Quantum Physics
Novel Encodings of Homology, Cohomology, and Characteristic Classes
Itai Maimon
Topological
quantum error-correcting codes (QECC) encode a variety of topological invariants in their code space. A classic structure that has not been encoded directly is that of obstruction classes of a fiber bundle, such as the Chern or Euler class. Here, we construct and analyze extensions of toric codes. We then analyze the topological structure of their errors and finally construct a novel code using these errors to encode the obstruction class to a fiber bundle. In so doing, we construct an encoding of characteristic classes such as the Chern and Pontryagin class in topological QECC. An example of the Euler class of $S^2$ is constructed explicitly.
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Quantum Physics
Controlled growth of rare-earth-doped TiO$_{2}$ thin films on III-V semiconductors for hybrid quantum photonic interfaces
Henry C. Hammer, Caleb Whittier, Nathan A. Helvy et al. (+3 more)
Quantum photonic networks require two distinct functionalities: bright single-
photon sources and long-lived
quantum memories. III-V
semiconductor quantum dots excel as deterministic and coherent
photon emitters, while rare-earth ions such as erbium (Er$^{3+}$) in crystalline
oxides offer exceptional
spin and optical coherence at telecom wavelengths. Combining these systems and their functionalities via direct epitaxy is challenging due to
lattice mismatch and incompatible growth conditions. Here we demonstrate low-temperature pulsed
laser deposition of Er$^{3+}$-doped TiO$_{2}$ thin films directly on GaAs and GaSb substrates. Controlled surface preparation with an arsenic cap and an oxygen-deficient buffer layer enables the growth of epitaxial anatase TiO$_{2}$ (001) at 390$^{o}$C with sub-300 pm surface roughness, while avoiding interface degradation. In contrast, high-temperature
oxide desorption or growth temperatures drive the transition to rough, polycrystalline rutile film, as confirmed by transmission electron microscopy. Minimal coincident interface area (MCIA) modeling explains the orientation-selective growth on GaAs and GaSb. Raman and cryogenic photoluminescence excitation spectroscopy verify the
crystal phase and optical activation of Er$^{3+}$ ions. This multi-parameter growth strategy helps preserve III-V
quantum dot functionality and yields smooth surfaces suitable for low-loss nanophotonic structures. Our results establish a materials platform for monolithically integrating rare-earth
quantum memories with
semiconductor photon sources, paving the way toward scalable hybrid
quantum photonic chips.
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All authors Henry C. Hammer, Caleb Whittier, Nathan A. Helvy, Christopher Rouleau, Nabil D. Bassim, Ravitej Uppu
Quantum Physics
Realistic Gottesman-Kitaev-Preskill stabilizer states enable universal quantum computation
Fariba Hosseinynejad, Pavithran Iyer, Guillaume Dauphinais et al. (+1 more)
Physical Gottesman-Kitaev-Preskill (GKP) states are inherently noisy as ideal ones would require infinite energy. While this is typically considered as a deficiency to be actively corrected, this work demonstrates that imperfect GKP stabilizer states can be leveraged in order to apply non-Clifford gates using only linear optical elements. In particular, Gaussian operations on normalizable GKP states, combined with homodyne measurements, permit two key primitives: clean projection onto Pauli eigenstates in the normalizable GKP codespace, thereby implementing Clifford gates with high fidelity; and probabilistic projection of unmeasured modes onto non-Pauli eigenstates. These results demonstrate that normalizable GKP stabilizer states combined with Gaussian operations provide a practical framework for computational universality within the measurement-based model of
quantum computation in a realistic continuous-variable setting.
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All authors Fariba Hosseinynejad, Pavithran Iyer, Guillaume Dauphinais, David L. Feder
Quantum Physics
On universality of hardware-efficient ansatzes
Hokuto Iwakiri and Keita Kanno
The hardware-efficient ansatz (HEA) is one of the most important class of parametrized
quantum circuits for near-term applications of
quantum computing. We show that the problem of simulating some major classes of the HEA is BQP-complete by explicitly demonstrating that any relevant
quantum circuit can be efficiently represented as an HEA
circuit of those classes.
