In briefRecovering hidden conserved densities in quantum simulators from snapshot measurements
SummaryProjective snapshots on quantum simulators directly probe only observables diagonal in the measurement basis. The paper combines local equilibration with an independently calibrated equilibrium equation of state to reveal hidden conserved-density profiles. Numerical demonstrations show recovery of energy fronts and a diffusion constant, and separation of spin transport from energy spreading.
In briefRenormalization for stable memory from independent local updates without synchronization
SummaryThe paper develops a spacetime renormalization framework showing how independently acting local updates can collectively preserve classical information when sites evolve at random, unsynchronized times. It gives sufficient conditions under which stable interfaces and suppressed defect propagation yield reliable erosion at large scales. Applying this, the authors prove stability of an asynchronous R squeezing code and introduce robust processes in two and three dimensions, where both encoded phases persist under sufficiently weak noise.
In briefComparing entangling strategies for unitary synthesis, a study of how multiqubit gates on trapped-ion computers perform in building target quantum operations.
SummaryThis paper examines whether multiqubit gates on trapped-ion quantum computers are worth their added engineering complexity. The authors use unitary synthesis, a task not tied to any specific application, as a benchmark for gate sets built from native Mølmer–Sørensen multiqubit gates. They also develop a toolset for evaluating such gate sets and identify the hardware requirements under which multiqubit gates become advantageous.
Jonas Wunder, Hendrik Weimer, Ricardo Costa de Almeida
In briefEntanglement diagnostics in stochastic-resetting steady states, tested on superconducting qubits
SummaryThe paper studies entanglement in nonequilibrium steady states of the transverse-field Ising chain under stochastic resetting, giving closed-form results for two qubits and exact calculations for chains up to 12 qubits. Measurements on an IBM superconducting processor show averaged entropies closely matching noiseless predictions, while concurrence mostly falls below prediction, captured by a depolarizing model with one fitted parameter. The difference between the two entropies, the Jensen gap, equals the Holevo information a subsystem retains about the time since the last reset, which grows with chain length.</summary>
Jakob Murauer, Sabine Tornow, Manas Kulkarni et al.
In briefLocality in Dissipative Ground-State Preparation: Whether Local Dissipation Can Prepare a Local Hamiltonian's Ground State
SummaryThis paper asks whether the ground state of a free-fermion Hamiltonian can be prepared using local dissipation. The authors use a quadratic Lindbladian with linear jump operators and link spatial locality to momentum-space analyticity via Fourier correspondence. They derive a complete spectral criterion for exponentially local jump operators that prepare the ground state. The results show that sign-changing Fermi-level crossings rule out such preparation in one dimension, while additional obstructions arise in higher dimensions.
In briefLeft-handed transmission lines for generating photons via the dynamical Casimir effect
SummaryThis paper studies superconducting transmission lines built with series capacitors and shunt inductors, terminated by a flux-modulated SQUID. The authors derive the quantum Hamiltonian and compare the line with a right-handed line and a coplanar waveguide built from the same elements. With equal elements, the left-handed coupling exceeds the right-handed one above a crossover pump frequency, and the created particles stay in the target mode.
Valentin E. Salari, Fernando C. Lombardo, and Paula I. Villar
In briefOptimal estimation of diamond distance between unitary channels
SummaryThis paper presents a quantum algorithm that estimates the diamond distance between two unknown d-dimensional unitary channels to within additive error ε. It uses O(√d/ε) queries to the unitary channels and their inverses. The query complexity matches the lower bound due to Jeon and Oh (npj Quantum Inf., 2026), so the algorithm is optimal.
In briefUsing Exceptional Points to Detect Non-Gaussian Noise
SummaryThe paper shows that exceptional points (EPs) in the noise-averaged dephasing response of quantum devices can reveal non-Gaussian noise statistics that the power spectrum alone cannot distinguish. It introduces a model describing dephasing environments as identical independent noise sources while preserving the power spectrum. Given a calibrated single-source model, the largest EP order extracted from the measured response determines the number of sources and predicts higher-order statistics of the combined noise.
