Strongly Correlated Electrons
Eigenstate thermalization at the edge of the many-body spectrum
Arnav Pushkar, Pranay Patil, Soumya Bera et al. (+2 more)
It is well-known that thermalization breaks down in presence of an extensive number of
symmetries or conservation laws that are mutually compatible or commuting with each other. We ask here how an extensive number of mutually incompatible local
symmetries govern eigenstate thermalization (ETH). We will investigate this through models within the class of bond-dependent $\mathbb{Z}_2$-symmetric
quantum spin-$\frac{1}{2}$
Hamiltonians that naturally admit this structure. This leads to exponentially large degeneracies in the spectrum governed by the incompatible
symmetry structure. Here, using spectral diagnostics, we show that non-integrability can survive despite extensively many conserved quantities when they are incompatible. Furthermore, we show that ETH behavior persists deep into the many-body spectral edge due to this structure. In other words, incompatible local
symmetries enable a mechanism to obtain enough thermodynamic
entropy at low excitation energy densities to make ETH operational or predictive near the ground state.
Read the full abstract ▾
All authors Arnav Pushkar, Pranay Patil, Soumya Bera, Masaki Tezuka, Sumiran Pujari
High Energy Physics (Phenomenology)
Inclusive diffraction in eA at small x with the Sartre event generator
Tobias Toll, Bhakta Naik, Jaswant Singh et al. (+1 more)
We present an extension of the Sartre event generator that implements inclusive diffractive deep inelastic scattering for both
proton and
nuclear targets at small $x$. The calculation is performed in the colour-dipole picture using the IPsat and IPnonsat dipole amplitudes that Sartre also employs for exclusive processes, and includes the transverse and longitudinal $q\bar q$ contributions together with the $q\bar qg$ Fock state that dominates at large $M_X$. The partonic diffractive system is hadronised with \pythia, giving fully exclusive hadronic final states. We compare to the combined H1 and ZEUS inclusive diffractive measurements and to diffractive $D^*$ production, and present predictions for the Electron-Ion
Collider. This makes Sartre the only event generator providing inclusive diffractive DIS in small-$x$ for both $ep$ and $eA$ collisions.
Read the full abstract ▾
All authors Tobias Toll, Bhakta Naik, Jaswant Singh, Thomas Ullrich
Quantum Physics
The Commuting Local Hamiltonian Problem: Relativized Evidence Against BQP-Hardness
Itay Shalit and Mark Zhandry
The commuting local-
Hamiltonian (CLH) problem is a restriction of the local-
Hamiltonian problem, in which the terms of the
Hamiltonian are required to pairwise commute. A long line of work has shown that the problem lies in $\mathsf{NP}$ for certain families of commuting local
Hamiltonians. Nevertheless, there has been no formal evidence against the possibility that the general CLH problem is $\mathsf{QMA}$-complete. CLH is complete for the complexity class $\mathsf{QIMA}$, defined through
quantum verifiers whose local gates commute. Therefore, CLH is $\mathsf{QMA}$-complete if and only if $\mathsf{QIMA}=\mathsf{QMA}$. In this work, we introduce a classical-oracle analogue $\mathsf{QIMA}^{\mathcal{O}}$ and construct a classical oracle $\mathcal{O}$ such that $\mathsf{BQP}^{\mathcal{O}}\not\subseteq\mathsf{QIMA}^{\mathcal{O}}$. Since $\mathsf{BQP}^{\mathcal{O}}\subseteq\mathsf{QMA}^{\mathcal{O}}$ for any classical oracle $\mathcal{O}$, this implies $\mathsf{QIMA}^{\mathcal{O}}\neq\mathsf{QMA}^{\mathcal{O}}$ for our constructed oracle. Thus, our result provides relativized evidence against the possibility that the general commuting local-
Hamiltonian problem is $\mathsf{BQP}$-hard, and hence also against the possibility that it is $\mathsf{QMA}$-complete.
Read the full abstract ▾
Quantum Physics
Certified Randomness with Optimal Rate
Siddhartha Jain, Saachi Mutreja and Bhaskar Roberts
The generation of certified random bits is an emerging near-term application of
quantum computers. Potential applications, such as randomness beacons and CRS generation, require nearly uniform randomness, whose rate (the ratio of min-
entropy to bitlength) is ~ 1. However, existing protocols for certified randomness either produce weakly random strings with rate o(1), or they require a trusted random seed. We show how to certify randomness with the optimal rate ~ 1 without requiring any trusted randomness from the verifier. Our protocol is secure unconditionally in the
quantum random oracle model (QROM). This improves the result of Coladangelo et al., who certified weakly random strings unconditionally in the QROM, and answers a question posed by Aaronson and Hung. We also define and construct a proof of conditional min-
entropy, which certifies optimal min-
entropy even conditioned on an adversarially chosen transcript. We show an application of this primitive to randomness beacons, where each pulse should have high min-
entropy conditioned on all previous messages.