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Quantum Physics
Temporal entanglement transition in chaotic quantum many-body dynamics
Ilya Vilkoviskiy, Michael Sonner, Qi Camm Huang et al. (+3 more)
Temporal
entanglement (TE) of an influence
matrix (IM) has been proposed as a measure of complexity of simulating dynamics of local observables in a many-body system. Foligno et al. [Phys. Rev. X 13, 041008 (2023)] recently argued that the TE in chaotic 1d
quantum circuits obeys linear (volume-law) scaling with
evolution time. To reconcile this apparent high complexity of IM with the rapid thermalization of local observables, here we study the relation between TE, non-Markovianity, and local temporal correlations for chaotic
quantum baths. By exactly solving a random-
unitary bath model, and bounding distillable
entanglement between future and past degrees of freedom, we identify a regime where TE is extensive and reflects genuine non-Markovianity. This
memory, however, is entirely contained in highly complex temporal correlations, and its effect on few-point temporal correlators is negligible. An IM coarse-graining procedure, reducing the allowed frequency of measurements of the probe system, results in a transition from volume- to {subvolume- (area or logarithmic)} law TE scaling. We demonstrate the generality of this TE transition in 1d
circuits by analyzing the kicked Ising model analytically at dual-
unitary points, as well as numerically away from them. This finding indicates that dynamics of local observables are fully captured by a subvolume-law IM. We provide evidence that the compact IM MPS obtained via standard compression
algorithms accurately describes local~
evolution.
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All authors Ilya Vilkoviskiy, Michael Sonner, Qi Camm Huang, Wen Wei Ho, Alessio Lerose, Dmitry A. Abanin
Quantum Physics · Cross-listed from cond-mat.stat-mech
Quantum Inaccessibility
Ira Wolfson
Loschmidt's paradox asks why macroscopic irreversibility is universal despite the time-reversal
symmetry of microscopic dynamics. We argue that irreversibility is not a property of the dynamics but of accessibility: chaotic
evolution drives phase-space structure below the
quantum resolution scale $\ell_\hbar$, at a critical time $t_c = \lambda^{-1}\ln(\delta_0/\ell_\hbar)$, after which the time-reversed microstate exists as a valid solution of Hamilton's equations but cannot be selected by any physically admissible operation. The mechanism operates entirely within the semiclassical regime $t_c \leq t_E$, where classical geometry is exact. This provides a dynamical resolution of the Loschmidt paradox. The
quantum foundation is established using a Krylov-complexity framework: we prove that for any $H(t)=H(-t)$, the
quantum Lyapunov exponent satisfies $\lambda_L^{\rm forward} = \lambda_L^{\rm backward}$. The arrow of time is not in the dynamics. The mechanism predicts sigmoid fidelity decay, logarithmic scaling of $t_c$ with $\lambda^{-1}$, and ensemble-size independence of the inaccessibility threshold – all consistent with three decades of Loschmidt echo experiments and confirmed in a stadium-billiard simulation reported here. Underlying everything:
quantum mechanics conserves information exactly.
Entropy, defined as the logarithm of the multiplicity $\Omega$ – the number of possibilities consistent with the available information – can only increase when information becomes operationally inaccessible. The second law reflects not a breakdown of microscopic reversibility, but the dynamical inaccessibility of the information required to reverse it.
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Quantum Physics · Cross-listed from physics.ins-det
Quadrature-witness readout for backscatter mitigation in gravitational-wave detectors limited by back-action
Niels Böttner, Roman Schnabel and Mikhail Korobko
Disturbances in gravitational wave (GW) observational data are often caused by non-stationary noise in the detector itself, such as back-scattering of
laser stray light into the signal field. Unlike GW signals, non-stationary noise can appear in both the GW-signal quadrature and the orthogonal quadrature, which is usually not measured. Simultaneous sensing of this orthogonal quadrature provides a witness channel that can be used to reconstruct the disturbance in the signal quadrature enabling a subtraction of non-stationary noise. Here, we present the concept of quadrature witness that is compatible with frequency-dependent squeezing, which is already used to simultaneously reduce
photon shot noise and
photon radiation pressure noise. We demonstrate that implementing this approach in a GW detector could reduce noise caused by loud back-scatter events, thereby improving the overall sensitivity and robustness of GW observatories.
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Quantum Physics
Boltzmann Sampling of Frustrated J1 - J2 Ising Models with Programmable Quantum Annealers
Elijah Pelofske
One of the surprising, and potentially very useful, capabilities of analog
quantum computers, such as D-Wave
quantum annealers, is sampling from the Boltzmann, or Gibbs, distribution defined by a classical
Hamiltonian. In this study, we thoroughly examine the ability of D-Wave
quantum annealers to sample from the Boltzmann distribution defined by a canonical type of competing
magnetic frustration $J_1$-$J_2$ model; the 1-dimensional ANNNI (axial next-nearest-neighbor Ising) model. Boltzmann sampling error rate is quantified for standard linear-ramp anneals ranging from $5$ nanosecond annealing times up to $2000$ microseconds on two different D-Wave
quantum annealing processors. Interestingly, we find some analog hardware parameters which result in a very high accuracy (down to a TVD of $0.0003$) and low temperature sampling (down to $\beta=32.2$) in a frustrated region of the ANNNI model
magnetic phase diagram. This bolsters the viability of current analog
quantum computers for thermodynamic sampling applications of highly frustrated
magnetic spin systems.