Aritra Ghosh, Subhashish Banerjee, M. Bhattacharya
In briefAlgebraic theory of abelian fractons: fusion, mobility and statistics in gapped fracton phases
SummaryThis paper develops an algebraic framework for fusion, mobility and statistics in abelian gapped fracton orders and topological phases, generalizing the algebraic description of abelian anyons to systems with restricted mobility and extended excitations. It introduces braided fusion complexes, which encode fusion, mobility and statistics, and defines braided fusion theories as their equivalence classes. The authors also study mutual statistics and remote detection for nondegenerate theories, and prove that the excitation-detector principle is equivalent to nondegeneracy under a unique infinite-space ground state assumption.
In briefOptimal detuning and gate time for strong single-qubit gates beyond the rotating-wave approximation
SummaryThis paper studies how single-qubit quantum gates lose accuracy when strong driving is used, since the rotating-wave approximation no longer holds. The authors analyse the error using an effective Magnus-Taylor Hamiltonian through second order in the inverse driving frequency. They correct the driving frequency with an amplitude-dependent Bloch-Siegert-type shift and rescale the gate time to restore the RWA gate conditions. Numerical solutions of the Schrödinger equation show that these corrections reduce gate infidelity by several orders of magnitude, widening the usable range of driving amplitudes.
Alejandro D. Bendersky, Sergio S. Gomez, Rodolfo H. Romero
In briefProbing photon emission fluctuations in spin-injected quantum dots using time-dependent electrical excitation
SummaryThis paper studies electrically spin-injected InGaAs/GaAs quantum dot ensembles that emit circularly polarized single photons without an external pump laser. Using an extended Hanbury Brown-Twiss interferometer with four detectors, the authors measure time-resolved photon-number statistics and find that two-photon statistics fluctuate at several points within each excitation pulse. These fluctuations disappear when the spin-injection layer is demagnetized, linking multi-photon emission dynamics to the spin polarization of injected carriers.
Chiran Wijesundara, Vincent Iglesias-Cardinale, Yuan Lu et al.
In briefNested toric codes: decoupling translation-invariant topological CSS codes in higher dimensions
SummaryThis paper studies topological CSS quantum error-correcting codes in three or more spatial dimensions, which are useful for fault-tolerant quantum computation. The authors show that such a code can be decoupled into a stack of higher-form toric codes by a finite-depth local Clifford circuit once, after coarse-graining to a superlattice, translations act trivially on each excitation layer and the gluing between layers vanishes. They also give an explicit algorithm that builds this decoupling circuit from SUM and SWAP gates.
In briefCollaborating AI agents that run autonomous quantum spin experiments
SummaryThis paper presents an autonomous research laboratory in which large language model agents review each other's work and can stop or redirect investigations. The agents study ensembles of quantum spins in diamond, deriving the minimum number of calibration settings needed to predict responses to a family of microwave pulse sequences. An initial experiment matched the predictions, but repeated reference measurements revealed signal drift, so the agents revised the protocol without relaxing their acceptance criteria. The revised experiment met those criteria and supported the theoretical predictions.
El Mustapha Mansouri, Eikichi Kimura, Masato Koga et al.
In briefClassical communication over quantum channels: does entanglement help?
SummaryThis paper examines whether entangling codewords across independent uses of a quantum channel can increase the rate of classical communication. The authors propose a general Schur-weighted block entropy inequality. They show that phase-covariant channels, including multi-level amplitude damping, generalized dephasing, and damping-dephasing channels, have no entanglement advantage. The result also recovers the known conclusion for all qubit channels.
WhyThe authors propose a Schur-weighted block entropy inequality and show no entanglement advantage for phase-covariant channels, recovering the qubit result.
In briefWhat Can Be Computed with Indefinite Causal Structure? A study of whether quantum computing gains power when operations lack a fixed causal order.
