Materials Science · Cross-listed from quant-ph
Quantization and Mirror Reduction Do Not Commute in Hamiltonian Embeddings of Nonreciprocal Dynamics
Gaurav Sarmah and Ramakrishna Podila
Hamiltonian embeddings can represent dissipative nonreciprocal classical dynamics exactly on invariant
manifolds of enlarged reciprocal systems. We show that canonical quantization of such an
embedding need not commute with reduction to the target dynamics. For the mirror construction recently introduced for pairwise nonreciprocal interactions, the invariant
manifold is Lagrangian. Exact
quantum enforcement of the mirror condition therefore removes the dynamical sector rather than producing a
quantum analogue of the reduced flow. If the constraint is imposed only semiclassically, contraction of the target dynamics generates inverse-transpose expansion in the conjugate mirror directions.
Quantum uncertainty then gives $\ln D\ge\Xi(t)+n\ln[\pi/(\sigma\epsilon)]$, where $\Xi=-\ln|\det M|$ is the accumulated contraction and $D$ the
torus Hilbert-space dimension. Exact finite-dimensional Weyl
evolution of one- and two-degree-of-freedom nonreciprocal models confirms the resulting logarithmic correspondence time, including its predicted change when the initial localization scales with $\hbar$. Thus the classical
embedding is exact, but its direct canonical quantization is a singular semiclassical construction.
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Statistical Mechanics · Cross-listed from physics.flu-dyn
V. E. R. Lemes
We formalize the gauge structure of the Navier–Stokes equation for incompressible fluids, interpreting $\nabla\cdot\mathbf{v}=0$ as a gauge fixing analogous to the Coulomb gauge in electromagnetism. We construct the Martin–Siggia–Rose action and its full BRST
symmetry, introducing BRST doublets for the Gribov parameter $\gamma$ and the monodromy phase $\theta$. Through a
Higgs mechanism, $\gamma$ acquires a
vacuum expectation value $\gamma_{0}$, generating a mass scale for the vorticity and the ghosts; we compute the one-loop effective potential and analyze
vacuum stability. Intermittency — measured by the exponents $\zeta_{n}$ — is described by fluctuations of the
Higgs field $\sigma$ around the condensate, via a Gribov-inspired log-Poisson hierarchy that satisfies exactly $\zeta_{3}=1$ (Kolmogorov's four-fifths law). Fits to DNS data favor filamentary vorticity structures, with $D_{f}\approx1$ (one parameter) or $D_{f}\approx2.1$, $\Delta\approx0.44$ (two parameters). The one-loop anomalous dimension in $d=3$, $\Delta_{\sigma}\approx0.50$, supports the identification $D_{f}=2\Delta_{\sigma}$. The formalism unifies classical hydrodynamics with gauge theory and spontaneous
symmetry breaking, opening the study of
turbulence and intermittency to
quantum field theory methods.
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Soft Condensed Matter
Physics-Informed Neural Networks for Depth-Averaged Granular Avalanche Dynamics on Curved Topography
Pujan Pranavkumar Purohit, Pradyumn Singh Sikarwar, Vishal Sharma et al. (+1 more)
Physics-informed neural networks (PINNs) provide a mesh-free framework for solving governing equations, but their application to granular avalanche dynamics over curved terrain remains largely unexplored. This study extends a depth-averaged PINN formulation based on the Savage-Hutter equations to an exponentially curved chute with spatially varying inclination and a strain-rate-dependent Mohr-Coulomb earth-pressure closure. The model is validated against measured front- and rear-edge trajectories from a laboratory granular-avalanche experiment, with selected observations withheld from training. A staged temporal curriculum proved essential for accurate prediction, reducing the held-out trajectory error by approximately two orders of magnitude compared with training over the full time domain from the outset. Sparse-data experiments further showed that observation placement was more influential than observation number within the configurations tested. Four observations bracketing the transition from acceleration to deceleration achieved nearly the same accuracy as the eight-observation reference configuration, whereas observations clustered at early or late times performed poorly. The results demonstrate the importance of both training strategy and informative data placement when applying PINNs to granular flows over curved topography.