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Quantum Physics · Cross-listed from hep-th
Holographic Black Hole Formation and Scrambling in Time-Ordered Correlators
Pratyusha Chowdhury, Felix M. Haehl, Adrián Sánchez-Garrido et al. (+1 more)
We describe a
holographic mechanism for black hole formation via the collision of two shock waves in three-dimensional anti-de Sitter spacetime. In the dual conformal field theory (CFT), a two-shock-wave state corresponds to the insertion of two boosted precursor operators in complementary Rindler patches. Their operator product expansion is initially described by a universal mean-field spectrum of exchanged states, which is dominated by operator dimensions that grow exponentially in the boost parameter. We propose their mean value as diagnosing the mass of the collision product in the bulk. It crosses the CFT heavy state threshold after two scrambling times, in accordance with expectations about black hole formation in general relativity. Our analysis also allows us to identify the scrambling characteristics usually associated with out-of-time-order correlation functions, using only the internal composition of thermal in-time-order correlators.
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All authors Pratyusha Chowdhury, Felix M. Haehl, Adrián Sánchez-Garrido, Ying Zhao
Quantum Physics · Cross-listed from cond-mat.stat-mech
Krylov Complexity Meets Confinement
Xuhao Jiang, Jad C. Halimeh and N. S. Srivatsa
In high-energy physics, confinement denotes the tendency of fundamental particles to remain bound together, preventing their observation as free, isolated entities. Interestingly, analogous confinement behavior emerges in certain condensed matter systems, for instance, in the Ising model with both transverse and longitudinal fields, where domain walls become confined into
meson-like bound states as a result of a longitudinal field-induced linear potential. In this work, we employ the Ising model to demonstrate that Krylov state complexity–a measure quantifying the spread of
quantum information under the repeated action of the
Hamiltonian on a
quantum state–serves as a sensitive and quantitative probe of confinement. We show that confinement manifests as a pronounced suppression of Krylov complexity growth following quenches within the
ferromagnetic phase in the presence of a longitudinal field, reflecting slow correlation dynamics. In contrast, while quenches within the paramagnetic phase exhibit enhanced complexity with increasing longitudinal field, reflecting the absence of confinement, those crossing the critical point to the
ferromagnetic phase reveal a distinct regime characterized by orders-of-magnitude larger complexity and display trends of weak confinement. Notably, in the confining regime, the complexity oscillates at frequencies corresponding to the
meson masses, with its power-spectrum peaks closely matching the semiclassical predictions.
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Quantum Physics · Cross-listed from hep-th
Cosmological Entanglement Entropy from the von Neumann Algebra of Double-Scaled SYK & Its Connection with Krylov Complexity
Sergio E. Aguilar-Gutierrez
We investigate
entanglement entropy between the pair of type II$_1$
algebras of the double-scaled SYK (DSSYK) model given a chord state, its
holographic interpretation as generalized horizon
entropy; particularly in the (anti-)de Sitter ((A)dS) space limits of the bulk dual; and its connection with Krylov complexity. The density
matrices in this formalism are operators in the
algebras, which are specified by the choice of global state; and there exists a trace to evaluate their von Neumann
entropy since the
algebras are commutants of each other, which leads to a notion of algebraic
entanglement entropy. We match it in triple-scaling limits to an area computed through a Ryu-Takayanagi formula in (A)dS$_2$ space with entangling surfaces at the asymptotic timelike or spacelike boundaries respectively; providing a first-principles example of
holographic entanglement entropy for (A)dS$_2$ space. This result reproduces the Bekenstein-Hawking and Gibbons-Hawking
entropy formulas for specific entangling regions points, while it decreases for others. This construction does not display some of the puzzling features in dS holography. The
entanglement entropy remains real-valued since the theory is
unitary, and it depends on the Krylov spread complexity of the Hartle-Hawking state. At last, we discuss higher dimensional extensions.
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Quantum Physics · Cross-listed from hep-th
Variations on a Theme of Krylov
Vijay Balasubramanian, Pawel Caputa and Joan Simón
Spread complexity uses the distribution of support of a time-evolving state in the Krylov basis to quantify dispersal across accessible dimensions of a
Hilbert space. Here, we describe how variations in initial conditions, the
Hamiltonian, and the dimension of the
Hilbert space affect spread complexity and Krylov basis structure. We introduce Koherence, the
entropy of coherence between perturbed and unperturbed Krylov bases, which can, e.g., quantify dynamical amplification of differences in initial conditions in chaos. To illustrate, we show that dynamics on SL(2,R), SU(2), and Heisenberg-Weyl group
manifolds, often used as paradigmatic settings for contrasting chaotic and integrable (semi-)classical behavior, display distinctively different responses to variations of the initial state or
Hamiltonian. We then describe a
lattice model that displays linear growth of spread complexity, saturating for bounded
lattices and continuing forever in a thermodynamic limit. The latter example illustrates a breakdown of continuum/classical effective descriptions of complexity growth in bounded
quantum systems.