Read the full abstract ▾
Optics
Frequency comb generation in active optomechanical cavities
Madhurendra Mishra and Adarsh Ganesan
We numerically investigate frequency-comb generation in an electrically pumped vertical-cavity surface-emitting
laser coupled to two mechanical modes of a suspended mirror. Displacement-dependent cavity loss and radiation-pressure feedback couple the mechanical motion to the carrier and
photon densities, producing harmonics and combination-frequency components in the
photon-density spectrum. Mechanical quality factors primarily control the intensity of comb lines, whereas resonance frequencies determine their spectral distribution. The initial mechanical amplitudes influence the threshold current and relative spectral intensities, with the simultaneous excitation of both modes yielding a broader set of observable components. These results establish the dependence of the calculated comb structure on mechanical dissipation, resonance frequencies, and initial conditions in an active optomechanical cavity.
Read the full abstract ▾
Quantum Physics
Quantum-echo Markov process for combinatorial optimization
Tatsuhiko Shirai
We introduce a
quantum-echo Markov process for combinatorial optimization.
Quantum dynamics based on
quantum annealing (QA) or the
quantum approximate optimization
algorithm (QAOA) is used to engineer the transition kernel. Increasing the annealing time in QA or the number of layers in QAOA enables transitions to explore distant configurations while suppressing large energy changes. The Hamming-space delocalization originates from operator spreading, whereas the energy-space localization arises from a dynamically generated correlation. For optimization, we propose
quantum-echo local optimization with and without greedy descent. We find that its performance is governed by the interplay between Hamming-space nonlocality and energy-space locality, and that excessive energy-space localization can degrade optimization performance. Incorporating greedy descent substantially improves the performance, highlighting the complementary roles of
quantum dynamics for exploration and greedy descent for exploitation. These results establish
quantum-echo dynamics as a framework for engineering structured transition kernels and provide a route to using finite-resource
quantum many-body dynamics as a computational primitive for iterative optimization.
Read the full abstract ▾
Materials Science
First-Principles Study of Two-Dimensional CeN: Interplay between Structural Stability, Electronic Structure, and Magnetism
Jose Mario Galicia Hernandez, Jose Jorge Rios Ramirez, Gregorio Hernandez Cocoletzi et al. (+1 more)
In this work, the structural stability, and the electronic and
magnetic properties of a novel CeN monolayer derived from the (111) surface of bulk rock salt CeN are investigated using first-principles calculations. Dimensional reduction produces substantial changes in the local atomic environment, decreasing the Ce-N coordination from sixfold in the bulk to threefold in the monolayer and shortening the Ce-N bond length, while preserving an essentially planar hexagonal structure. Moreover, the electronic and
magnetic properties are significantly modified, which may be useful for practical applications. Both
ferromagnetic (FM) and
antiferromagnetic (AFM) configurations were investigated and found to be strongly bound, with the FM state slightly lower in energy. The
magnetic moments are predominantly localized on the Ce atoms and mainly originated from the Ce 4f states. The electronic structure also exhibits a pronounced dependence on
magnetic ordering, highlighting the connection between localized 4f states and the
spin-dependent electronic properties of the system. In addition, the calculated elastic properties confirm the mechanical stability of the monolayer, while
phonon calculations support its dynamical stability. Ab initio molecular dynamics simulations further indicate that the two-dimensional structure preserves its integrity under finite-temperature conditions. Overall, these results demonstrate that dimensional reduction significantly modifies the structural, electronic, and
magnetic behavior of CeN without compromising the stability of the resulting two-dimensional
lattice. The combination of structural robustness, localized Ce 4f magnetism, and
spin-dependent electronic properties make the CeN monolayer an interesting system for further exploration in two-dimensional magnetism and
spin-dependent applications.
Read the full abstract ▾
All authors Jose Mario Galicia Hernandez, Jose Jorge Rios Ramirez, Gregorio Hernandez Cocoletzi, Juan Francisco Rivas Silva
Quantum Physics
Tight Post-Quantum Parallel Repetition for Private-Coin Arguments
Zvika Brakerski, Andrew Huang, Yael Tauman Kalai et al. (+1 more)
We show that assuming the existence of homomorphic encryption, parallel repetition of all interactive arguments (after being run under homomorphic encryption) reduces the soundness error at a tight exponential rate even in the post-
quantum setting. Moreover, we generalize this result to hold for threshold verifiers, where the parallel repeated verifier accepts if and only if at least $t$ of the executions are accepted (for some threshold $t$). Prior to this work, these results were known only when the cheating prover was assumed to be classical, and it was not known how to achieve tight bounds. As a corollary, we construct the first constant-round succinct argument for $\mathsf{QMA}$ with negligible completeness and soundness errors assuming only the existence of
quantum homomorphic encryption.
Read the full abstract ▾
All authors Zvika Brakerski, Andrew Huang, Yael Tauman Kalai, Nicholas Spooner
Nuclear Theory
Universal empirical coupled channel calculations for capture cross sections in synthesis of superheavy nuclei
H. Yao, Y. J. Duan, N. Wang et al. (+9 more)
A universal empirical coupled channel model, ECC2, is proposed for the systematic description of capture cross sections in heavy-ion fusion reactions. The model combines a modified Broglia–Winther potential, an effective barrier
curvature, and a deformation-dependent barrier distribution width. The most probable barrier heights predicted by ECC2 are in good agreement with the extracted values based on measured excitation functions for 367 systems, and the root-mean-square (rms) deviation is 1.39 MeV. ECC2 is applied to 25 fusion reactions ranging from $^{16}$O+$^{197}$Au to $^{54}$Cr+$^{248}$Cm. The predicted capture excitation functions are consistent with the EBD2.2 predictions for all systems and agree well with the available experimental data.