SummaryThe paper studies whether quantum computation becomes more powerful when operations need not follow a definite causal order, using the process matrix formalism of Oreshkov et al. The authors give polynomial-time algorithms in two settings. General process matrices can solve every problem in NP, using valid processes that satisfy the purification postulate and generate unitary channels. Requiring the process matrices to be pure, they solve unique-sink orientation in polynomial time, which suggests indefinite causal order can exceed BQP while preserving unitarity.
WhyThe authors show indefinite causal order yields computational power beyond BQP, solving NP problems and unique-sink orientation in polynomial time within the process matrix formalism.
In briefOn the Quantum Chromatic Gap II: a proof of a strong form of pseudo-telepathy
SummaryThis paper confirms a conjecture from the first author's SODA'26 paper about Khot's d-to-1 games. It constructs label-cover games with classical value below any given epsilon that still admit a perfect quantum strategy. As a consequence, there are graphs with quantum chromatic number 3 and arbitrarily large classical chromatic number, the first improvement on this gap since Brassard, Cleve, and Tapp.
WhyThe authors construct graphs with quantum chromatic number 3 and arbitrarily large classical chromatic number, improving on prior exponential gap results.
In briefAlgebraic strong-to-weak symmetry breaking and partial decodability in the surface code
SummaryThis paper studies how coherent noise produces unusual regimes of quantum error recovery and mixed-state order. It links a triangular-lattice surface code under single-qubit Z rotations with a Z2 paramagnet under strongly symmetric decoherence through Wegner duality. Increasing the rotation angle leads to a partially decodable critical phase in the code and an algebraic Z2 strong-to-weak symmetry breaking phase in the dual model. The authors derive universal observables using a weakly coupled SO(n) sigma model in the replica limit n→1, and large-scale simulations confirm these predictions.
WhyThe authors link surface-code decoding and strong-to-weak symmetry breaking via Wegner duality, proposing an algebraic SWSSB phase with universal power-law and fidelity predictions checked numerically
In briefGrow, Compress, and Perturb: A Hybrid Quantum-Classical Method for Scalable Quantum Chemistry
SummaryThis paper introduces VULCAN, a layered variational quantum eigensolver framework that avoids Hamiltonian gradient measurements by building ansatz operators dynamically with variational double bracket flow. Emulations on up to 32 logical qubits reach chemical accuracy for hydrogen chains, BeH2, and H2O using 5-20% of the measurement cost of batched ADAPT-VQE. For the 32-qubit C3H6 case, a single VULCAN layer combined with a GPU-accelerated stochastic ENPT2 correction reaches chemical accuracy, where batched ADAPT-VQE does not.
Hugo D. Nogueira, Siwar Badreddine, Olivier Adjoua et al.
In briefQuasi-Phases of Quantum Matter: Distinct Gapped Regimes Near a Critical Point
SummaryThe paper introduces quasi-phases, gapped regimes near a critical point that are connected in the broader phase diagram but not by any gapped path reachable through small perturbations of the critical theory. In spin-chain examples with central charge c=1, the authors identify multicritical c=3/2 and c=9/5 orbifolds that describe these quasi-phases. The work also argues that such quasi-phases can carry interface modes with higher-dimensional linear representations.
Nick G. Jones, Paul Fendley, Nathanan Tantivasadakarn et al.
In briefGauge-invariant orbital angular momentum of vector optical vortices beyond the paraxial approximation
SummaryThis paper presents a gauge-invariant formalism for describing the spin and orbital angular momenta of scalar and vector optical vortices. A correction term arising from consistent treatment of the transverse vector potential's nonlocality restores gauge invariance and allows the total angular momentum to be separated into spin and orbital parts. The authors show that the orbital angular momentum of multimode vector vortex beams has two qualitatively different components and discuss the limits of applicability of the formalism.
