Quantum Physics
Quantum circuit algorithm for topological invariants of second order topological many-body quantum magnets
Sebastián Domínguez-Calderón, Marcel Niedermeier, Jose L. Lado et al. (+1 more)
Topological
quantum matter represents a flexible playground to engineer unconventional excitations. While non-interacting topological single-particle systems have been studied in detail,
topology in
quantum many-body systems remains an open problem. Specifically, in the
quantum many-body limit, one of the challenges lies in the computational complexity of obtaining the many-body ground state and its many-body topological invariant. While
algorithms to compute ground states with
quantum computers have been heavily investigated,
algorithms to compute topological invariants in a
quantum computer are still under active development. Here we demonstrate a
quantum circuit to compute the many-body topological invariant of a second-order topological
quantum magnet encoded in
qubits. Our
algorithm relies on a
quantum circuit adiabatic
evolution in transverse paths in parameter space, and we uncover hidden topological invariants depending on the traversed path. Our work puts forward an
algorithm to leverage
quantum computers to characterize many-body topological
quantum matter.
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All authors Sebastián Domínguez-Calderón, Marcel Niedermeier, Jose L. Lado, Pascal M. Vecsei
Quantum Physics · Cross-listed from hep-lat
Higher lattice gauge theory from representations of 2-groups and 3+1D topological phases
Latévi M. Lawson and Prince K. Osei
We construct a higher
lattice gauge theory based on the representation of 2-groups described by a category of crossed modules on a
lattice model described by path 2-groupoids. Using these
lattice gauge representations, an exactly solvable
Hamiltonian for topological phases in 3+1 dimensions is constructed. We show that the ground states of this model are topological observables.
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Quantum Physics
Nonequilibrium quantum thermometry with noncommutative system-bath couplings
Youssef Aiache, Abderrahim El Allati, İlkay Demir et al. (+1 more)
Accurate temperature estimation in the
quantum and cryogenic regimes remains a fundamental challenge. Here, we investigate nonequilibrium
quantum thermometry using a single-
qubit probe coupled to a bosonic bath through noncommuting interaction operators, which unify pure dephasing and dissipative dynamics within a
spin-
boson model. We show that the interference between these two coupling channels induces strong non-Markovian feedback between populations and coherences, leading to coherence trapping and enhanced thermal sensitivity. Remarkably, by tuning the coupling structure, the probe's temperature sensitivity exhibits a quadratic low-temperature scaling, even under weak coupling. Moreover, while coherence-based measurements are formally suboptimal, they become the most informative in the early nonequilibrium regime, where
memory effects dominate. Our findings identify noncommutative system-bath couplings as a practical and tunable resource for achieving high-precision
quantum thermometry in realistic open-system architectures.
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All authors Youssef Aiache, Abderrahim El Allati, İlkay Demir, Khadija El Anouz
Quantum Physics
Input phase noise in Gaussian Boson sampling
Magdalena Parýzková, Craig S. Hamilton, Igor Jex et al. (+2 more)
Gaussian
boson sampling is an important protocol for testing the performance of photonic
quantum simulators. As such, various noise sources have been investigated that degrade the operation of such devices. In this paper, we examine a situation with phase noise between different modes of the input state leading to dephasing of the system. This models the phase fluctuations which remain even when the mean phase is controlled. We aim to determine whether these phase-noisy input states still form a computationally difficult problem. To do this, we use
Matrix Product Operators to model the system, a technique recently used to model
boson sampling scenarios. Our investigation finds that the
Entanglement entropy grows linearly with the number of input states even for noisy input states. This implies that, unlike
boson loss, this form of experimentally relevant noise remains difficult to simulate with tensor networks and may allow for the demonstration of
quantum advantage without the need for implementing the challenging task of input-state phase stabilisation.
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All authors Magdalena Parýzková, Craig S. Hamilton, Igor Jex, Michael Stefszky, Christine Silberhorn
Quantum Physics
Extracting quantum field theory dynamics from an approximate ground state
Sophie Mutzel and Antoine Tilloy
We develop a linear-programming method to extract dynamical information from static ground-state correlators in
quantum field theory. We recast the Källén-Lehmann inversion as a convex optimization problem, in a spirit similar to the recent approach of Lawrence [arXiv:2408.11766]. This produces robust estimates of the smeared spectral density, the real-time propagator, and the mass gap directly from an approximate equal-time two-point function, and simultaneously yields an a posteriori lower bound on the correlation-function error. We test the method on the $1+1$-dimensional $\phi^4$ model, using a variational approximation to the
vacuum – relativistic continuous
matrix product states – that provides accurate correlators in the continuum and thermodynamic limits. The resulting mass gaps agree with renormalized
Hamiltonian truncation and Borel-resummed perturbation theory across a wide range of couplings, demonstrating that accurate dynamical data can be recovered from a single equal-time slice.