Read the full abstract ▾
All authors H. Yao, Y. J. Duan, N. Wang, D. D. Zhang, X. T. He, T. L. Zhao, P. H. Chen, P. W. Wen, L. Zhu, X. J. Bao, J. J. Li, L. Guo
Quantum Physics
Defect-Aware Parallel Atom Reloading Protocol for Neutral-Atom Quantum Computers
Koki Aoyama and Fumihiko Ino
In this work, we propose a defect-aware parallel atom reloading protocol that reloads atoms based on defect information to increase the atom filling rate. The proposed protocol is useful for neutral-atom
quantum computers, where reloading atoms into the defects, or atom-loss positions, is mandatory for continuous operation against atom loss. Our protocol takes advantage of both parallelism and defect awareness to improve atom-reloading efficiency. The proposed protocol consists of the coherent atom reloading operation and the defect-aware planner. The former replenishes the defects with atoms preserving the
quantum information coherently. This coherence allows us to adaptively choose the reloading strategy based on the current defect configuration. The latter determines the atom reloading pattern to efficiently replenish the defects. In numerical experiments assuming a low-noise environment, we confirmed that the average atom filling rate improved from 98.61% to 99.94% for a 36 x 90 atom array, matching the filling rate obtained with a mixed integer programming solver to within 0.001 percentage points while planning each reload in under 0.1 ms. These results demonstrate that defect-aware parallel reloading can achieve and sustain high atom filling rates while the performance of the defect-aware planner meets the real-time requirements of neutral-atom
quantum computers.
Read the full abstract ▾
Astrophysics of Galaxies
The impact of the turbulent Mach number on star formation and the initial mass function
Sajay Sunny Mathew, Christoph Federrath and Amit Seta
Turbulence regulates
star formation by influencing the density structure and fragmentation of molecular clouds, and therefore it is expected to play a key role in setting the initial mass function (IMF). We study how the strength of the turbulent shocks affects
star formation and the IMF by comparing a series of magnetohydrodynamical (MHD) simulations of
star cluster formation in clouds with three different rms Mach number values, $M=2.5, 5$, and $10$, but otherwise the same Alfvén Mach number ($M_\mathrm{A}\sim3$) and virial parameter ($\alpha_\mathrm{vir}\sim0.5$). All three simulations include
stellar feedback in the form of protostellar jets/
outflows and
accretion heating. We find that the
star formation rate per freefall time ($\mathrm{SFR_{ff}}$) for the $M=10$ model is higher by a factor of $\sim3$ compared to the $M=2.5$ and $5$ cases, which have similar $\mathrm{SFR_{ff}}$. In terms of the IMF, the $M=5$ and $10$ models produce almost similar distributions, resembling typical observed IMFs. The $M=2.5$ model, on the other hand, produces a bimodal IMF with a primary peak at supersolar masses ($\sim 2\, \mathrm{M_\odot}$) and a secondary peak in the substellar regime ($< 0.1\, \mathrm{M_\odot}$). The $M=2.5$ and $5$ simulations producing significantly different IMFs while having similar $\mathrm{SFR_{ff}}$, suggest that a distinct set of physical processes governs the SFR and IMF. Through a resolution study for the $M=2.5$ case, we find our base models have reached near numerical convergence, potentially only slightly underestimating close-binary formation. We also see signatures of bimodality in the $M=2.5$ model for the multiplicity fraction and
stellar angular momentum distribution.
Read the full abstract ▾
Quantum Physics
Boundary-rank obstructions and measurement-assisted recovery in dissipative flat-band preparation
Mingdi Xu
Number-conserving cooling can fail to prepare an interacting flat-band target when Pauli exclusion blocks its transfer destinations. We study this failure on vertex-edge decorated graphs at one particle per flat orbital. The rank of a cut block of the flat-orbital Gram
matrix bounds the number of residual source directions that can remain flat. For sublinear-range cooling with no
Hamiltonian term, separated
spin domains on periodic decorated hypercubic
lattices support exponentially many stationary states with a nonzero bright-particle density. For a chain with fixed finite cooling range, we construct a physical Fock initial state whose overlap with a wrong dark state is independent of system size. This gives fidelity and bright-density bounds valid at every time. In higher dimensions, the bare overlap decays with boundary area, while local boundary rotations prepare states with a finite failure weight in constant
circuit depth. Dephasing the occupations of all compact bright modes restores global attraction to the
ferromagnetic target when the graph and cooling destinations satisfy the stated conditions. The result allows
Hamiltonians that preserve the target. The compressed dynamics in the strong-dephasing limit also remains attractive and has a positive gap at each fixed size. Gram calculations, finite-system dynamics, and Liouvillian spectra test the analytic results. Weak-dephasing and particle-transport bounds constrain the preparation time despite eventual convergence.