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Quantum Physics
A Transferable Machine Learning Approach to Predict Quantum Circuit Parameters for Electronic Structure Problems
Davide Bincoletto, Korbinian Stein, Jonas Motyl et al. (+1 more)
The individual optimization of
quantum circuit parameters is currently one of the main practical bottlenecks in variational
quantum eigensolvers for electronic systems. To this end, several machine learning approaches have been proposed to mitigate the problem. However, such method predominantly aims at training and predicting parameters tailored to individual molecules: either a specific structure, or several structures of the same molecule with varying bond lengths. This work explores machine learning based modeling strategies to include transferability between different molecules. We use a well investigated
quantum circuit design and apply it to model properties of hydrogenic systems where we show parameter prediction that is systematically transferable to instances significantly larger than the training instances.
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All authors Davide Bincoletto, Korbinian Stein, Jonas Motyl, Jakob S. Kottmann
Quantum Physics · Cross-listed from physics.ed-ph
Introducing Quantum Computing into Statistical Physics: Random Walks and the Ising Model with Qiskit
Zihan Li, Dan A. Mazilu and Irina Mazilu
Quantum computing offers a powerful new perspective on probabilistic and collective behaviors traditionally taught in statistical physics. This paper presents two classroom-ready modules that integrate
quantum computing into the undergraduate curriculum using Qiskit: the
quantum random walk and the Ising model. Both modules allow students to simulate and contrast classical and
quantum systems, deepening their understanding of concepts such as superposition, interference, and statistical distributions. We outline the
quantum circuits involved, provide sample code and student activities, and discuss how each example can be used to enhance student engagement with statistical physics. These modules are suitable for integration into courses in statistical mechanics, modern physics, or as part of an introductory unit on
quantum computing.
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Quantum Physics
Realization of a Quantum Streaming Algorithm on Long-lived Trapped-ion Qubits
Pradeep Niroula, Shouvanik Chakrabarti, Steven Kordonowy et al. (+30 more)
Large classical
datasets are often processed in the streaming model, with data arriving one item at a time. In this model,
quantum algorithms have been shown to offer an unconditional exponential advantage in space. However, experimentally implementing such streaming
algorithms requires
qubits that remain coherent while interacting with an external data stream. In this work, we realize such a data-streaming model using Quantinuum Helios trapped-ion
quantum computer with long-lived
qubits that communicate with an external server. We implement a
quantum pair sketch, which is the primitive underlying many
quantum streaming
algorithms, and use it to solve Hidden Matching, a problem known to exhibit a theoretical exponential
quantum advantage in space. Furthermore, we compile the
quantum streaming
algorithm to fault-tolerant
quantum architectures based on surface and bivariate bicycle codes and show that the
quantum space advantage persists even with the overheads of fault-tolerance.
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All authors Pradeep Niroula, Shouvanik Chakrabarti, Steven Kordonowy, Niraj Kumar, Sivaprasad Omanakuttan, Michael A. Perlin, M.S. Allman, J.P. Campora III, Alex Chernoguzov, Samuel F. Cooper, Robert D. Delaney, Joan M. Dreiling, Brian Estey, Caroline Figgatt, Cameron Foltz, John P. Gaebler, Alex Hall, Ali A. Husain, Akhil Isanaka, Colin J. Kennedy, Nikhil Kotibhaskar, Ivaylo S. Madjarov, Michael Mills, Alistair R. Milne, Louis Narmour, Annie J. Park, Adam P. Reed, Kartik Singhal, Anthony Ransford, Justin G. Bohnet, Brian Neyenhuis, Rob Otter, Ruslan Shaydulin
Quantum Physics
Frequency shifts heralding ground state squeezing and entanglement of two coupled harmonic oscillators
Safoura Mirkhalaf, Helmut Ritsch and Karol Gietka
It is often argued that two linearly coupled
quantum harmonic oscillators, even when cooled to their ground state, display no inherently
quantum features beyond quantized energy levels. Here, we challenge this view by showing that their classical observables encode genuinely
quantum features. In particular, we demonstrate that the characteristic frequency shifts observed in coupled oscillators signal non-classical correlations and ground-state
entanglement at zero temperature corresponding to two-mode squeezing between the uncoupled modes. From a complementary perspective, these two effects, frequency shifts and squeezing, represent the same underlying phenomenon but expressed in different mode bases. What appears as a spectral renormalization in one description manifests itself as
entanglement in the other. Frequency shifts therefore constitute an
entanglement witness accessible via standard spectroscopy. While the underlying squeezing is not directly measurable, it can be exploited to enhance the signal-to-noise ratio in precision frequency measurements of individual oscillators without requiring squeezed
quantum noise. This uncovers a new route to
quantum-enhanced sensing within systems traditionally regarded as classical, offering fresh insight into how signatures of quantumness persists across the
quantum-to-classical boundary.