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All authors Pujan Pranavkumar Purohit, Pradyumn Singh Sikarwar, Vishal Sharma, Gaurav Bhutani
Materials Science
A Strategy Toward Room Temperature Topological Hall Effect via Local Moment Magnetism
Karthik Rao, Kevin Allen, Yuxiang Gao et al. (+10 more)
Topological
spin textures in local moment systems hold great promise for technological applications due to their large
magnetic moments, strong
spin-orbit coupling (SOC), and high tunability. Finding new
spin textures that are stable near room temperature is paramount to maximizing their potential for applications. Here, we provide a strategy for realizing topological
spin textures at high temperatures by identifying rare earth ($R$) magnets ordering at or near room temperature. We demonstrate the feasibility of this strategy in one of these magnets, hexagonal Gd$_5$Pb$_3$, which orders at $T_C$ = 285 K. The indication for topological
spin textures comes from topological Hall effect (THE), which, in Gd$_5$Pb$_3$, occurs between $T$ = 100 - 200 K, an order of magnitude higher temperature than in other reported $R$-based systems. Our results present an opportunity to explore the role of SOC, anisotropic exchange,
geometric frustration, and
magnetic interactions in stabilizing topological
spin textures, and provide a pathway toward realizing them near room temperature in $R$-based magnets.
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All authors Karthik Rao, Kevin Allen, Yuxiang Gao, Arushi, Sanu Mishra, Birender Singh, Kenneth S. Burch, Liangzi Deng, Shanta R. Saha, Johnpierre Paglione, Minseong Lee, Vivien Zapf, Emilia Morosan
Statistical Mechanics
Optimal Control of Periodic Nonequilibrium Mechanochemical Systems via Automatic Differentiation
W. Callum Wareham and David A. Sivak
Biological molecular machines are mesoscopic systems that act repeatedly and periodically to perform important cellular tasks while contending with strong fluctuations and operating in an overdamped regime. Optimal control theory is a tool that can be used to understand the design principles behind efficient operation of these machines; however, most studies on optimal control of classical mesoscopic systems have focused on control problems that do not repeat periodically. Here, we automatically differentiate Fokker-Planck simulations to design efficient nonequilibrium control strategies for simple models of periodic molecular machines with and without explicit changes in the machine's chemical state. The designed protocols and theoretical analysis provide insight into the design principles governing efficient driving in these nonequilibrium systems. Designed control protocols should seek to reduce mechanical heat by rotating the entire angular probability distribution at a constant speed without changing its shape, and should reduce chemical heat by reducing the proportion of chemical transitions with large heat.
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Materials Science
Thermal history controls the optoelectronic response of lead halide perovskites through structure and dynamics
Milos Dubajic, Xia Liang, Johan Klarbring et al. (+26 more)
Lead halide perovskites are promising optoelectronic materials for photovoltaics, light emission and detection. Their efficiencies in PV now approach the detailed-balance limit, leaving stability as the principal barrier. The intrinsic instabilities studied to date centre on ionic motion within a fixed, homogeneous
lattice. Here we identify a further source of intrinsic structural instability, hidden in the
lattice dynamics. Mapping caesium, methylammonium and formamidinium-based compositions with Cl, Br, I and mixed X-sites through all accessible phases, using single
crystal X-ray and
neutron diffuse scattering, machine-learning-assisted molecular dynamics, a phenomenological octahedral tilt model and hyperspectral photoluminescence, we find that nearly every composition hosts
equilibrium local structural fluctuations: dynamic nanodomains of correlated octahedral tilts, a few nanometres in size, that locally break the crystallographic
symmetry. Three complementary levers control them. The A-site cation sets their
symmetry, shape and anisotropy, from sparse, isotropic and tetragonal in formamidinium-based compositions to dense, anisotropic and orthorhombic in nominally cubic caesium-based ones, the most locally disordered we studied. The halide controls the dynamic disorder and the phase-transition sequence. Thermal history is the third: different ramp rates drive nominally identical compositions into distinct crystallographic phases, each with its own hidden local order. In MAPbI3, the heating rate alone changes the photoluminescence
quantum efficiency across the phase transition. Because these transitions lie within device operating ranges, from terrestrial thermal cycling to the extremes of space, thermal history may shape the local structure, and hence the optoelectronic response, throughout fabrication and operation, establishing it as a design variable alongside composition.
