Quantum Physics
Hybrid Lattice Surgery: Non-Clifford Gates via Non-Abelian Surface Codes
Sheng-Jie Huang, Alison Warman, Sakura Schafer-Nameki et al. (+1 more)
In universal fault-tolerant
quantum computing, implementing logical non-Clifford gates often demands substantial spacetime resources for many error-correcting codes, including the high-threshold surface code. A critical mission for realizing large-scale
quantum computing is to develop simple and resource-efficient implementations of logical non-Clifford gates. We propose a novel way of implementing non-Clifford operations in the standard surface code based on hybrid
lattice surgery. First we generalize the standard
lattice surgery to hybrid
lattice surgery, where operations of rough merge and rough split happen across different topological codes. Then we apply such procedures between Abelian and non-Abelian codes and show that this can provide non-Clifford operations in the standard surface code, in the form of a magic state or a non-Clifford gate teleportation. Complementing this, we provide a continuum topological field theory description of this hybrid
lattice surgery utilizing interfaces between (2+1)d topological orders. From these considerations, we can generalize our protocol to non-Clifford gates and magic states at all finite levels of the Clifford hierarchy, as well as gates beyond the hierarchy. We also discuss protocols extending this framework to qutrits.
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All authors Sheng-Jie Huang, Alison Warman, Sakura Schafer-Nameki, Yanzhu Chen
Quantum Physics
Picosecond Wireless Synchronization with Entangled Photons via Grid-Based Quantum Coverage in Indoor Optical Systems
Hossein Safi, Mohammad Taghi Dabiri, Mazen Hasna et al. (+2 more)
In this paper, we present a robust
entanglement-assisted synchronization framework for indoor optical wireless systems that explicitly captures the coupling between spatial beam geometry and temporal synchronization accuracy. Unlike conventional approaches that treat beam steering and timing estimation independently, a unified spatio temporal model is developed that links user position uncertainty to the Cramer Rao lower bound of the synchronization error. The framework incorporates key physical impairments, including multipath dispersion, non Gaussian detector jitter, and spatially correlated localization errors. Through analytical modeling and extensive simulations, we show that the proposed system exhibits graceful performance degradation under heavy tailed positioning uncertainty and remains stable in the presence of multipath induced bias. Using realistic single
photon detector parameters, the results indicate that synchronization accuracy below $10$ picoseconds can be maintained across a wide range of operating conditions. This level of precision provides a scalable foundation for
quantum enabled indoor wireless networks.
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All authors Hossein Safi, Mohammad Taghi Dabiri, Mazen Hasna, Iman Tavakkolnia, Harald Haas
Quantum Physics
Quantum Coherence as a Thermodynamic Resource Beyond the Classical Uncertainty Bound
Shanhe Su, Cong Fu, Ousi Pan et al. (+3 more)
Thermodynamic uncertainty relations (TURs) establish a fundamental trade-off between current precision and
entropy production in nonequilibrium systems, yet the role of genuine
quantum coherence in these bounds remains unresolved. Here we develop a general framework that explicitly incorporates
quantum coherence into TURs for Markovian open
quantum systems. By combining the
quantum Cramér-Rao inequality with a Dyson series expansion of the parametrically deformed Lindblad dynamics, we derive a generalized TUR containing a coherence-sensitive correction that naturally separates classical and
quantum contributions. The coherent term originates from the off-diagonal components of the nonequilibrium steady-state density
matrix and systematically relaxes the classical precision-dissipation bound, allowing enhanced current precision without additional
entropy production. Applying our theory to a three-level
quantum maser, we demonstrate that steady-state coherence enables precision beyond the classical limit over a broad parameter regime while remaining consistent with the generalized bound. Our results identify
quantum coherence as a genuine thermodynamic resource and provide a unified framework bridging classical and
quantum uncertainty relations.
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All authors Shanhe Su, Cong Fu, Ousi Pan, Shihao Xia, Fei Liu, Jincan Chen
Quantum Physics
Analog Quantum Feature Selection with Neutral-Atom Quantum Processors
Jose J. Orquin-Marques, Carlos Flores-Garrigos, Alejandro Gomez Cadavid et al. (+5 more)
We present a
quantum-native approach to
quantum feature selection (QFS) based on analog
quantum simulation with neutral atom arrays, adaptable to a variety of academic and industrial applications. In our method, feature relevance-measured via mutual information with the target-is encoded as local detuning amplitudes, while feature redundancy is embedded through distance-dependent van der Waals interactions, constrained by the Rydberg blockade radius. The system is evolved adiabatically toward low-energy configurations, and the resulting measurement bitstrings are used to extract physically consistent subsets of features. The protocol is evaluated through simulations on three
benchmark binary classification
datasets: Adult Income, Bank Marketing, and Telco Churn. Compared to classical methods such as mutual information ranking and Boruta, combined with XGBoost and Random Forest classifiers, our
quantum-computing approach achieves competitive or superior performance. In particular, for compact subsets of 2-5 features, analog QFS improves mean AUC scores by 1.5-2.3% while reducing the number of features by 75-84%, offering interpretable, low-redundancy solutions. These results demonstrate that programmable Rydberg arrays offer a viable platform for intelligent feature selection with practical relevance in machine learning pipelines, capable of transforming computational
quantum advantage into industrial
quantum usefulness.
