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Physics Quantum Physics

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Thursday 25 December

Quantum Physics · Cross-listed from math-ph

Quantum Mean-Fields Spin Systems in a Random External Field

Chokri Manai

In this work, we consider general exchangeable quantum mean-field Hamiltonian such as the prominent quantum Curie-Weiss model under the influence of a random external field. Despite being arguably the simplest class of disordered quantum systems, the random external field breaks the symmetry of the mean-field Hamiltonian and hence standard quantum de Finetti type or semiclassical arguments are not directly applicable. We introduce a novel strategy in this context, which can be seen as non-commutative large deviation analysis, allowing us to characterize the limiting free energy in terms of a simple and explicit variational formula. The proposed method is general enough to be used for other classes of mean-field models such as multi species Hamiltonians.
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Quantum Physics

Quantum Nondecimated Wavelet Transform: Theory, Circuits, and Applications

Brani Vidakovic

The nondecimated or translation-invariant wavelet transform (NDWT) is a central tool in classical multiscale signal analysis, valued for its stability, redundancy, and shift invariance. This paper develops two complementary quantum formulations of the NDWT that embed these classical properties coherently into quantum computation. The first formulation is based on the epsilon-decimated interpretation of the NDWT and realizes all circularly shifted wavelet transforms simultaneously by promoting the shift index to a quantum register and applying controlled circular shifts followed by a wavelet analysis unitary. The resulting construction yields an explicit, fully unitary quantum representation of redundant wavelet coefficients and supports coherent postprocessing, including quantum shrinkage via ancilla-driven completely positive trace preserving maps. The second formulation is based on the Hadamard test and uses diagonal phase operators to probe scale-shift wavelet structure through interference, providing direct access to shift-invariant energy scalograms and multiscale spectra without explicit coefficient reconstruction. Together, these two approaches demonstrate that redundancy and translation invariance can be exploited rather than avoided in the quantum setting. Applications to denoising, feature extraction, and spectral scaling illustrate how quantum NDWTs provide a flexible and physically meaningful foundation for multiscale quantum signal processing.
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Quantum Physics · Cross-listed from physics.flu-dyn

Topological guidance of a self-propelled particle

Ethan Andersson and Valeri Frumkin

Topological phenomena typically govern the behavior of delocalized waves, giving rise to robust transport in electronic, photonic, and mechanical systems. Whether similar principles can directly control the motion of a localized particle, particularly one dynamically coupled to the field that guides it, has remained largely unexplored. Here we show that topology can govern the dynamics of a self-guided particle. Using a walking droplet whose motion is coupled to a self-generated wave field, we demonstrate that structuring the wave environment enables band-gap mediated particle exclusion, edge-guided transport, and chirality-dependent orbital dynamics arising from an emergent gauge structure. Unlike conventional topological systems, where topology constrains wave propagation alone, the present system allows global geometric structure to act directly on particle trajectories. These results extend topological control from waves to particles and establish a route toward directing matter through global geometric design rather than local forcing.
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Quantum Physics

Electrical Control of Optically Active Single Spin Qubits in ZnSe

Amirehsan Alizadehherfati, Yuxi Jiang, Nils von den Driesch et al. (+6 more)

Electrons bound to shallow donors in ZnSe quantum wells are promising candidates for optically addressable spin qubits and single-photon sources. However, their optical coherence and indistinguishability are often limited by spectral broadening arising from charge fluctuations in the local environment. Here, we report electrical control of single donor qubits in ZnSe quantum wells. The applied field induces a DC Stark shift that tunes the emission energy over a range exceeding 30 times the inhomogeneous linewidth, effectively compensating for emitter-to-emitter variations. Concurrently, the field stabilizes trap occupancy, yielding a twofold reduction in optical linewidth and the suppression of spectral wandering. A statistical model based on trap dynamics qualitatively reproduces these observations and elucidates the mechanism of field-assisted charge noise suppression. Our results identify electrical control as a versatile pathway to significantly improve optical and spin addressability.
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All authors Amirehsan Alizadehherfati, Yuxi Jiang, Nils von den Driesch, Christine Falter, Yurii Kutovyi, Jasvith Raj Basani, Amirehsan Boreiri, Alexander Pawlis, Edo Waks

Wednesday 24 December

Quantum Physics

Algebraic Fusion in a (2+1)-dimensional Lattice Model with Generalized Symmetries

Chinmay Giridhar, Philipp Vojta, Zohar Nussinov et al. (+2 more)

The notion of quantum symmetry has recently been extended to include reduced-dimensional transformations and algebraic structures beyond groups. Such generalized symmetries lead to exotic phases of matter and excitations that defy Landau's original paradigm. Here, we develop an algebraic framework for systematically deriving the fusion rules of topological defects in higher-dimensional lattice systems with non-invertible generalized symmetries, and focus on a (2+1)-dimensional quantum Ising plaquette model as a concrete illustration. We show that bond-algebraic automorphisms, when combined with the so-called half-gauging procedure, reveal the structure of the non-invertible duality symmetry operators, which can be explicitly represented as a sequential quantum circuit. The resulting duality defects are constrained by the model's rigid higher symmetries (lower-dimensional subsystem symmetries), leading to restricted mobility. We establish the fusion algebra of these defects. Finally, in constructing the non-invertible duality transformation, we explicitly verify that it acts as a partial isometry on the physical Hilbert space, thereby satisfying a recent generalization of Wigner's theorem applicable to non-invertible symmetries.
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All authors Chinmay Giridhar, Philipp Vojta, Zohar Nussinov, Gerardo Ortiz, Andriy H. Nevidomskyy

