Quantum Physics
Random Construction of Quantum LDPC Codes
Koki Okada and Kenta Kasai
We propose a method for modifying orthogonal sparse
matrix pairs used in CSS codes while preserving their
matrix row and column weight distributions, which play a crucial role in determining the performance of belief-propagation decoding. Unlike simple row or column permutations that merely reorder existing elements, the proposed local modification introduces genuine structural randomness through small $2\times2$ cross-swap operations followed by integer-linear-program-based local repairs that restore orthogonality. By applying this procedure repeatedly in a random manner, ensembles of randomized
quantum LDPC codes can be constructed. The computational complexity of each repair depends only on the maximum row and column weights and is independent of the overall
matrix size, ensuring scalability to large code blocks.
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Quantum Physics
Unclonable Cryptography in Linear Quantum Memory
Omri Shmueli and Mark Zhandry
Quantum cryptography is a rapidly-developing area which leverages
quantum information to accomplish classically-impossible tasks. In many of these protocols,
quantum states are used as long-term cryptographic keys. Typically, this is to ensure the keys cannot be copied by an adversary, owing to the
quantum no-cloning
theorem. Unfortunately, due to
quantum state's tendency to decohere, persistent
quantum memory will likely be one of the most challenging resources for
quantum computers. As such, it will be important to minimize persistent
memory in
quantum protocols. In this work, we consider the case of one-shot signatures (OSS), and more general
quantum signing
tokens. These are important unclonable primitives, where
quantum signing keys allow for signing a single message but not two. Naturally, these
quantum signing keys would require storage in long-term
quantum memory. Very recently, the first OSS was constructed in a classical oracle model and also in the standard model, but we observe that the
quantum memory required for these protocols is quite large. In this work, we significantly decrease the
quantum secret key size, in some cases achieving asymptotically optimal size. To do so, we develop novel techniques for proving the security of cryptosystems using coset states, which are one of the main tools used in unclonable cryptography.
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Quantum Physics
Unifying Qubit Routing Across Diverse Quantum ISAs via Canonical Representation
Zhaohui Yang, Kai Zhang, Xinyang Tian et al. (+6 more)
Qubit mapping/routing is a critical stage in compilation for both near-term and fault-tolerant
quantum computers, yet existing scalable methods typically impose several times the routing overhead in terms of
circuit depth or duration. This inefficiency stems from a fundamental disconnect: compilers rely on an abstract routing model (e.g., three-CX-unrolled SWAP insertion) that completely ignores the idiosyncrasies of native gates supported by physical devices. Recent hardware breakthroughs have enabled high-precision implementations of diverse instruction set architectures (ISAs) beyond standard CX-based gates. Advanced ISAs involving gates such as $\mathrm{\sqrt{iSWAP}}$ and $\mathrm{ZZ}(\theta)$ gates offer superior
circuit synthesis capabilities and can be realized with higher fidelities. However, systematic compiler optimization strategies tailored to these advanced ISAs are lacking. To address this, we propose Canopus, a unified
qubit mapping/routing framework applicable to diverse
quantum ISAs. Built upon the canonical representation of two-
qubit gates, Canopus centers on
qubit routing to perform deep co-optimization in an ISA-aware approach. Canopus leverages the two-
qubit canonical representation and the monodromy polytope theory to model the synthesis cost for more intelligent SWAP insertion during
qubit routing. We also formalize the commutation relations between two-
qubit gates through the canonical form, providing a generalized approach to commutativity-based optimization. Experiments show that Canopus consistently reduces routing overhead by 15%-35% compared to state-of-the-art methods across various backend ISAs and device
topologies. More broadly, this work establishes a coherent method for co-exploration of program patterns,
quantum ISAs, and hardware
topologies, yielding concrete guidelines for hardware-software co-design.
