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We generalize the Bush-Mosteller learning, the Roth-Erev learning, and the social learning to include mistakes, such that the nonlinear replicator-mutator equation with either additive or multiplicative mutation is generated in an asymptotic limit. Subsequently, we exhaustively investigate the ubiquitous rock-paper-scissors game for some analytically tractable motifs of mutation pattern for which the replicator-mutator flow is seen to exhibit rich dynamics that include limit cycles and chaotic orbits. The main result of this paper is that in both symmetric and asymmetric game interactions, mistakes can sometimes help the players learn; in fact, mistakes can even control chaos to lead to rational Nash-equilibrium outcomes. Furthermore, we report a hitherto-unknown Hamiltonian structure of the replicator-mutator equation.

The existence of neutral species carries profound ecological implications that warrant further investigation. In this paper, we study the impact of neutral species on biodiversity in a spatial tritrophic system of cyclic competition, in which the neutral species are identified as the fourth species that may affect the competition process of the other three species under the rock-paper-scissors (RPS) rule. Extensive simulations showed that neutral species can promote coexistence in a high mobility regime within the system. When coexistence occurs, we found that the state can be maintained by two mechanisms: Species can either (i) adhere to traditional RPS rule or (ii) form patches to resist invasion. Our findings might aid in understanding the impact of neutral species on biodiversity in ecosystems.

The rock-paper-scissors (RPS) model successfully reproduces some of the main features of simple cyclic predator-prey systems with interspecific competition observed in nature. Still, lattice-based simulations of the spatial stochastic RPS model are known to give rise to significantly different results, depending on whether the three-state Lotka-Volterra or the four-state May-Leonard formulation is employed. This is true independently of the values of the model parameters and of the use of either a von Neumann or a Moore neighborhood. In this paper, we introduce a simple modification to the standard spatial stochastic RPS model in which the range of the search of the nearest neighbor may be extended up to a maximum Euclidean radius R. We show that, with this adjustment, the Lotka-Volterra and May-Leonard formulations can be designed to produce similar results, both in terms of dynamical properties and spatial features, by means of an appropriate parameter choice. In particular, we show that this modified spatial stochastic RPS model naturally leads to the emergence of spiral patterns in both its three- and four-state formulations.

In the evolutionary dynamics of a rock-paper-scissor model, the effect of natural death plays a major role in determining the fate of the system. Coexistence, being an unstable fixed point of the model, becomes very sensitive toward this parameter. In order to study the effect of mobility in such a system which has explicit dependence on mortality, we perform Monte Carlo simulation on a two-dimensional lattice having three cyclically competing species. The spatiotemporal dynamics has been studied along with the two-site correlation function. Spatial distribution exhibits emergence of spiral patterns in the presence of mobility. It reveals that the joint effect of death rate and mobility (diffusion) leads to new coexistence and extinction scenarios.

Antipredator behavior is present in many biological systems where individuals collectively react to an imminent attack. The antipredator response may influence spatial pattern formation and ecosystem stability but requires an organism's cost to contribute to the collective effort. We investigate a nonhierarchical tritrophic system, whose predator-prey interactions are described by the rock-paper-scissors game rules. In our spatial stochastic simulations, the radius of antipredator response defines the maximum prey group size that disturbs the predator's action, determining the individual cost to participate in antipredator strategies. We consider that each organism contributes equally to the collective effort, having its mobility limited by the proportion of energy devoted to the antipredator reaction. Our outcomes show that the antipredator response leads to spiral patterns, with the segregation of organisms of the same species occupying departed spatial domains. We found that a less localized antipredator response increases the average size of the single-species patches, improving the protection of individuals against predation. Finally, our findings show that although the increase of the predation risk for a more localized antipredator response, the high mobility constraining benefits species coexistence. Our results may help ecologists understand the mechanisms leading to the stability of biological systems where locality is crucial to behavioral interactions among species.

We offer a fractonic perspective on a familiar observation-a flat sheet of paper can be folded only along a straight line if one wants to avoid the creation of additional creases or tears. Our core underlying technical result is the establishment of a duality between the theory of elastic plates and a fractonic gauge theory with a second rank symmetric electric field tensor, a scalar magnetic field, a vector charge, and a symmetric tensor current. Bending moment and momentum of the plate are dual to the electric and magnetic fields, respectively. While the flexural waves correspond to the quadratically dispersing photon of the gauge theory, a fold defect is dual to its vector charge. Crucially, the fractonic condition constrains the latter to move only along its direction, i.e., the fold's growth direction. By contrast, fracton motion in the perpendicular direction amounts to tearing the paper.

We theoretically demonstrate the realization of a chiral edge mode in a system beyond natural science. Specifically, we elucidate that a kagome network of rock-paper-scissors (K-RPS) hosts a chiral edge mode of the population density which is protected by the nontrivial topology in the bulk. The emergence of the chiral edge mode is demonstrated by numerically solving the Lotka-Volterra (LV) equation. This numerical result can be intuitively understood in terms of the cyclic motion of a single rock-paper-scissors cycle, which is analogous to the cyclotron motion of fermions. Furthermore, we point out that a linearized LV equation is mathematically equivalent to the Schrödinger equation describing quantum systems. This equivalence allows us to clarify the topological origin of the chiral edge mode in the K-RPS; a nonzero Chern number of the payoff matrix induces the chiral edge mode of the population density, which exemplifies the bulk-edge correspondence in two-dimensional systems described by evolutionary game theory.