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All authors Jose J. Orquin-Marques, Carlos Flores-Garrigos, Alejandro Gomez Cadavid, Anton Simen, Enrique Solano, Narendra N. Hegade, Jose D. Martin-Guerrero, Yolanda Vives-Gilabert
Quantum Physics · Cross-listed from cond-mat.quant-gas
Trapping, manipulating and probing ultracold atoms: a quantum technologies tutorial
Louise Wolswijk, Luca Cavicchioli, Giuseppe Vinelli et al. (+12 more)
Engineered ultracold atomic systems are a valuable platform for fundamental
quantum mechanics studies and the development of
quantum technologies. At near zero absolute temperature, atoms exhibit macroscopic phase coherence and collective
quantum behavior, enabling their use in precision metrology,
quantum simulation, and even information processing. This review provides an introductory overview of the key techniques used to trap, manipulate, and detect ultracold atoms, while highlighting the main applications of each method. We outline the principles of
laser cooling,
magnetic and optical trapping, and the most widely used techniques, including optical
lattices and tweezers. Next, we discuss the manipulation methods of atomic internal and external degrees of freedom, and we present atom interferometry techniques and how to leverage and control interatomic interactions. Next, we review common ensemble detection strategies, including absorption and fluorescence imaging, state-selective readout, correlation and
quantum non-demolition measurements and conclude with high-resolution approaches. This review aims to provide newcomers to the field with a broad understanding of the experimental toolkit that underpins research in ultracold atom physics and its applications across
quantum science and technology.
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All authors Louise Wolswijk, Luca Cavicchioli, Giuseppe Vinelli, Mauro Chiarotti, Ludovica Donati, Marcia Frometa Fernandez, Diego Hernández Rajkov, Christian Mancini, Paolo Vezio, Tianwei Zhou, Giulia Del Pace, Chiara Mazzinghi, Nicolò Antolini, Leonardo Salvi, Vladislav Gavryusev
Quantum Physics
The complexity of perfect quantum state classification
Nathaniel Johnston, Benjamin Lovitz, Vincent Russo et al. (+1 more)
The problem of
quantum state classification asks how accurately one can identify an unknown
quantum state that is promised to be drawn from a known set of pure states. In this work, we introduce the notion of $k$-learnability, which captures the ability to identify the correct state using at most $k$ guesses, with zero error. We show that deciding whether a given family of states is $k$-learnable can be solved via semidefinite programming. When there are $n$ states, we present
polynomial-time (in $n$)
algorithms for determining $k$-learnability for two cases: when $k$ is a fixed constant or the dimension of the states is a fixed constant. When both $k$ and the dimension of the states are part of the input, we prove that there exist succinct certificates placing the problem in NP, and we establish NP-hardness by a reduction from the classical $k$-clique problem. Together, our findings delineate the boundary between efficiently solvable and intractable instances of
quantum state classification in the perfect (zero-error) regime.
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All authors Nathaniel Johnston, Benjamin Lovitz, Vincent Russo, Jamie Sikora
Quantum Physics
Quantum Sensing of Gravitational Frame-Dragging with a Superfluid $^4$He Gyrometer
Kai-Isaak Ellers, Marios Christodoulou, K.C. Schwab et al. (+1 more)
We propose a laboratory-scale experiment to locally measure the general relativistic frame-dragging effect on Earth using the macroscopic
quantum properties of a novel superfluid $^4$He single Josephson junction gyrometer. We derive the frame-dragging and related geodetic and Thomas effects in the superfluid gyrometer and present a procedure for their experimental measurement. We compute the expected thermal noise floor and find that very high sensitivity can be expected at millikelvin temperatures, where near-future Josephson junctions using nanoporous 2D materials are expected to operate. Assuming utilization of the lowest mechanical loss materials, we find a noise spectral density of $5\times 10^{-17}$ rads/s/$\sqrt{\mathrm{Hz}}$ at 10 mK, which is sufficient to resolve the frame-dragging rate to 0.2% within one second of measurement, giving a rotational sensitivity of 1 revolution in 4 Byrs. This extreme sensitivity to rotation corresponds to a measurement of proper time differences as small as $10^{-35}$ s.