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All authors Zhaohui Yang, Kai Zhang, Xinyang Tian, Xiangyu Ren, Yingjian Liu, Yunfeng Li, Dawei Ding, Jianxin Chen, Yuan Xie
Quantum Physics
Controlling Hong-Ou-Mandel antibunching via parity governed local spectral shaping of biphoton states
Mikhail Guselnikov, Alexei D. Kiselev, Andrei Gaidash et al. (+2 more)
We investigate into experimentally detectable effects such as the Hong-Ou-Mandel (HOM) bunching and antibunching. These regimes can be characterized using the
symmetry degree parameter $D_S$ that enters the two-
photon coincidence probability $P_{2c}=(1-D_S)/2$. In the case of HOM bunching (antibunching), $D_S$ is positive (negative). Though the
symmetry degree can generally be expressed in terms of the difference between the contributions coming from the symmetric and antisymmetric parts of the biphoton joint spectral amplitude (JSA), $\psi(\omega_1,\omega_2)$, for a certain physically realizable class of the JSA, where $\psi(\omega_1,\omega_2)$ is proportional to the product of amplitudes $\varphi_1(\omega_1)\varphi_2(\omega_2)$ multiplied by a Gaussian shaped entangling factor, we find the sign of $D_S$ is primarily governed by the parity properties of the spectral function, $\varphi_{12}(\omega)=\varphi_1(\omega)\varphi_2^*(\omega)$. It is the even (odd) part of $\varphi_{12}=\varphi_{12}^{(+)}+\varphi_{12}^{(-)}$ that meets the parity condition $\varphi_{12}^{(+)}(\omega-\Omega)=\varphi_{12}^{(+)}(\Omega-\omega)$ ($\varphi_{12}^{(-)}(\omega-\Omega)=- \varphi_{12}^{(-)}(\Omega-\omega)$) to yield the positive (negative) contribution, $D_S^{(+)}$ ($-D_S^{(-)}$), to the
symmetry degree parameter: $D_S=D_S^{(+)}-D_S^{(-)}$. We have shown that switching between the bunching and antibunching regimes can be realized using the experimentally accessible family of modulated biphoton states produced using the spectral phase modulation fine-tuned via the sub-nanometer scale variation of the path length. For this class of modulated states, the Schmidt number has been computed as a function of the modulation parameter. This dependence reveals the structure of narrow resonance peaks strongly correlated with the corresponding narrow dips of the
symmetry degree where the HOM antibunching occurs.
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All authors Mikhail Guselnikov, Alexei D. Kiselev, Andrei Gaidash, George Miroshnichenko, Anton Kozubov
Quantum Physics
Homodyne detection for pulse-by-pulse squeezing measurements
Tiphaine Kouadou, Elie Gozlan, Loïc Garcia et al. (+11 more)
Homodyne detection is a phase-sensitive measurement technique, essential for the characterization of continuous-variable (CV)-encoded
quantum states of light. It is a key component to the implementation of CV
quantum-information protocols and benefits from operating, by design, at room temperature. However, performing high-speed
quantum information processing remains a major challenge, as conventional homodyne detectors often fail to sustain pulsed operation at high repetition rates due to electronic limitations. We present wideband homodyne detectors operating at near-infrared (NIR) and telecom wavelengths, with optimized performance at repetition rates up to 150 MHz. We demonstrate their performance by resolving the pulse-by-pulse structure of squeezed states of light at telecom wavelengths while preserving their spectral multimode properties.
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All authors Tiphaine Kouadou, Elie Gozlan, Loïc Garcia, David Polizzi, David Fainsin, Iris Paparelle, R. L. Rincón Celis, Bastien Oriot, Anthony Abi Aad, Peter Namdar, Ganaël Roland, Nicolas Treps, Bérengère Argence, Valentina Parigi
Quantum Physics · Cross-listed from cond-mat.quant-gas
Superfluid Fraction of a 2D Bose-Einstein Condensate in a Triangular Lattice
F. Rabec, G. Brochier, S. Wattellier et al. (+5 more)
We experimentally investigate the superfluid properties of a two-dimensional, weakly interacting Bose-Einstein condensate in the zero-temperature regime, when it is subjected to a triangular optical
lattice potential. We implement an original method, which involves solving the hydrodynamic continuity equation to extract the superfluid fraction tensor from the measured in situ density distribution of the fluid at rest. In parallel, we apply an independent dynamical approach that combines compressibility and sound velocity measurements to determine the superfluid fraction. Both methods yield consistent results in good agreement with simulations of the Gross-Pitaevskii equation as well as with the Leggett bounds determined from the measured density profiles.
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All authors F. Rabec, G. Brochier, S. Wattellier, G. Chauveau, Y. Li, S. Nascimbene, J. Dalibard, J. Beugnon
Quantum Physics
QEF: Reproducible and Exploratory Quantum Software Experiments
Vincent Gierisch and Wolfgang Mauerer
Commercially available Noisy Intermediate-Scale
Quantum (NISQ) devices now make small hybrid
quantum-classical experiments practical, but many tools hide configuration or demand ad-hoc scripting. We introduce the
Quantum Experiment Framework (QEF): A lightweight framework designed to support the systematic, hypothesis-driven study of
quantum algorithms. Unlike many existing approaches, QEF emphasises iterative, exploratory analysis of evolving experimental strategies rather than exhaustive empirical evaluation of fixed
algorithms using predefined quality metrics. The framework's design is informed by a comprehensive review of the literature, identifying principal parameters and measurement practices currently reported in the field. QEF captures all key aspects of
quantum software and
algorithm experiments through a concise specification that expands into a Cartesian product of variants for controlled large-scale parameter sweeps. This design enables rigorous and systematic evaluation, as well as precise reproducibility. Large sweeps are automatically partitioned into asynchronous jobs across simulators or cloud hardware, and ascertain full hyper-parameter traceability. QEF supports parameter reuse to improve overall experiment runtimes, and collects all metrics and metadata into a form that can be conveniently explored with standard statistical and visualisation software. By combining reproducibility and scalability while avoiding the complexities of full workflow engines, QEF seeks to lower the practical barriers to empirical research on
quantum algorithms, whether these are designed for current NISQ devices or future error-corrected
quantum systems.