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Quantum Physics
Certified randomness amplification by dynamically probing remote random quantum states
Minzhao Liu, Pradeep Niroula, Matthew DeCross et al. (+49 more)
Cryptography depends on truly unpredictable numbers, but physical sources emit biased or correlated bits.
Quantum mechanics enables the amplification of imperfect randomness into nearly perfect randomness, but prior demonstrations have required physically co-located, loophole-free Bell tests, constraining the feasibility of remote operation. Here we realize certified randomness amplification across a network by dynamically probing large, entangled
quantum states on Quantinuum's 98-
qubit Helios trapped-ion
quantum processor. Our protocol is secure even if the remote device acts maliciously or is compromised by an intercepting adversary, provided the samples are generated quickly enough to preclude classical simulation of the
quantum circuits. We stream
quantum gates in real time to the
quantum processor, maintain
quantum state coherence for $\approx 0.9$ seconds, and then reveal the measurement bases to the
quantum processor only milliseconds before measurement. This limits the time for classical spoofing to 30 ms and constrains the location of hypothetical adversaries to a $4{,}500$ km radius. We achieve a fidelity of 0.586 on random
circuits with 64
qubits and 276 two-
qubit gates, enabling the amplification of realistic imperfect randomness with a low
entropy rate into nearly perfect randomness.
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All authors Minzhao Liu, Pradeep Niroula, Matthew DeCross, Cameron Foreman, Wen Yu Kon, Ignatius William Primaatmaja, M.S. Allman, J.P. Campora III, Akhil Isanaka, Kartik Singhal, Omar Amer, Shouvanik Chakrabarti, Kaushik Chakraborty, Samuel F. Cooper, Robert D. Delaney, Joan M. Dreiling, Brian Estey, Caroline Figgatt, Cameron Foltz, John P. Gaebler, Alex Hall, Zichang He, Craig A. Holliman, Travis S. Humble, Shih-Han Hung, Ali A. Husain, Yuwei Jin, Fatih Kaleoglu, Colin J. Kennedy, Nikhil Kotibhaskar, Nathan K. Lysne, Ivaylo S. Madjarov, Michael Mills, Alistair R. Milne, Kevin Milner, Louis Narmour, Sivaprasad Omanakuttan, Annie J. Park, Michael A. Perlin, Adam P. Reed, Chris N. Self, Matthew Steinberg, David T. Stephen, Joseph Sullivan, Alex Chernoguzov, Florian J. Curchod, Anthony Ransford, Justin G. Bohnet, Brian Neyenhuis, Michael Foss-Feig, Rob Otter, Ruslan Shaydulin
Quantum Physics
Singlet-Like Correlations: Equal Peak Work, Unequal Robustness
Karl Svozil
Initial system-environment correlations are a thermodynamic resource, enabling work extraction through their erasure. We compare three representative singlet-like, rotationally covariant correlation laws – a local classical
benchmark, the
quantum cosine law, and an idealized stronger-than-
quantum step law – under measurement misalignment. In the binary-outcome, uniform-marginal setting, all three can attain the same peak extractable work, k_{\mathrm B}T\ln 2. Their operational value differs, however, in robustness away from perfect
alignment. For the chosen classical
benchmark the mutual information degrades as \Theta(\delta\theta\ln(1/\delta\theta)), whereas for the
quantum cosine law it degrades as \Theta(\delta\theta^2\ln(1/\delta\theta)). The stronger-than-
quantum step law is perfectly flat except at a critical angle. Accordingly, the paper establishes a robustness hierarchy within this restricted comparison class, rather than a no-go
theorem for all classical correlations.