Rotating gantries are commonly used in ion-therapy facilities to assist and support optimizing the dose distribution delivered to the patient. They are installed at the end of the beamlines and rotated mechanically in the treatment room. In synchrotron-based facilities, the gantries must be able to transport slowly extracted beams with essentially different emittance patterns in the two transverse planes. Such beams will be referred to as the asymmetric beams. A special device called rotator has been proposed as a possible solution. The worldwide first beamline with the rotator has been recently commissioned. The original rotator concept uses an “external” rotator that is a part (a module) of the beamline the gantry is connected to. In this paper, a novel gantry ion-optical concept integrating the rotator optics into the gantry optics is introduced. The first-order gantry transfer matrix satisfies the so-called sigma-matching ion-optical constraints, and—at the same time—it possesses the format of a rotator transfer matrix. The rotator-matching and the sigma-matching principles are combined in the gantry transfer matrix, which means that the sigma-matching gantry acts simultaneously as a rotator without the need for an extra rotator device. In addition, scattering in the gantry nozzle is used to balance the asymmetric beam emittances in the two transverse planes without an additional scattering foil. In this way, the presented ion-optical concept combines all three known matching techniques—the sigma matching, the rotator matching, and the scattering-foil matching—within the gantry beam transport system. Such a beam transport system provides the best matching result and full angular independence of the beam parameters at the gantry isocenter. It also makes it possible to optimize the beam parameters not only at the gantry isocenter but also at the beam monitors located in the gantry nozzle without increasing the number of gantry quadrupoles. There are two possible versions of such gantry optics: the point-to-point and the parallel-to-point optics. They both are presented in this paper. Theoretical calculations are supported by beam transport simulations performed with the winagile code. Feasibility of the newly proposed ion-optical concept is demonstrated on the MedAustron proton gantry. However, it can be applied to any rotating gantry at any ion-therapy facility. The presented design is the first rotatorlike gantry ion-optical concept worldwide.

Quantum computation is expected to accelerate certain computational tasks over classical counterparts. Its most primitive advantage is its ability to sample from classically intractable probability distributions. A promising approach to make use of this fact is the so-called quantum-enhanced Markov-chain Monte Carlo (qe-MCMC) method [D. Layden et al., Nature (London) 619, 282 (2023)0028-083610.1038/s41586-023-06095-4], which uses outputs from quantum circuits as the proposal distributions. In this paper, we propose the use of a quantum alternating operator ansatz (QAOA) for qe-MCMC and provide a strategy to optimize its parameters to improve convergence speed while keeping its depth shallow. The proposed QAOA-type circuit is designed to satisfy the specific constraint which qe-MCMC requires with arbitrary parameters. Through our extensive numerical analysis, we find a correlation in a certain parameter range between an experimentally measurable value, acceptance rate of MCMC, and the spectral gap of the MCMC transition matrix, which determines the convergence speed. This allows us to optimize the parameter in the QAOA circuit and achieve quadratic speedup in convergence. Since MCMC is used in various areas such as statistical physics and machine learning, this paper represents an important step toward realizing practical quantum advantage with currently available quantum computers through qe-MCMC.

Quantum computing technology has the potential to revolutionize the simulation of materials and molecules in the near future. A primary challenge in achieving near-term quantum advantage is effectively mitigating the noise effects inherent in current quantum processing units (QPUs). This challenge is also decisive in the context of quantum-classical hybrid schemes employing variational quantum eigensolvers (VQEs) that have attracted significant interest in recent years. In this paper, we present a method that employs parametric Gaussian process regression (GPR) within an active learning framework to mitigate noise in quantum computations, focusing on VQEs. Our approach, grounded in probabilistic machine learning, exploits a custom prior based on the VQE ansatz to capture the underlying correlations between VQE outputs for different variational parameters, thereby enhancing both accuracy and efficiency. We demonstrate the effectiveness of our method on a two-site Anderson impurity model and a eight-site Heisenberg model, using the IBM open-source quantum computing framework, Qiskit, showcasing substantial improvements in the accuracy of VQE outputs while reducing the number of direct QPU energy evaluations. This paper contributes to the ongoing efforts in quantum-error mitigation and optimization, bringing us a step closer to realizing the potential of quantum computing in quantum matter simulations.

Searching via quantum walk is a topic that has been extensively studied. Most previous results provide approximate solutions, while in this paper we prove an algorithm that can find a marked vertex certainly. We adopt the coined discrete-time quantum walk (DTQW) model with adjusted operators and prove that, on complete bipartite graphs, when parameters are set properly, coined DTQW can deterministically find a marked vertex, i.e., the success probability is exactly 1. Before this paper there have been results of an alternating continuous-time quantum walk method that achieve deterministic spatial search, but this paper provides a deterministic quantum spatial search result via DTQW, while maintaining a quadratic speedup compared to classical algorithms. We also provide the quantum circuit implementation.

Variational quantum algorithms rely on the optimization of parameterized quantum circuits in noisy settings. The commonly used back-propagation procedure in classical machine learning is not directly applicable in this setting due to the collapse of quantum states after measurements. Thus, gradient estimations constitute a significant overhead in a gradient-based optimization of such quantum circuits. This paper introduces a random coordinate descent algorithm as a practical and easy-to-implement alternative to the full gradient descent algorithm. This algorithm only requires one partial derivative at each iteration. Motivated by the behavior of measurement noise in the practical optimization of parameterized quantum circuits, this paper presents an optimization problem setting that is amenable to analysis. Under this setting, the random coordinate descent algorithm exhibits the same level of stochastic stability as the full gradient approach, making it as resilient to noise. The complexity of the random coordinate descent method is generally no worse than that of the gradient descent and can be much better for various quantum optimization problems with anisotropic Lipschitz constants. Theoretical analysis and extensive numerical experiments validate our findings.

The orbital Hall effect can generate currents of angular momentum more efficiently than the spin Hall effect in most metals. However, so far, it has only been understood as a steady-state phenomenon. In this theoretical study, the orbital Hall effect is extended into the time domain. We investigate the orbital angular momenta and their currents induced by a femtosecond laser pulse in a Cu nanoribbon. Our numerical simulations provide detailed insights into the laser-driven electron dynamics on ultrashort timescales with atomic resolution. The ultrafast orbital Hall effect described in this paper is consistent with the familiar pictorial representation of the static orbital Hall effect, but we also find pronounced differences between physical quantities that carry orbital angular momentum and those that carry charge. For example, there are deviations in the time series of the respective currents. This paper lays the foundations for investigating ultrafast Hall effects in confined metallic systems.