Quantum Physics · Cross-listed from physics.atom-ph

Atomic clock frequency ratios with fractional uncertainty $\leq 3.2 \times 10^{-18}$

Alexander Aeppli, Willa J. Arthur-Dworschack, Kyle Beloy et al. (+24 more)

We report high-precision frequency ratio measurements between optical atomic clocks based on $^{27}$Al$^+$, $^{171}$Yb, and $^{87}$Sr. With total fractional uncertainties at or below $3.2 \times 10^{-18}$, these measurements meet an important milestone criterion for redefinition of the second in the International System of Units. Discrepancies in $^{87}$Sr ratios at approximately $1\times10^{-16}$ and the Al$^+$/Yb ratio at $1.6\times10^{-17}$ in fractional units compared to our previous measurements underscore the importance of repeated, high-precision comparisons by different laboratories. A key innovation in this work is the use of a common ultrastable reference delivered to all clocks via a 3.6 km phase-stabilized fiber link between two institutions. Derived from a cryogenic single-crystal silicon cavity, this reference improves comparison stability by a factor of 2 to 3 over previous systems, with an optical lattice clock ratio achieving a fractional instability of $1.3 \times 10^{-16}$ at 1 second. By enabling faster comparisons, this stability will improve sensitivity to non-white noise processes and other underlying limits of state-of-the-art optical frequency standards.
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All authors Alexander Aeppli, Willa J. Arthur-Dworschack, Kyle Beloy, Caitlin M. Berry, Tobias Bothwell, Angela Folz, Tara M. Fortier, Tanner Grogan, Youssef S. Hassan, Zoey Z. Hu, David B. Hume, Benjamin D. Hunt, Kyungtae Kim, Amanda Koepke, Dahyeon Lee, David R. Leibrandt, Ben Lewis, Andrew D. Ludlow, Mason C. Marshall, Nicholas V. Nardelli, Harikesh Ranganath, Daniel A. Rodriguez Castillo, Jeffrey A. Sherman, Jacob L. Siegel, Suzanne Thornton, William Warfield, Jun Ye

Quantum Physics · Cross-listed from math-ph

Asymptotic Momentum of Dirac Particles in One Space Dimension

Kabir Narayanan, Abigail Perryman and A. Shadi Tahvildar-Zadeh

We analyze the trajectories of a massive particle in one space dimension whose motion is guided by a spin-half wave function that evolves according to the free Dirac equation, with its initial wave function being a Gaussian wave packet with a nonzero expected value of momentum $k$. We prove that at large times, the wave function is approximately equal to the superposition of two wave packets traveling in opposite directions, which results in trajectories with approximately constant asymptotic momentum $k$ and asymptotic energy $\pm c^2\sqrt{m^2+k^2}$, with $m$ the rest mass of the particle and $c$ the speed of light. The sign of the asymptotic energy is determined by the initial position of the particle. Particles with negative energy will have an asymptotic velocity that is in the opposite direction of their momentum. The proof uses the stationary phase approximation method, for which we establish a rigorous error bound.
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Quantum Physics

Observation of disorder-induced superfluidity

Nicole Ticea, Elias Portoles, Eliott Rosenberg et al. (+299 more)