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All authors Kai-Isaak Ellers, Marios Christodoulou, K.C. Schwab, K. Birgitta Whaley
Quantum Physics · Cross-listed from hep-th
Theta-term in Russian Doll Model: phase structure, quantum metric and BPS multifractality
Alexander Gorsky and Ilya Liubimov
We investigate the phase structure of the deterministic and disordered versions of the Russian Doll Model (RDM), which is a generalization of Richardson model of superconductivity in a finite system with time-reversal
symmetry breaking parameter $\theta$. It is one of the simplest examples of the cyclic RG where $\log N$ plays the role of the RG time. The deterministic model is integrable and shares the same Bethe Ansatz (BA) equations with the inhomogeneous twisted XXX
spin chain. We analyze the
quantum metric, the Berry
curvature, and the fractal dimension in the sector with a single Cooper pair. A rich phase structure in the $(\theta,\gamma)$ parameter plane is found, where $\gamma \log N$ quantifies the hopping term. For the deterministic RDM we clearly identify the extended domain of non-ergodic multifractal phase on the $(\theta,\gamma)$ parameter plane supporting the reentrance transitions between the localized, ergodic, and multifractal phases. We find the pattern of phase transitions in the global charge $Q(\theta,\gamma)$, which arises from the BA equation. In particular, in the multifractal phase in the deterministic model $Q(\gamma)$ exhibits the analogue of "charge concentration" and fortuity phenomena discussed in the context of black hole microstates at finite $N$. The BA equations in RDM exactly coincide with the equations defining the ground states in the theory on the worldvolume of the
vortex strings in $N_F=2N_C$ ${\cal N}=2$ SQCD at a strong coupling point $\frac{1}{g_{YM}^2}=0$ with identification $\theta_{RDM}= \theta_{4D}-\pi$. We
conjecture that the
Hamiltonian of the RDM model describes the mixing in particular 2d-4d BPS sector of the
Hilbert space. Our findings provide an example of the BPS multifractality regime for the probe operator in the sector of
Hilbert space, and we comment on the possible application to dense QCD with $\theta$ term.
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Quantum Physics
Optimal constant-cost implementations of Clifford operations using global interactions
Jonathan Nemirovsky, Lee Peleg, Amit Ben Kish et al. (+1 more)
We investigate
quantum circuits built from arbitrary single-
qubit operations combined with programmable all-to-all multiqubit entangling gates that are native to, among other systems, trapped-ion
quantum computing platforms. We report a constant-cost of no more than four applications of such Clifford entangling multiqubit gates to realize any sequence of Clifford operations of any length, without ancillae, which is the theoretically optimal gate count cost. We do this by implementing any sequence of CNOT gates of any length with four applications of such gates, without ancillae, and show that the extension to general Clifford operations incurs no additional cost. We investigate the required
qubit drive power that is associated with our implementation and show that it is lower than that of a standard approach. Our work introduces a practical and computationally efficient
algorithm to realize these compilations.
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All authors Jonathan Nemirovsky, Lee Peleg, Amit Ben Kish, Yotam Shapira
Quantum Physics
Co-Designing Quantum Codes with Transversal Diagonal Gates via Multi-Agent Systems
Xi He, Sirui Lu and Bei Zeng
Exact scientific discovery requires more than heuristic search: candidate constructions must be turned into exact objects and checked independently. We address this gap by extending TeXRA with an independent Lean 4 verification layer, turning it into a human-guided multi-
agent platform for exact scientific discovery. The platform couples symbolic synthesis, combinatorial and linear-programming search, exact reconstruction of numerical candidates, and formal verification in Lean. We apply this platform to nonadditive
quantum error-correcting codes with prescribed transversal diagonal gates within the subset-sum linear-programming (SSLP) framework. In the distance-2 regime where logical states occupy distinct residue classes, the platform yields a Lean-certified catalogue of 14,116 codes for $K\in\{2,3,4\}$ and up to six physical
qubits, realizing cyclic logical orders 2 through 18, from which we extract closed-form infinite families. We also construct a residue-degenerate $((6,4,2))$ code implementing the logical controlled-phase gate $\mathrm{diag}(1,1,1,i)$. At distance 3, we resolve the transversal-$T$ problem for $((7,2,3))$ codes within the complementary binary-dihedral $\mathrm{BD}_{16}$ setting: among the 12 candidates surviving the SSLP filters, 10 admit exact realizations and 2 are excluded by no-go proofs. All accepted constructions, families, and no-go results are formalized and checked in Lean, illustrating how AI-assisted workflows can bridge search, exact reconstruction, and formal proof in the physical sciences.