This paper provides an overview of the worldwide first commissioning of a gantry beamline with a rotator at the MedAustron synchrotron-based proton/ion cancer therapy facility in Wiener Neustadt, Austria. The gantry beamline consists of the high energy beam transfer (HEBT) line and the gantry beam transport system. It transports the beam from the synchrotron to the gantry-room isocenter. The HEBT transports the beam from the synchrotron to the gantry entrance, which is the coupling point between the HEBT and the gantry. The rotator is one of the HEBT modules, thus it is an integral part of the gantry beamline. The MedAustron rotator is the worldwide first rotator system used to match slowly extracted asymmetric beams from the synchrotron to the rotating gantry. In this paper, main attention is paid to ion-optical and beam-alignment aspects of the beamline commissioning. A novel orbit-correction and beam-alignment technique has been developed specifically for the beamline with the rotator. While the theoretical concept of the rotator has existed for almost two decades, the MedAustron rotator is the first hardware implementation of this concept all over the world. The presented overview of the beamline commissioning includes a description of the principal technical solutions and main results of the first beam-transport measurements. Since the measured beam size and beam position agree well with theoretical predictions, one can conclude that the proof-of-concept of the rotator-matching has been successfully accomplished.

The High Intensity Proton Accelerator facility (HIPA) delivers a 590 MeV cw (50.6 MHz) proton beam with up to 1.4 MW beam power (2.4 mA) to spallation and meson production targets serving particle physics experiments and material research. The main accelerator is the ring cyclotron, an isochronous proton machine accelerating an injected 72 MeV beam to a final 590 MeV. A few meters downstream of the ring cyclotron, an electrostatic beam splitter was installed in the 1980s and originally designed to peel off from a 200 μA beam up to 20 μA (12 kW beam power). Future initiatives will also make use of the splitter. Specifically, as part of the Isotope and Muon Production using Advanced Cyclotron and Target technologies (IMPACT) upgrade project, Targeted Alpha Tumour Therapy and Other Oncological Solutions (TATTOOS), an online isotope separation facility will allow to produce promising radionuclides for diagnosis and therapy of cancer in quantities sufficient for clinical studies. The TATTOOS facility includes a dedicated beamline intended to operate at a beam intensity of 100 μA (60 kW beam power), requiring continuous splitting of the high-power main beam via the splitter. As a step forward toward reaching the desired beam intensity, a beam study was carried out to test the viability of the existing splitter for TATTOOS. The results of this study show that a record of 90 μA (53 kW beam power) was peeled off a horizontally and vertically enlarged beam by the splitter. The successful beam strategy employed during the study as well as the results of several key measurements are presented in this paper, with particular emphasis on diagnostic measurements. Additionally, to support the measurements, a computational model of the splitter has been implemented using Monte Carlo simulation tools, including realistic geometry, electrostatic fields, beam optics, and power deposition calculations. Overall, the results of this paper show that through the combination of beam measurements and simulations, the existing splitter can be used to reach the 100-μA beam intensity requirement for TATTOOS.

Coherent-one-way (COW) quantum key distribution (QKD) is a significant communication protocol that has been implemented experimentally and deployed in practical products due to its simple equipment requirements. However, existing security analyses of COW-QKD either provide a short transmission distance or lack immunity against coherent attacks in the finite-key regime. In this paper, we present a tight finite-key security analysis within the universally composable framework for a variant of COW-QKD, which has been proven to extend the secure transmission distance in the asymptotic case. We combine the quantum leftover hash lemma and entropic uncertainty relation to derive the key rate formula. When estimating statistical parameters, we use the recently proposed Kato's inequality to ensure security against coherent attacks and achieve a higher key rate. Our paper confirms the security and feasibility of COW-QKD for practical application and lays the foundation for further theoretical study and experimental implementation.

From bacteria and sperm cells to artificial microrobots, self-propelled microscopic objects at low Reynolds numbers often perceive fluctuating mechanical and chemical stimuli and contact exterior wall boundaries both in nature and the laboratory. In this paper, we theoretically investigate the fundamental features of microswimmers by focusing on their reciprocal deformation. Although the scallop theorem prohibits the net locomotion of reciprocal microswimmers, by analyzing a two-sphere swimmer model, we show that in a fluctuating and geometrically confined environment, reciprocal deformations can afford a statistically average displacement. After designing the shape gait, a reciprocal swimmer can migrate in any direction, even in the statistical sense, while the statistical average of passive rigid particles statistically diffuses in a particular direction in the presence of external boundaries. To elucidate this symmetry breakdown, by introducing an impulse response function, we derive a general formula for predicting the nonzero net displacement of a reciprocal swimmer. Using this theory, we determine the relation between the shape gait and net locomotion as well as the net diffusion constant increase and decrease, owing to a reciprocal deformation. Based on these findings and a theoretical formulation, we provide a fundamental basis for environment-coupled statistical locomotion. Thus, this paper is valuable for understanding biophysical phenomena in fluctuating environments, designing artificial microrobots, and conducting laboratory experiments.