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Quantum Physics
Annual-modulation fingerprint of the axion wind induced sideband triplet in quantum dot spin qubit sensors
Xiangjun Tan and Zhanning Wang
We propose a phase-coherent, narrowband magnetometer for searching couplings between
axions or
axion-like particles (ALPs) and electron
spins, using gate-defined silicon
quantum-dot
spin qubits. With repeated Ramsey echo sequences and dispersive readout, the
qubit precession response can be tracked with sub-Hz spectral resolution. The accessible
axion mass window is determined using a series of filtering protocols that take into account sensing noise, including readout errors and $1/f$ noise. We demonstrate clear evidence of sidereal modulation of the signal due to Earth's rotation, while Earth's orbital motion produces an annual amplitude envelope that generates sidebands at fixed frequency spacing $\pm \Omega_\oplus$ around the sidereal component. For
axion masses between $1$-$10~\mu{\rm eV}$, the proposed method covers
axion-electron coupling strengths $g_{ae}$ ranging from $10^{-14}$ to $10^{-10}$. Including both daily and annual modulation patterns in the likelihood analysis enhances the rejection of stationary or instrumental noise. Our results indicate that
spin-
qubit magnetometry can achieve sensitivities approaching those suggested by astrophysical considerations, providing a complementary, laboratory-based probe of
axion-electron interactions. Although we focus on silicon
spin-
qubit architectures, the approach is broadly applicable to
spin-based
quantum sensors.
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Quantum Physics
Directional quantum walks of two bosons on the Hatano-Nelson lattice
Sk Anisur, Kartik Singh and Sayan Choudhury
We theoretically investigate the interplay of interactions and non-Hermiticity in the dynamics of two
bosons on the one-dimensional Hatano-Nelson
lattice with non-reciprocal tunneling. We find that the non-reciprocity in the tunneling leads to the formation of an asymmetric density cone during the time-
evolution of the system; the degree of asymmetry can be tuned by tuning the non-reciprocity parameter, $\delta$. Next, we analyze the dynamics of this system in the presence of a static external force and demonstrate that non-Hermiticity leads to asymmetric two-particle Bloch oscillations. Interestingly, when $F=0$ ($F \ne 0$), strong interactions leads to the formation of an inner density-cone (density-hourglass) structure; this inner structure also becomes asymmetric in the presence of non-Hermiticity. We further analyze the spatial correlations and establish that the system exhibits non-reciprocal bunching (anti-bunching) in the presence of weak (strong) interactions. Finally, we examine the growth of the
Quantum Fisher Information, $F_Q$, with time, and demonstrate that $F_Q \propto t^{\alpha}$ where $\alpha \sim 3$. This feature persists for both one- and two-particle walks, thereby demonstrating that this system can be employed as a
quantum-enhanced sensor for detecting weak forces.
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Quantum Physics · Cross-listed from nlin.PS
Stability of the Quantum Coherent Superradiant States in Relation to Exciton-Phonon Interactions and the Fundamental Soliton in Hybrid Perovskites
A. A. Gladkij, N. A. Veretenov, N. N. Rosanov et al. (+3 more)
The use of macroscopic coherent
quantum states at room temperature is crucial in modern
quantum technologies. In light of recent experiments demonstrating high-temperature superfluorescence in hybrid perovskite thin films, in this work we investigate the stability of the superradiant state concerning
exciton-
phonon interactions, taking into account the specifics of perovskites. We focused on quasi-2D Wannier
excitons interacting with longitudinal optical (LO)
phonons in polar
crystals, as well as with acoustic
phonons. Our study leads to the derivation of nonlinear equations in the coordinate space that govern the
exciton wavefunction's coefficient in the single-
exciton basis for the lowest
exciton state, which translates to the complex-valued polarization. The resulting equations take the form of a 2D nonlocal nonlinear Schrodinger (NLS) equation. We perform a linear stability analysis of the plane wave solutions for the equations in question, which allows us to establish stability criteria. This analysis is particularly important for evaluating the stability of the superradiant state in the considered quasi-2D structures, as the superradiant state represents a specific case of the plane wave solution. In scenarios involving the weakly nonlocal NLS equation, we find that it transitions into a purely nonlocal form. Furthermore, interactions between the
exciton and acoustic
phonons reduce the intensity of modulationally stable waves compared to the case without such interactions. Our analytical results are corroborated by numerical calculations. We also numerically solve the 2D nonlocal NLS equation in the polar coordinates and obtain its fundamental
soliton solution, which is stable.
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All authors A. A. Gladkij, N. A. Veretenov, N. N. Rosanov, B. A. Malomed, V. Al. Osipov, B. D. Fainberg
Quantum Physics
Spontaneous symmetry breaking in nonlinear superradiance
Nikolai D. Klimkin and Misha Ivanov
Creation and manipulation of non-classical states of light is rapidly becoming the focus of modern attosecond science. Here, we demonstrate numerically how interaction with such states can trigger the emergence of a many-body system with spontaneously broken
symmetry by considering a modification of the well-known problem of superradiance encountered already by Dicke. Similarly to him, we investigate
photon emission by ensembles of indistinguishable atoms. In contrast to him, however, we leverage
symmetry-based selection rules to suppress emission of single
photons by single atoms. A steady state is therefore only reached following a spontaneous transition into a collective
symmetry-broken state of atoms and photonic modes. This transition permanently locks the atomic dipoles to the
quantum field experienced by the system at a particular instant, transforming the entire setup into a potent
quantum sensor reproducing the phase of the recorded
quantum fluctuation.