Read the full abstract ▾
Earth and Planetary Astrophysics
Planetesimal Formation under Realistic Gas Dynamics: Dust Concentration in Turbulent and Windy Protoplanetary Disks
Pinghui Huang and Xue-Ning Bai
Planetesimals are a key intermediate stage of
planet formation and originate from
dust concentration in protoplanetary disks, which is strongly regulated by gas dynamics. In this study, we use the multifluid
dust module of Athena++ to investigate
dust concentration in 2D axisymmetric global non-ideal MHD (ambipolar
diffusion, AD) simulations of outer disks. Our simulations simultaneously launch large-scale MHD disk winds and resolve both streaming instability (SI) and vertical shear instability (VSI). We systematically explore the effects of
magnetic field strength, cooling timescale, ambipolar Elsasser number, and
dust size on
dust concentration. We find that strong
dust clumping persists across a broad range of magnetized and wind-launching disk conditions. MHD winds also enhance
dust clumping by modifying background conditions in the following ways: (1) secular gas depletion by MHD wind mass loss, and (2)
dust trapping in zonal flows as a result of
magnetic flux concentration (which occurs in more strongly magnetized cases). Overall, our results demonstrate that strong
dust clumping can persist in global magnetized disks with AD and large-scale MHD winds, leading to conditions favorable for planetesimal formation.
Read the full abstract ▾
Quantum Physics · Cross-listed from cs.CR
Semi-Quantum Cryptography with Certified Deletion
Yael Tauman Kalai and Justin Raizes
Certified deletion allows a client to upload encrypted data to a server as a
quantum state, then later request that the server delete their data and detect whether the server complies. If verification passes, then the data on the server will remain hidden even if the decryption key is later leaked. In publicly verifiable certified deletion, the verification key is published so that anyone may check for deletion compliance. In this work, we give a general compiler to publicly verifiable certified deletion that allows the client to initially upload the *
quantum* ciphertext using purely *classical* communication, assuming the post-
quantum hardness of LWE in the plain model. Our approach can be applied to a wide variety of primitives, including commitments and public-key, attribute-based, identity-based, and fully-homomorphic encryption. Moreover, our constructions allow the client to classically manage the encrypted data beyond just verifying its deletion. The classical client may non-destructively audit the ciphertext via a Proof of No Intrusion to check whether it has been leaked to a third party. The classical client may also retrieve the data while simultaneously verifying its deletion from the server. Thus, they do not have to choose between retrieving the data and protecting it against future key leakage. As our core technical contribution, we give a classical-communication protocol and simulation technique that allows adapting purification-based security arguments for BB84-style states which are prepared through classical interaction. It makes the required purification available in a hybrid experiment, despite the classical transcript uniquely determining the prepared state in a real execution.
Read the full abstract ▾
Quantum Physics
Quantum Time-Lock Puzzles in the Quantum Random Oracle Model
Prabhanjan Ananth and Yao-Ting Lin
A time-lock puzzle allows a sender to hide a message in a puzzle such that recovering the message requires substantially more sequential computation than the time required to generate the puzzle, even when parallel computation is allowed. Applications of time-lock puzzles include timed-release encryption, sealed-bid auctions, electronic voting, fair contract signing, coin flipping, and Byzantine consensus. However, time-lock puzzles are known to be impossible in the classical random oracle model. To overcome the classical barrier, in this work we consider
quantum time-lock puzzles, in which the puzzle itself is a
quantum state. Our construction in the
quantum random oracle model achieves generation in one oracle round, solving in at most $T$ oracle rounds, and security against
polynomial-width
quantum adversaries of depth $o(T)$ for every polynomially bounded delay $T=T(\lambda)$, resolving an open problem posed by Mahmoody, Moran, and Vadhan (2011).
Read the full abstract ▾
Quantum Physics
Optical studies of negative g-factor dopants in an antiferromagnet: Nd:GdVO$_4$
Lachlan W. Cronin, Masaya Hiraishi, Luke S. Trainor et al. (+1 more)
Neodymium-doped gadolinium vanadate (Nd:GdVO$_4$) is a popular
laser material at room temperature. It has received limited
attention for
quantum technologies because of the linebroadening effects of disordered gadolinium
spins in the host. Here we investigate the optical properties at temperatures below the 2.5 K Néel temperature, revealing narrow optical transitions. We demonstrate that rare earth ions in
magnetic hosts give us a new way of observing the signs of
magnetic g-factors. The interplay between the exchange and Zeeman interactions means that we see clear evidence of negative g-factors. These results provide a detailed spectroscopic foundation for Nd:GdVO$_4$ and expand the understanding of its candidacy as a material for hybrid
quantum systems.