The Mandelstam-Tamm and Margolus-Levitin quantum speed limits are two well-known evolution time estimates for isolated quantum systems. These bounds are usually formulated for fully distinguishable initial and final states, but both have tight extensions to systems that evolve between states with an arbitrary fidelity. However, the foundations of these extensions differ in some essential respects. The extended Mandelstam-Tamm quantum speed limit has been proven analytically and has a clear geometric interpretation. Furthermore, which systems saturate the limit is known. The derivation of the extended Margolus-Levitin quantum speed limit, on the other hand, is based on numerical estimates. Moreover, the limit lacks a geometric interpretation, and no complete characterization of the systems reaching it exists. In this paper, we derive the extended Margolus-Levitin quantum speed limit analytically and describe the systems that saturate the limit in detail. We also provide the limit with a symplectic-geometric interpretation, which indicates that it is of a different character than most existing quantum speed limits. At the end of the paper, we analyze the maximum of the extended Mandelstam-Tamm and Margolus-Levitin quantum speed limits and derive a dual version of the extended Margolus-Levitin quantum speed limit. The maximum limit is tight regardless of the fidelity of the initial and final states. However, the conditions under which the maximum limit is saturated differ depending on whether or not the initial state and the final state are fully distinguishable. The dual limit is also tight and follows from a time reversal argument. We describe the systems that saturate the dual quantum speed limit.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] Physics instructional labs have long been an area of pedagogical innovation and educational research. While current stakeholders in instructional labs are undoubtedly aware of the day’s concerns, reform efforts, and empirical research within lab settings, likely less apparent are the deep-rooted connections today’s deliberations have with those from multiple educational eras across the last 200 years. To this end, this paper provides a historical analysis of instructional laboratories in undergraduate physics education in the United States, with the goal of elucidating recurring themes in educational reform and research aimed at improving these learning environments. This work aims to synthesize the recursive themes present in the instructional laboratory landscape while summarizing how new research and pedagogical trends can promote further growth in this important learning environment. Through this analysis, commonly recurring themes are identified related to the longitudinal criticism of confirmatory, “cookbook” lab structures, the community’s skepticism of instructional labs’ abilities to reinforce lecture content, and the possibility of technological and societal obstructions which may implicitly limit innovative ideas, pedagogy, and research. By bringing to light these latent recursive themes, this work hopes to work toward helping break the cycle of criticism and stifled innovation alongside recent positive movements in evidence-based reforms and promising empirical research into student learning and engagement in instructional labs.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] National organizations set goals of engaging students in experimentation and authentic scientific reasoning while developing normative concepts to help them develop essential skills and competencies necessary to succeed in our rapidly changing world. One framework that meets these goals is the investigative science learning environment (ISLE) approach to teaching and learning physics. While studies have been conducted on student development of scientific abilities in ISLE-based classrooms, little is known about how formative assessment helps promote student growth in this setting. This paper presents on the findings from an empirical study on how the revision of written laboratory reports positively impacts first-year high school student development of scientific abilities in an ISLE-approach classroom. We argue that the opportunity to revise written work provides students with additional exposures that are necessary to support their scientific ability development. Furthermore, we explore positive correlations between student involvement in the collaborative writing process and attitudes regarding experimental physics.

A recent paper evaluating a new rubric-based graduate admissions approach using generic methods tentatively suggested that its decisions differed noticeably from the previous approach in an unspecified way. Using prior knowledge that the often-stated specific goal was to open a path to increased diversity by reducing barriers to the admission of applicants with low undergraduate grade point averages and graduate record exam (GRE) scores allows simple statistical tests of changes in the distributions of the metrics. The simple tests confirm with good statistical confidence that the barrier-reduction changes were achieved. Nevertheless, the paper’s argument that the de-emphasized tests and grades are not predictive of graduate outcomes is not supported by the prior literature. On technique, although a method used in some of the analyses for dropping data points before running the machine algorithm is likely to bias those results, it helps to clarify why models of the rubric-based system were only weakly predictive.

B-rich metal compounds have garnered significant attention due to their diverse polymeric boron structures and versatile properties including high melting temperature, exceptional hardness, and superconductivity. In this paper, we systematically investigate the ternary phase diagram of the Li-Mn-B system at 0–100 GPa, employing a combination of crystal structure prediction methods and first-principles calculations. We identify five pressure-stabilized compounds with stoichiometries of Li_{2}MnB_{2}, LiMnB_{3}, LiMnB_{4}, Li_{2}MnB_{8}, and LiMnB_{10}. These pressure-induced compounds can be recovered to ambient pressure conditions. Notably, the boron atoms in these compounds exhibit diverse polymerization patterns, forming structures such as dimers, zigzag chains, ribbons, kagome lattices, and three-dimensional channel frameworks. The five Li-Mn-B compounds are potential hard materials, with LiMnB_{4} standing out with a remarkable hardness value of 39.47 GPa. LiMnB_{4} and LiMnB_{10} are indirect semiconductors with band gaps of 0.92 and 0.64 eV, respectively. Notably, LiMnB_{10} exhibits a lower effective mass than silicon, superior solar cell efficiency compared with silicon, and a work function comparable with that of silicon. These properties highlight the considerable potential of LiMnB_{10} as a viable material for photovoltaic applications. Li_{2}MnB_{8} is predicted to be a superconductor with a critical temperature of 15 K at 50 GPa. When the pressure is reduced to 0 GPa, Li_{2}MnB_{8} displays antiferromagnetic properties. LiMnB_{3} is a suitable precursor to obtain a B_{20}-caged structure with remarkable superconductivity at ambient pressure, reaching a T_{c} of 31 K. In this paper, we provide comprehensive insights into the ternary phase diagram of the Li-Mn-B system at high pressure, elucidating the formation of various stable compounds with intriguing properties.