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Quantum Physics
Trigonometric continuous-variable gates and hybrid quantum simulations of the sine-Gordon model
Tommaso Rainaldi, Victor Ale, Matt Grau et al. (+5 more)
Hybrid
qubit-qumode
quantum computing platforms provide a natural setting for simulating interacting bosonic
quantum field theories. However, existing continuous-variable gate constructions rely predominantly on
polynomial functions of canonical quadratures. In this work, we introduce a complementary universality paradigm based on trigonometric continuous-variable gates, which enable a
Fourier-like representation of bosonic operators and are particularly well suited for periodic and non-perturbative interactions. We present a deterministic ancilla-based method for implementing
unitary and non-
unitary trigonometric gates whose arguments are arbitrary Hermitian functions of qumode quadratures. As a concrete application, we develop a hybrid
qubit-qumode
quantum simulation of the
lattice sine-Gordon model. Using these gates, we prepare ground states via
quantum imaginary-time
evolution, simulate real-time dynamics, compute time-dependent vertex two-point correlation functions, and extract
quantum kink profiles under topological boundary conditions. Our results demonstrate that trigonometric continuous-variable gates provide a physically natural framework for simulating interacting field theories on near-term hybrid
quantum hardware, while establishing a parallel route to universality beyond
polynomial gate constructions. We expect that the trigonometric gates introduced here to find broader applications, including
quantum simulations of condensed matter systems,
quantum chemistry, and biological models.
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All authors Tommaso Rainaldi, Victor Ale, Matt Grau, Dmitri Kharzeev, Enrique Rico, Felix Ringer, Pubasha Shome, George Siopsis
Quantum Physics
A Spin-Photon Interface in the Telecom C-Band with Long Hole Spin Dephasing Time
Johannes M. Michl, Reza Hekmati, Mohamed Helal et al. (+9 more)
Matter
qubits that maintain coherence over extended timescales are essential for many pursued applications in
quantum communication and
quantum computing. Significant progress has already been made on extending coherence times of
spins in
semiconductor quantum dots while interfacing them with
photons in the near-infrared wavelength range. However, similar results for
quantum dots emitting at the telecom range, crucial for many applications, have so far lagged behind. Here, we report on InAs/InAlGaAs
quantum dots integrated in a deterministically placed circular Bragg grating emitting at $1.55\,\mu\mathrm{m}$. We quantify the g-factors of electrons and holes from polarization-resolved measurements of a positive trion in an in-plane
magnetic field and study the dynamics of the ground-state hole
spin qubit. We then herald the hole
spin in a pulsed two-
photon correlation measurement and determine its inhomogeneous dephasing time to $T_{2}^{*}=(15.9 \pm 1.7)$ ns.
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All authors Johannes M. Michl, Reza Hekmati, Mohamed Helal, Giora Peniakov, Yorick Reum, Jochen Kaupp, Quirin Buchinger, Jaewon Kim, Andreas T. Pfenning, Yong-Hoon Cho, Sven Höfling, Tobias Huber-Loyola
Quantum Physics
$W$- and Dicke-state engineering using optimal global control in nearest-neighbor coupled ring-shaped qubit arrays
Andrea Muratori, Vladimir M. Stojanovic, Eloisa Cuestas et al. (+2 more)
Motivated by a compelling need for time-efficient and robust schemes for
quantum-state engineering in systems of neutral atoms in optical tweezers, we consider a ring-shaped array of
qubits with nearest-neighbor Ising-type ($zz$) coupling and transverse ($x$ and $y$) global control fields. This system to a large extent mimics – outside of the Rydberg-blockade regime – a circular array of neutral atoms interacting through van-der-Waals type interaction. We investigate the preparation of $W$ and Dicke states in this system starting from the default initial state $|00\ldots 0\rangle$ using two different optimal-control approaches: (i) NMR-like pulse sequence, which consists of instantaneous (delta-shaped) control- and Ising-interaction pulses, and (ii) time-dependent control scheme, which entails shaped control pulses in the presence of always-on Ising interaction between adjacent
qubits. By making use of the underlying dihedral
symmetry of this system – which allows one to use a
symmetry-adapted computational basis with $\mathcal{O}(2^N / N)$ states in an $N$-
qubit system – and utilizing advanced global-optimization methods, we find optimal sequences of pulses for realizing $W$ and Dicke states within both approaches. In addition, we demonstrate robustness of these sequences against unavoidable control errors. Finally, using typical values of parameters in realistic Rydberg-atom systems, we show that our control schemes enable the preparation of the desired multiqubit states on time scales much shorter than the relevant coherence times of those systems.