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All authors Milos Dubajic, Xia Liang, Johan Klarbring, Yang Lu, Thomas A. Selby, Erik Fransson, Philippe Holzhey, Benjamin M Gallant, Qichun Gu, Ganbaatar Tumen-Ulzii, Khasim Saheb Bayikadi, Isaiah Gilley, Martin v. Zimmermann, Christian Orr, Chwenhaw Liao, Josh S. Moon, Jacek Jasieniak, Makhsud Saidaminov, Michael P. Nielsen, Tom Wu, Stephen P. Bremner, Anita Ho-Baillie, Julia Wiktor, Paul Erhart, Steve Albrecht, Mercouri Kanatzidis, Henry J Snaith, Aron Walsh, Samuel D. Stranks
Statistical Mechanics
Generative Nested Sampling of Atomistic Thermodynamic Landscapes
Alessandro Coretti, Nico Unglert, Sebastian Falkner et al. (+2 more)
Nested sampling (NS) resolves the thermodynamics of an atomistic system from a single simulation, but its practical reach is limited by the Markov-chain updates needed to decorrelate walkers within each likelihood-constrained ensemble. Flow-based NS has reduced this bottleneck for gravitational-wave (GW) inference, yet its transfer to atomistic systems is not merely a change of application. Comparing a GW150914-like binary-black-hole likelihood with an eight-particle two-dimensional Lennard-Jones (LJ) system of comparable dimensionality, we show that the two landscapes differ fundamentally: atomistic multimodality is discrete and combinatorial, generated by particle permutations separated by hard collision walls, and its coordinate coupling is dense and collective, whereas the GW posterior exhibits smooth degeneracies and localized parameter coupling. Guided by this diagnosis, we introduce NS-Flows: a single conditional normalizing flow, conditioned on the NS energy bound and trained on a sliding window of recent live sets, that replaces MCMC by direct parallel draws corrected by importance-weighted rejection resampling. Live sets supply the data self-consistently, allowing flow training without structured priors or a pre-existing
dataset. For LJ disks under periodic boundary conditions, the
algorithm can reduce energy evaluations by two orders of magnitude and wall-clock time by about 30%, an advantage that becomes more favorable as the cost of the potential grows. The flow's generative efficiency further acts as a physical diagnostic: it varies non-monotonically along the annealing trajectory, is lowest in the dense disordered regime, and is quantitatively captured by the constrained ensemble's internal mode complexity together with target drift across the training window, identifying
liquid-like ensembles, not prior-target separation, as the hard case for current flow architectures.
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All authors Alessandro Coretti, Nico Unglert, Sebastian Falkner, Georg K. H. Madsen, Christoph Dellago
Statistical Mechanics
Accelerating stochastic processes through nonequilibrium driving: Thermodynamic constraints on the maximum speed-up
Davide Santolin and Gianmaria Falasco
We derive a new set of bounds controlling the speed-up of the survival rate of trajectory-dependent observables induced by the application of a perturbation. Via the study of survival probabilities in two different contexts, continuous-time Markov jump processes and overdamped
diffusions, we obtain different fashions of the bound on the achievable boost. These bounds, obtained by a nonlinear response theory of constrained path probabilities, are explicitly linked to thermodynamics. For arbitrary time-dependent survival rates, we find a linear bound that depends on both the perturbation strength and the
entropy production rate prior to the perturbation. For rare processes characterized by a constant survival rate, the bound is exponential and is determined by the excess heat generated by the perturbation. We exemplify the inequalities on two prototypical model systems, namely, a unicyclic network and forced
diffusion in a bistable potential.