The emergence of states with long-range correlations in a disordered landscape is rare, as disorder typically suppresses the particle mobility required for long-range coherence. But when more than two energy levels are available per site, disorder can induce resonances that locally enhance mobility. Here we explore phases arising from the interplay between disorder, kinetic energy, and interactions on a superconducting processor with qutrit readout and control. Compressibility measurements distinguish an incompressible Mott insulator from surrounding compressible phases and reveal signatures of glassiness, reflected in non-ergodic behavior. Spatially-resolved two-point correlator measurements identify regions of the phase diagram with a non-vanishing condensate fraction. We also visualize the spectrum by measuring the dynamical structure factor. A linearly-dispersing phonon mode materializes in the superfluid, appearing even when disorder is introduced to the clean Mott insulator. Our results provide strong experimental evidence for disorder-induced superfluidity.
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All authors Nicole Ticea, Elias Portoles, Eliott Rosenberg, Alexander Schuckert, Aaron Szasz, Bryce Kobrin, Nicolas Pomata, Pranjal Praneel, Connie Miao, Shashwat Kumar, Ella Crane, Ilya Drozdov, Yuri Lensky, Sofia Gonzalez-Garcia, Thomas Kiely, Dmitry Abanin, Amira Abbas, Rajeev Acharya, Laleh Aghababaie Beni, Georg Aigeldinger, Ross Alcaraz, Sayra Alcaraz, Markus Ansmann, Frank Arute, Kunal Arya, Walt Askew, Nikita Astrakhantsev, Juan Atalaya, Ryan Babbush, Brian Ballard, Hector Bates, Andreas Bengtsson, Majid Bigdeli Karimi, Alexander Bilmes, Simon Bilodeau, Felix Borjans, Alexandre Bourassa, Jenna Bovaird, Dylan Bowers, Leon Brill, Peter Brooks, Michael Broughton, David A. Browne, Brett Buchea, Bob B. Buckley, Tim Burger, Brian Burkett, Jamal Busnaina, Nicholas Bushnell, Anthony Cabrera, Juan Campero, Hung-Shen Chang, Silas Chen, Zijun Chen, Ben Chiaro, Liang-Ying Chih, Agnetta Y. Cleland, Bryan Cochrane, Matt Cockrell, Josh Cogan, Paul Conner, Harold Cook, Rodrigo G. Cortiñas, William Courtney, Alexander L. Crook, Ben Curtin, Sayan Das, Martin Damyanov, Dripto M. Debroy, Stijn J. de Graaf, Laura De Lorenzo, Sean Demura, Lucia B. De Rose, Agustin Di Paolo, Paul Donohoe, Andrew Dunsworth, Valerie Ehimhen, Alec Eickbusch, Aviv Moshe Elbag, Lior Ella, Mahmoud Elzouka, David Enriquez, Catherine Erickson, Lara Faoro, Vinicius S. Ferreira, Marcos Flores, Leslie Flores Burgos, Sam Fontes, Ebrahim Forati, Jeremiah Ford, Brooks Foxen, Masaya Fukami, Alan Wing Lun Fung, Lenny Fuste, Suhas Ganjam, Gonzalo Garcia, Christopher Garrick, Robert Gasca, Helge Gehring, Robert Geiger, Élie Genois, William Giang, Dar Gilboa, James E. Goeders, Edward C. Gonzales, Raja Gosula, Alejandro Grajales Dau, Dietrich Graumann, Joel Grebel, Alex Greene, Jonathan A. Gross, Jose Guerrero, Tan Ha, Steve Habegger, Tanner Hadick, Ali Hadjikhani, Monica Hansen, Matthew P. Harrigan, Sean D. Harrington, Jeanne Hartshorn, Stephen Heslin, Paula Heu, Oscar Higgott, Reno Hiltermann, Jeremy Hilton, Hsin-Yuan Huang, Mike Hucka, Christopher Hudspeth, Ashley Huff, William J. Huggins, Evan Jeffrey, Shaun Jevons, Zhang Jiang, Xiaoxuan Jin, Cody Jones, Chaitali Joshi, Pavol Juhas, Andreas Kabel, Dvir Kafri, Hui Kang, Kiseo Kang, Amir H. Karamlou, Ryan Kaufman, Kostyantyn Kechedzhi, Julian Kelly, Tanuj Khattar, Mostafa Khezri, Seon Kim, Paul V. Klimov, Can M. Knaut, Alexander N. Korotkov, Fedor Kostritsa, John Mark Kreikebaum, Ryuho Kudo, Arun Kumar, Ben Kueffler, Vladislav D. Kurilovich, Vitali Kutsko, Nathan Lacroix, Tiano Lange-Dei, Brandon W. Langley, Pavel Laptev, Kim-Ming Lau, Emma Leavell, Loick Le Guevel, Justin Ledford, Joy Lee, Kenny Lee, Brian J. Lester, Wendy Leung, Matthew T. Lloyd, Lily L Li, Wing Yan Li, Ming Li, Alexander T. Lill, William P. Livingston, Aditya Locharla, Erik Lucero, Daniel Lundahl, Aaron Lunt, Sid Madhuk, Aniket Maiti, Ashley Maloney, Salvatore Mandrà, Leigh S. Martin, Orion Martin, Eric Mascot, Paul Masih Das, Dmitri Maslov, Melvin Mathews, Cameron Maxfield, Jarrod R. McClean, Matt McEwen, Seneca Meeks, Anthony Megrant, Kevin C. Miao, Reza Molavi, Sebastian Molina, Shirin Montazeri, Charles Neill, Michael Newman, Anthony Nguyen, Murray Nguyen, Chia-Hung Ni, Murphy Yuezhen Niu, Nicholas Noll, Logan Oas, William D. Oliver, Raymond Orosco, Kristoffer Ottosson, Alice Pagano, Sherman Peek, David Peterson, Alex Pizzuto, Rebecca Potter, Orion Pritchard, Michael Qian, Chris Quintana, Arpit Ranadive, Ganesh Ramachandran, Matthew J. Reagor, Rachel Resnick, David M. Rhodes, Daniel Riley, Gabrielle Roberts, Roberto Rodriguez, Emma Ropes, Eliott Rosenberg, Emma Rosenfeld, Dario Rosenstock, Elizabeth Rossi, David A. Rower, Robert Salazar, Kannan Sankaragomathi, Murat Can Sarihan, Kevin J. Satzinger, Sebastian Schroeder, Henry F. Schurkus, Aria Shahingohar, Michael J. Shearn, Aaron Shorter, Vladimir Shvarts, Volodymyr Sivak, Spencer Small, W. Clarke Smith, David A. Sobel, Barrett Spells, Sofia Springer, George Sterling, Jordan Suchard, Alexander Sztein, Madeline Taylor, Jothi Priyanka Thiruraman, Douglas Thor, Dogan Timucin, Eifu Tomita, Alfredo Torres, M. Mert Torunbalci, Hao Tran, Abeer Vaishnav, Justin Vargas, Sergey Vdovichev, Benjamin Villalonga, Catherine Vollgraff Heidweiller, Meghan Voorhees, Steven Waltman, Jonathan Waltz, Shannon X. Wang, Danni Wang, Brayden Ware, James D. Watson, Yonghua Wei, Travis Weidel, Theodore White, Kristi Wong, Bryan W. K. Woo, Christopher J. Wood, Maddy Woodson, Cheng Xing, Z. Jamie Yao, Ping Yeh, Bicheng Ying, Juhwan Yoo, Noureldin Yosri, Elliot Young, Grayson Young, Adam Zalcman, Ran Zhang, Yaxing Zhang, Ningfeng Zhu, Nicholas Zobrist, Zhenjie Zou, Sergio Boixo, Hartmut Neven, Vadim Smelyanskiy, Guifre Vidal, Erich Mueller, Trond Andersen, Lev Ioffe, Andre Petukhov, Mohammad Hafezi, Pedram Roushan