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Quantum Physics
Preferred Basis in Coupled Electron-Nuclear Dynamics
Junhyeok Bang
Beyond the adiabatic regime, our understanding of
quantum dynamics in coupled systems remains limited, and the choice of representation continues to obscure physical interpretation and simulation accuracy. Here we propose a natural and efficient basis for electron
nuclear dynamics by drawing on the concepts of pointer and preferred states from decoherence theory, adapted to systems where electrons and
nuclei interact strongly. Within this framework, we show that 1) the independent dynamics exploited by mixed
quantum classical (MQC) methods is best understood as a manifestation of
entanglement viewed in a preferred basis, rather than a consequence of decoherence, and 2) the adiabatic Born Oppenheimer states satisfy the conditions of an approximate preferred basis. This perspective reconciles widely used approximations with a more fundamental structure of the theory and provides a systematic route to more reliable MQC strategies. In effect, we revisit MQC methods through the lens of preferred states, clarifying when they succeed and how they can be improved.
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Quantum Physics
Scaling advantage with quantum-enhanced memetic tabu search for LABS
Alejandro Gomez Cadavid, Pranav Chandarana, Sebastián V. Romero et al. (+4 more)
We introduce
quantum-enhanced memetic tabu search (QE-MTS), a non-variational hybrid
algorithm that achieves state-of-the-art scaling for the low-autocorrelation binary sequence (LABS) problem. By seeding the classical MTS with high-quality initial states from digitized counterdiabatic
quantum optimization (DCQO), our method suppresses the empirical time-to-solution scaling to $\mathcal{O}(1.24^N)$ for sequence length $N \in [27,37]$. This scaling surpasses the best-known classical heuristic $\mathcal{O}(1.34^N)$ and improves upon the $\mathcal{O}(1.46^N)$ of the
quantum approximate optimization
algorithm, achieving superior performance with a $6\times$ reduction in
circuit depth. A two-stage bootstrap analysis confirms the scaling advantage and projects a crossover point at $N \gtrsim 47$, beyond which QE-MTS outperforms its classical counterpart. These results provide evidence that
quantum enhancement can directly improve the scaling of classical optimization
algorithms for the paradigmatic LABS problem.
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All authors Alejandro Gomez Cadavid, Pranav Chandarana, Sebastián V. Romero, Jan Trautmann, Enrique Solano, Taylor Lee Patti, Narendra N. Hegade
Quantum Physics · Cross-listed from hep-th
Fermionic Casimir densities for a uniformly accelerating mirror in the Fulling-Rindler vacuum
A. A. Saharian, L. Sh. Grigoryan and V. Kh. Kotanjyan
We investigate the local characteristics of the Fulling-Rindler
vacuum for a massive Dirac field induced by a planar boundary moving with constant proper acceleration in $(D+1)$-dimensional flat spacetime. On the boundary, the field operator obeys the bag boundary condition. The boundary divides the right Rindler wedge into two separate regions, called RL and RR regions. In both these regions, the
fermion condensate and the
vacuum expectation value (VEV) of the energy-momentum tensor are decomposed into two contributions. The first one presents the VEVs in the Fulling-Rindler
vacuum when the boundary is absent and the second one is the boundary-induced contribution. For points away from the boundary, the renormalization is reduced to the one for the boundary-free geometry. The total VEVs are dominated by the boundary-free parts near the Rindler horizon and by the boundary-induced parts in the region near the boundary. For a massive field the boundary-free contributions in the
fermion condensate and the
vacuum energy density and effective pressures are negative everywhere. The boundary-induced contributions in the
fermion condensate and the energy density are positive in the RL region and negative in the RR region. For a massless field the
fermion condensate vanishes in spatial dimensions $D\geq 2$, while the VEV of the energy-momentum tensor is different from zero. This behavior contrasts with that of the VEVs in the Minkowski
vacuum for the geometry of a boundary at rest relative to an inertial observer. In the latter case, the
fermion condensate for a massless field is nonzero, while the VEV of the energy-momentum tensor becomes zero. The obtained results are used to investigate the VEV of the fermionic energy-momentum tensor in weak gravitational fields and background geometries that are conformally related to Rindler spacetime.
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Quantum Physics
Continuous matrix product operators for quantum fields
Erickson Tjoa and J. Ignacio Cirac
In this work we introduce an ansatz for continuous
matrix product operators for
quantum field theory. We show that (i) they admit a closed-form expression in terms of finite number of
matrix-valued functions without reference to any
lattice parameter; (ii) they are obtained as a suitable continuum limit of
matrix product operators; (iii) they preserve the
entanglement area law directly in the continuum, and in particular they map continuous
matrix product states (cMPS) to another cMPS. As an application, we use this ansatz to construct several families of continuous
matrix product
unitaries beyond
quantum cellular automata.