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Materials Science
An Ultrathin Laterally Conductive Mesh Interphase Enables Spatially Extended Zinc Deposition for Aqueous Zinc Batteries
Yirong Zhao, Xingyuan Chu, Bing Wu et al. (+15 more)
Zn metal anodes often suffer from nonuniform interfacial reactions during cycling, resulting in uneven deposition and dendrite growth. Existing artificial interphases can mitigate side reactions or regulate nucleation, but rarely achieve regulation of the interfacial electron/field distribution to sustain uniform deposition at the evolving Zn/electrolyte interface. Here, we develop an Au mesh interphase (AuMI), an ultrathin two-dimensional Au aerogel network that couples lateral electron redistribution with open pathways for ions. During Zn plating/stripping, the conductive AuMI distributes electron transport across the Zn surface, while its porous mesh preserves Zn$^{2+}$ access, enabling more uniform interfacial reactions. Experiments and simulations show that AuMI homogenizes the interfacial electric field and current distribution, promotes more uniform Zn plating/stripping, and limits dendrite growth. As a result, this regulated interfacial reaction mode enables AuMI Zn symmetric
cells to operate stably for 3000 h at 1 mA cm$^{-2}$/1 mAh cm$^{-2}$ and for 1100 h at 10 mA cm$^{-2}$/10 mAh cm$^{-2}$, while AuMI Zn||NVO (NaV$_3$O$_8$\cdot$1.5H$_2$O) full cells retain 80.8 % capacity after over 5000 cycles at 1 A g$^{-1}$. These findings highlight the importance of combining ultrathin architecture, lateral electron transport, and open Zn2+ access in artificial interphases for stable aqueous Zn metal anodes.
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All authors Yirong Zhao, Xingyuan Chu, Bing Wu, Pavel Khavlyuk, Johannes Kresse, Yue Dong, Jingwei Du, Xinmei Song, Songshan Bi, Vlastimil Mazanek, Xia Wang, Xiaodong Li, Shilei Liu, Shuangying Wei, Jan Luxa, Junming Zhang, Zdenek Sofer, Alexander Eychmuller
Mesoscale and Nanoscale Physics
Topological Boundary States and the Edge Chain in Semi-Infinite Two-Dimensional Insulators
Ilya Iakoub, Nicolas Levasseur and Richard MacKenzie
We show that it is possible to compute the adiabatically protected edge and corner states of semi-infinite, two-dimensional, topological
insulators by considering the first layer of
lattice sites, what we call the "edge chain," independently from the bulk. We start by accepting this claim as an ansatz, then, using the Shemesh
theorem, we show that the edge states one finds using our procedure are adiabatically protected, provided we restrict ourselves to adiabatic evolutions that do not break chiral
symmetry. We show explicit examples of our method in a 2D extension of the SSH model, the SSH3 model, the Haldane model and the Breathing Kagome
Lattice.
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Strongly Correlated Electrons
Antiferromagnetism-altered plasmon dynamics
Yifan Su, Suheng Xu, Rocco A. Vitalone et al. (+17 more)
The interaction between plasmons and
magnons is a long-sought phenomenon with implications for fundamental physics and spintronics applications. In three-dimensional systems, this coupling is suppressed by the large mismatch in energy scales, but two-dimensional (2D) plasmons with gapless dispersion can overlap with
magnons over a broad spectral range. Despite numerous theoretical predictions, experimental observation of
magnon-plasmon interaction has remained elusive. In this work, we study a first-of-its-kind hybrid plasmon-
magnon platform based on 2D materials. By deploying scattering-type scanning near-field optical microscopy (s-SNOM) with terahertz radiation, we image propagating plasmon wavepackets at a
graphene/NiPS$_3$ interface and track their dynamics across the antiferromagnetic transition of NiPS$_3$. We observe a clear renormalization of the plasmon-polariton dispersion concurrent with the onset of antiferromagnetic order. With complementary Raman scattering and nano-terahertz spectroscopy, we unveil spectral weight redistribution and dielectric screening changes, potentially associated with the multi-
magnon continuum, as the underlying mechanism. These results provide solid evidence of coupling between plasmon and antiferromagnetic order, marking a cornerstone for a potential platform for hybrid
magnon-plasmon interactions in 2D materials, opening avenues for coherent
spin-plasmon devices and tunable terahertz spintronic components.
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All authors Yifan Su, Suheng Xu, Rocco A. Vitalone, Ziyu Liu, Emil Viñas Boström, Na Wu, Chun-Ying Huang, Zhuquan Zhang, Jaehoon Jung, Daniel G. Chica, Vinícius da Silveira Lan Avelar, Yiping Wang, Takashi Taniguchi, Kenji Watanabe, James C. Hone, Xiaoyang Zhu, Cory R. Dean, Xavier Roy, Angel Rubio, D. N. Basov
Statistical Mechanics · Cross-listed from gr-qc
Relativistic transformation of temperature for exotic cosmological fluids
Soroor Pouryazdan and Babak Vakili
We study the relativistic transformation of temperature for effective cosmological fluids with negative pressure within a covariant thermodynamic framework. The Lorentz transformation of temperature is derived for barotropic fluids with $p=w\rho$ and for the (generalized) Chaplygin gas with $p=-A/\rho^\alpha$. For barotropic fluids with constant negative equation-of-state parameter, we show that negative pressure suppresses the growth of temperature under relativistic boosts. In contrast, the Chaplygin gas exhibits a qualitatively different behavior due to its density-dependent pressure, leading to a monotonic increase of the transformed temperature with velocity. The dependence of the relativistic temperature on the relative velocity and background energy density is illustrated through representative examples.