Quantum Physics

Simulating Circuit Layout for Distributed Quantum Computing

Sen Zhang, Yipie Liu, Brian Mark et al. (+3 more)

The proposed framework represents the first tool to compile a quantum circuit across photonic-connected distributed quantum processors. Its design follows a divide-and-conquer paradigm for circuit partitioning, transpilation, and assembly, producing simulable and implementable circuit layouts.
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All authors Sen Zhang, Yipie Liu, Brian Mark, Weiwen Jiang, Zebo Yang, Lei Yang

Quantum Physics

Geometry and quantum brachistochrone analysis of multiple entangled spin-1/2 particles under all-range Ising interaction

B. Amghar, M. Yachi, M. Amghar et al. (+3 more)

We present a unified geometric and dynamical framework for a physical system consisting of $n$ spin-$1/2$ particles with all-range Ising interaction. Using the Fubini-Study formalism, we derive the metric tensor of the associated quantum state manifold and compute the corresponding Riemann curvature. Our analysis reveals that the system evolves over a smooth, compact, two-dimensional manifold with spherical topology and a dumbbell-like structure shaped by collective spin interactions. We further investigate the influence of the geometry and topology of the resulting state space on the behavior of geometric and topological phases acquired by the system. We explore how this curvature constrains the system's dynamical behavior, including its evolution speed and Fubini-Study distance between the quantum states. Within this geometric framework, we address the quantum brachistochrone problem and derive the minimal time required for optimal evolution, a result useful for time-efficient quantum circuit design. Subsequently, we explore the role of entanglement in shaping the state space geometry, modulating geometric phase, and controlling evolution speed and brachistochrone time. Our results reveal that entanglement enhances dynamics up to a critical threshold, beyond which geometric constraints begin to hinder evolution. Moreover, entanglement induces critical shifts in the geometric phase, making it a sensitive indicator of entanglement levels and a practical tool for steering quantum evolution. This approach offers valuable guidance for developing quantum technologies that require time-efficient control strategies rooted in the geometry of quantum state space.
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All authors B. Amghar, M. Yachi, M. Amghar, M. Almousa, A. A. Abd El-Latif, A. Slaoui

Quantum Physics

Hybrid digital-analog protocols for simulating quantum multi-body interactions

Or Katz, Alexander Schuckert, Tianyi Wang et al. (+3 more)

While quantum simulators promise to explore quantum many-body physics beyond classical computation, their capabilities are limited by the available native interactions in the hardware. On many platforms, accessible Hamiltonians are largely restricted to one- and two-body interactions, limiting access to multi-body Hamiltonians and to systems governed by simultaneous, non-commuting interaction terms that are central to condensed matter, quantum chemistry, and high-energy physics. We introduce and experimentally demonstrate a hybrid digital-analog protocol that overcomes these limitations by embedding analog evolution between shallow entangling-gate layers. This method produces effective Hamiltonians with simultaneous non-commuting three- and four-body interactions that are generated non-perturbatively and without Trotter error – capabilities not practically attainable on near-term hardware using purely digital or purely analog schemes. We implement our scheme on a trapped-ion quantum processor and use it to realize a topological spin chain exhibiting prethermal strong zero modes persisting at high temperature, as well as models featuring three- and four-body interactions. Our hardware-agnostic and scalable method opens new routes to realizing complex many-body physics across quantum platforms.
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All authors Or Katz, Alexander Schuckert, Tianyi Wang, Eleanor Crane, Alexey V. Gorshkov, Marko Cetina

Quantum Physics

Bose polarons as relativistic Unruh-DeWitt detectors: Entanglement harvesting from Bose-Einstein condensates

T. Rick Perche, Francesco Gozzini and Markus K. Oberthaler

We show that a bound impurity in a Bose-Einstein condensate can be directly mapped to an Unruh-DeWitt detector interacting with a relativistic quantum field. We provide explicit experimental parameters for an implementation using ${}^{41}\text{K}$ impurities coupled to a ${}^{87}\text{Rb}$ condensate via finite-time Feshbach tuning. As an application, we study the extraction of vacuum entanglement from distant regions of the condensate and find viable parameters for the implementation of entanglement harvesting.
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Quantum Physics · Cross-listed from cond-mat.stat-mech

Universality of equilibration dynamics after quantum quenches

Vincenzo Alba, Sanam Azarnia, Gianluca Lagnese et al. (+1 more)

We investigate the distribution of the eigenvalues of the reduced density matrix (entanglement spectrum) after a global quantum quench. We show that in an appropriate scaling limit the lower part of the entanglement spectrum exhibits “universality”. In the scaling limit and at asymptotically long times the distribution of the entanglement spectrum depends on two parameters that can be determined from the Rényi entropies. We show that two typical scenarios occur. In the first one, the distribution of the entanglement spectrum levels is similar to the one describing the ground-state entanglement spectrum in Conformal Field Theories. In the second scenario, the lower levels of the entanglement spectrum are highly degenerate and their distribution is given by a series of Dirac deltas. We benchmark our analytical results in free-fermion chains, such as the transverse field Ising chain and the XX chain, in the rule 54 chain, and in Bethe ansatz solvable spin models.
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All authors Vincenzo Alba, Sanam Azarnia, Gianluca Lagnese, Federico Rottoli