The variational quantum eigensolver (VQE) is a hybrid algorithm to find the minimum eigenvalue/vector of the given Hamiltonian by optimizing a parameterized quantum circuit (PQC) using a classical computer. Sequential optimization methods, which are often used in quantum circuit tensor networks, are popular for optimizing the parameterized gates of PQCs. In this paper, we focus on the case where the components to be optimized are single-qubit gates, in which the analytic optimization of a single-qubit gate is sequentially performed. The analytical solution is given by diagonalization of a matrix whose elements are computed from the expectation values of observables specified by a set of predetermined parameters, which we refer to as the parameter configurations. In this paper, we first show that the optimization accuracy significantly depends on the choice of parameter configurations owing to the statistical errors in the expectation values. We then identify a metric that quantifies the optimization accuracy of a parameter configuration for all possible statistical errors, named configuration overhead/cost or C-cost. We theoretically provide the lower bound of C-cost and show that, for the minimum size of parameter configurations, the lower bound is achieved if and only if the parameter configuration satisfies the so-called equiangular line condition. Finally, we provide numerical experiments demonstrating that the optimal parameter configuration exhibits the best result in several VQE problems. We hope that this general statistical methodology will enhance the efficacy of sequential optimization of PQCs for solving practical problems with near-term quantum devices.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] In this paper, we describe the results of a research project whose goals were to (1) develop and implement video-based experimental investigations using the Investigative Science Learning Environment (ISLE) approach and (2) study how students who engage with video experiments develop scientific abilities and learn physics ideas in comparison to students who do the same investigations using physical apparatus. We developed six parallel ISLE-based investigations for the students to engage in, either with apparatus or with video arrays created in the Pivot platform. We found that substituting 30% of the apparatus-based activities with video-based activities did not affect student development of conceptual physics knowledge. On the other hand, the development of certain scientific abilities was significantly affected by whether students experimented with physical apparatus or used video experiments.

Ground-state preparation is an important task in quantum computation. The probabilistic imaginary-time evolution (PITE) method is a promising candidate for preparing the ground state of the Hamiltonian, which comprises a single ancilla qubit and forward- and backward-controlled real-time evolution operators. The ground state preparation is a challenging task even in the quantum computation, classified as complexity-class quantum Merlin-Arthur. However, optimal parameters for PITE could potentially enhance the computational efficiency to a certain degree. In this paper, we analyze the computational costs of the PITE method for both linear and exponential scheduling of the imaginary-time step size for reducing the computational cost. First, we analytically discuss an error defined as the closeness between the states acted on by exact and approximate imaginary-time evolution operators. The optimal imaginary-time step size and rate of change of imaginary time are also discussed. Subsequently, the analytical discussion is validated using numerical simulations for a one-dimensional Heisenberg chain. From the results, we find that linear scheduling works well in the case of unknown eigenvalues of the Hamiltonian. For a wide range of eigenstates, the linear scheduling returns smaller errors on average. However, the linearity of the scheduling causes problems for some specific energy regions of eigenstates. To avoid these problems, incorporating a certain level of nonlinearity into the scheduling, such as by inclusion of an exponential character, is preferable for reducing the computational costs of the PITE method. The findings of this paper can make a significant contribute to the field of ground-state preparation of many-body Hamiltonians on quantum computers.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] All people vary in their needs and abilities; however, typical research practices do not consider these variations, which likely impacts who participates in research studies. Additionally, few PER studies have investigated aspects of disability or reported disability identity. Combined, this means that PER researchers typically do not seek out the experiences of disabled people and disabled people might not have access to participate in research studies. In this paper, we demonstrate how a research team can use principles from Universal Design for Learning and the Variation Planning Tool to anticipate expectations of ability and create flexible options in a qualitative research study. We then demonstrate how different interview structures can impact disabled participants through a case study with three participants, all of whom self-identified as students with attention deficit-hyperactivity disorder. Finally, we conclude with implications and suggestions for researchers in planning their study designs. It is critical that, as physics education researchers, we anticipate, welcome, and support disabled participants in our research, particularly as interviews are a prevalent method in the field. Through the example presented in this paper, we hope to encourage researchers to examine their own methods through the lens of accessibility and to offer alternative formats in their research design as a means to combat ableism and to provide access to all research participants.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] Research on nontraditional laboratory (lab) activities in physics shows that students often expect to verify predetermined results, as takes place in traditional lab activities. This understanding of what is taking place, or epistemic framing, may impact students’ behaviors in the lab, either productively or unproductively. In this paper, we present an analysis of student epistemic framing in a nontraditional lab with the aim of understanding how instructional context, specifically instructor behaviors, may shape student framing. We present video data from a lab section taught by an experienced teaching assistant (TA), with 19 students working in seven groups. We argue that student framing in this lab is evidenced by whether or not students articulate experimental predictions and by the extent to which they take up cognitive authority when constructing knowledge (epistemic agency). We show that the TA’s attempts to shift student frames generally succeed with respect to experimental predictions but are less successful with respect to epistemic agency. In part, we suggest, the success of the TA’s attempts reflects whether and how they are responsive to students’ current framing. This work offers evidence that instructors can shift students’ frames in nontraditional labs, while also illuminating the complexities of both student framing and the role of the instructor in shifting that framing in this context.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] Identifying student ideas about particular physics topics is one of the earliest and longest-standing foci of physics education research. This paper presents a method for identifying common conceptual resources for understanding physics, using large numbers of written student responses to conceptual questions. We walk researchers step by step through how we have done this ourselves, from collecting data, to identifying candidate resources, to turning our lists of candidate resources into a coding scheme that can then be applied to datasets of >200 responses. The outcome of these methods are lists of common conceptual resources for understanding particular topics in physics, such as forces, energy, circuits, and heat and temperature.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] Measurement uncertainty is a critical feature of experimental research in the physical sciences, and the concepts and practices surrounding measurement uncertainty are important components of physics lab courses. However, there has not been a broadly applicable, research-based assessment tool that allows physics instructors to easily measure students’ knowledge of measurement uncertainty concepts and practices. To address this need, we employed evidence-centered design to create the Survey of Physics Reasoning on Uncertainty Concepts in Experiments (SPRUCE). SPRUCE is a pre-post assessment instrument intended for use in introductory (first and second year) physics lab courses to help instructors and researchers identify student strengths and challenges with measurement uncertainty. In this paper, we discuss the development of SPRUCE’s assessment items guided by evidence-centered design, focusing on how instructors’ and researchers’ assessment priorities were incorporated into the assessment items and how students’ reasoning from pilot testing informed decisions around item answer options. We also present an example of some of the feedback an instructor would receive after implementing SPRUCE in a pre-post fashion, along with a brief discussion of how that feedback could be interpreted and acted upon.