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All authors Andrea Muratori, Vladimir M. Stojanovic, Eloisa Cuestas, Tommaso Calarco, Felix Motzoi
Quantum Physics · Cross-listed from cond-mat.mes-hall
Spin Response of a Magnetic Monopole and Quantum Hall Response in Topological Lattice Models through Local Invariants and Light
Karyn Le Hur and Andrea Baldanza
Here, we elaborate on and develop the geometrical approach introduced in K. Le Hur, Physics Reports 1104 1-42 (2025) between the
magnetic monopole created from a radial field,
quantum physics and topological
lattice models through
quantum phase transitions. We introduce an effective
magnetic moment for a monopole when applying an additional source field along z-direction which also mediates the
quantum phase transition. We present its relation with the transverse pumped
quantum Hall current. The
magnetic susceptibility can be introduced as a measure of the topological invariant i.e. it remains quantized within the topological phase until the transition. We show the relation with two-dimensional topological
lattice models such as a honeycomb Haldane model in real space. We develop the theory and present a numerical analysis between local invariants in momentum space introduced from Dirac points, correlation functions and the responses to circularly polarized light. We develop the formalism for coupled-planes materials including the possibility of
quantum spin Hall effect and address a relation between the Ramanujan infinite alternating series and an interface in real space with a topological number one-half.
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Quantum Physics
Harnessing non-Hermiticity for efficient quantum state transfer
Sejal Ahuja, Keshav Das Agarwal and Aditi Sen De
The non-Hermitian
Hamiltonian describes the effective dynamics of a system coupled to a continuously measured bath, and can exhibit anti-
unitary symmetries that give rise to exceptional points and broken phases with complex
eigenvalues, features unique to non-Hermitian systems. Going beyond conventional Hermitian physics, we analyze the impact of non-Hermiticity in the
quantum state transmission by employing a non-Hermitian
spin chain that functions as a
quantum data bus. By deriving a general expression for the fidelity of
quantum state transfer for a U(1)-symmetric non-Hermitian
Hamiltonian, we analyze PT-symmetric XX and SSH models, complemented by a numerical study of the RT-symmetric iXY model. We demonstrate that, in several parameter regimes, the transfer fidelity in the non-Hermitian setting exceeds the classical threshold and can even exceed the performance of the corresponding Hermitian models. In particular, for the SSH model with dominant inter-
cell coupling, the broken phase supports near-unit-fidelity
quantum state transfer, a level of performance that the corresponding Hermitian model fails to attain. Moreover, we establish a correspondence between the non-Hermitian and Hermitian descriptions by identifying related parameter regions in which the fidelity fails to surpass the classical bound.
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Quantum Physics · Cross-listed from math-ph
Open Quantum Systems as Regular Holonomic $\mathcal{D}$-Modules: The Mixed Hodge Structure of Spectral Singularities
Prasoon Saurabh
The
geometric description of open
quantum systems via the
Quantum Geometric Tensor (QGT) traditionally relies on the assumption that the physical states form a differentiable vector bundle over the parameter
manifold. This framework becomes ill-posed at spectral singularities, such as Exceptional Points, where the eigen-bundle admits no local trivialization due to dimension reduction. In this work, we resolve this obstruction by demonstrating that the family of Liouvillian superoperators $\mathcal{L}(k)$ over a complex parameter
manifold $X$ canonically defines a \textbf{regular holonomic $\mathcal{D}_X$-module} $\mathcal{M}$. By identifying the physical coherence order with the Hodge filtration and the decay rate hierarchy with the Kashiwara filtration, we show that the open
quantum system underlies a Mixed Hodge Module (MHM) structure in the sense of Saito. This identification allows us to apply the Grothendieck six-functor formalism rigorously to dissipative dynamics. We prove that the divergence corresponds to a non-trivial
cohomology class in $\text{Ext}^1_{\mathcal{D}_X}$, thereby regularizing the
Quantum Geometric Tensor without ad-hoc cutoffs. Specifically, the “singular component” of the Complete QGT arises as the residue of the connection on the Brieskorn
lattice associated with the vanishing cycles functor.