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Quantum Physics · Cross-listed from cond-mat.mes-hall
Automatic tuning of a donor in a silicon quantum device using machine learning
Brandon Severin, Tim Botzem, Federico Fedele et al. (+12 more)
Donor
spin qubits in silicon offer one- and two-
qubit gates with fidelities beyond 99%, coherence times exceeding 30 seconds, and compatibility with industrial manufacturing methods. This motivates the development of large-scale
quantum processors using this platform, and the ability to automatically tune and operate such complex devices. In this work, we present the first machine learning
algorithm with the ability to automatically locate the charge transitions of an ion-implanted donor in a silicon device, tune single-shot charge readout, and identify the gate voltage parameters where tunnelling rates in and out the donor site are the same. The entire tuning pipeline is completed on the order of minutes. Our results enable both automatic characterisation and tuning of a donor in silicon devices faster than human experts.
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All authors Brandon Severin, Tim Botzem, Federico Fedele, Xi Yu, Benjamin Wilhelm, Holly G. Stemp, Irene Fernández de Fuentes, Daniel Schwienbacher, Danielle Holmes, Fay E. Hudson, Andrew S. Dzurak, Alexander M. Jakob, David N. Jamieson, Andrea Morello, Natalia Ares
Quantum Physics · Cross-listed from hep-ph
Probing quantum entanglement with Generalized Parton Distributions at the Electron-Ion Collider
Yoshitaka Hatta and Jakob Schoenleber
Within the collinear factorization framework based on Generalized Parton Distributions (GPDs), we calculate the
spin density
matrix of exclusively produced
quark and antiquark pairs $u\bar{u}$, $d\bar{d}$, $s\bar{s}$, $c\bar{c}$, $b\bar{b}$ in electron-
proton scattering. The presence of both real and imaginary parts in the scattering amplitudes leads to a rich pattern of
entanglement between the
quark and the antiquark. We map out kinematical regions where the pairs exhibit
entanglement, Bell nonlocality and non-stabilizerness (`magic'). We also predict that massive
quarks and antiquarks are transversely polarized, similar to the well-known transverse hyperon polarization in unpolarized collisions. In strangeness, charm and bottom productions, the polarization can reach 50-80% in certain kinematic regions in the low-energy runs of the Electron-Ion
Collider.
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Quantum Physics
Hybrid Single-Ion Atomic-Ensemble Node for High-Rate Remote Entanglement Generation
Benedikt Tissot, Soubhadra Maiti, Emil R. Hellebek et al. (+1 more)
Different
quantum systems possess different favorable qualities. On the one hand, ensemble-based
quantum memories are suited for fast multiplexed long-range
entanglement generation. On the other hand, single-atomic systems provide access to gates for processing of information. Both of those can provide advantages for high-rate
entanglement generation within
quantum networks. We develop a hybrid architecture that takes advantage of these properties by combining trapped-ion nodes and nodes comprised of spontaneous parametric down conversion
photon pair sources and absorptive
memories based on rare-earth ion ensembles. To this end, we solve the central challenge of matching the different bandwidths of
photons emitted by those systems in an initial
entanglement-generation step. This enables the parallel execution of multiple probabilistic tasks in the initial stage. As a particular example, we show that our approach can lead to a significant speed-up for the fundamental task of creating ion-ion
entanglement over hundreds of kilometers in a
quantum network.
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All authors Benedikt Tissot, Soubhadra Maiti, Emil R. Hellebek, Anders Søndberg Sørensen
Quantum Physics
Robust certification of non-projective measurements: theory and experiment
Raphael Brinster, Peter Tirler, Shishir Khandelwal et al. (+7 more)
Determining the conditions under which positive operator-valued measures (POVMs), the most general class of
quantum measurements, outperform projective measurements remains a challenging and largely unresolved problem. Of particular interest are projectively simulable POVMs, which can be realized through probabilistic mixtures of projective measurements, and therefore offer no advantage over projective schemes. Characterizing the boundary between simulable and non-simulable POVMs is, however, a difficult task, and existing tools either fail to scale efficiently, provide limited experimental feasibility or work only for specific POVMs. Here, we introduce and demonstrate a general method to certify non-simulability of a POVM by introducing a complete hierarchy of semidefinite programs. It provides upper bounds on the non-simulability measure of critical visibility of arbitrary POVMs which are tight in many cases and outperform previously known criteria. We experimentally certify the non-simulability of two- and three-dimensional POVMs using a trapped-ion qudit
quantum processor by constructing non-simulability witnesses and introduce a modification of our framework that makes them robust against state preparation errors. Finally, we extend our results to the setting where an additional ancilla system is available.