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Statistical Mechanics
Death by mutants: unusual multicritical dynamics in a two-species model for absorbing state transitions
Astik Haldar and Abhik Basu
We explore the phases and active-to-absorbing state phase transitions (AAPT) in a two-species model, where the species A and its mutant B are asymmetrically or nonreciprocally coupled. We identify a multicritical point that connects the global absorbing state of both the species and its mutant, with a uniform active state. The critical dynamics at this multicritical point is studied within the lowest order perturbation theory. This asymmetric coupling between species A and mutant B leads to unequal and distinct upper critical dimensions $d_c^A$ and $d_c^B$ respectively for A and B dynamics. We show that the multicritical point in this model is characterised by an unusual breakdown of scale-invariance by fluctuation-induced logarithmic modulations with power law behaviour of the order parameter and correlation lengths of the species A at all dimensions $d<d_c^A$. Above $d_c^A$, conventional scale-invariance is restored. The dynamics of the mutant species B belongs to the DP universality class with an upper critical dimension of $d_c^B=4$
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Statistical Mechanics · Cross-listed from math.MG
The stealthiest particle configurations in 8 and 24 dimensions
Alex Cohen, Henry Cohn and Maryna Viazovska
We show that the $E_8$ and Leech
lattices generate the stealthiest isometry-invariant, locally square-integrable point processes of intensity $1$ in $\mathbb{R}^8$ and $\mathbb{R}^{24}$, respectively, and that they are the unique stealthiest processes. We also apply the proof technique to sphere packing and energy minimization, and we construct a $20$-dimensional periodic configuration that is stealthier than any known $20$-dimensional
lattice with the same particle density. This periodic configuration is a formal dual of Vardy's $20$-dimensional sphere packing.
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Statistical Mechanics
Large deviations for linear regressions
Silvia Bartolucci, Fabio Caccioli, Francesco Caravelli et al. (+1 more)
Linear regression is one of the simplest and most widely used tools to learn patterns from data: it fits a set of coefficients so that a linear combination of predictors best matches observed responses. The quality of the fit is measured by the residual sum of squares, the total squared mismatch between predictions and data, whose minimum defines the training loss. We consider Gaussian design and noise, with teacher coefficients independently drawn from a general distribution $p(\beta)$, and a general class of separable regularizers, including Ridge and Lasso. Using the zero-temperature replica method, we compute analytically the large-deviation statistics of the minimum training loss for large numbers $P$ of predictors and $N$ of observations, with $r=P/N$ fixed. The rate function we compute governs rare sample-to-sample fluctuations of the optimal loss. Extensive numerical simulations are in excellent agreement with our theory and clearly show a pronounced deviation from the Gaussian regime of typical fluctuations in the tails.
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All authors Silvia Bartolucci, Fabio Caccioli, Francesco Caravelli, Pierpaolo Vivo
Soft Condensed Matter
Critical scaling and soft granular rheology of frictionless non-Brownian suspensions across jamming
Rohan Vernekar, Romain Mari, Bruno Chareyre et al. (+1 more)
We carry out 3D computer simulations to study suspension rheology across the jamming transition for deformable non-Brownian frictionless particles. The simulations are carried out at constant shear rates and suspension densities ($\dot{\gamma} , \phi$), for polydisperse spherical particles. The suspension is probed at densities in the neighbourhood of the jamming point $\phi_c$ , as well as across much wider density ranges. We carry out critical scaling analysis of our close-to-jamming data and confirm that shear-driven jamming is a second-order critical phenomenon requiring strong corrections on shear. We build maps of the local strain rate exponent to classify flow regimes and examine the effect of the corrections on the suspension rheology. Further, using the critical scaling jamming density, we carry out soft granular rheological scaling over the wider density range, demonstrating an excellent data collapse. The soft granular rheology relations are able to predict our data over almost the entire dynamical and density range.