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Quantum Physics · Cross-listed from hep-ph
Analytical study of birefringent cavities for axion-like dark matter search
Tadashi Kuramoto, Yasutaka Imai, Takahiko Masuda et al. (+3 more)
Light polarization plays a crucial role in optical-cavity experiments; however, mirror birefringence presents a significant challenge that must be addressed carefully. In this study, a rigorous, nonperturbative framework is developed to quantify birefringence effects by incorporating variations in reflectance and polarization misalignment. We analyze the impact of this framework on the sensitivity of
axion-like particle (ALP) dark-matter searches. The results show that both birefringence and misalignment contribute to sensitivity degradation in the low-mass regime; however, the adverse effects of misalignment can be mitigated by selecting a postselection angle greater than the misalignment angle. Furthermore, birefringence produces an additional resonance peak in the high-mass region, which remains largely unaffected by misalignment and postselection variations. This rigorous framework underscores the importance of considering birefringence in high-precision optical-cavity experiments for ALP detection.
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All authors Tadashi Kuramoto, Yasutaka Imai, Takahiko Masuda, Yutaka Shikano, Sayuri Takatori, Satoshi Uetake
Quantum Physics · Cross-listed from hep-th
Holographic Tensor Networks as Tessellations of Geometry
Qiang Wen, Mingshuai Xu and Haocheng Zhong
Holographic tensor networks serve as toy models for the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence, capturing many of its essential features in a concrete manner. However, existing
holographic tensor network models remain far from a complete theory of
quantum gravity. A key obstacle is their discrete structure, which only approximates the semi-classical geometry of
gravity in a qualitative sense. In \cite{Lin:2024dho}, it was shown that a network of partial-
entanglement-
entropy (PEE) threads, which are bulk geodesics with a specific density distribution, generates a perfect tessellation of AdS space. Moreover, such PEE-network tessellations can be constructed for more highly symmetric geometries using the Crofton formula. In this paper, we assign a
quantum state to each vertex in the PEE network and develop several
holographic tensor network models: (1) the factorized PEE tensor network, which takes the form of a tensor product of EPR pairs; (2) the HaPPY-like PEE tensor network constructed from perfect tensors; and (3) the random PEE tensor network. In all these models, we reproduce the exact Ryu-Takayanagi formula by showing that the minimal number of cuts along a homologous surface in the network exactly equals the area of that surface.
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Quantum Physics
Generative Krylov Subspace Representations for Scalable Quantum Eigensolvers
Changwon Lee and Daniel K. Park
Predicting ground state energies of
quantum many-body systems is one of the central computational challenges in
quantum chemistry, physics, and materials science. Krylov subspace methods, such as Krylov
Quantum Diagonalization and Sample-based Krylov
Quantum Diagonalization, are promising approaches for this task on near-term
quantum computers. However, both require repeated
quantum circuit executions for each Krylov subspace and for every new
Hamiltonian, posing a major bottleneck under noisy hardware constraints. We introduce Generative Krylov Subspace Representations (GenKSR), a framework that learns a classical generative representation of the entire Krylov diagonalization process. To enable effective modeling of
quantum systems, GenKSR leverages a conditional generative model framework. We investigate two representative backbone architectures, the standard
Transformer and the Mamba state-space model. By learning the distribution of measurement outcomes conditioned on
Hamiltonian parameters and
evolution time, GenKSR generates Krylov subspace samples for unseen
Hamiltonians and for larger subspace dimensions than those used in training. This enables full energy reconstruction purely from the classical model, without additional
quantum experiments. We validate our approach through simulations of 15-
qubit 1D and 16-
qubit 2D Heisenberg models, as well as a hardware experiment on a 20-
qubit XXZ chain executed on an IBM
quantum processor. Our model successfully learns the distribution from experimental data and generates a high-fidelity representation of the
quantum process. This representation enables classical reproduction of experimental outcomes, supports reliable energy estimates for unseen
Hamiltonians, and significantly reduces the need for further
quantum computation.
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Quantum Physics
Clifford Volume and Free Fermion Volume: Complementary Scalable Benchmarks for Quantum Computers
Attila Portik, Orsolya Kálmán, Thomas Monz et al. (+1 more)
As
quantum computing advances toward the late-NISQ and early fault-tolerant eras, scalable and platform-independent
benchmarks are essential for quantifying computational capacity in a classically verifiable manner. We introduce two volumetric
benchmarks, Clifford Volume and Free
Fermion Volume, that assess
quantum hardware by testing the execution of random Clifford and free
fermion operations. These two groups of
unitaries possess a combination of properties that make them ideal for benchmarking: (i) each is individually efficient to simulate classically, enabling verification at scale; (ii) together they form a universal gate set; (iii) they serve as essential algorithmic primitives in practical applications (including shadow
tomography and
quantum chemistry); and (iv) their definitions are formulated abstractly, without explicit reference to hardware-specific features such as
qubit connectivity or native gate sets. This framework thus enables scalable and fair cross-platform comparisons and tracks meaningful computational advancement. We demonstrate the practical feasibility of these
benchmarks through extensive numerical simulations across realistic noise parameters and through experimental validation on Quantinuum's H2-1 trapped-ion
quantum computer, which achieves a Clifford Volume of 34.