Quantum Physics

Optimizing Quantum State Transformation Under Locality Constraint

Sasan Sarbishegi and Maryam Sadat Mirkamali

In this paper, we present a general numerical framework for both deterministic and probabilistic quantum state transformations, under locality constraints. For a given arbitrary bipartite initial state and a desired bipartite target state, we construct an optimized local quantum channel that transforms the initial state into the target state with high fidelity. To achieve this goal, local quantum channels are parametrized on a complex Stiefel manifold and optimized using gradient-based methods. We demonstrate that this approach significantly enhances entanglement distillation for weakly entangled states via two complementary strategies: optimized local state transformation and probabilistic local transformation. These results establish our method as a powerful and versatile tool for a broad class of quantum information processing tasks.
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Quantum Physics

A Note on Publicly Verifiable Quantum Money with Low Quantum Computational Resources

Fabrizio Genovese and Lev Stambler

In this work we present a publicly verifiable quantum money protocol which assumes close to no quantum computational capabilities. We rely on one-time memories which in turn can be built from quantum conjugate coding and hardware-based assumptions. Specifically, our scheme allows for a limited number of verifications and also allows for quantum tokens for digital signatures. Double spending is prevented by the no-cloning principle of conjugate coding states. An implementation of the concepts presented in this work can be found at https://github.com/neverlocal/otm_billz.
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Quantum Physics

Quantum computation of mass gap in an asymptotically free theory

Paulo F. Bedaque, Edison M. Murairi, Gautam Rupak et al. (+1 more)

In relativistic field theories, the mass spectrum is given by the difference between the energy of the vacuum and the excited states. Near the continuum limit, the cancellation between these two values leads to loss of precision. We propose a method to extract the mass gap directly using quantum computers and apply it to a particular version of the nonlinear $\sigma$-model with the correct continuum limit and perform calculations in quantum hardware (at strong coupling) and simulation in classical computers (at weak coupling).
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All authors Paulo F. Bedaque, Edison M. Murairi, Gautam Rupak, Valery S. Simonyan

Quantum Physics · Cross-listed from math-ph

Hamilton-Jacobi as model reduction, extension to Newtonian particle mechanics, and a wave mechanical curiosity

Amit Acharya

The Hamilton-Jacobi equation of classical mechanics is approached as a model reduction of conservative particle mechanics where the velocity degrees-of-freedom are eliminated. This viewpoint allows an extension of the association of the Hamilton-Jacobi equation from conservative systems to general Newtonian particle systems involving non-conservative forces, including dissipative ones. A geometric optics approximation leads to a dissipative Schrödinger equation, with the expected limiting form when the associated classical force system involves conservative forces.
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Quantum Physics

Characterizing quantum synchronization in the van der Pol oscillator via tomogram and photon correlation

Kingshuk Adhikary, K. M. Athira and M. Rohith

Scalable methods for detecting and quantifying the nonclassical nature of a quantum state in noisy environments are challenging due to a complex relationship between noise and quantum coherence. In particular, identifying experimentally accessible signatures of synchronization in such regimes remains an open problem. By leveraging promising experimental implementation, we underpin what possible direct measures of nonclassicality are available. This work outlines accessing quantum synchronization (QS) in the steady state of a driven quantum van der Pol oscillator (vdPo) using two distinct figures of merit: (i) the nonclassical area $\delta$ and (ii) the second-order correlation function $g^{(2)}(0)$, both of which are viable in experimental architectures. The nonclassical area quantifier based on homodyne tomography allows us to assess the nonclassical nature of the vdPo state directly from the tomogram without requiring full state reconstruction or Wigner function negativity. Within a well-defined parameter regime of drive strength and detuning, both $\delta$ and $g^{(2)}(0)$ exhibit pronounced signatures of synchronization that complements the phase coherence between the drive and the vdPo. We derive an analytical expression for the steady state density matrix and the corresponding tomogram of the system, valid for arbitrary strengths of the harmonic drive. Analysis of the quantum tomogram uncovers clear phase locking behaviour, enabling the identification of the synchronization region (Arnold tongue) directly in terms of $g^{(2)}(0)$ and $\delta$. Furthermore, the behaviour of $g^{(2)}(0)$ provides a statistical perspective that reinforces the tomographic signatures of QS. By analyzing the interplay between the aforementioned metrics, our findings indicate a scalable and experimentally relevant framework for characterizing QS in the driven vdPo.
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Quantum Physics · Cross-listed from physics.flu-dyn

Observation of the Aharonov-Bohm Effect in Pilot-Wave Hydrodynamics

Georgi Gary Rozenman, Kyle I. McKee, Arnaud Lazarus et al. (+2 more)