E. V. Maliutina, E. A. Vashukevich, V. A. Leonov et al.
In briefBenchmarking fast quantum annealing with domain walls
SummaryThis paper studies the distribution of domain walls in ground states of frustrated one-dimensional Ising spin chains with anti-parallel boundary spins. Ideal chains are expected to show a sine-squared distribution quantumly and a uniform distribution classically, while chains with random imperfections on a physical device show a U-shaped profile. Using D-Wave's fast anneal feature, the authors observe a sine-squared distribution consistent with coherent quantum behavior and propose the extent of the domain wall distribution tail as a platform-independent metric.
Shushmi Chowdhury, Asa Hopkins, Nick Chancellor et al.
In briefFast, accurate neural decoding for ultra-high-rate quantum error-correcting codes
SummaryThis paper introduces neural triage decoding, a framework that uses syndrome consistency to adaptively allocate neural computation for decoding quantum error-correction codes. A local neural message-passing network quickly predicts corrections, extra iterations reduce residual syndrome violations, and a rarely used diversification stage searches for consistent corrections for the remaining cases. The authors demonstrate the Triage decoder on ultra-high-rate quantum LDPC codes encoding a few hundred logical qubits, including lifted-product and Kasai codes, reporting accuracy comparable to near-optimal algorithmic decoders with latency reduced by roughly one to two orders of magnitude.
WhyThe authors propose a syndrome-consistency-guided neural decoder, reporting near-optimal accuracy with substantially lower latency on high-rate qLDPC codes.
SummaryThe paper shows that the ensemble of unimodular Gottesman-Kitaev-Preskill distributions does not form a rigged quantum 3-design. It quantifies the replica defect responsible for this failure. The result is established by rederiving a second moment formula for symplectic lattices in a self-contained way.
In briefEntropic fluctuations in quantum statistical mechanics: a review of how classical entropy fluctuation theorems are extended to quantum systems.
SummaryThis paper reviews and compares several ways the Evans-Searles and Gallavotti-Cohen fluctuation theorems for entropy production can be extended to quantum systems. It introduces a recent approach and adds an extension of the steady-state version to two-time measurement entropy production in the algebraic setting. The authors discuss open quantum systems, the connection to modular theory, and a quantum principle of regular entropic fluctuations. They also relate these entropy production statistics to spectral resonances of quantum transfer operators, applied to the spin-fermion model.
Tristan Benoist, Laurent Bruneau, Vojkan Jak\v{s}i\'c et al.
SummaryThis paper studies a static dipolar impurity immersed in a Fermi gas, examining how dipolar interactions shape few-body scattering and the resulting polaron physics. Using Fumi's theorem, the authors link anisotropic phase shifts directly to the ground-state energy and compute the exact impurity spectrum with a functional determinant approach. The spectrum is a convolution of independent even- and odd-wave contributions, yielding a ground state with both even- and odd-wave bound states occupied, whose separation is tunable via the dipole length.
WhyThe authors apply Fumi's theorem and functional determinants to a dipolar impurity, reporting a doubly occupied ground state that a one-excitation variational ansatz misses.
In briefSpectral metrics inspired by quantum walks for judging QAOA mixer choices
SummaryInspired by quantum-walk mixing theory, the paper proposes two spectral indicators for QAOA mixer topologies: the normalized minimum eigenvalue separation of the mixer Hamiltonian, and the long-time averaged minimum eigenvalue separation of the mixer unitary. The authors derive exact expressions and asymptotic bounds for the complete graph, hypercube, cycle, and balanced 2-D torus. For random permutation-invariant cost Hamiltonians the spectral ordering broadly matches observed QAOA performance, but for structured 1-D and 2-D Ising QUBOs it breaks down, suggesting mixer-cost alignment matters.
In briefSharpening particle trajectories by changing quantum reference frames
SummaryThis paper links quantum reference frame transformations to experimental effects. Using a toy model of free particles with signed masses, it shows that trajectory sharpening from correlating a system with a negative-mass reference can be read as a transformation to a negative-mass frame. The authors define frame-invariant sharpness measures and derive monogamy relations limiting sharpness with respect to two negative-mass frames.