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All authors Rohan Vernekar, Romain Mari, Bruno Chareyre, Hugues Bodiguel
Statistical Mechanics · Cross-listed from quant-ph
Optimal control theory for measured quantum Schrödinger bridges
Masayuki Ohzeki and Andrew N. Jordan
Schrödinger bridges and entropic optimal transport are usually formulated as
stochastic interpolation problems between initial and final probability distributions. In their computational form, the bridge potentials are obtained by Sinkhorn or iterative proportional fitting, and are often regarded as auxiliary scaling functions. We show that for continuously monitored
quantum systems, these potentials acquire a direct measurement-theoretic meaning. The mathematical structure of conditional
quantum trajectory theory induces a Fokker–Planck equation on
quantum state space. Conditioning this
diffusion on a terminal distribution or a terminal measurement effect produces a Doob/Sinkhorn potential whose directional derivative along a
unitary control vector field is the imaginary part of a generalized weak value. The same construction connects the Schrödinger-bridge viewpoint to the optimal-path framework for continuously monitored trajectories: the backward bridge potential plays the role of an effect-like costate, and its weak-value directional derivative gives the local control signal. By specifying the desired endpoint distribution, the induced drift produced by the Schrödinger bridge solution is the control solution that minimizes the quadratic cost feedback law, guiding the distribution to its desired endpoint. We quantify the control score of the available control
Hamiltonian as a logarithmic directional derivative of the bridge potential, or an imaginary weak value. Three explicit examples identify weak measurement as a natural entropic regularization mechanism for
quantum state transport and gives a route from Sinkhorn scaling to
quantum feedback and
Hamiltonian control synthesis for practical optimal control.
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Statistical Mechanics · Cross-listed from quant-ph
Non-Kolmogorov-Arnold-Moser Quantum Sensors for Quantum Parameter Estimation
Naga Dileep Varikuti, Sourav Manna, Athreya Shankar et al. (+2 more)
Non-KAM (Kolmogorov-Arnold-Moser) systems, when subjected to weak time-dependent perturbations, exhibit an abrupt transition to classical chaos through the breakdown of invariant phase-space
tori. We showcase the utilization of non-KAM systems in the
quantum regime as
quantum sensors, leveraging their sensitivity at resonances.
Quantum Fisher information (QFI) is a central quantity in
quantum parameter estimation theory that measures how much information a
quantum state contains about an unknown parameter that is encoded into it. In other words, it quantifies the sensitivity of a
quantum state to small changes in that parameter. In this work, through numerical analysis in conjunction with analytical results, we study the performance of the non-KAM systems for
quantum sensing applications by computing the QFI. We find that the growth of the QFI is remarkably enhanced when the resonance condition is satisfied. For frequency estimation under Floquet
unitary encodings, we derive a transport bound: if the mean excitation number grows as $\langle\hat n(t)\rangle\sim t^{\alpha}$, the QFI obeys $I(t)\lesssim t^{2\alpha+2}$. The
quantum kicked harmonic oscillator, a paradigmatic non-KAM system, realizes the full hierarchy: localized dynamics ($\alpha=0$) yield quadratic growth, delocalized
diffusion along
stochastic webs ($\alpha=1$) yields quartic growth, and translationally invariant resonances ($\alpha=2$) saturate the bound with anomalous hexic growth, $I(t)\sim t^{6}$, established analytically at resonance $R=2$ and numerically at $R=4$. The enhancement stems from resonance-induced translational
symmetry rather than exponential instability, identifying non-KAM resonances as a metrological resource distinct from chaos-assisted and criticality-based sensing.