In this paper, we propose three physical images, namely, asymmetric external inputs, discretization of the low rate region, and secondary outbreak, to understand the mystery of the relative timescales in the coevolution dynamics on multiplex networks. We carry out our analysis on an irreversible information-epidemic coevolution dynamics. In this dynamics, we found five kinds of anomalous behaviors, which are that with the increase of relative information processing speed, the final epidemic size may be monotonically increasing, monotonically decreasing, first decreasing and then increasing, first increasing and then decreasing but increasing again, and suddenly increasing with large fluctuation. Such complex behavior can be fully explained by our three physical images. Moreover, these five behaviors may transform into one another, which is far more complex than cyclic dynamics. Of course, our physical images easily provide an explanation for the results of cyclic coevolution dynamics. Since our discussion does not rely on specific dynamics and networks, our research may readily be extended to a broader field, rather than the network epidemiology in this paper.

Conventional direct-drive direct current (dc) septum magnets suffer from a high current density in the drive coil, which can cause magnet failures such as coil shorting due to the strong heat cycles, and result in large power consumption. Requirements for a thin septum and narrow gap in the magnet design naturally limit the space for coils, causing a high current density to be inevitably applied to the small cross-section coils. In this paper, we presented a new design for a dc septum magnet that largely decreased the current density and power consumption, while keeping an injection amplitude using a thin dogleg-shaped septum. According to our design comparison, the current density and power consumption were reduced from 145 A/mm^{2} and 24.5 kW for the conventional direct-drive configuration to 4.5 A/mm^{2} and 1.0 kW, respectively. The primary idea presented in paper leads to a power reduction of a factor of 25. We also detailed the fabrication process and magnet performance of the dc septum magnet developed for the next generation light source.

This paper presents a new approach to space charge dominated beamline design using an artificial intelligence (AI)-based optimization code named giotto. The code incorporates advanced algorithms for multiobjective genetic optimizations in particle accelerators, allowing efficient exploration of the parameter space and improved beam quality. The study demonstrates the application of giotto in the design of a high-brightness injector for an Energy Recovery Linac (ERL) called BriXSinO. The optimized injector features a low energy (4.5 MeV) and relatively high bunch charge (100 pC) operation. The results show promising beam parameters comparable to other ERL projects. Furthermore, the paper introduces innovative techniques, including bunches back-rotation the use of Lorentzian distributions in the fitness function. The approach successfully achieves dispersion closure in a space charge dominated dogleg. Overall, this work contributes to the advancement of accelerator science, offering a powerful methodology for beamline design and optimization. The new techniques and methodologies introduced have the potential to enhance the performance and stability of particle accelerators in various applications.

We develop a class of matrix models that implement and formalize the eigenstate thermalization hypothesis (ETH) and point out that, in general, these models must contain non-Gaussian corrections in order to correctly capture thermal mean-field theory or to capture nontrivial out-of-time-order correlation functions (OTOCs) as well as their higher-order generalizations. We develop the framework of these ETH matrix models and put it in the context of recent studies in statistical physics incorporating higher statistical moments into the ETH ansatz. We then use the ETH matrix model in order to develop a matrix-integral description of Jackiw-Teitelboim (JT) gravity coupled to a single scalar field in the bulk. This particular example takes the form of a double-scaled ETH matrix model with non-Gaussian couplings matching disk correlators and the density of states of the gravitational theory. Having defined the model from the disk data, we present evidence that the model correctly captures the JT+matter theory with multiple boundaries and, conjecturally, at higher genus. This is a shorter companion paper to the work [D. L. Jafferis et al., companion paper, Jackiw-Teitelboim gravity with matter, generalized eigenstate thermalization hypothesis, and random matrices, Phys. Rev. D 108, 066015 (2023).PRVDAQ2470-001010.1103/PhysRevD.108.066015], serving as a guide to the much more extensive material presented there, as well as developing its underpinning in statistical physics.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] Qualitative research methods have provided key insights in physics education research (PER) by drawing on non-numerical data such as text or video data. While different methods towards qualitative research exist, they share two essential steps: recognizing patterns in the data and interpreting these patterns. Although these methods have led to the development of rigorous theory, there are challenges: As such methods require a series of judgments by the analyst, they are difficult to validate and reproduce. Further, they are hard to scale so that they are unavailable to the analysis of large-scale data. In this way, important phenomena may remain inaccessible to qualitative analysis. Reacting to these challenges and leveraging the potential of emerging methods of artificial intelligence (AI) such as machine learning and natural language processing, sociologist Nelson has proposed the concept of computational grounded theory (CGT). CGT proceeds in a process of three consecutive steps: In the first step, one leverages the power of computational techniques, especially natural language processing and unsupervised machine learning techniques, for pattern detection in large datasets—those of a size and scope that may prohibit human-driven analysis from the outset. In the second step, one relies on the integrative and interpretative capabilities of human researchers to add quality and depth to the quantity and breadth of the first step. In the last step, one again uses computational techniques to test the extent to which the detected and refined patterns from the first and second step hold throughout the whole dataset under investigation. Interestingly, CGT does not aim at simply automating parts of the qualitative process by using AI, but rather aims at integrating AI into the human analyst’s workflow within a qualitative analysis. This leads to an analytical system that can do something that is quantitatively and qualitatively different from what a human or machine can do alone. In this way, CGT aims at addressing questions about validity, reproducibility, and scalability in qualitative research while preserving the theoretical sensitivity and unique inferencing capabilities of the human analyst. In this paper, we provide a primer on CGT, present how it can be used to investigate the physics problem-solving approaches of N=417 students based on textual data, and discuss CGT’s potentials and challenges in PER. In consequence, this paper can provide critical input to the discussion of how emerging AI technologies can provide new avenues in qualitative PER.