In briefProcess matrices for generalised physical theories, extending indefinite causal order beyond quantum theory.
SummaryThe paper extends the process-matrix framework for indefinite causal orders to a broad class of generalised physical theories. It re-axiomatises spacetime contexts through naturality over classical probes, capturing non-contextual assignment with compatibility for convexity and coarse-graining. It characterises which theories admit a process-matrix representation of abstract spacetime contexts, and identifies when supermap and process-matrix perspectives coincide in classical, quantum, and Boxworld-like theories.
Matt Wilson, James Hefford, and Timoth\'ee Hoffreumon
In briefA universal gauge structure in the photon content of light-matter systems
SummaryAfter truncating the matter space of single-mode light-matter models, gauge changes leave the spectrum unchanged but alter the ground-state photon number, whose meaning has been disputed. The paper shows that when the gauge transformation is a field displacement coupled to a matter operator, this photon number is an exact quadratic polynomial in the gauge parameter. Its minimum over all gauges is gauge-invariant and, for the quantum Rabi model, is set by the ground-state energy alone.
In briefStructural limits of QAOA mixer design: transport and causal reach
SummaryThe paper examines mixer design in the Quantum Approximate Optimization Algorithm (QAOA), identifying two structural bottlenecks for shallow circuits: probability transport across configuration space and finite-depth causal reach. It derives mixer-dependent first-order objective bounds and a non-perturbative spreading condition. For MaxCut, it adds problem-graph-aligned two-local interactions to the transverse-field mixer, and reports that X+XX and X+YY improve approximation ratios over the standard X mixer at equal depth.
In briefElectric field control of spin transport anisotropy in a layered antiferromagnet
SummaryThis paper studies a dual-gate field-effect transistor built on CrSBr, a layered A-type antiferromagnetic semiconductor. The measurements show that the displacement field, rather than carrier doping, mainly determines the sign and magnitude of the magnetoresistance ratio. The authors explain the effect using ab initio calculations and an effective spin-circuit model. They conclude that the displacement field is an efficient electrical knob for controlling spin transport in CrSBr.
Mohamed Soliman, Jaime Garrido Aldea, Davy Borowski et al.
In briefMicromagnetic Lagrangian and Hamiltonian formulation of magnon-photon coupling in cavities
SummaryThis paper studies how magnons and photons interact inside a resonant microwave cavity, starting from linearized Maxwell and Landau-Lifshitz equations. The authors introduce an electric vector potential and an interaction Lagrangian, expand fields in normal modes, and derive a Hamiltonian using the Faddeev-Jackiw approach. A generalized Bogoliubov transformation then diagonalizes the coupled system into polariton variables. As an example, a perpendicularly magnetized YIG disk in a rectangular cavity shows hybridization of the cavity mode with several magnetostatic modes and frequency shifts near conducting walls.
In briefFault-tolerant Heisenberg-limited quantum sensing using bosonic probes
SummaryThis paper proposes a fault-tolerant protocol that uses bosonic probes to estimate displacements in the presence of dephasing noise. The authors construct an optimal error-correcting code under a mean photon-number constraint, with a repetition-encoded qubit register and repeated boson-parity measurements. Under circuit-level bit-flip noise, a distance-d code suppresses logical failures to order p^((d+1)/2). The Fisher information scales as NT² over interrogation times of order γ_A^(-(d+1)/2), compared with γ_A^(-1) for the non-fault-tolerant approach.
Daniel G. Li, Lorc\'an O Conlon, Yu-Xin Wang et al.