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All authors Raphael Brinster, Peter Tirler, Shishir Khandelwal, Michael Meth, Hermann Kampermann, Dagmar Bruß, Rainer Blatt, Martin Ringbauer, Armin Tavakoli, Nikolai Wyderka
Quantum Physics
Limiting one-way distillable secret key via privacy testing of extendible states
Vishal Singh, Karol Horodecki, Aby Philip et al. (+1 more)
The notions of
privacy tests and $k$-extendible states have both been instrumental in
quantum information theory, particularly in understanding the limits of secure communication. In this paper, we determine the maximum probability with which an arbitrary $k$-extendible state can pass a
privacy test, and we prove that it is equal to the maximum fidelity between an arbitrary $k$-extendible state and the standard maximally entangled state. Our findings, coupled with the resource theory of $k$-unextendibility, lead to an efficiently computable upper bound on the one-shot, one-way distillable key of a bipartite state, and we prove that it is equal to the best-known efficiently computable upper bound on the one-shot, one-way distillable
entanglement. We also establish efficiently computable upper bounds on the one-shot, forward-assisted private capacity of channels. Extending our formalism to the independent and identically distributed setting, we obtain single-letter efficiently computable bounds on the $n$-shot, one-way distillable key of a state and the $n$-shot, forward-assisted private capacity of a channel. For some key examples of interest, our bounds are significantly tighter than other known efficiently computable bounds.
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All authors Vishal Singh, Karol Horodecki, Aby Philip, Mark M. Wilde
Quantum Physics
Estimating ground-state properties in quantum simulators with global control
Cristian Tabares, Dominik S. Wild, J. Ignacio Cirac et al. (+3 more)
Accurately determining ground-state properties of
quantum many-body systems remains one of the major challenges of
quantum simulation. In this work, we present a protocol for estimating the ground-state energy using only global time
evolution under a target
Hamiltonian. This avoids the need for controlled operations that are typically required in conventional
quantum phase estimation and extends the
algorithm applicability to analog simulators. Our method extracts energy differences from measurements of the Loschmidt echo over an initial ground-state approximation, combines them with direct energy measurements, and solves a set of equations to infer the individual eigenenergies. We
benchmark this protocol on free-
fermion systems, showing orders-of-magnitude precision gains over direct energy measurements on the initial state, with accuracy improving rapidly with initial-state fidelity and persisting for hundreds of modes. We further demonstrate applicability to the 2D Ising and
Fermi-Hubbard models and show that the approach extends naturally to other observables such as order parameters. Finally, we analyze the effect of experimental imperfections and propose error-mitigation strategies. These results establish a practical route to compute physically relevant quantities with high precision using globally controlled
quantum simulators.
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All authors Cristian Tabares, Dominik S. Wild, J. Ignacio Cirac, Peter Zoller, Alejandro González-Tudela, Daniel González-Cuadra
Quantum Physics · Cross-listed from cond-mat.str-el
Symmetry-enriched topological order and quasifractonic behavior in $\mathbb{Z}_N$ stabilizer codes
Siyu He and Hao Song
We study a broad class of qudit stabilizer codes, termed $\mathbb{Z}_N$ bivariate-bicycle (BB) codes, arising either as two-dimensional realizations of modulated gauge theories or as $\mathbb{Z}_N$ generalizations of binary BB codes. Our central finding, derived from the
polynomial representation, is that the essential topological properties of these $\mathbb{Z}_N$ codes can be determined by the properties of their $\mathbb{Z}_p$ counterparts, where $p$ are the
prime factors of $N$, even when $N$ contains
prime powers ($N = \prod_i p_i^{k_i}$). This result yields a significant simplification by leveraging the well-studied framework of codes with
prime qudit dimensions. In particular, this insight directly enables the generalization of the algebraic-
geometric methods (e.g., the Bernstein-Khovanskii-Kushnirenko
theorem) to determine anyon fusion rules in the general qudit situation. Moreover, we elucidate the
symmetry-enriched topological (SET) order underlying the quasifractonic behavior in qudit BB codes (including the Delfino-Chamon-You model), resolving the associated anyon mobility puzzle. We also develop an efficient computational algebraic method, based on Gröbner bases over the ring of integers, to determine both the topological order and its SET properties.
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Quantum Physics
Quantum doubles in symmetric blockade structures
Hans Peter Büchler, Tobias F. Maier, Simon Fell et al. (+1 more)
Exactly solvable models of topologically ordered phases with non-abelian anyons typically require complicated many-body interactions which do not naturally appear in nature. This motivates the "inverse problem" of
quantum many-body physics: given microscopic systems with experimentally realistic two-body interactions, how to design a
Hamiltonian that realizes a desired topological phase? Here we solve this problem on a platform motivated by Rydberg atoms, where elementary two-level systems couple via simple blockade interactions. Within this framework, we construct
Hamiltonians that realize topological orders described by non-abelian
quantum double models. We analytically prove the existence of topological order in the ground state, and present efficient schemes to prepare these states. We also introduce protocols for the controlled adiabatic braiding of anyonic excitations to probe their non-abelian statistics. Our construction is generic and applies to
quantum doubles $\mathcal{D}(G)$ for arbitrary finite groups $G$. We illustrate braiding for the simplest non-abelian
quantum double $\mathcal{D}(S_3)$.