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Quantum Physics · Cross-listed from physics.chem-ph
Encoding electronic ground-state information with variational even-tempered basis sets
Weishi Wang, Casey Dowdle and James D. Whitfield
We propose a system-oriented basis-set design based on even-tempered basis functions to variationally encode electronic ground-state information into molecular orbitals. First, we introduce a reduced formalism of concentric even-tempered orbitals that achieves hydrogen energy accuracy on par with the conventional formalism, with lower optimization cost and improved scalability. Second, we propose a
symmetry-adapted, even-tempered formalism specifically designed for molecular systems. It requires only primitive S-subshell Gaussian-type orbitals and uses two parameters to characterize all exponent coefficients. In the case of the diatomic hydrogen molecule, the basis set generated by this formalism produces a dissociation curve more consistent with cc-pV5Z than cc-pVTZ at the size of aug-cc-pVDZ. Finally, we test our even-tempered formalism against several types of tetra-atomic hydrogen molecules for ground-state computation and point out its current limitations and potential improvements.
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Quantum Physics
Atom-Field Non-Markovian Dynamics in Open and Dissipative Systems: An Efficient Memory-Kernel Approach Linked to Dyadic Greens Function and CEM Treatments
Hyunwoo Choi, Jisang Seo, Weng C. Chew et al. (+1 more)
In this work, we present a numerical framework for modeling single
photon emission from a two level system in open and dissipative systems beyond the Markovian approximation. The method can be readily integrated into standard computational electromagnetic (CEM) solvers such as finite difference time domain (FDTD) and finite element method (FEM). We numerically verify the completeness of boundary and medium assisted modes in the modified Langevin noise formalism by reconstructing the imaginary part of the dyadic Greens function through modal expansion in three dimensions. This reconstruction enables a first principles description of atom field interaction via the multi mode Jaynes Cummings model in open and dissipative environments. Within the single excitation
manifold, we show that the
memory kernel of a two level system is determined by the imaginary part of the Greens function, implying that radiative modes alone govern the relevant dynamics. The proposed framework thus provides a Greens function based approach for describing atomic population and single
photon dynamics, directly compatible with Maxwell solvers. We then present concrete strategies for implementing our method in both FDTD and FEM frameworks, demonstrating its practical applicability. We further verify numerical results for a lossy Lorentz Drude type mirror, including both the case of a TLS near a finite sized metallic mirror and that of a TLS centered in a Fabry Perot cavity. This work establishes a rigorous foundation for incorporating
quantum emitter dynamics into computational electromagnetics, thereby extending classical solvers toward
quantum light matter interactions.
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All authors Hyunwoo Choi, Jisang Seo, Weng C. Chew, Dong-Yeop Na
Quantum Physics
Quantum error mitigation using energy sampling and extrapolation enhanced Clifford data regression
Zhongqi Zhao, Erik Rosendahl Kjellgren, Sonia Coriani et al. (+3 more)
Error mitigation is essential for the practical implementation of
quantum algorithms on noisy intermediate-scale
quantum (NISQ) devices. This work explores and extends Clifford Data Regression (CDR) to mitigate noise in
quantum chemistry simulations using the Variational
Quantum Eigensolver (VQE). Using the H$_4$ molecule with the tiled
Unitary Product State (tUPS) ansatz, we perform noisy simulations with the ibm torino noise model to investigate in detail the effect of various hyperparameters in CDR on the error mitigation quality. Building on these insights, two improvements to the CDR framework are proposed. The first, Energy Sampling (ES), improves performance by selecting only the lowest-energy training
circuits for regression, thereby further biasing the sample energies toward the target state. The second, Non-Clifford Extrapolation (NCE), enhances the regression model by including the number of non-Clifford parameters as an additional input, enabling the model to learn how the noisy-ideal mapping evolves as the
circuit approaches the optimal one. Our numerical results demonstrate that both strategies outperform the original CDR.