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Quantum Physics
Typicality of Contextuality
Vinicius P. Rossi, Beata Zjawin, Roberto D. Baldijão et al. (+3 more)
Identifying when observed statistics cannot be explained by any reasonable classical model is a central problem in
quantum foundations. A principled and universally applicable approach to defining and identifying nonclassicality is given by the notion of generalized noncontextuality. Here, we study the typicality of contextuality – namely, the likelihood that randomly chosen
quantum preparations and measurements produce nonclassical statistics. Using numerical linear programs to test for the existence of a generalized-noncontextual model, we find that contextuality is fairly common: even in experiments with only a modest number of random preparations and measurements, contextuality arises with probability over 99%. We also show that while typicality of contextuality decreases as the purity (sharpness) of the preparations (measurements) decreases, this dependence is not especially pronounced, so contextuality is fairly typical even in settings with realistic noise. Finally, we show that although nonzero contextuality is quite typical, quantitatively high degrees of contextuality are not as typical, and so large
quantum advantages (like for parity-oblivious multiplexing, which we take as a case study) are not as typical. We provide an open-source toolbox that outputs the typicality of contextuality as a function of tunable parameters (such as lower and upper bounds on purity and other constraints on states and measurements). This toolbox can inform the design of experiments that achieve the desired typicality of contextuality for specified experimental constraints.
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All authors Vinicius P. Rossi, Beata Zjawin, Roberto D. Baldijão, David Schmid, John H. Selby, Ana Belén Sainz
Quantum Physics · Cross-listed from cond-mat.quant-gas
Radial selection rule for the breathing mode of a harmonically trapped gas
Miguel Tierz
Within a fixed hyperangular channel $s>0$ of a harmonically trapped system, the $1/R^2$ perturbation is absorbed exactly into a shift of the channel parameter, $s\to s_\eta$, so the single-channel model remains a harmonic oscillator with a shifted inverse-square term: radial gaps stay at $2\hbar\omega$ exactly and no monopole spectral weight appears at forbidden frequencies at any order. The first-order cancellation is also proved independently by a compact algebraic argument in which the ket and bra contributions cancel pairwise; this is the main new result. Substituting single-channel quantities into the established $m_1/m_{-1}$ sum-rule bound yields $Q^{-1}$ scaling of the sum-rule estimate ($Q\equiv 2q+s+1$, $q$ the radial
quantum number) with an explicit coefficient; its finite-temperature average has a low-$T$ plateau and a $1/T$ high-$T$ tail. All results hold for any real $s>0$. The Laguerre
polynomial identities extend formally to three dimensions, but exact 3D results show $q$-dependent contact corrections along $SO(2,1)$ ladders, so the physical interpretation there requires a separate derivation.
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Quantum Physics
Experimental differentiation and extremization with analog quantum circuits
Evan Philip, Julius de Hond, Vytautas Abramavicius et al. (+8 more)
Solving and optimizing differential equations (DEs) is ubiquitous in both engineering and fundamental science. The promise of
quantum architectures to accelerate scientific computing thus naturally involved interest towards how efficiently
quantum algorithms can solve DEs. Differentiable
quantum circuits (DQC) offer a viable route to compute DE solutions using a variational approach amenable to existing
quantum computers, by producing a machine-learnable surrogate of the solution.
Quantum extremal learning (QEL) complements such approach by finding extreme points in the output of learnable models of unknown (implicit) functions, offering a powerful tool to bypass a full DE solution, in cases where the crux consists in retrieving solution extrema. In this work, we provide the results from the first experimental demonstration of both DQC and QEL, displaying their performance on a synthetic usecase. Whilst both DQC and QEL are expected to require digital
quantum hardware, we successfully challenge this assumption by running a closed-loop instance on a commercial analog
quantum computer, based upon neutral atom technology.
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All authors Evan Philip, Julius de Hond, Vytautas Abramavicius, Kaonan Micadei, Mario Dagrada, Panagiotis Barkoutsos, Mourad Beji, Louis-Paul Henry, Vincent E. Elfving, Antonio A. Gentile, Savvas Varsamopoulos
Quantum Physics
Note on Energy Shifts of Oscillators in Blackbody Radiation
Peter Milonni
The energy shift of an oscillator in blackbody radiation is calculated based simply on the total energy of the interacting field-oscillator system as a function of the refractive index. For high temperatures T the energy and free-energy shifts are found to vary as -T^2 and +T^2, respectively, in agreement with the result originally obtained by Ford, Lewis, and O'Connell [Phys. Rev. Lett. 55, 2273 (1985)].