In recently published papers [M. J. J. Vrakking, Phys. Rev. Lett. 126, 113203 (2021)0031-900710.1103/PhysRevLett.126.113203; J. Phys. B 55, 134001 (2022)0953-407510.1088/1361-6455/ac6e17], Vrakking proposed an inventive scheme to control the entanglement or coherence of the vibrational states in a hydrogen molecular ion and a continuum electron, both of which were generated via the photoionization of a hydrogen molecule irradiated by a coherent pair of extreme ultraviolet (XUV) attosecond pulses and a few-femtosecond ultraviolet (UV) pulse. He clarified, for the first time to our knowledge, how the coherence of the XUV attosecond pulse pair is transferred to the molecular ion system accompanying a detached continuum electron by numerically solving a time-dependent Schrödinger equation (TDSE) governing the evolution of the ion and the electron in a rigorous manner. Nevertheless, it was not straightforwardly resolved how and why the specific characteristics of the resultant joint energy spectrogram emerged and how the entanglement or coherence was altered with the irradiation of the UV pulse. In this paper, we present an analytical solution of the TDSE using time-dependent perturbation theory, and we utilize the resultant solution to explain what causes the particular features in the entanglement or coherence between the electron and the ion spectra.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] Inquiring about students’ learning and their difficulties understanding the concepts and models of physics is a familiar challenge in physics education research. Researchers have developed various methodologies, such as phenomenography, to address it. Phenomenography is an empirical approach to determining how people experience and understand aspects of their surroundings and the physical world in qualitatively different ways. Rigorous phenomenographic analysis can be used to define categories to describe general ways the students experience the research phenomenon. The phenomenographic analysis process focuses on critical aspects of the collective experience rather than the richness of individual experience, assuming that there are a limited number of categories to describe the variations of experience for a given phenomenon. The possibility of defining a limited number of categories for experiencing a phenomenon on a collective level is one characteristic that makes phenomenographic analysis particularly appropriate for research that aims to enhance teaching and learning. We shall critically examine the strengths and weaknesses of phenomenographic research in this paper. The strengths include integral and holistic descriptions of people’s conceptions. Weaknesses include the risks of equating participants’ experiences with their descriptions of their own experiences. Our contribution weighs up the literature’s warnings about the validity and reliability of phenomenographic research. To provide an overview of phenomenography in physics education research, we conducted a literature review which identified and analyzed different approaches to data collection, data analysis, rigor, presentation of the results, and scope. We conclude by considering phenomenography as a research approach to learn how students perceive a concrete learning phenomenon, thus, providing an essential teaching design and preparation guide for instructors.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] Qualitative studies in the domain of physics education research have become more common in the last several decades. Methodologically, this has been marked by an expansion of the types of data collected in physics education research (PER): namely, in the use of individual and group interviews, problem-solving sessions, and classroom observations—often in the form of video data. However, depictions of those video data in publications, a key opportunity for communicating analytic approaches and results, are often left out or are constructed without addressing some important implications of video data depictions. In this paper, we critically examine how video data can be depicted, first providing a rough taxonomy of depiction approaches. We then emphasize the case of line illustrations as a depiction approach with significant potential for improving (i) the transparency of analytic perspectives, (ii) communicational clarity, and (iii) the handling of ethical issues, such as participant anonymization, followed by a discussion of the limitations and challenges of using illustrations. In the Appendix, we provide a practical guide for researchers interested in making their own illustrations for academic publishing purposes.

A relatively simple method of a guess of multipactor appearance on a cavity cell equator was described earlier in Phys. Rev. Accel. Beams 19, 102002 (2016PRABCJ2469-988810.1103/PhysRevAccelBeams.19.102002). For this guess, evaluation of electric field components in two definite points near the equator is sufficient, it gives the value of a so-called geometrical parameter p of the cell. If this parameter is big enough, for niobium superconducting cavities, it was found as p>0.28÷0.3, conditions for multipactor exist. However, this method works, as described, only for the inner cells of a multicell cavity or for single-cell cavities. An explanation is in the breakdown of symmetry of the electric field near the equator when the end cell consists of asymmetric half-cells and has a regular inner cell from one side and a beam pipe from another side. Multipactor in such cells shifts from the equator point. This paper is an addendum to the earlier presented paper, here it is shown how to find a correct value of the geometrical parameter p taking the asymmetry into account.

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] Within physics education research (PER), resource theory has proven to be a useful framework for investigating knowledge and learning and informing instructional design. To analyze learning over longer timescales and across cases, PER scholars must first identify and describe the resources activated within and across physics contexts and domains. Despite its importance, a reliable method for identifying resources has not been clearly outlined. This paper presents guidelines for the design of research aimed at identifying knowledge resources. We begin by describing the origin, assumptions, and utility of resource theory. We then introduce methods of data collection and analysis. We end with a discussion of validity and reliability, drawing connections with general principles of qualitative research. With this work, we hope to promote coordination among the many PER scholars who utilize resource theory and to invite new scholars to join in its application and development.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] This paper presents a historical analysis of the development, implementation, research, and assessment of an evidence-based introductory algebra-based physics course. The course is laboratory based and taught with an inquiry-based pedagogy. The course has remained unique and has been taught consistently for over 20 years. It is taught predominantly to health science majors and is completely laboratory based without a lecture and without a required text. Students learn by working through a guided inquiry manual in groups, doing experiments to explore the nature of the world around them. They develop both quantitative and qualitative models based on their experiments. The focus is as much on critical thinking, modeling, and thinking like a scientist, as on physics content. I discuss the course throughout the years, presented in the context of the field of physics education research historically and the state of our department locally. The results of multiple forms of assessment are presented chronologically. The assessments were designed to answer research questions about the students’ conceptual understanding and thinking skills, the effects of class size expansion, and questions about learning assistants’ pedagogical content knowledge. One finding was that the conceptual understanding of students in the inquiry-based course was significantly higher than students taught traditionally but not significantly different from students taught by other research-informed pedagogies. However, we found that students taught in the inquiry-based format showed more evidence of the application of thinking skills as assessed by our thinking skills rubric in free-response exam problems. We have demonstrated that it is possible to expand a laboratory-based, inquiry-based physics course from sections of 24 students to sections of 60 students with the help of learning assistants and we have developed and validated a set of questions that can be used to measure learning assistants’ pedagogical content knowledge or for learning assistant training purposes.