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All authors Zhongqi Zhao, Erik Rosendahl Kjellgren, Sonia Coriani, Jacob Kongsted, Stephan P. A. Sauer, Karl Michael Ziems
Quantum Physics
The Converse Madelung Question
Jonathan R Dunkley
We pose the converse Madelung question: not whether Fisher information can reproduce
quantum mechanics, but whether it is necessary. We work with minimal, physically motivated axioms on density and phase: locality, probability conservation, Euclidean invariance with a global phase
symmetry, reversibility, and convex regularity. Within the resulting class of first order local
Hamiltonian field theories, these axioms single out the canonical Poisson bracket on density and phase under the Dubrovin and Novikov assumptions for local hydrodynamic brackets. Using a pointwise, gauge covariant complex change of variables that maps density and phase to a single complex field, we show that the only convex, rotationally invariant, first derivative local functional of the density whose Euler Lagrange term yields a reversible completion that is exactly projectively linear is the Fisher functional. When its coefficient equals Planck constant squared divided by twice the mass, the dynamics reduce to the linear Schrodinger equation. For many body systems, a single local complex structure across sectors enforces the same relation species by species, fixing a single Planck constant. Galilean covariance appears through the Bargmann central extension, with the usual superselection consequences. Comparison with the Doebner and Goldin family identifies the reversible zero
diffusion corner with linear Schrodinger dynamics. We provide operational falsifiers via residual diagnostics for the continuity and Hamilton Jacobi equations and report numerical minima at the Fisher scale that are invariant under Galilean boosts. In this setting,
quantum mechanics emerges as a reversible fixed point of Fisher regularised information hydrodynamics. A code archive enables direct numerical checks, including a superposition stress test that preserves exact projective linearity within our axioms.
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Quantum Physics
Mutually Unbiased Bases and Orthogonal Latin Squares – version 3
Stefan Joka
In this paper, we prove that the existence of a complete set of mutually unbiased bases (MUBs) in N-dimensional
Hilbert space implies the existence of a complete set of mutually orthogonal Latin squares (MOLSs) of order N. In particular, we prove that a complete set of MUBs does not exist in dimension six (the first dimension which is not a power of
prime).
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Quantum Physics · Cross-listed from cond-mat.str-el
Quantum effects in the magnon spectrum of 2D altermagnets via continuous similarity transformations
Raymond Wiedmann, Dag-Björn Hering, Vanessa Sulaiman et al. (+3 more)
We investigate
quantum effects on
magnon excitations in a minimal
spin-1/2 Heisenberg model for 2D altermagnets on the square
lattice. A continuous similarity transformation is applied in momentum space to derive an effective
Hamiltonian that conserves the number of
magnon excitations. This allows us to quantitatively calculate the one-
magnon dispersion, the effects of
magnon-
magnon interactions, and the dynamic structure factor in a certain range of parameters. In particular, we focus on the altermagnetic
spin splitting of the
magnon bands and the size of the roton minimum. We further map out divergencies of the continuous similarity transformation for different types of generators, which signal either the breakdown of the Néel-ordered phase or the presence of significant
magnon decay.
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All authors Raymond Wiedmann, Dag-Björn Hering, Vanessa Sulaiman, Matthias R. Walther, Kai P. Schmidt, Götz S. Uhrig
Quantum Physics · Cross-listed from cond-mat.other
Inertial Repulsion from Quantum Geometry
Maike Fahrensohn and R. Matthias Geilhufe
We derive a repulsive, charge-dipole-like interaction for a Dirac particle in a rotating frame, arising from a
geometric $U(1)$ gauge
symmetry associated with the Berry phase. The Lagrangian of this system includes a non-inertial correction due to centrifugal field coupling. By imposing gauge
symmetry and treating it as a full gauge theory, the Lagrangian is extended to include Berry connection and
curvature terms. Upon integrating out the
geometric gauge field, the effective action is obtained. This leads to the emergence of a repulsive, long-range effective interaction in the Lagrangian. Explicitly, in the non-inertial frame of the observer, the
geometric gauge invariance effectively leads to a repulsive Coulomb-interaction in momentum space. In real space, the inertial repulsion manifests in a $1/\vert r\vert^{2}$ potential, which is symmetric about the origin of rotation and mirrors charge-dipole interaction.
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Quantum Physics · Cross-listed from cond-mat.stat-mech
Integrability of a family of clean SYK models from the critical Ising chain
Kohei Fukai and Hosho Katsura
We establish the integrability of a family of Sachdev-Ye-Kitaev (SYK) models with uniform $p$-body interactions. We derive the R-
matrix and mutually commuting transfer
matrices that generate the
Hamiltonians of these models, and obtain their exact eigenspectra and eigenstates. Remarkably, the R-
matrix is that of the critical transverse-field Ising chain. This work reveals an unexpected connection between the SYK model, central to many-body
quantum chaos, and the critical Ising chain, a cornerstone of statistical mechanics.
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