Read the full abstract ▾
All authors Lachlan W. Cronin, Masaya Hiraishi, Luke S. Trainor, Jevon J. Longdell
Quantum Physics
Classical Algorithms for Function Computation in Gaussian Boson Sampling
Ruoting Dou, Hao Zhan, Shengjun Wu et al. (+2 more)
Gaussian
boson sampling (GBS) seeks
quantum advantage by sampling
photon-number patterns generated with squeezed inputs and passive linear optics. Many proposed GBS applications instead target function computation by applying functions to mode-resolved
photon-number outcomes—a natural form of experimental postprocessing that produces classical outputs. Sampling hardness alone, however, does not determine the complexity of these tasks. By analyzing the irreducible decomposition of fixed-
photon-number operator spaces, we prove that the expectation value of every such function in the average case over passive linear-optical networks can be classically evaluated for inputs with finite squeezing strength. We also provide a classical
algorithm that estimates this value to inverse-
polynomial additive error. The result provides new theoretical tools for analyzing linear-optical
quantum systems, helps clarify the origin of current GBS hardness evidence, and inspires new applications of GBS with genuine
quantum advantages.
Read the full abstract ▾
All authors Ruoting Dou, Hao Zhan, Shengjun Wu, Lijian Zhang, Penghui Yao
Optics
Surface quantum response of plasmonic heterodimers: revealing the hidden nonlocality
Ida Juliane Bundgaard, Christos Mystilidis, Frederik Wulff Christensen et al. (+7 more)
We probe the
quantum response of plasmonic heterodimers with extended (plane waves) and localized (point dipoles and electron beams) sources. Implementing the surface-response formalism based on Feibelman parameters, we explore nanosphere heterodimers where one particle is characterized by electron spill-in, while the other by spill-out. We identify situations where the two
quantum surface corrections that act in opposite spectral-shift directions can cancel out, producing mesoscopic spectra that do not differ from the predictions of the local-response approximation. This picture changes dramatically once localized sources are implemented, allowing one to selectively probe the
quantum response of the particles independently. Such probing occurs in terms of higher-order modes in the case of electron beams, or for the complete modal landscape in the case of point dipole sources. This description offers a new insight into the mechanisms governing light–matter interactions in extreme plasmonic architectures, and opens new perspectives for the understanding and tailoring of plasmonic–
quantum emitter architectures.
Read the full abstract ▾
All authors Ida Juliane Bundgaard, Christos Mystilidis, Frederik Wulff Christensen, Lorenz Huber, P. Elli Stamatopoulou, Carsten Rockstuhl, P. A. D. Gonçalves, Ulrich Hohenester, N. Asger Mortensen, Christos Tserkezis
Instrumentation and Methods for Astrophysics
MATCH: Performance Characterization and Scientific Observations of the Wuhan University 1-m Optical Telescope
Sai-En Xu, Bei You, Han He et al. (+22 more)
The Multi-mode Autonomous Terminal for Compatible Hybrid-optics (MATCH), operated by Wuhan University and located at Lenghu, is a 1-m Ritchey–Chrétien
telescope equipped with imaging and spectroscopic instruments. MATCH has been in trial operation since October 2025. In this work, we present the
telescope and instrument configuration, characterize its performance during the first year of operation, and describe the integrated observing workflow developed for routine and time-domain observations, including the observatory control system, observation scheduler, and automated data reduction pipelines. Under typical observing conditions, the imaging system reaches 60-s-equivalent $5\sigma$ limiting magnitudes of approximately 18–20 mag across the $ugri$ bands, while the spectroscopic system reaches approximately 15–16~mag in the B and G channels in a 30-minute integration at the effective spectral resolution of the instrument. In the best-quality imaging observations, the $g$- and $r$-band depths approach 21~mag. Together with flexible scheduling and Target-of-Opportunity capability, MATCH provides photometric and spectroscopic follow-up and long-term monitoring of transient and variable sources.
Read the full abstract ▾
All authors Sai-En Xu, Bei You, Han He, Shuai-Kang Yang, Xiao Fan, Yi-Fei Qu, Rui-Xiang Hu, Hui-Bo Fei, Bo-An Chen, Zong-Hong Zhu, Zheng-Yang Li, Xiao-Yan Li, Zi-Jian Han, Jia-Nan Cong, Chao Chen, Jia-Li Chen, Kai-Wen Zheng, Yi-Qiao Yang, Qing-Shan Li, Zhen-Guang Sun, Tong Zhou, Kai Zhang, Jiajia Wu, Xuhang Yin, Liang Yuan
Strongly Correlated Electrons
Quantum quenches of scar states in the Affleck-Kennedy-Lieb-Tasaki model via Clifford augmented tensor network simulation
Azar C. Nakhl, Ben Harper, Muhammad Usman et al. (+1 more)
Clifford augmented methods have emerged as a powerful technique to simulate
quantum circuits and many-body systems by exploiting the stabiliser structure found in said systems, whilst additionally enabling one to readily quantify the non-stabilizerness (i.e.\ magic) present. In this work, we utilise a qudit Clifford augmented simulation method to probe the presence of magic in the Affleck-Kennedy-Lieb-Tasaki (AKLT) model, finding that its ground state and scar states are highly magical as quantified by their Stabiliser Rényi
Entropy (SRE). Nevertheless, owing to its low
entanglement structure, these states are still readily expressible as a Clifford augmented
Matrix Product State with low bond-dimension and moreover may be time-evolved using the Clifford augmented time-dependent variational principle (TDVP)
algorithm. We utilise Clifford augmented TDVP to study the string order dynamics in the scar states of the AKLT model after a quench within the Haldane phase to the anti-
ferromagnetic Heisenberg
Hamiltonian. We observe that there is a decay of string order following the quench, which is more pronounced with increasing bimagnon number. This finding highlights the sensitivity of string order in the AKLT scar states to
symmetry-preserving quenches, even when the initial and final
Hamiltonians belong to the same topological phase.