One of the fundamental challenges for future leptonic colliders and neutrino factories as well as for high-sensitivity studies of lepton universality is to design and construct new high-intensity sources of muons and positrons. The next-generation sources should increase the intensity of the presently operating ones by at least 3 orders of magnitude and include an important option of producing longitudinally polarized leptons. The main effort to achieve this goal has been focused, so far, on the proton-beam-driven muon sources and electron-beam-driven positron sources. In this paper, we present exploratory studies of an alternative scheme which is based on high-intensity megawatt-class photon beams. Such beams could be delivered in the future by the Gamma Factory (GF) project. One of the GF multiple goals is to increase the energy range (by more than one order of magnitude) and the intensity (by more than 6 orders of magnitude) of presently operating photon sources. Such a leap can be achieved by extending the present hadron-collider modus operandi of the LHC with a new GF-operation-mode, allowing the collisions of beams with laser pulses. The exploratory studies presented in this paper demonstrate that more than 10^{13} muons of both signs and more than 10^{16} electrons/positrons per second can be produced by a GF source.

Understanding the fundamental mechanisms of optoelectronic excitation and relaxation pathways on the single-molecule level has only recently been started by combining scanning tunneling microscopy (STM) and spectroscopy (STS) with STM-induced luminescence (STML). In this paper, we investigate cationic and anionic fluorescence of individual zinc phthalocyanine (ZnPc) molecules adsorbed on ultrathin NaCl films on Ag(111) by using STML. They depend on the tip-sample bias polarity and appear at threshold voltages that are correlated with the onset energies of particular molecular orbitals, as identified by STS. We also find that the fluorescence is caused by a single-electron tunneling process. Comparing with results from density functional theory calculations, we propose an alternative many-body picture to describe the charging and electroluminescence mechanism. In this paper, we provide aspects toward well-defined voltage selectivity of bipolar electrofluorochromism as well as fundamental insights regarding the role of transiently charged states of emitter molecules within organic light-emitting diode devices.

[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] We present the pedagogical design and implementation of “ESSENCe”: Experimental problem solving using Staging, Scaffolding, Embedded information sources, iNstruments, and Collaboration. Research in experimental physics requires problem-solving skills that include designing investigations, developing instrumentation techniques, troubleshooting, planning data analysis, and evaluating experimental outcomes. Most of these skills can be taught at the undergraduate level but are unfortunately skipped in traditional cookbook-recipe style labs. Since many physics experiments require electronics, the ESSENCe pedagogy presented here has been developed in the context of undergraduate electronics laboratory courses. The goals of ESSENCe labs are to help students apply their theoretical knowledge of electronics to hands-on open-ended experiments, understand properties of physical systems and limitations of measurements, and to learn how to work with sophisticated instruments used in experimental research. ESSENCe emphasizes collaboration with peers and teaching assistants. This paper presents the results of ESSENCe implementation in a sophomore undergraduate analog electronics lab of 45–60 students over multiple years in a top-ranked technological university in India. A mixed methods study was conducted to analyze students’ development of experimental problem-solving skills through repeated measures of performance on experimental tests and video analysis of students working on the experiments. We found statistically significant improvement in students’ experimental problem-solving skills over the course of a semester. The study also analyzed students’ perceptions about the benefits and challenges of the open-ended collaborative lab.

We present a variant of the Caldeira-Leggett (CL) model of a harmonic oscillator coupled to an environment. The CL model is a standard tool for studying the physics of decoherence. Our “adapted Caldeira-Leggett” (ACL) model is built in a finite Hilbert space which makes it suitable for numerical studies. Taking a numerical approach allows us to avoid the limitations of standard approximation schemes used with the CL model. We are able to evolve the ACL model in a fully reversible unitary manner, without the built-in time asymmetry and other assumptions that come with the master equation methods typically used. We have used the ACL model to study topics in the field of decoherence and einselection where the full unitary evolution is essential to our work. Those results (reported in companion papers) include an examination of the relationship between einselection and the arrow of time, and studies of the very earliest stages of einselection. This paper provides details about the ACL model and our numerical methods. Our numerical approach makes it straightforward to explore and plot any property of the physical system. Thus we believe the examples and illustrations we present here may provide a helpful resource for those wishing to improve their familiarity with standard decoherence results, as well as those looking to probe the underpinnings of our companion papers. We expect the ACL model will be a useful tool for exploring additional phenomena that cannot be studied using traditional approximation schemes.

The Bennett-Brassard 1984 (BB84) protocol is the most widely implemented quantum key distribution (QKD) scheme. However, despite enormous theoretical and experimental efforts in the past decades, the security of this protocol with imperfect sources has not yet been rigorously established. In this paper, we address this shortcoming and prove the security of the BB84 protocol in the presence of multiple source imperfections, including state preparation flaws and side channels, such as Trojan-horse attacks, mode dependencies and classical correlations between the emitted pulses. To do so, we consider a modified BB84 protocol that exploits the basis mismatched events, which are often discarded in standard security analyses of this scheme; and employ the reference technique, a powerful mathematical tool to accommodate source imperfections in the security analysis of QKD. Moreover, we compare the achievable secret-key rate of the modified BB84 protocol with that of the three-state loss-tolerant protocol, and show that the addition of a fourth state, while redundant in ideal conditions, significantly improves the estimation of the leaked information in the presence of source imperfections, resulting in a better performance. This paper demonstrates the relevance of the BB84 protocol in guaranteeing implementation security, taking us a step further towards closing the existing gap between theory and practice of QKD.