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Quantum Physics
Classical Noise Inversion for Error-Propagatable Circuits with Minimal Overhead under General Gate-Dependent Noise
Dayue Qin, Ying Li and You Zhou
Quantum error mitigation (QEM) is critical for extracting reliable computations from noisy
quantum processors, proving itself essential not only in the near term but also as a valuable supplement to fully fault-tolerant systems in the future. Despite the necessity, practical QEM deployment still confronts challenges, including the excessive cost of sampling
quantum circuits and reliance on unrealistic assumptions such as gate-independent noise. In this paper, we propose Classical Noise Inversion (CNI), which shifts the QEM from sampling diverse
quantum circuits to repeated single-
circuit measurement, a drastic cost reduction given that the former incurs far heavier time overhead than the latter on realistic
quantum hardware. We target general noise models and establish critical conditions for their classical tractability, under which CNI remains effective. For noise models that violate the condition, we propose partial CNI, which mitigates the classically tractable factor of noise via CNI and mitigates the other part via probabilistic error cancellation tailored to gate-dependent noise. To minimize the sampling overhead, we introduce noise compression, which groups noise components with equivalent effects on measurement outcomes, thereby attaining theoretically optimal error-mitigation overhead. The proposed protocols are particularly efficient for error-propagatable
circuits, including adaptive universal
quantum computing represented by Clifford+T fault-tolerant
circuits, and generalized measurement represented by classical shadows. To demonstrate the practical merits of CNI, we integrate it with thrifty classical shadow, and use analysis and numerical simulations to show its advantages in both efficiency and accuracy over existing approaches.
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Quantum Physics
Computing time-dependent reduced models for classical and quantum dynamics
Tommaso Grigoletto
This paper introduces a novel method for approximating the dynamics of a large autonomous system projected onto a fixed subspace. The core contribution is a novel recursive
algorithm to construct an effective time-dependent generator that is
polynomial in the time variable, ensuring accuracy for short time scales. The derivation is based on the Taylor expansion of the exponential map and a new result for computing the time-ordered exponential of
polynomial generators. This work is motivated by the challenge of deriving time-convolutionless master equations in
quantum physics and the proposed method offers an alternative to typical derivations based on expansions in the coupling strength. The resulting approximation is accurate for small times, does not require a weak-coupling assumption, performs better than a truncation of the exponential map at low orders, and crucially, guarantees a completely positive and trace-preserving map at the lowest orders. The proposed method is validated against several prototypical models: a dephasing
spin-
boson model, a central
spin model, and an Ising
spin chain.
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Quantum Physics · Cross-listed from math-ph
Topological Orders from Reflection Positive Frustration-free Hamiltonians
Zhengwei Liu and Zishuo Zhao
We establish a framework based on reflection positivity for analyzing topologically ordered
quantum spin systems and reconstructing their boundary
algebras. For any reflection positive frustration-free
Hamiltonian, we prove that the local topological
quantum order (LTQO) condition of ground states on a disk holds, if and only if the ground state on the sphere obtained by gluing the disk with its reflection is nondegenerate. Furthermore, we show that Osterwalder-Schrader reconstruction produces the local net of boundary operator
algebras from the local ground states, offering a constructive approach to topological holography through spatial reflection positivity.
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Quantum Physics
Quantum Processing Unit (QPU) processing time Prediction with Machine Learning
Lucy Xing, Sanjay Vishwakarma, David Kremer et al. (+3 more)
This paper explores the application of machine learning (ML) techniques in predicting the QPU processing time of
quantum jobs. By leveraging ML
algorithms, this study introduces predictive models that are designed to enhance operational efficiency in
quantum computing systems. Using a
dataset of about 150,000 jobs that follow the IBM
Quantum schema, we employ ML methods based on Gradient-Boosting (LightGBM) to predict the QPU processing times, incorporating data preprocessing methods to improve model accuracy. The results demonstrate the effectiveness of ML in
forecasting quantum jobs. This improvement can have implications on improving resource management and scheduling within
quantum computing frameworks. This research not only highlights the potential of ML in refining
quantum job predictions but also sets a foundation for integrating AI-driven tools in advanced
quantum computing operations.