In briefClassifying cavity-modified reaction types via linear free-energy relationships
SummaryThis paper extends nonempirical linear free-energy relationships to reactions inside optical cavities and finds that they fall into four reaction types set by simple response-crossing rules. Reactions may follow conventional Bell-Evans-Polanyi (BEP) or counterintuitive Opposite-BEP behavior, or switch between them as cavity frequency changes. The framework is demonstrated in the Shin-Metiu model and four molecular reactions, and the complexity is reduced to competition between permanent-dipole and polarizability responses.
Jillian G. Hoffstadt, Davis M. Welakuh, Norah M. Hoffmann
In briefQuantum computing via computational imaging: representation, measurement, and inference
SummaryThis paper, aimed at computational-imaging and engineering readers, examines how the representation, measurement, and decoding of a quantum state determine what information can be returned. It distinguishes amplitude encodings of input values from encodings of complete candidate labelings, and studies unknown-phase inference under complex-field interference. It links singular-value decomposition of reshaped joint amplitudes to pure-state entanglement. In a four-pixel segmentation example, one QAOA layer lowers mean energy relative to uniform sampling yet makes a nonoptimal labeling more probable than the optimum.
George Kourousias, Sergio Carrato, Roberto Pugliese et al.
In briefFast mixing of Gibbs samplers for quantum spin systems with all-to-all coupling
SummaryThis paper studies how quickly Gibbs states of two-local quantum Hamiltonians on arbitrary interaction graphs, including fully connected systems, can be prepared using Lindblad dynamics satisfying KMS detailed balance. The authors adapt the classical Dobrushin condition to the quantum setting and use the order-1 quantum Wasserstein distance to measure how local perturbations spread. In a high-temperature regime set by the maximum total interaction strength per site, they derive contraction estimates that yield mixing times logarithmic in system size and inverse error tolerance.
In briefQuantum communication via a state discrimination method
SummaryThis paper proposes a state discrimination approach to unassisted quantum communication over a noisy quantum channel. Building on the operational duality between entanglement recovery and state discrimination, the authors construct entanglement-generation codes with explicit decoders based on Petz recovery maps. The error bounds hold for any number of channel uses and are expressed in terms of Petz-Rényi coherent information. For product sources, the error decays exponentially at rates below the coherent information.
In briefSubsystem Spacetime Code: A Quantum Error-Correction Framework for Measuring Clifford Circuit Fault Distance
SummaryThe paper constructs a subsystem spacetime code and uses it to characterize the distances of Clifford circuits. Its gauge group can be explicitly constructed and classified using masking properties of instantaneous stabilizer groups, and consists of faults that are harmless to the circuit. The framework is also used to identify where a dynamical code loses distance and to analyze how fault distance changes when circuits are composed from smaller components.
Esther Xiaozhen Fu, Aranya Chakraborty, Daniel Gottesman
In briefMultidimensional Revival Dynamics in a Bosonic Many-Body System: A study of how localized quantum states collapse and revive in a two-site Bose-Hubbard model
SummaryThis paper studies quantum interference in a symmetric two-site Bose-Hubbard model. Starting from a coherent state prepared on one site in the strongly self-trapping regime, the authors derive revival behaviors in expectation values, coherences, and the autocorrelation function, and illustrate the entanglement behavior. They identify several new features and show that a comprehensive semiclassical theory explains them, with excellent agreement to quantitative comparisons.
In briefLocal determination of low-energy states in weakly interacting gapped fermion systems
SummaryThis paper studies gapped fermion systems obtained by adding sufficiently weak even many-body interactions to a free Hamiltonian with a spectral gap. It proves that if another interaction matches the bulk interaction inside a region U, its low-energy states in the range [0, 3g/4] have local expectations close to the bulk ground state deep inside U, with errors decaying with distance from the complement of U. The results imply, among other things, that the bulk interaction has a unique algebraic ground state.