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All authors Hans Peter Büchler, Tobias F. Maier, Simon Fell, Nicolai Lang
Quantum Physics
Robustness of quantum data hiding against entangled catalysts and memory
Aby Philip and Alexander Streltsov
Quantum data hiding stores classical information in bipartite
quantum states that are, in principle, perfectly distinguishable, yet remain almost indistinguishable without access to a
quantum communication channel. Here, we investigate whether this limitation can be overcome when the communicating parties are assisted by additional
quantum resources. We develop a general framework for state discrimination that unifies catalytic and
memory-assisted local discrimination protocols and analyze their power to reveal hidden information. We prove that when the hiding states are separable, neither entangled catalysts nor
quantum memory can increase the optimal discrimination probability, establishing the robustness of separable data-hiding schemes. In contrast, for some entangled states, a reusable
quantum memory turns locally indistinguishable states into ones that can be discriminated almost perfectly. Our results delineate the fundamental limits of catalytic and
memory-assisted state discrimination and identify separable encodings as a robust strategy for
quantum data hiding.
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Quantum Physics
Mixed-State Phase Transitions in Measurement-Dressed Imaginary-Time Evolution
Yi-Ming Ding, Zenan Liu, Xu Tian et al. (+3 more)
Motivated by the ubiquity of decoherence in
quantum hardware and the growing role of imaginary-time
evolution (ITE) in
quantum algorithms, we investigate how many-body correlations generated by imaginary-time filtering are modified by local decoherence. We introduce measurement-dressed imaginary-time
evolution (MDITE), which alternates ITE with projective-measurement channels, producing a competition between low-energy filtering and local dephasing. By developing a new efficient
quantum Monte Carlo method, we uncover MDITE mixed-state transitions with spontaneous-
symmetry-breaking signatures in the driving of 1D transverse-field Ising and 2D columnar dimerized Heisenberg
Hamiltonians in the resulting density
matrices. In the continuous limit, the Choi-Jamiolkowski mapping yields a tractable
equilibrium description with conformal criticality that qualitatively captures the phase transitions. At finite protocol parameters, however, the four-point correlator violates the conformal cross-ratio form and the critical exponents deviate from their continuous-limit values, signaling the loss of conformal
symmetry and richer nonequilibrium criticality. Our results establish MDITE as a controlled setting for exploring mixed-state phases and critical phenomena driven by the interplay between imaginary-time filtering and decoherence.
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All authors Yi-Ming Ding, Zenan Liu, Xu Tian, Zhe Wang, Yanzhang Zhu, Zheng Yan
Quantum Physics
Tight Analysis of a One-Shot Quantum Secret Sharing Scheme
Santanu Majhi and Debajyoti Bera
Quantum communication protocols can be designed to detect eavesdropping attacks, something that classical technologies are unable to do since classical information can be replicated in a non-destructive manner. Eavesdropping detection is, therefore, a standard feature in all the proposed
quantum secret sharing (QSS) protocols. However, detection is often done by a statistical analysis of the outcome of multiple decoy rounds, and this causes a significant communication overhead. In our quest for a QSS protocol that works even in one round, we came across a one-shot secret-sharing framework proposed by Hsu (Phys. Rev. A 2003). The scheme was designed to work over public channels without requiring multiple rounds to detect eavesdropping but it lacked a thorough security analysis. In this work we present a complete characterisation of the correctness and security properties of this framework. Our characterisation allowed us to improve the original protocol to be more resistant towards eavesdropping. However, we prove a couple of impossibility results, including one that dictates that complete security against an eavesdropper is not possible in this framework. Thus, it is not possible to design a perfect QSS using this framework.
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Quantum Physics
Microwave Output Stabilization of a Qubit Controller via Device-Level Temperature Control
Yoshinori Kurimoto, Dongjun Lee, Koichiro Ban et al. (+8 more)
We present the design and performance of QuEL-1 SE, which is a multichannel
qubit controller developed for superconducting
qubits. The system incorporates the active thermal stabilization of critical analog integrated
circuits, such as phase-locked loops, amplifiers, and mixers, to suppress the long-term amplitude and phase drift. To evaluate the amplitude and phase stability, we simultaneously monitor 15 microwave output channels over 24 h using a common analog-to-digital converter. Across the channels, the normalized amplitude exhibits standard deviations of 0.09%–0.22% (mean: 0.15%), and the phase deviations are 0.35$^\circ$–0.44$^\circ$ (mean: 0.39$^\circ$). We further assess the impact of these deviations on
quantum gate operations by estimating the average fidelity of an $X_{\pi/2}$ gate under the coherent errors corresponding to the deviations. The resulting gate infidelities are $2\times 10^{-6}$ for amplitude errors and $2\times 10^{-5}$ for phase errors, which are significantly lower than typical fault-tolerance thresholds such as those of the surface code. These results demonstrate that the amplitude and phase stability of QuEL-1 SE enables reliable long-duration
quantum operations, thus highlighting its utility as a scalable control platform for superconducting and other
qubit modalities.