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All authors Lucy Xing, Sanjay Vishwakarma, David Kremer, Francisco Martin-Fernandez, Ismael Faro, Juan Cruz-Benito
Quantum Physics
A Gateway to Quantum Computing for Industrial Engineering
Emily L. Tucker and Mohammadhossein Mohammadisiahroudi
Quantum computing is rapidly emerging as a new computing paradigm with the potential to improve decision-making, optimization, and simulation across industries. For industrial engineering (IE) and operations research (OR), this shift introduces both unprecedented opportunities and substantial challenges. The learning curve is high, and to help researchers navigate the emerging field of
quantum operations research, we provide a road map of the current field of
quantum operations research. We introduce the foundational principles of
quantum computing, outline the current hardware and software landscape, and survey major algorithmic advances relevant to IE/OR, including
quantum approaches to linear
algebra, optimization, machine learning, and
stochastic simulation. We then highlight applied research directions, including the importance of problem domains for driving long-term value of
quantum computers and how existing classical OR models can be reformulated for
quantum hardware. Recognizing the steep learning curve, we propose pathways for IE/OR researchers to develop technical fluency and engage in this interdisciplinary domain. By bridging theory with application, and emphasizing the interplay between hardware and research development, we argue that industrial engineers are uniquely positioned to shape the trajectory of
quantum computing for practical problem-solving. Ultimately, we aim to lower the barrier to entry into
quantum computing, motivate new collaborations, and chart future directions where
quantum technologies may deliver tangible impact for industry and academia.
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Quantum Physics · Cross-listed from cond-mat.mes-hall
Anyonic time exchange in hierarchical Hall states: emergent Luttinger scaling and cross-correlations at finite temperature
Aleksander Latyshev and Ines Safi
We address hierarchical fractional
quantum Hall edges coupled by a spatially local
quantum point contact within the Unified Nonequilibrium Perturbative (UNEP) framework. Without assuming a Tomonaga-Luttinger
liquid (TLL) tunneling correlator, we impose a local anyonic time-exchange (ATE) constraint with phase $\bar{\theta}$, yielding a nonequilibrium fluctuation-dissipation integral equation relating DC tunneling current and noise. For thermal initial states, detailed balance closes this equation for the current. Using the Wiener-
Hopf method, we find a unique physical solution of local TLL form, with scaling dimension $\delta$ determined by $\bar{\theta}=\pi\delta\pmod{\pi}$, emerging from the solution rather than being imposed via a TLL correlator. By contrast, ATE and inversion
symmetry alone fix the exchange monodromy but not the full transport dynamics. We then study the "anyon
collider" beyond Laughlin states at finite temperatures. Detailed balance is broken and noise becomes super-Poissonian, but the relation between nonequilibrium and
equilibrium correlators determines current and noise. The output cross-correlation and balanced generalized Fano factor depend on both $\delta$ and statistical phase $\theta$, identical to $\bar{\theta}$ for co-propagating modes with short-range interactions. A temperature-dependent current scale separates the zero-temperature asymptotic regime from the low-current regime, where the balanced Fano factor saturates to a function of $\theta$ and $\delta$ distinct from its zero-temperature value. This latter regime is particularly relevant to “anyon
collider” experiments. These complementary regimes constrain the statistical phase and scaling dimension, subject to the
symmetry $\delta\mapsto1-\delta$ at fixed $\theta$. For independent statistical phase and scaling dimension, the thermal crossover can reverse the sign of output cross-correlations.
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Quantum Physics
Gravitationally mediated entanglement of fermionic qubits: from static to dynamical limits
Moslem Zarei, Mehdi Abdi, Nicola Bartolo et al. (+1 more)
We employ the
quantum Boltzmann equation to analyze the gravitationally generated
entanglement between two remote
qubits by considering two explicit microscopic models. A graviton propagator is employed as the mediator of the interactions, while the
qubits are considered in a spatial superposition state. Such a setup, in the case of any
entanglement generation, could potentially offer experimental evidence for the quantization of
gravity. By treating the
qubits as
spin-1/2 particles in wave packets, we establish that the
entanglement arises from forward scattering processes involving graviton exchanges. In our study, we consider both static and dynamical limits of the propagator and show that only in the dynamical limit such entangled states can be generated. These effects are observed to be diminished as the wave packet size increases. Our findings sheds more light into the
gravity mediated
entanglement between two
spin-1/2 particles.
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All authors Moslem Zarei, Mehdi Abdi, Nicola Bartolo, Sabino Matarrese
Quantum Physics
Generating pseudo-random unitaries with a Floquet driven chaotic quantum system
Alice C. Quillen and Abobakar Sediq Miakhel
We explore using an ergodic Floquet
quantum system on a
torus to generate pseudo-random
unitary operators. We choose a regime of the perturbed Harper model with strong perturbations and perturbation frequency exceeding the libration frequency to ensure that the system has an ergodic region that covers phase space and lacks resonant substructure. We generate a sample of
unitary operators in a finite dimensional space by computing Floquet propagators from a distribution of its control parameters. To compare the distribution of
unitaries to that of a Haar-random distribution, we compute k-frame potentials from samples of numerically generated
unitaries. We find that uniform distributions of 4 control parameters can generate an approximate 3-design. Distributions of fewer control parameters are required to create an approximate 3-design if the Floquet system parameters drift.