We report the results of an experimental study of an analog of the Aharonov-Bohm (AB) effect achieved with the hydrodynamic pilot-wave system. A walking droplet is confined to an annular cavity that encircles a shielded vortex, but lies outside its range of direct influence. While there is no vortex-induced flow in the immediate vicinity of the droplets, the vortex modifies the droplet's spatially extended pilot-wave field that guides its motion, producing a vortex-dependent bias in the droplet's orbital speed. High-speed tracking and delay-embedding reconstructions yield Wigner-like phase-space distributions for this hydrodynamic system that exhibits a rigid, flux-dependent translation, providing a force-free, gauge-like realization of an AB-type phase.
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All authors Georgi Gary Rozenman, Kyle I. McKee, Arnaud Lazarus, Valeri Frumkin, John W M Bush

Quantum Physics

Random dilation superchannel

Satoshi Yoshida, Ryotaro Niwa, Takeru Utsumi et al. (+2 more)

We present a quantum circuit that implements the random dilation superchannel, transforming parallel queries of an unknown quantum channel into the same number of parallel queries of a randomly chosen dilation isometry of the input channel. This is a natural generalization of the random purification channel, that transforms copies of an unknown mixed state to copies of a randomly chosen purification state. The circuit complexity of our construction is $O(\mathrm{poly}(n, \log d_I, \log d_O))$, where $n$ is the number of queries and $d_I$ and $d_O$ are the input and output dimensions of the input channel, respectively. This random dilation superchannel is extended to the sequential queries approximately, by transforming the parallel random dilation isometry into sequential random dilation unitaries with $O(\mathrm{poly}(d_I))$ overhead in the number of queries. We also show that our results can be further extended to the case of quantum superchannels. On the other hand, we show a no-go theorem on the exact random dilation of sequential queries with $o(\mathrm{poly}(\min\{d_I, d_O\}))$ query overhead, showcasing a fundamental difference between the parallel and sequential cases. As an application, we show an efficient storage-and-retrieval of an unknown quantum channel, which improves the program cost exponentially in the retrieval error $\varepsilon$. For the case where the Kraus rank $r$ is the least possible (i.e., $r = d_I/d_O$), we show quantum circuits that transform $n$ parallel queries of an unknown quantum channel $\Lambda$ to $\Theta(n^\alpha)$ parallel queries of $\Lambda$ for any $\alpha<2$ approximately, and implement its Petz recovery map for the maximally mixed reference state probabilistically and exactly.
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All authors Satoshi Yoshida, Ryotaro Niwa, Takeru Utsumi, Ryuji Takagi, Mio Murao

Quantum Physics

Squeezed quantum multiplets: properties and phase space representation

Juan Pablo Paz, Corina Révora and Christian Tomás Schmiegelow

We define and study the properties of “squeezed quantum multiplets”. Ordinary multiplets are sets of $D$-orthonormal quantum states formed by superpositions of states squeezed along $D$ equally spaced directions in quadrature space. More generally, we also discuss superpositions of “higher-order squeezed states”, including tri-squeezed and quad-squeezed states. All these states involve superpositions of multiples of $p$ photons. We compare states in ordinary ($p=2$) multiplets and higher-order ones ($p>2$) in the most relevant cases, showing that ordinary squeezed multiplets and higher-order ones share some important similarities, as well as some differences. Finally, we present analytical expressions for phase-space distributions (Wigner and characteristic functions) representing ordinary squeezed multiplets. We use this to show that some squeezed multiplets are highly sensitive to perturbations in all phase-space directions, making them interesting for metrological applications.
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Quantum Physics · Cross-listed from hep-ph

Quantum entanglement between partons in a strongly coupled quantum field theory

Wenyu Zhang, Wenyang Qian, Yiyu Zhou et al. (+2 more)

We perform a first-principles, non-perturbative investigation of quantum entanglement between partonic constituents in a strongly coupled 3+1-dimensional scalar Yukawa theory, using light-front Hamiltonian methods with controlled Fock-space truncations. By explicitly constructing reduced density matrices for (mock) nucleon, pion, and anti-nucleon subsystems from light-front wave functions, we compute key entanglement witnesses, including von Neumann entropy, mutual information, and linear entropy, in both quenched (no sea pairs) and unquenched frameworks. We find that the entanglement entropy is closely related to the Shannon entropy of the transverse momentum dependent distribution, establishing a link between quantum information and parton structure. In contrast, the unquenched theory reveals genuinely non-classical correlations: the entanglement entropy cannot be reduced to any Shannon entropy of normalized parton distributions, demonstrating that the full hadronic wave function encodes quantum information beyond classical probabilities. Our findings highlight the role of entanglement as a fundamental probe of non-perturbative dynamics in relativistic quantum field theory and lay the groundwork for extending these concepts to QCD and future collider phenomenology.
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All authors Wenyu Zhang, Wenyang Qian, Yiyu Zhou, Yang Li, Qun Wang

Quantum Physics

3D cavity-based graphene superconducting quantum circuits in two-qubit architectures

Kuei-Lin Chiu, Avishma J. Lasrado, Cheng-Han Lo et al. (+4 more)

We construct a series of graphene-based superconducting quantum circuits and integrate them into 3D cavities. For a single-qubit device, we demonstrate flux-tunable qubit transition, with a measured $T_1$ $\approx$ 48 ns and a lower bound estimate of $T_2^\ast$ $\approx$ 17.63 ns. By coupling the device to cavities with different resonant frequencies, we access multiple qubit-cavity coupling regimes, enabling the observation of vacuum Rabi splitting and flux-dependent spectral linewidths. In a two-qubit device consisting of a SQUID and a single junction, power-dependent measurements reveal a two-stage dispersive shift. By flux-tuning the cavity frequency at different readout powers, we attribute the first shift to the fixed-qubit and the second to the SQUID-qubit, indicating successful coupling between the two circuits and a single cavity mode. Our study demonstrates the flexible coupling achievable between 2D-material-based superconducting circuits and 3D cavities, and paves the way toward constructing multi-qubit 3D transmon devices from 2D materials.
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All authors Kuei-Lin Chiu, Avishma J. Lasrado, Cheng-Han Lo, Yen-Chih Chen, Shih-Po Shih, Yen-Hsiang Lin, Chung-Ting Ke