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All authors Yoshinori Kurimoto, Dongjun Lee, Koichiro Ban, Shinichi Morisaka, Toshi Sumida, Hidehisa Shiomi, Yosuke Ito, Yuuya Sugita, Makoto Negoro, Ryutaro Ohira, Takefumi Miyoshi
Quantum Physics
Minimum measurements quantum protocol for band structure calculation
Michal Krejčí, Lucie Krejčí, Ijaz Ahamed Mohammad et al. (+2 more)
Protocols for
quantum measurement are an essential part of
quantum computing. Measurements are no longer confined to the final step of computation but are increasingly embedded within
quantum circuits as integral components of noise-resilient
algorithms. However, each observable typically requires a distinct measurement basis, often demanding a different
circuit configuration. As the number of such configurations typically grows with the number of
qubits, measurements constitute a major bottleneck. Focusing on electronic structure calculations in crystalline systems, we propose a measurement protocol that restricts the required measurement configurations to an absolute minimum of just three, independent of the number of
qubits. This makes it one of the few known protocols that do not scale with
qubit number. In particular, we derive the measurement protocol from the
symmetries of tight-binding (TB)
Hamiltonians and implement it within the Orthogonal-Ansatz Variational
Quantum Eigensolver (OA-VQE)
algorithm. We demonstrate its performance on three systems, namely a two-dimensional CuO$_2$ square
lattice (3
qubits),
bilayer graphene with hexagonal (Honeycomb)
lattice (4
qubits) and three-dimensional diamond
lattice (10
qubits). Beyond tight-binding systems, the protocol can be extended to enable efficient initial state preparation for many-body
Hamiltonians, such as multi-orbital Hubbard models in a momentum space.
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All authors Michal Krejčí, Lucie Krejčí, Ijaz Ahamed Mohammad, Martin Plesch, Martin Friák
Quantum Physics
Non-relativistic Quantum Mechanics on a Twisted Cylindrical Surface
G. M. Delgado and J. E. G. Silva
Twisted cylindrical tubes are important model systems for nanostructures,
heterostructures, and curved
quantum devices. In this work, we investigate the
quantum behavior of an electron confined to a twisted cylindrical surface. By first calculating the strain tensor to obtain the induced surface metric, we employ da Costa's formalism to derive the geometry-induced
quantum potential. This potential modifies the Schrödinger equation even in the absence of external forces, allowing us to determine the bound states and energy
eigenvalues. This was made in the linear and non-linear torsion regime. Furthermore, we analyze two distinct scattering problems: (i) scattering within an infinite cylinder containing a twisted section, and (ii) scattering of a free particle incident upon a finite twisted cylinder. Our goal is to understand how geometry and strain influence the properties of analogous untwisted systems. It turns out that both the linear and non-linear twists yield to a
geometric phase into the wave function, while the da Costa potential is kept unchanged. Consequently, the system supports bound states whose energie spectrum is twist independent. For both scattering problems, we find that the transmission probability is insensitive to torsion, whereas it is significantly affected by the particle angular momentum and the cylinder's radius, exhibiting distinct oscillatory behavior. These findings suggest relevant implications for engineering
quantum devices based on materials with controlled
curvature and twist.
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Quantum Physics · Cross-listed from math.NA
Normalized tensor train decomposition
Renfeng Peng, Chengkai Zhu, Bin Gao et al. (+2 more)
Tensors with unit Frobenius norm are fundamental objects in many fields, including scientific computing and
quantum physics, which are able to represent normalized eigenvectors and pure
quantum states. While the tensor train decomposition provides a powerful low-rank format for tackling high-dimensional problems, it does not intrinsically enforce the unit-norm constraint. To address this, we introduce the normalized tensor train (NTT) decomposition, which aims to approximate a tensor by unit-norm tensors in tensor train format. The low-rank structure of NTT decomposition not only saves storage and computational cost but also preserves the underlying unit-norm structure. We prove that the set of fixed-rank NTT tensors forms a smooth
manifold, and the corresponding Riemannian geometry is derived, paving the way for
geometric methods. We propose NTT-based methods for low-rank tensor recovery, high-dimensional
eigenvalue problem, estimation of stabilizer rank, and calculation of the minimum output Rényi 2-
entropy of
quantum channels. Numerical experiments demonstrate the superior efficiency and scalability of the proposed NTT-based methods.