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All authors Attila Portik, Orsolya Kálmán, Thomas Monz, Zoltán Zimborás
Quantum Physics · Cross-listed from cond-mat.mtrl-sci
Ab initio prediction of strain-tunable spin defects in quasi-1D TiS3 and NbS3 nanowires
Jordan Chapman, Arindom Nag, Thang Pham et al. (+1 more)
Defects in atomically thin van der Waals materials have recently been investigated as sources of
spin-
photon entanglement with sensitivity to strain tuning. Unlike many two-dimensional materials, quasi-one-dimensional materials such as transition metal trichalcogenides exhibit in-plane anisotropy resulting in axis-dependent responses to compressive and tensile strains. Herein, we characterize the tunable
spin and optical properties of intrinsic vacancy defects in titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires. Within our ab initio approach, we show that sulfur vacancies and divacancies (VS and VD , respectively) in TiS3 and NbS3 adopt strain-dependent defect geometries between in-plane strains of -3 % and 3 %. The calculated electronic structures indicate that both VS and VD possess in-gap defect states with optically bright electronic transitions whose position relative to the conduction and valence bands varies with in-plane strain. Further, our calculations predict that VS in TiS3 and VD in NbS3 exhibit transitions in their ground state
spins; specifically, a compressive strain of 0.4 % along the direction of nanowire growth causes a shift from a triplet state to a singlet state for the VS defect in TiS3, whereas a tensile strain of 2.9 % along the same direction in NbS3 induces a triplet ground state with a zero-
phonon line of 0.83 eV in the VD defect. Our work shows that the anisotropic geometry of TiS3 and NbS3 nanowires offers exceptional tunability of optically active
spin defects that can be used in
quantum applications.
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All authors Jordan Chapman, Arindom Nag, Thang Pham, Vsevolod Ivanov
Quantum Physics · Cross-listed from physics.optics
A deterministic approach for integrating an emitter in a nanocavity with subwavelength light confinement
Valdemar Bille-Lauridsen, Rasmus Ellebæk Christiansen, Yi Yu et al. (+1 more)
We introduce a novel light-matter interface that integrates a nanoscale buried
heterostructure emitter into a dielectric bowtie cavity, co-localising the optical hotspot and the electronic wavefunction. This platform enables strong light-matter interaction through deep subwavelength confinement while remaining compatible with scalable fabrication. We show that in this regime an explicit treatment of the emitter's spatial extent is required, and that a confinement-factor approximation more accurately predicts the coupling, revealing design rules inaccessible to dipole-based metrics. For an InP/InGaAsP system, we predict coupling strengths of 0.4-0.7 meV for gap sizes of 50-10 nm, establishing the buried
heterostructure-bowtie architecture as a practical route to deterministic strong coupling in solid-state nanophotonics.
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All authors Valdemar Bille-Lauridsen, Rasmus Ellebæk Christiansen, Yi Yu, Jesper Mørk
Quantum Physics · Cross-listed from physics.ins-det
Talking with a ghost: semi-virtual coupled levitated oscillators
Ronghao Yin, Yugang Ren, Deok Young Seo et al. (+4 more)
Mesoscopic particles levitated by optical, electrical or
magnetic fields act as mechanical oscillators with a range of surprising properties, such as tuneable oscillation frequencies, access to rotational motion, and remarkable quality factors. Coupled levitated particles display rich dynamics and non-reciprocal interactions, with applications in sensing and the exploration of non-
equilibrium and
quantum physics. In this work, we present a single levitated particle displaying coupled-oscillator dynamics by generating an interaction with a virtual or “ghost” particle. This ghost levitated particle is simulated on an analogue computer, and its properties can thus be dynamically varied. Our work represents a new angle on measurement-based bath engineering and physical simulation and, in the future, could lead to the generation of novel cooling mechanisms and complex physical simulation.