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Quantum Physics
Phase Transitions and Virtual Exceptional Points in Quantum Emitters Coupled to Dissipative Baths
Stefano Longhi
Controlling atom-
photon interactions in engineered environments is central to
quantum optics and emerging
quantum technologies. Non-Hermitian (NH) photonic baths, where dissipation fundamentally reshapes spectral and dynamical properties, provide versatile platforms for such control. Here we investigate the relaxation dynamics of a single two-level
quantum emitter coupled to the edge of a semi-infinite dissipative bosonic
lattice with uniform loss. Despite the simplicity of this bath, we uncover rich dynamical phase transitions, i.e. qualitative changes in spontaneous emission decay as system parameters are varied. In particular, we establish the existence of an optimal dissipative environment for accelerated spontaneous emission. The phase transitions are traced to spectral restructuring of the resolvent, in some cases governed by the coalescence of resonance states on the second Riemann sheet. We identify these coalescences as virtual exceptional points (EPs) of resonance origin, providing a conceptual bridge with EP physics while highlighting distinctive features of infinite-dimensional NH systems. More broadly, our results illustrate how the specific nature of dissipation – whether uniform losses, staggered losses, or dephasing – can profoundly impact emitter relaxation, pointing to dissipation engineering as a versatile tool for
quantum technologies.
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Quantum Physics
Measuring weak microwave signals via current-biased Josephson Junctions II: Arriving at single-photon detection sensitivity
Y. Q. Chai, M. Y. Wang, S. N. Wang et al. (+2 more)
It is well known that the current-biased Josephson junction (CBJJ) can serve as a Josephson threshold detector (JTD) for the sensitive detection of weak microwave signals. Based on the recent work (PRB 111, 024501 (2025)) on the detection sensitive limit of the usual
equilibrium JTD, here we numerically demonstrate that a non-
equilibrium JTD can be alternatively utilized to implement the higher sensitive detection of a weak microwave signal, arriving at its energy
quantum limit. In the presence of thermal noise, we numerically simulate the phase dynamics for the CBJJ in the JTD with the different sweep rates of the biased currents, and find that the SCDs of the JTD with and without the microwave signal input show different behaviors. It is demonstrated that, depending on how high the sweep rate of the biased current being applied, the JTD can be operated in either the
equilibrium- or the non-
equilibrium state. Specifically, under the rapidly non-adiabatic driving, the SCDs of the JTD are obviously insensitive to the thermal noises, which means that the non-
equilibrium JTD can possess a higher achievable detection sensitivity, compared with its
equilibrium state counterpart. Consequently, the non-
equilibrium JTD can be utilized to implement the desired single microwave-
photon detection. Also, some of the achievable performance indexes, such as the dynamic range, detection bandwidth, and the
photon-number resolvability, etc., of the non-
equilibrium JTD have been estimated, when it serves as a wideband microwave single-
photon detector.
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All authors Y. Q. Chai, M. Y. Wang, S. N. Wang, P. H. Ouyang, L. F. Wei
Quantum Physics
Nontrivial topological phases in "Zig-Zag" arrays of polarization transmons
Ekaterina Konopleva, Gleb Fedorov and Oleg Astafiev
In recent years,
quantum simulators of topological models have been extensively studied across a variety of platforms and regimes. A new promising research direction makes use of meta-atoms with multiple intrinsic degrees of freedom, which to date have been predominantly studied in the classical regime. Here, we propose a superconducting
quantum simulator to study an extension of the well-known "Zig-Zag" model with long-range cross-polarization couplings using polarization transmons hosting degenerate dipole orbitals. We map the phase transitions of the extended "Zig-Zag" model both numerically and analytically using inverse participation ratios and topological invariants. We demonstrate the existence of in-gap localized trivial and Tamm edge states. With linearized meta-atoms, we show via electromagnetic modeling that the proposed arrangement closely reproduces the extended "Zig-Zag" model. This work paves the way towards experimental investigation of the previously inaccessible topological
quantum many-body phenomena.
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Quantum Physics · Cross-listed from cond-mat.mes-hall
Quantifying robustness and locality of Majorana bound states in interacting systems
William Samuelson, Juan Daniel Torres Luna, Sebastian Miles et al. (+4 more)
Protecting
qubits from perturbations is a central challenge in
quantum computing. Topological
superconductors with separated Majorana bound states (MBSs) provide a strong form of protection that only depends on the locality of perturbations. While the link between MBS separation, robust degeneracy, and protected braiding is well understood in non-interacting systems, recent experimental progress in short
quantum-dot-based Kitaev chains highlights the need to establish these connections rigorously for interacting systems. We do this by defining MBSs from many-body ground states and show how their locality constrains their coupling to an environment. This, in turn, quantifies the protection of the energy degeneracy and the feasibility of non-abelian braiding.