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All authors Renfeng Peng, Chengkai Zhu, Bin Gao, Xin Wang, Ya-xiang Yuan
Quantum Physics · Cross-listed from cond-mat.dis-nn
Emergent Dynamical Translational Symmetry Breaking as an Order Principle for Localization and Topological Transitions
Yucheng Wang
Localization transitions represent a fundamental class of continuous phase transitions, yet they occur without any accompanying
symmetry breaking. We resolve this by introducing the concept of dynamical translational
symmetry (DTS), which is defined not by the
Hamiltonian but by the long-time dynamics of local observables. Its order parameter, the time-averaged local translational contrast (TLTC), quantitatively diagnoses whether
evolution restores or breaks translational equivalence. We demonstrate that the TLTC universally captures the Anderson localization transition, the many-body localization transition, and topological phase transitions, revealing that these disparate phenomena are unified by the emergent breaking of DTS. This work establishes a unified dynamical-
symmetry framework for phases transitions beyond the
equilibrium paradigm.
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Quantum Physics
Neutral-atom quantum computation using multi-qubit geometric gates via adiabatic passage
Sinchan Snigdha Rej and Bimalendu Deb
Adiabatic
geometric phase gates offer enhanced robustness against fluctuations compared to con- ventional Rydberg blockade-based phase gates that rely on dynamical phase accumulation. We theoretically demonstrate two- and multi-
qubit phase gates in a neutral atom architecture, relying on a double stimulated Raman adiabatic passage (double-STIRAP) pulse sequence that imprints a controllable
geometric phase on the
qubit systems. The system is designed in such a way that every atom is individually addressable, and moreover, no extra
laser is required to be applied on the target atom while scaling up the system from two- to multi-
qubit quantum gates. The gate fidelity has been numerically analyzed by changing the gate operation time, and we find that 98% to 99% fidelity can be achieved for gate time $\simeq$ 0.6 $\mu$s. We perform a systematic error analysis, which re- veals that our proposed gates can exhibit strong resilience against fluctuations in Rabi frequencies, finite blockade strength, and atomic position variations. These results establish our approach as a physically feasible and scalable pathway toward fault-tolerant
quantum computation with neutral atoms. We simulate Grover's search
algorithm for two-, three-, and four-
qubit systems with high success probability and thereby demonstrate the utility and scalability of our proposed gates for
quantum computation.
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Quantum Physics · Cross-listed from hep-th
Gauge and diffeomorphism invariance from quantum information principles
Claudia Núñez, Miguel Pardina, Manuel Asorey et al. (+2 more)
Entanglement is a hallmark of
quantum theory, yet it alone does not capture the full extent of
quantum complexity: some highly entangled states can still be classically simulated. Non-classical behavior also requires magic, the non-Clifford component that enables universal
quantum computation. Here, we investigate whether the interplay between
entanglement and magic-state resources constrains the structure of fundamental interactions. We study
gluon-
gluon and graviton-graviton scattering at tree level. We focus on the high-energy limit, where mass-dependent terms are negligible, and conformal
symmetry is preserved. In this regime, all particles behave as massless degrees of freedom, allowing to isolate their transverse helicities as two-
qubit states. We explicitly break gauge and general covariance by modifying the quartic vertices and analyzing the resulting generation of
entanglement and magic. We find that imposing maximal
entanglement (MaxEnt) alone does not uniquely recover gauge-invariant and diffeomorphism invariant interactions, but adding the condition of minimal, but nonzero, magic-state generation singles it out. Our results indicate that nature favors MaxEnt and low magic: maximal
quantum correlations with limited non-Cliffordness, sufficient for universal
quantum computing but close to classical simulability. This dual informational principle may underlie the emergence of gauge invariance in fundamental physics.
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All authors Claudia Núñez, Miguel Pardina, Manuel Asorey, José Ignacio Latorre, Alba Cervera-Lierta
Quantum Physics
A General Strategy for Realizing Mpemba Effects in Open Quantum Systems
Yaru Liu and Yucheng Wang
The Mpemba effect, where a state farther from
equilibrium relaxes faster than one closer to it, is a striking phenomenon in both classical and
quantum systems. In open
quantum systems, however, the
quantum Mpemba effect (QME) typically occurs only for specifically chosen initial states, which limits its universality. Here we present a general and experimentally feasible strategy to realize both QME and anti-QME. By applying a temporary bond-dissipation quench, we selectively suppresses or enhances slow relaxation modes, thereby reshaping relaxation pathways independently of both the system and the initial state. We demonstrate this mechanism in systems with dephasing and boundary dissipation, and outline feasible cold-atom implementations. Our results establish controllable dissipation as a versatile tool for
quantum control, accelerated relaxation, and efficient nonequilibrium protocols.
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