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All authors Naga Dileep Varikuti, Sourav Manna, Athreya Shankar, Arul Lakshminarayan, Vaibhav Madhok
Mesoscale and Nanoscale Physics
Deterministic nanofabrication for engineering nanowire quantum dot devices
Tarun Patel, Matteo Pennacchietti, Greg Holloway et al. (+8 more)
Semiconductor quantum dots (QDs) are a leading platform for realising bright, wavelength-tunable sources of single and entangled
photon pairs for photonic
quantum technologies. Site-selected nanowire
quantum dots (NWQDs) are a promising platform for fabricating such photonic devices in a scalable manner. However, implementing additional structures around the photonic nanowire while maintaining its vertical growth geometry has remained a challenge. In this work, we develop a deterministic pick-and-place technique to conduct a vertical-to-vertical transfer of NWQDs from the growth substrate to arbitrary templates. Using this transfer technique, we enhance the
photon extraction efficiency to 75% by implementing a bottom gold mirror and tune the emission wavelength by 3.6 GHz via implementing electrostatic gates around the QD. Importantly, we measure low-multiphoton probability (g^(2)(0) = 0.002) and high indistinguishability (>80% for +/-100 ps) of the QD emission after the transfer process, yielding high-quality devices. These results demonstrate the repeatability and versatility of the developed transfer technique, which is an enabling step towards scalable single and entangled
photon sources.
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All authors Tarun Patel, Matteo Pennacchietti, Greg Holloway, Stephen R. Harrigan, Sayan Gangopadhyay, Anthony Drouin, Megha Jain, Dan Dalacu, Philip J. Poole, Sasan Vosoogh-Grayli, Michael E. Reimer
Strongly Correlated Electrons
Orbital current rectifier and linear magnon Edelstein effect in $p$-wave antialtermagnets
Kristian Mæland and Björn Trauzettel
We show that $p$-wave magnets efficiently generate magnetization via a linear thermal Edelstein effect arising from the orbital
magnetic moments of their
magnons. Furthermore, they can generate perfectly nonreciprocal orbital currents through a purely even-order nonlinear response. This makes them promising candidates for orbital-current rectification. Because these transport phenomena originate from the orbital
magnetic moment of
magnons, they connect magnonics and orbitronics. More generally, we find that odd-parity-wave magnets with coplanar ground states host
magnons with zero
spin magnetic moment. Instead the
magnons carry a collinear, out-of-plane orbital
magnetic moment, realizing an orbital version of antialtermagnetism. We establish these general results using
symmetry arguments and demonstrate them explicitly for a coplanar ground state with the minimal number of sublattices, inspired by the ground state of CeNiAsO. Our conclusions hold both in absence and presence of
spin-orbit coupling.
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Mesoscale and Nanoscale Physics
Flux noise without flux tunability in superconducting qubits
Daniel Kruti and Roman-Pascal Riwar
Flux noise is unanimously recognised as a leading dephasing mechanism for flux-tunable superconducting
qubits. However, our microscopic understanding remains incomplete, and basic effects like Faraday's law of induction have only very recently come into focus. Based on a
quantum geometric description of the Faraday effect, we provide an in-depth derivation of the coupling of generic
magnetic sources to thin film superconducting structures, under appropriate consideration of the device geometry. We apply the resulting framework to time-varying
magnetic dipoles, describing surface or substrate
spins, as well as current-carrying flux lines. We show that flux noise not only affects dephasing, but also provides a fundamental limit for the
qubit quality factor - notably, even when the
qubit contains no loops and is thus nominally not flux-tunable. Assuming surface
spins as the origin for universal flux noise, we expect that this quality factor limit might be reached in the near term. For flux lines, we formulate a minimal safety distance to conserve the
qubit performance, potentially constraining the scale-up of
quantum hardware. This distance is boosted in the presence of large capacitor wings typical for transmons, due to a
lensing of the electromotive field which is largely independent of Meissner screening.
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Quantum Gases · Cross-listed from quant-ph
Robust Hamiltonian engineering with subensemble control
Wenjie Gong, Matteo Votto and Soonwon Choi
We present a robust protocol to reshape interactions in a
spin ensemble based on global control pulse sequences applied to multiple subensembles in parallel. This setting arises naturally from ensembles of solid-state defects or multi-species atomic arrays. We show that it is provably computationally hard to find pulse sequences that simultaneously engineer interactions both within and between subensembles. Despite its formal hardness, we identify a set of necessary or sufficient conditions under which one can synthesize a target
Hamiltonian from the native one. Moreover, we introduce efficient numerical strategies for designing pulse sequences that engineer target
Hamiltonians robust against common control imperfections. As a specific application, we discuss the robust generation of two-mode
spin squeezing in dual-species atomic ensembles, which is a challenging task without subensemble control. Our results provide a practical toolbox to design novel
quantum simulation and sensing experiments with minimal control overhead.
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