinguishing statistically equivalent models with differing causal structures. In this study, we use physics identity model as an example to discuss the importance of considering statistically equivalent models and how other data can help to distinguish them. Previous research has identified three dimensions of physics identity: perceived recognition, self-efficacy, and interest. However, the relationships between these dimensions have not been thoroughly understood. In this paper, we specify a model with perceived recognition predicting self-efficacy and interest, which is inspired by individual interviews with students in physics courses to make physics learning environments equitable and inclusive. We test our model with fit indices and discuss its statistically equivalent models with different causal inferences among perceived recognition, self-efficacy, and interest. We then discuss potential experiments that could further empirically test the causal inferences underlying the models, aiding the refinement to a more accurate causal model for guiding educational improvements.
In this article, a quasi-elliptical geometry and the iris technique are applied to a multimode cavity to manipulate the resonant mode in the desired direction for quantum memories. By applying quasi-elliptical geometry, the characteristics of monotonically increasing, equally spaced, and monotonically decreasing frequency intervals between the modes are realized. To manipulate a certain mode, an iris is applied to the multimode storage cavity. As an example, the entire mode, including the readout cavity, is implemented at equal intervals to minimize the interference and maximize the mode number from adjacent modes for the 5–8 GHz frequency band.
Atomic physics. Constitution and properties of matter, Materials of engineering and construction. Mechanics of materials
Natasha Tomm, Sahand Mahmoodian, Nadia O. Antoniadis
et al.
The interaction between photons and a single two-level atom constitutes a fundamental paradigm in quantum physics. The nonlinearity provided by the atom means that the light-matter interaction depends strongly on the number of photons interacting with the two-level system within its emission lifetime. This nonlinearity results in the unveiling of strongly correlated quasi-particles known as photon bound states, giving rise to key physical processes such as stimulated emission and soliton propagation. While signatures consistent with the existence of photon bound states have been measured in strongly interacting Rydberg gases, their hallmark excitation-number-dependent dispersion and propagation velocity have not yet been observed. Here, we report the direct observation of a photon-number-dependent time delay in the scattering off a single semiconductor quantum dot coupled to an optical cavity. By scattering a weak coherent pulse off the cavity-QED system and measuring the time-dependent output power and correlation functions, we show that single photons, and two- and three-photon bound states incur different time delays of 144.02\,ps, 66.45\,ps and 45.51\,ps respectively. The reduced time delay of the two-photon bound state is a fingerprint of the celebrated example of stimulated emission, where the arrival of two photons within the lifetime of an emitter causes one photon to stimulate the emission of the other from the atom.
Antoine Tenart, Gaétan Hercé, Jan-Philipp Bureik
et al.
Quantum fluctuations play a central role in the properties of quantum matter. In non-interacting ensembles, they manifest as fluctuations of non-commuting observables, quantified by Heisenberg inequalities. In the presence of interactions, additional quantum fluctuations appear, from which many-body correlations and entanglement arise. In the context of many-body physics, the Bogoliubov theory provides us with an illuminating microscopic picture of how this occurs for weakly-interacting bosons, with the appearance of the quantum depletion formed by pairs of bosons with opposite momenta. Here, we report the observation of these atom pairs in the depletion of an equilibrium interacting Bose gas. A quantitative study of atom-atom correlations, both at opposite and close-by momenta, allows us to fully characterise the equilibrium many-body state. We show that the atom pairs share the properties of two-mode squeezed states, including relative number squeezing. Our results illustrate how interacting systems acquire non-trivial quantum correlations as a result of the interplay between quantum fluctuations and interactions