Quantum Physics

All-optical control and multiplexed readout of multiple superconducting qubits

Xiaoxuan Pan, Chuanlong Ma, Jia-Qi Wang et al. (+12 more)

Superconducting quantum circuits operate at millikelvin temperatures, typically requiring independent microwave cables for each qubit for connecting room-temperature control and readout electronics. However, scaling to large-scale processors hosting hundreds of qubits faces a severe input/output (I/O) bottleneck, as the dense cable arrays impose prohibitive constraints on physical footprint, thermal load, wiring complexity, and cost. Here we demonstrate a complete optical I/O architecture for superconducting quantum circuits, in which all control and readout signals are transmitted exclusively via optical photons. Employing a broadband traveling-wave Brillouin microwave-to-optical transducer, we achieve simultaneous frequency-multiplexed optical readout of two qubits. Combined with fiber-integrated photodiode arrays for control signal delivery, this closed-loop optical I/O introduces no measurable degradation to qubit coherence times, with an optically driven single-qubit gate fidelity showing only a 0.19% reduction relative to standard microwave operation. These results establish optical interconnects as a viable path toward large-scale superconducting quantum processors, and open the possibility of networking multiple superconducting quantum computers housed in separate dilution refrigerators through a centralized room-temperature control infrastructure.
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All authors Xiaoxuan Pan, Chuanlong Ma, Jia-Qi Wang, Zheng-Xu Zhu, Linze Li, Jiajun Chen, Yuan-Hao Yang, Yilong Zhou, Jia-Hua Zou, Xin-Biao Xu, Weiting Wang, Baile Chen, Haifeng Yu, Chang-Ling Zou, Luyan Sun

Quantum Physics · Cross-listed from physics.optics

Controlling photothermal forces and backaction in nano-optomechanical resonators through strain engineering

Menno H. Jansen, Cauê M. Kersul and Ewold Verhagen

In micro- and nanoscale optomechanical systems, radiation pressure interactions are often complemented or impeded by photothermal forces arising from thermal strain induced by optical heating. We show that the sign and magnitude of the photothermal force can be engineered through deterministic nanoscale structural design, by considering the overlap of temperature and modal strain profiles. We demonstrate this capability experimentally in a specific system: a nanobeam zipper cavity by changing the geometry of its supporting tethers. A single design parameter, corresponding to a nanoscale geometry change, controls the magnitude of the photothermal backaction and even its sign. These insights will allow engineering the combined photothermal and radiation pressure forces in nano-optomechanical systems, such that backaction-induced linewidth variations are deterministically minimized if needed, or maximized for applications that require cooling or amplification at specific laser detuning.
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Quantum Physics

Interaction-Resilient Scalable Fluxonium Architecture with All-Microwave Gates

Andrei A. Kugut, Grigoriy S. Mazhorin and Ilya A. Simakov

Fluxonium qubits demonstrate exceptional potential for quantum processing; yet, realizing scalable architectures using them remains challenging. We propose a fluxonium-based square-grid design with fast $\sim63$~ns controlled-Z (CZ) gates, achieving coherent errors below $10^{-4}$, activated via microwave-driven transmon couplers. A central difficulty in such large-scale systems with all-microwave gates and, therefore, strong static couplings, is suppressing parasitic interactions that extend beyond nearest neighbors to include next-nearest elements. We address this issue by introducing several design strategies: the frequency allocation of both qubits and couplers, the localization of coupler wavefunctions, and a differential oscillator that suppresses residual long-range interactions. In addition, the architecture natively supports fast $\sim70$~ns CZZ gates – three-qubit operations composed of two CZ gates sharing a common qubit – which reduce the incoherent error by $\sim 35\%$ compared to performing the corresponding CZs sequentially. Together, these advances establish an interaction-resilient platform for large-scale fluxonium processors and can be adapted to a variety of fluxonium layouts.
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Quantum Physics

Quantum Approximate Optimization Algorithm with Fixed Number of Parameters

Sebastián Saavedra-Pino, Ricardo Quispe-Mendizábal, Gabriel Alvarado Barrios et al. (+3 more)

We introduce a novel quantum optimization paradigm: the Fixed-Parameter-Count Quantum Approximate Optimization Algorithm (FPC-QAOA). It is a scalable variational framework that maintains a constant number of trainable parameters regardless of the number of qubits, Hamiltonian complexity, or circuit depth. By separating schedule function optimization from circuit digitization, FPC-QAOA enables accurate schedule approximations with minimal parameters while supporting arbitrarily deep digitized adiabatic evolutions, constrained only by NISQ hardware capabilities. This separation allows depth to scale without expanding the classical search space, mitigating overparameterization and optimization challenges typical of deep QAOA circuits, such as barren plateaus-like behaviors. We benchmark FPC-QAOA on random MaxCut instances and the Tail Assignment Problem, achieving performance comparable to or better than standard QAOA with nearly constant classical effort and significantly fewer quantum circuit evaluations. Experiments on the IBM Kingston superconducting processor with up to 50 qubits confirm robustness and hardware efficiency under realistic noise. These results position FPC-QAOA as a practical and scalable paradigm for variational quantum optimization on near-term quantum devices.
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All authors Sebastián Saavedra-Pino, Ricardo Quispe-Mendizábal, Gabriel Alvarado Barrios, Enrique Solano, Juan Carlos Retamal, Francisco Albarrán-Arriagada