WhyThe authors prove quantitative local determination of low-energy states in gapped fermion systems with weak long-range interactions, yielding uniqueness of the algebraic ground state and localization
In briefHigh-fidelity universal quantum gates in a cryogenic atom array
SummaryThis paper demonstrates a universal quantum gate set in a cryogenic cesium-133 atom array. Single-qubit gates reach 99.970(2)% fidelity and raw two-qubit entangling gates reach 99.76(8)%, within the range of leading room-temperature implementations. The entangling gate uses direct single-photon coupling to a Rydberg P state, avoiding the scattering and light shifts of two-photon coupling.
WhyThe authors demonstrate a universal gate set in a cryogenic cesium atom array, using direct single-photon Rydberg coupling for entangling gates, and report single-qubit fidelity of 99.970(2)% and raw
In briefQDMin: Quantum Search for Energy Minima in Nuclear Shape Landscapes
SummaryThis paper presents QDMin, a method for locating the minimum of a nuclear collective energy landscape. It searches a parameterized Hamiltonian family using a coherent collective-coordinate register and an on-demand ground-energy threshold oracle, avoiding point-by-point construction of the landscape. The method is implemented for a schematic pairing-plus-multipole model, with calculations at four points and on a 4×4 quadrupole–octupole grid.
In briefTransport in spinful non-Hermitian gauge lattices: spin-dependent skin effects and transmission in one-dimensional lattices with gauge fields
SummaryThis paper extends a generalized transfer-matrix method to one-dimensional non-Hermitian tight-binding lattices with spin and matrix-valued Abelian and non-Abelian gauge couplings. In the Abelian case the spin sectors separate, giving exact spectra and closed transport expressions with spin-dependent skin localization. In the non-Abelian case noncommuting couplings mix the spin sectors, producing spin-hybridized lasing, coherent perfect absorption, and direction-dependent reflectionless transport with spin conversion.
In briefStability of the bulk gap and spectral flow for fermions with weak long-range interactions
SummaryThe paper proves that weak long-range many-body interactions preserve the bulk gap of a free fermion system. It constructs a quasi-local spectral flow that maps the free ground state to ground states of the interacting system. The results hold under polynomial decay conditions on the coefficients and interactions.
WhyThe authors prove bulk gap stability and construct a quasi-local spectral flow under weak long-range interactions, with polynomial decay conditions.
In briefUpper bounds on general (r,δ) quantum locally recoverable codes
SummaryThis paper studies general (r,δ) quantum locally recoverable codes without assuming purity or stabilizer structure, allowing recovery blocks to overlap arbitrarily. It establishes a Singleton-like upper bound for general quantum subspaces and tightens it with an explicit remainder correction. The authors also extend a known pure-code parameter bound to arbitrary pure quantum subspaces and analyze three code families that attain these bounds.
In briefThree-dimensional quantum cellular automata that cannot be stabilized into circuits
SummaryThe paper proves that for every odd prime p, the three-dimensional chiral Z_p Clifford quantum cellular automata of Haah and of Sun, Yang, Wang, Tantivasadakarn and Chen are not finite-depth quantum circuits, even after tensoring with arbitrary ancillary degrees of freedom and composing with translations. Previously such results were known only within the Clifford category. As a consequence, the group of three-dimensional QCA modulo stabilized circuits and translations is not finitely generated.
WhyThe authors introduce a new invariant for invertible subalgebras, proving 3D QCA are not finite-depth circuits beyond the Clifford setting; one key claim remains conjectural.
In briefStabilizing fluctuating Cooper pairs using a terahertz resonator
SummaryThis paper develops an equilibrium theory of a mesoscopic, disordered two-dimensional superconductor coupled to a subwavelength terahertz resonator, focusing on how superconducting phase fluctuations interact with the resonator's electromagnetic fluctuations. Modeling the resonator as a lumped-element circuit, the authors find that coupling raises the superconducting transition temperature Tc rather than suppressing it. For a 1 µm × 1 µm, 8 nm-thick disordered film, they estimate a relative Tc enhancement of about 1%, roughly ten times the 0.1% obtained when phase fluctuations are neglected.
Frieder Lindel, Jonathan B. Curtis, J\'er\^ome Faist et al.