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All authors Ronghao Yin, Yugang Ren, Deok Young Seo, Anoushka Sinha, Jonathan D. Pritchett, Qiongyuan Wu, James Millen
Quantum Physics
Lorentz Invariant Master Equation for Quantum Systems
Pranav Vaidhyanathan and Gerard J. Milburn
Irreversibility implies a preferred flow of time, yet special relativity denies the existence of a preferred clock. This tension has long obstructed the formulation of a relativistic master equation: standard Markovian approximations either break Lorentz covariance, trigger catastrophic
vacuum heating, or depend arbitrarily on the observer's foliation. In this work, we derive a Lorentz-invariant description of irreversibility for
quantum fields. We take an approach that explicitly models the measurements required to observe irreversible dynamics. Instead of evolving the system along an abstract
geometric time parameter, we anchor the dynamics to a physical, relational scalar clock field. Using a relational Tomonaga-Schwinger framework, we derive a local, non-Markovian master equation that is manifestly covariant and completely positive. We show that the finite resolution of the physical clock acts as a covariant regulator, preventing the
vacuum instability that plagues white-noise models. This framework demonstrates that a consistent relativistic theory of decay exists, provided the reference frame is treated as a dynamical
quantum resource rather than a gauge choice. In a gravitating context, the resulting dynamics is described by a hybrid classical-
quantum (CQ)
evolution that remains completely positive and trace preserving (CPTP).
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Quantum Physics
The Perspectives of Non-Ideal Quantum Reference Frames
Sébastien Christophe Garmier, Ladina Hausmann and Esteban Castro-Ruiz
We define the perspective of any
quantum reference frame (QRF) and construct reversible transformations between different perspectives. Our construction is based on two principles motivated operationally by the change from relative to absolute coordinates and leads to an incoherent group averaging approach with general
symmetry group. Thereby, it extends the framework of [arXiv:2110.13199] from ideal QRFs, which generally require infinite resources like energy or angular momentum, to non-ideal QRFs, with only finite resources. We find that the perspective of a non-ideal QRF deviates significantly from that of an ideal QRF: Firstly, systems described relative to a non-ideal QRF appear superselected. Secondly, the structure of the perspective of a non-ideal QRF attests that successive relational operations on a system lead to back-reaction on this QRF.
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Quantum Physics
EMU circulation planning for Silesian Railways: case study and a quantum approach
Ewa Kędziera, Wojciech Gamon, Mátyás Koniorczyk et al. (+3 more)
We study daily rolling stock circulation planning for electric multiple units (EMUs) on a regional passenger network, focusing on services where identical EMUs may be coupled in pairs on selected routes. Motivated by the operational needs of the regional operator Silesian Railways in Poland, we formulate an acyclic mixed-integer linear program on a one-day horizon that incorporates depot balance constraints, demand-driven seat and bicycle capacity limits, and simple crew availability constraints. Using a graph/hyper-graph representation of train movements, we first solve an ILP formulation. We then derive a Quadratic Unconstrained Binary Optimization (QUBO) reformulation and evaluate its solution by
quantum annealing on D-Wave Advantage systems and by the classical
quantum-inspired VeloxQ solver. In computational experiments on real-world instances from the Silesian network, with up to 404 train trips and 11 EMU types, the ILP approach yields high-quality daily circulation plans within at most about 40 minutes. The
quantum and
quantum-inspired solvers are restricted to substantially smaller sub-instances due to the large number of terms in the QUBO and
embedding limitations in the case of
quantum hardware. These results quantify the present frontier of QUBO-based methods for rolling stock circulation. They can be helpful in designing a hybrid classical-
quantum approach.
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All authors Ewa Kędziera, Wojciech Gamon, Mátyás Koniorczyk, Zakaria Mzaouali, Andrea Galadíková, Krzysztof Domino
Quantum Physics · Cross-listed from cs.CR
Protecting Quantum Circuits Through Compiler-Resistant Obfuscation
Pradyun Parayil, Amal Raj and Vivek Balachandran
Quantum circuit obfuscation is becoming increasingly important to prevent theft and reverse engineering of
quantum algorithms. As
quantum computing advances, the need to protect the intellectual property contained in
quantum circuits continues to grow. Existing methods often provide limited defense against structural and statistical analysis or introduce considerable overhead. In this paper, we propose a novel
quantum obfuscation method that uses randomized U3 transformations to conceal
circuit structure while preserving functionality. We implement and assess our approach on QASM
circuits using Qiskit AER, achieving over 93% semantic accuracy with minimal runtime overhead. The method demonstrates strong resistance to reverse engineering and structural inference, making it a practical and effective approach for
quantum software protection.