Quantum Physics · Cross-listed from cond-mat.mes-hall

Coupled-wire construction of non-Abelian higher-order topological phases

Jiaxin Pan and Longwen Zhou

Non-Abelian topological charges (NATCs), characterized by their noncommutative algebra, offer a framework for describing multigap topological phases beyond conventional Abelian invariants. While higher-order topological phases (HOTPs) host boundary states at corners or hinges, their characterization has largely relied on Abelian invariants such as winding and Chern numbers. Here, we propose a coupled-wire scheme of constructing non-Abelian HOTPs and analyze a non-Abelian second-order topological insulator as its minimal model. The resulting Hamiltonian supports hybridized corner modes, protected by parity-time-reversal plus sublattice symmetries and described by a topological vector that unites a non-Abelian quaternion charge with an Abelian winding number. Corner states emerge only when both invariants are nontrivial, whereas weak topological edge states of non-Abelian origins arise when the quaternion charge is nontrivial, enriching the bulk-edge-corner correspondence. The system further exhibits both non-Abelian and Abelian topological phase transitions, providing a unified platform that bridges these two distinct topological classes. Our work extends the understanding of HOTPs into non-Abelian regimes and suggests feasible experimental realizations in synthetic quantum systems, such as photonic or acoustic metamaterials.
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Quantum Physics

Information-Scrambling-Enhanced Quantum Sensing Beyond the Standard Quantum Limit

Yangyang Ge, Haoyu Zhou, Wen Zheng et al. (+16 more)

Quantum sensing promises measurement precision beyond classical limits, but its practical realization is often hindered by decoherence and the challenges of generating and stabilizing entanglement in large-scale systems. Here, we experimentally demonstrate a scalable, scrambling-enhanced quantum sensing protocol, referred to as butterfly metrology, implemented on a cross-shaped superconducting quantum processor. By harnessing quantum information scrambling, the protocol converts local interactions into delocalized metrologically useful correlations, enabling robust signal amplification through interference of the scrambled and polarized quantum states. We validate the time-reversal ability via Loschmidt echo measurements and quantify the information scrambling through out-of-time-ordered correlators, establishing the essential quantum resources of our protocol. Our measurements reveal that the sensing sensitivity surpasses the standard quantum limit (SQL) with increasing qubit number, reaching 3.78 in a 9-qubit configuration, compared to the SQL of 3.0. The scheme further exhibits inherent robustness to coherent control errors and probed signal noise. This work demonstrates a readily scalable path toward practical quantum sensing advantages with prevalent experimental platforms.
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All authors Yangyang Ge, Haoyu Zhou, Wen Zheng, Xiang-Min Yu, Wei Fang, Zhenchuan Zhang, Wanli Huang, Xiang Deng, Haoyang Cai, Xianke Li, Kun Zhou, Hanxin Che, Tao Zhang, Lichang Ji, Yu Zhang, Jie Zhao, Shao-Xiong Li, Xinsheng Tan, Yang Yu

Quantum Physics · Cross-listed from cond-mat.str-el

Microscopic Constructions of the $BF+AAB$ Topological Field Theory and Borromean-Rings Braiding in $(3+1)$ Dimensions

Yizhou Huang, Zhi-Feng Zhang, Qing-Rui Wang et al. (+1 more)

Topological order was first studied in fractional quantum Hall states, where anyons reflect electron fractionalization. Recent advances in continuum topological field theories have revealed braiding, fusion, shrinking, and diagrammatic consistency relations in higher dimensions [e.g., Huang, Zhang, Ye, JHEP 11 (2023) 210; JHEP 06 (2025) 238]. As the next step of research, these advances call for explicit microscopic lattice constructions that faithfully reproduce the structures and processes described by continuum field theories. Here we construct, step by step, microscopic counterparts of the $(3+1)$-dimensional $BF$ field theory with an $AAB$ twist and gauge group $(\mathbb{Z}_2)^3$. This field theory was introduced in our earlier work on Borromean-Rings braiding [Chan, Ye, Ryu, Phys. Rev. Lett. 121, 061601 (2018)]. We start with the construction of string and thickened membrane operators that create, fuse, shrink, and braid particle and loop excitations, providing microscopic counterparts of Wilson operators in continuum field theories. We derive fusion and shrinking rules and the operators governing particle–loop and Borromean-Rings braiding. We demonstrate selective control of non-Abelian shrinking channels through the internal degrees of freedom of loop operators and establish fusion–shrinking consistency for arbitrary finite groups. An explicit correspondence between all 22 excitations of the $\mathbb{D}_4$ quantum double lattice model and the $BF+AAB$ theory preserves fusion and shrinking rules and particle–loop and Borromean-Rings braiding phases. These constructions place the continuum results on a microscopic lattice footing with tensor-product local Hilbert spaces and short-range interactions.
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All authors Yizhou Huang, Zhi-Feng Zhang, Qing-Rui Wang, Peng Ye