Read the full abstract ▾
All authors Azar C. Nakhl, Ben Harper, Muhammad Usman, Thomas Quella
Materials Science
Defect Dynamics and Isomer Quenching in $^{229}$Th:CaF$_2$ Crystals
Ming Guan, Michael Bartokos, Kjeld Beeks et al. (+16 more)
Thorium-229 doped calcium fluoride ($^{229}$Th:CaF$_2$) is a leading candidate for a solid-state
nuclear clock, owing to the unusually low energy of the $^{229}$Th isomer transition at 8.3557\,eV and the very high banggap of CaF$_2$ around 12\,eV. Here we report a temperature-dependent study of $^{229}$Th:CaF$_2$ luminescence, covering radioluminescence, photoluminescence, thermoluminescence, and afterglow. Using synchrotron x-ray excitation together with a cryo-
vacuum system, we resolve the thermal quenching of the self-trapped
exciton (STE) scintillation into its triplet and singlet components, identify eleven thermoluminescence glow peaks together with their associated emission bands, and separate the temperature-dependent components that make up the long-lived afterglow. The trap depths obtained in this way are closely correlated with the temperature dependence of x-ray-induced isomer quenching, including the enhanced isomer yield near \SI{-60}{\celsius} and the minimum near \SI{-80}{\celsius}, supporting the carrier-trapping picture in which trapped carriers are unavailable to quench the
nucleus. Taken together, these results connect the optical and
nuclear observables of $^{229}$Th:CaF$_2$ through a unified picture of electron defects and Th-related traps, while providing a comprehensive characterization of the material relevant to solid-state
nuclear clock operation.
Read the full abstract ▾
All authors Ming Guan, Michael Bartokos, Kjeld Beeks, Takahiro Hiraki, Shinji Kitao, Takahiko Masuda, Nobumoto Nagasawa, Koichi Okai, Ryoichiro Ogake, Martin Pimon, Noboru Sasao, Fabian Schaden, Thorsten Schumm, Makoto Seto, Kenji Tamasaku, Sayuri Takatori, Yoshitaka Yoda, Akihiro Yoshimi, Koji Yoshimura
High Energy Astrophysical Phenomena
Pulsar glitches triggered by quakes when stress reaches a threshold
Zixuan Zhou, Ruipeng Lu, Weiyang Wang et al. (+2 more)
The starquake model of
pulsar glitches is revisited in light of accumulated observational data. A statistical comparison between the time-predictable and the magnitude-predictable models, borrowed from seismology and grounded in the classical spring-slider framework, is performed against a sample of 245 glitch events from 9
pulsars. It is found that the data supports the time-predictable model, i.e., a quake resulting in a glitch could be triggered when the developed stress reaches a critical threshold, $\tau_{\rm c}$, while the remaining elastic energy (correspondingly the residual stress, $\tau_{\rm r}$) after quakes is not fixed. The critical stress could be the order of $\tau_{\rm c}\simeq (10^{34}-10^{35})\ {\rm dyn\,cm^{-2}}$ if the residual stress after a quake with maximum stress drops could be considered negligible (i.e., $\tau_{\rm r}\simeq 0$), to explain the glitch amplitudes and the intervals. This $\tau_{\rm c}$-value is the order of the shear modulus of strangeon
stars, but would be several orders higher than that of conventional
neutron stars.
Read the full abstract ▾
All authors Zixuan Zhou, Ruipeng Lu, Weiyang Wang, Han Yue, Renxin Xu
Quantum Physics
Joint measurability of coplanar POVMs
Taro Yoshino, Koichi Tojo, Kei Hagihara et al. (+2 more)
An unbiased
qubit positive operator-valued measure (POVM) can be uniquely expressed in terms of the Bloch vector. We prove that for POVMs with coplanar Bloch vectors, they are jointly measurable if and only if the perimeter of the convex closure of Bloch vectors is less than or equal to 4. Moreover, as a corollary, we give an affirmative answer to the
conjecture suggested by [Andrejic-Kunjwal 2020] on the existence of a joint device for POVMs whose Bloch vectors lie on the same circle.