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Quantum Physics
Spectral Gap Estimation via Adiabatic Preparation
Davide Cugini, Francesco Ghisoni, Angela Rosy Morgillo et al. (+1 more)
Estimating energy gaps, i.e. the energy difference between two different states, in
quantum systems is crucial for understanding their properties. Conventionally, spectral gap estimation relies on independently computing the ground-state and first-excited-state energies and then taking their difference. This work introduces an alternative procedure for estimating spectral gaps on digital
quantum devices using the Adiabatic Preparation technique to create a specific superposition state. The expectation values of observables measured on such a state exhibit time-dependent fluctuations which, through a fitting process, can be used to estimate the energy gap. We successfully test our method on the 1D and 2D Ising models, and H2 and He2 molecules, implementing relatively shallow
circuits both on noiseless and noisy simulators. The robustness of the approach is corroborated by additional experiments on the real IonQ Aria device for the 1D Ising model up to 20
qubits, demonstrating the applicability of the proposed method for currently available digital
quantum devices and paving the way for more complex energy gap calculation requiring deeper
circuits in the fault-tolerant era to come.
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All authors Davide Cugini, Francesco Ghisoni, Angela Rosy Morgillo, Francesco Scala
Quantum Physics
Sonified Quantum Seizures. Sonification of time series in epileptic seizures and simulation of seizures via quantum modelling
Maria Mannone, Paulo Vitor Itaborai, Omar Costa Hamido et al. (+4 more)
We apply sonification strategies and
quantum computing to the analysis of an episode of seizure. We first sonify the signal from a selection of channels (from real ECoG data), obtaining a polyphonic sequence. Then, we propose two
quantum approaches to simulate a similar episode of seizure, and we sonify the results. The comparison of sonifications can give hints on similarities and discrepancies between real data and simulations, helping refine the in silico model. This is a pioneering approach, showing how the combination of
quantum computing and sonification can broaden the perspective of real-data investigation, and helping define a new test bench for analysis and prediction of seizures.
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All authors Maria Mannone, Paulo Vitor Itaborai, Omar Costa Hamido, Miriam Goldack, Norbert Marwan, Peppino Fazio, Patrizia Ribino
Quantum Physics
Limitations of Entangled Two-Photon Absorption detection
René Pollmann, Franz Roeder, Christine Silberhorn et al. (+1 more)
We introduce a method for determining the sensitivity of any given Entangled Two-
Photon Absorption (ETPA) measurement. By modeling all signal and noise contributions to the measurement, we derive a single numerical value that describes the sensitivity of the ETPA measurement in Göppert-Mayer units. This allows us to directly compare vastly different experimental approaches and, determine whether ETPA will be detectable under the given conditions. Therefore, we can quantify the effect of any change to a given experimental apparatus and identify the ideal optimization pathway.
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All authors René Pollmann, Franz Roeder, Christine Silberhorn, Benjamin Brecht
Quantum Physics
Quantifying superluminal signalling in Schrödinger-Newton model
Julia Osęka-Lenart, Marcin Płodzień, Maciej Lewenstein et al. (+1 more)
The Schrödinger-Newton equation aims at describing the dynamics of massive
quantum systems subject to the gravitational self-interaction. As a deterministic nonlinear
quantum wave equation, it is generally believed to conflict with the relativistic no-signalling principle. Here we challenge this viewpoint and show that it is of key importance to study the quantitative and operational character of the superluminal effects. To this end we employ a rigorous formalism of probability measures on spacetime and quantify the probability of a successful superluminal bit transfer via the single-particle Schrödinger-Newton equation. We demonstrate that such a quantity decreases with the increasing size and mass of the system. Furthermore, we prove that the Einstein-Dirac system, which yields the Schrödinger-Newton equation in the non-relativistic limit, is perfectly compatible with the relativistic causal structure. Our study demonstrates that the Schrödinger-Newton equation, which is by construction non-relativistic, is in fact `more compatible' with the no-signalling principle than the ordinary free Schrödinger equation.
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All authors Julia Osęka-Lenart, Marcin Płodzień, Maciej Lewenstein, Michał Eckstein
Quantum Physics · Cross-listed from physics.optics
Optical parametric free-electron–photon quantum interaction
Zetao Xie, Zehai Pang and Yi Yang
Optical parametric processes underpin
quantum photonics, while free-electron–
photon interactions offer agile pathways to generate nontrivial
quantum photonic states. These threads have so far largely progressed independently, whereas placing free electrons in a driven nonlinear system can potentially activate coherent parametric interaction channels for joint state engineering of both types of particles. Here we unify these paradigms by developing a general theoretical framework for parametric free-electron–
photon interactions in a nonlinear optical system driven by degenerate parametric down-conversion. Unlike free electrons in a linear bath, here they can couple to Bogoliubov quasiparticles through two detuned phase-matching channels, where the parametric process and free-electron interactions can
quantum amplify each other. Seeding the interaction with squeezed
vacuum yields gain-only or loss-only electron energy spectra, and enables electron-heralded squeezed Fock states; with bare
vacuum, postselecting electron energy sidebands generates high-fidelity Schrödinger cat states. Our results show how optical parametric interactions can
quantum shape free electrons and
photons, potentially enabling a
quantum parametric dielectric
laser accelerator that mitigates the need for temporal phase synchronization, thereby allowing acceleration probabilities to approach unity even for phase-random electrons.