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All authors William Samuelson, Juan Daniel Torres Luna, Sebastian Miles, A. Mert Bozkurt, Martin Leijnse, Michael Wimmer, Viktor Svensson
Quantum Physics
Higher-order quantum computing with known input states
Vanessa Brzić, Satoshi Yoshida, Mio Murao et al. (+1 more)
In higher-order
quantum computing (HOQC), one typically considers the universal transformation of unknown
quantum operations, treated as blackboxes. It is also implicitly assumed that the resulting operation must act on arbitrary, and thus unknown, input states. In this work, we explore a variant of this framework in which the operation remains unknown, but the input state is fixed and known. We argue that this assumption is well-motivated in certain practical contexts, such as
unitary programming, and show that classical knowledge of the input state can significantly enhance performance. We demonstrate that in the SAR protocol, this knowledge leads to an exponential advantage through a repeat-until-success strategy, highlighting the operational power of known-state higher-order transformations. Moreover, this assumption allows us to distinguish between protocols designed for pure, bipartite, and mixed states, which enables us to identify the class of mixed states for which deterministic and exact implementation becomes possible.
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All authors Vanessa Brzić, Satoshi Yoshida, Mio Murao, Marco Túlio Quintino
Quantum Physics
Feasibility of entanglement-based QKD protocols with SPDC and QD sources
Mariia Gumberidze and Vladyslav C. Usenko
We theoretically analyze the feasibility of
entanglement-based
quantum key distribution (QKD) protocols considering widely used spontaneous parametric down-conversion (SPDC) and novel
quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm that the presence of
vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations under standard detection strategies. Conversely, in the case of QD sources, accounting for the effects of FSS, results in reduced performance of protocols. Our findings are crucial for the practical implementation of
entanglement-based QKD protocols using realistic sources and detectors.
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Quantum Physics
Phenomenological Noise Models and Optimal Thresholds of the 3D Toric Code
Ji-Ze Xu, Yin Zhong, Miguel A. Martin-Delgado et al. (+2 more)
Three-dimensional (3D) topological codes offer the advantage of supporting fault-tolerant implementations of non-Clifford gates, yet their performance against realistic noise remains largely unexplored. In this work, we focus on the paradigmatic 3D toric code and investigate its fault-tolerance thresholds in the presence of both Pauli and measurement errors. Two randomly coupled
lattice gauge models that describe the code's correctability are derived, including a random 2-form $\mathbb{Z}_2$ gauge theory. By exploiting a generalized duality technique, we show that the 3D toric code exhibits optimal thresholds of $p^{X,M}_{th} \approx 11\%$ and $p^{Z,M}_{th} \approx 2\%$ against bit-flip and phase-flip errors, respectively. These threshold values show modest reductions compared to the case of perfect measurements, establishing the robustness of the 3D toric code against measurement errors. Our results constitute a substantial advance towards assessing the practical performance of 3D topological codes. This contribution is timely and in high demand, as rapid hardware advancements are bringing complex codes into experimental reach. Moreover, our work highlights the interdisciplinary nature of fault-tolerant
quantum computation and holds significant interest for
quantum information science, high-energy physics, and condensed matter physics.
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All authors Ji-Ze Xu, Yin Zhong, Miguel A. Martin-Delgado, Hao Song, Ke Liu
Quantum Physics
Mitigating Coherent Errors through a Decoherence-Resistant Variational Framework employing Stabilizer State
Giovanni Di Bartolomeo, Giulio Crognaletti, Angelo Bassi et al. (+1 more)
Stabilizer states are a central resource in
quantum information processing, underpinning a wide range of applications. While they can be efficiently generated via Clifford
circuits, the presence of coherent errors, such as small-angle miscalibrations in native gate implementations, can significantly impact their quality. In this work, we introduce Variational Coherent Error Mitigation (VCEM), a method that employs the stabilizer formalism to suppress coherent errors through variational optimization of native gates parameters. VCEM demonstrates robust performance, remaining largely unaffected by incoherent noise, enabling pre-compensation of coherent errors prior to the application of standard incoherent error mitigation techniques. We demonstrate the effectiveness and robustness of VCEM through numerical simulations.
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All authors Giovanni Di Bartolomeo, Giulio Crognaletti, Angelo Bassi, Michele Vischi