Read the full abstract ▾
All authors Taro Yoshino, Koichi Tojo, Kei Hagihara, Akinori Tanaka, Takuki Tomita
Quantum Physics
Average-and Last-Iterate Lower Bounds for Optimistic Matrix Mirror-Prox in Quantum Zero-Sum Games
Yiheng Su, Emmanouil-Vasileios Vlatakis-Gkaragkounis and Pucheng Xiong
Optimistic
matrix mirror-prox (OMMP) computes $\epsilon$-approximate Nash
equilibria in
quantum zero-sum games with an $O(1/\varepsilon)$ average-iterate guarantee [arXiv:2311.10859]. We investigate whether this dependence on accuracy is tight and whether
geometric last-iterate convergence can be guaranteed. We study these questions through explicit games with one
qubit per player. First, we prove an $\Omega(1/\varepsilon)$ lower bound for the uniform-average output that includes the maximally mixed initial state, independently of the regularizer and step size. Second, we construct a fixed game on which optimistic gradient descent-ascent (OGDA), initialized at the maximally mixed state, has last-iterate Frobenius distance to
equilibrium $\Theta(1/t)$ and duality gap $\Theta(1/t^3)$ for every sufficiently small fixed step size. A separate fixed game exhibits arbitrarily long delays in reducing the initial error by a constant factor across a family of initial states. Finally, we give a fixed game with a unique, strictly complementary
equilibrium on which optimistic
matrix multiplicative weights updates (OMMWU) converge only polynomially from the maximally mixed state for every fixed positive step size. The last-iterate Frobenius distance and
quantum relative
entropy from the
equilibrium to the iterates decay as $\Theta(1/t)$, while the duality gap decays as $\Theta(1/t^2)$.
Read the full abstract ▾
Optics
Experimental Demonstration of Chiral Bound States in the Continuum Enabled by Time-reversal Symmetry Breaking
Hao-Chang Mo, Wen-Jin Zhang, Ze-Yu Wu et al. (+3 more)
Bound states in the continuum (BICs) provide a powerful route to optical resonances with vanishing radiation loss and enhanced light-matter interactions. Of particular interest are
chiral BICs, whose resonant states exhibit intrinsic circular polarization and
spin-selective radiation. Magneto-optical photonic
crystals have recently been predicted to host such states through time-reversal-
symmetry breaking. Here, we experimentally demonstrate
chiral BICs induced by time-reversal
symmetry breaking in a magneto-optical photonic
crystal, where an out-of-plane
magnetic field lifts a degenerate BIC pair into two nondegenerate resonances with opposite circular polarizations. Numerical simulations reveal the associated
chiral phase
vortices and strong
spin-selective radiation, while microwave measurements confirm the predicted behavior through angle-resolved transmission spectra and pronounced broadband circular dichroism. Our results establish an experimental platform for exploring
chiral BIC physics in magneto-optical photonic structures, opening new opportunities for
spin-selective photonics.
Read the full abstract ▾
All authors Hao-Chang Mo, Wen-Jin Zhang, Ze-Yu Wu, Xin-Tao He, Xiao-Dong Chen, Jian-Wen Dong
Mesoscale and Nanoscale Physics
Optical observation of interlayer spin correlation
Akiyoshi Park, Pranshoo Upadhyay, Andrey Grankin et al. (+16 more)
Spin correlations govern numerous collective behaviors of
quantum materials, underpinning exotic phenomena such as unconventional superconductivity and topological magnetism. In layered materials, the interlayer
spin correlation is important because it characterizes the
magnetic ground state and determines
spin transport across the interface. Yet interlayer
spin correlations have remained hard to measure directly, leaving one of the most basic quantities of two-dimensional magnetism out of experimental reach. Here we provide the first direct optical probe of interlayer
spin correlations, using two-
magnon Raman scattering in the van der Waals antiferromagnet (AFM) CrSBr, in remarkable agreement with a microscopic
spin-wave model without any fitting parameter. Moreover, the two-
magnon channel switches on only in the AFM state and vanishes when a
magnetic field takes the
crystal to a
ferromagnetic state. We furthermore establish an
exciton-mediated variant of the technique, where tuning the
laser near the
exciton resonance enhances the signal roughly tenfold due to the
exciton's large oscillator strength.
Magnon-pair Raman spectroscopy thus opens a direct optical window into interlayer
spin correlations in van der Waals magnets, extendable to twisted
bilayers and proximity-coupled
heterostructures.
Read the full abstract ▾
All authors Akiyoshi Park, Pranshoo Upadhyay, Andrey Grankin, Emil Viñas Boström, Mahdi Ghafariasl, Hassan Alnatah, Masoud Mohammadi-Arzanagh, Gautam Nambiar, Beini Gao, Alireza Alvandi, Sakthi Rajmano Madhan Kumar, Ghadah Alshalan, Isaac Sherwood, Mahmoud Jalali Mehrabad, You Zhou, Arun Ramanathan, Xavier Roy, Angel Rubio, Mohammad Hafezi
High Energy Physics (Theory)
Relative entropy of entanglement and tripartite minimal surface
Takato Mori and Beni Yoshida
We propose a
holographic dual of the relative
entropy of
entanglement for a boundary tripartition $A:B:C$. Our proposal is that, at the leading order, \begin{align} E_R(\rho_{AB}) = \frac{1}{4G_N}\Big[\mathrm{Area}(\Gamma_{\min}) - \mathrm{Area}(\gamma_{AB})\Big] \notag \end{align} where $\Gamma_{\min}$ is the minimal bulk tripartition surface and $\gamma_{AB}$ is the minimal surface homologous to $AB$. For a general random tensor network, we prove the corresponding upper bound by constructing a separable state associated with $\Gamma_{\min}$ and evaluating its relative
entropy. We also establish the matching lower bound rigorously for networks of one, two, and three Haar random tensors by bounding the maximal tripartite product-state overlap. In appropriate geometries, the minimal tripartition surface can form a nontrivial tri-junction resembling the Mercedes logo. The proof proceeds by sequential optimization over candidate product states, which has a natural
geometric interpretation as a local search for the minimal tripartition surface.