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Quantum Physics
Learning Hamiltonians for $O(1)$ Oracle-Query Quantum State Preparation
Sadegh Salami, Mohammad T. Manzuri, Mehdi Ramezani et al. (+3 more)
We propose a
Hamiltonian-based
quantum state preparation method implemented via a shallow parametrized
quantum circuit. The approach learns the parameters of a diagonal
Hamiltonian through a classical training phase, while the
quantum circuit itself performs only fixed-depth
Hamiltonian evolution and mixing operations. With oracle access to the learned
Hamiltonian parameters, $N$ classical data values can be encoded into $n=\log_2{N}$
qubits using $O(1)$
quantum queries, shifting the overall computational cost to an $O(N\log{N})$ classical preprocessing stage. For structured
datasets generated by an underlying function, oracle access can be avoided by expressing the
Hamiltonian in the Walsh basis and retaining only a
polynomial number of significant terms. In this regime,
quantum state preparation is achieved in $\text{poly}(n)$ time using $\text{poly}(n)$ parameters, reaching infidelities on the order of $10^{-5}$. By restricting the
Hamiltonian to one-local and two-local terms, the method naturally yields hardware-efficient
circuits suitable for near-term
quantum devices. This separation keeps the
quantum execution shallow while moving optimization to classical computation.
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All authors Sadegh Salami, Mohammad T. Manzuri, Mehdi Ramezani, Sina Asadiyan Zargar, Abolfazl Bahrampour, Alireza Bahrampour
Quantum Physics · Cross-listed from cond-mat.quant-gas
Asymmetric and chiral dynamics of two-component anyons with synthetic gauge flux
Rui-Jie Chen, Ying-Xin Huang, Guo-Qing Zhang et al. (+1 more)
In this work, we investigate the non-
equilibrium dynamics in a one-dimensional two-component anyon-Hubbard model, which can be mapped to an extended Bose-Hubbard ladder with density-dependent hopping phase and synthetic gauge flux. Through numerical simulations of two-particle dynamics and the
symmetry analysis, we reveal the asymmetric transport with broken inversion
symmetry and two dynamical
symmetries in the expansion dynamics. The expansion of two-component anyons is dynamically symmetric under spatial inversion and component flip, when the sign of anyonic statistics phase or the signs of gauge flux and interaction are changed. In the non-interacting case, we show the dynamical suppression induced by both the statistics phase and gauge flux. In the interacting case, we demonstrate that both
chiral and antichiral dynamics can be exhibited and tuned by the statistics phase and gauge flux. The dynamical phase regimes with respect to the
chiral-antichiral dynamics are obtained. These findings highlight the rich dynamical phenomena arising from the interplay of anyonic exchange statistics, synthetic gauge fields, and interactions in multi-component anyons.
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All authors Rui-Jie Chen, Ying-Xin Huang, Guo-Qing Zhang, Dan-Wei Zhang
Quantum Physics
Narrowband Frequency-Entangled Photon Source for Hong-Ou-Mandel Interferometry
Yen-Ju Chen, Sheng-Hsuan Huang, Thomas Dirmeier et al. (+5 more)
Hong-Ou-Mandel (HOM) interferometry with entangled
photons exhibits distinctive
quantum features. By introducing frequency
entanglement (discrete-color entangled states) into HOM interference, the characteristic HOM dip is modulated by sinusoidal fringes, which significantly enhance the sensitivity of HOM sensors. The frequency-entangled
photon sources demonstrated to date rely on non-resonant parametric down-conversion (PDC), which limits the
photon coherence length and, consequently, restricts the sensing dynamic range to the sub-millimeter scale. In this work, we demonstrate narrowband frequency-entangled
photon source based on resonant PDC in a crystalline whispering gallery mode resonator. The MHz-level spectral bandwidth of
photons enables a meter-scale dynamic range. With highly nondegenerate frequency-entangled
photon pairs featuring a 96 THz frequency detuning, we observe high-contrast
quantum beating with sub-picosecond resolution in the HOM experiment. Our WGMR-based frequency-entangled
photon source has potential applications in
quantum metrology and
quantum information processing.
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All authors Yen-Ju Chen, Sheng-Hsuan Huang, Thomas Dirmeier, Kaisa Laiho, Dmitry V. Strekalov, Andrea Aiello, Gerd Leuchs, Christoph Marquardt