Read the full abstract ▾
Chaotic Dynamics · Cross-listed from cs.LG
Learning Chaos Without Seeing Chaos: Extrapolation of Global Dynamics in Autoregressive Transformers
Yilun Liu, Yi Zhang, Ganyu Wu et al. (+5 more)
Autoregressive models are trained to predict a system's behavior one step at a time, and recursive generation allows the learned dynamics to unfold over long horizons. To what extent can such dynamics learned from local observations recover broader organization of an underlying system that was only partially observed during training? Here we study small autoregressive
transformers trained from scratch on trajectories sampled from restricted parameter regimes of several non-linear dynamical systems, including logistic and sine maps, the Lorenz system, and the generalized
Hopf system, with control parameters and state trajectories represented as sequences of continuous
tokens. Under closed-loop evaluation at parameters far outside the training distribution, the models can recover self-similar period-doubling cascades, chaotic dynamics, and attractor structures with remarkable visual and numerical fidelity. For the logistic map, a
transformer reproduces successive period doublings up to period 128, yielding a finite-order scaling ratio of 4.6687, matching the Feigenbaum constant to within $5\times10^{-4}$. We further investigate how these structures emerge over the course of training, and reveal with causal interventions how control-parameter information is processed through
attention into state prediction and shapes the resulting closed-loop dynamics. These results suggest that a surprisingly narrow window into a system's local behavior may suffice for autoregressive
transformers to generalize to its unseen global dynamical organization.
Read the full abstract ▾
All authors Yilun Liu, Yi Zhang, Ganyu Wu, Sikuan Yan, Mengyue Wang, Alois Knoll, Volker Tresp, Yunpu Ma
Quantum Physics
Entangling Atomic Quantum Memories Using High-Order Modulated Coherent States
Chaohan Cui, Prajit Dhara and Saikat Guha
High-order coherent-state modulation and collective midpoint measurements enable multi-ebit
entanglement distribution between cavity-coupled atomic
memories. An SRM-inspired 16-QAM receiver achieves $1.75$ ebits per network mode use at $0.5$~dB end-to-end loss, exceeding single-
qubit-per-mode
benchmarks by $5.8$~dB and lying $3.8$~dB below the half-link capacity bound. The advantage persists for per-interface loss below $0.2$~dB and calibrated phase errors below $0.2\pi$. For 4-QAM, an optimized POVM with twice as many outcomes raises the achievable rate by $4.0\%$, revealing measurement-design headroom.
Read the full abstract ▾
Quantum Physics
Breaking the Shot-Noise Barrier: Cached Recycled Variance-Reduced Gradients for Quantum Optimization
Lam M. Nguyen, Sumanta Mukherjee and Dzung T. Phan
Variational
Quantum Algorithms (VQAs) rely heavily on classical optimization routines to navigate high-dimensional, noisy parameter landscapes. However, the evaluation of analytical gradients via the parameter-shift rule requires $\mathcal{O}(p)$
circuit executions, rendering this approach computationally prohibitive for deep
circuits. While simultaneous perturbation methods provide an $\mathcal{O}(1)$ alternative, their gradient estimates suffer from severe $\mathcal{O}(p)$ spatial variance, which impedes convergence. To resolve this tension, we introduce the Cached Recycled Variance-Reduced Gradient (CRVG) by leveraging variance reduction techniques. We formulate two variants: a 3-
Circuit (1-Sided) Non-Recursive CRVG and a Recursive CRVG. By introducing a center-point caching mechanism, the 3-
Circuit CRVG mathematically recycles
quantum measurements to reduce the inner-loop
circuit complexity by 25% across both variants. We establish a theoretical separation between the two routing paths to achieve an $\epsilon^2$-stationary point: the non-recursive variant reaches a sample complexity of $\mathcal{O}(\max\{p/\epsilon^2, p^{2/3}/\epsilon^{10/3}\})$, while the recursive variant achieves an improved complexity of $\mathcal{O}(\max\{p/\epsilon^2, \sqrt{p}/\epsilon^3\})$. Empirically, extensive evaluations on MaxCut and Maximum Independent Set (MIS)
benchmarks validate these findings. While standard simultaneous perturbation remains a robust baseline across varying depths, CRVG demonstrates targeted advantages in specific amortizable regimes, such as the non-recursive variant on EfficientSU2
circuits and both variants on depth-three QAOA, yielding superior energy minimums and tighter output variances. Ultimately, CRVG establishes a principled bias-throughput trade-off for scaling near-term
quantum optimization.
Read the full abstract ▾