September 3, 2026

Transversal Gates and Magic State Distillation in an Optimally Synthesized Spin-Qubit Shuttling BusTier 3

Fault-tolerant quantum computing requires not only reliable logical qubit storage, but also the ability to perform high-fidelity logical operations between error-corrected qubits at scale. While much of the existing literature focuses on optimizing syndrome extraction for a single logical qubit, the co-design of physical architectures that support both robust error correctio...

Single-Shot Fidelity Reveals Hard and Soft Limits: A Universal Yardstick for Photon-Number-Resolving DetectorsTier 3

Photon-number-resolving (PNR) detectors are essential for photonic quantum computing, where a single measurement outcome must reliably herald a specific quantum state. However, detector fidelity is conventionally evaluated using ensemble-averaged statistics obtained from many measurements, which can remain high even when individual photon-number assignments are frequently mi...

Programming anharmonic potentials in a superconducting harmonic oscillatorTier 3

Continuous-variable quantum systems offer a resource-efficient route to universal quantum information processing and analogue quantum simulation of real-world processes, such as molecular physics and chemical reactions. Realising these applications, however, requires non-Gaussian operations that implement anharmonic potentials, which are challenging to engineer on demand. He...

Implementation of quantum gates by Floquet analysis of kicked quantum systemTier 3

Precise control of multi-qubit architectures remains a critical bottleneck in superconducting quantum processors. In this work, we investigate the synthesis of high-fidelity quantum operations and state transfer protocols within an extended superconducting linear chain, scaling from three to seven sites. Using Floquet theory, we model the periodic drive as a train of delta-l...

Coherent microwave-to-optical transduction with Yb:YSO spins strongly coupled to a 3D resonatorTier 3

Microwave-to-optical quantum transducers are essential for entangling remote superconducting qubits. Among the available transduction platforms, ensembles of Er^(3+) and Yb^(3+) ions doped into solids have emerged as leading candidates. While external magnetic fields are needed to split the Zeeman levels of erbium ions and enable a microwave--qubit interface, superconduc...

Observation of Hong-Ou-Mandel interference between photon and polaritonTier 3

Light-matter interactions underlie many quantum technologies, yet whether quasiparticles formed from such interactions preserve the full quantum state of light remains unresolved. Surface plasmon polaritons (SPPs), a class of polaritons formed by interacting photons with free-electron oscillations at metal-dielectric interfaces, are prime candidates to explore this question....

Quandela Joins Canada’s Quantum Computing Sandbox With Photonic Quantum PlatformTier 2

PsiQuantum and Brookhaven Lab Partner on Fault-Tolerant Quantum AlgorithmsTier 2

Exponential speedup of polarization stabilization for long distance DWDM quantum networksTier 3

Fibre-based quantum networks distributing polarization entanglement require a stable and uninterrupted transmission basis for reliable operation. Bright classical reference light enables rapid polarization feedback but can introduce noise into quantum channels. Entangled-photon-based feedback avoids this noise, but typically interrupts the target entanglement channel during...

Conditional validity of quantum event classifiers under collider systematics and quantum estimation uncertaintyTier 3

Claims about a deployed quantum machine-learning classifier can fail when target data shift or when finite-shot quantum evaluation randomizes the model itself. We develop an information-conditional, fail-closed auditing framework that returns supported, refuted or unresolved verdicts with anytime-valid per-claim error control under a declared sampling protocol. On a Higgs-to...

Variational preparation of thermofield double states for SYK models via multi-angle QAOA: sequential angle pruning for circuit reductionTier 3

Variational preparation of thermofield double (TFD) states can require deep quantum circuits, particularly for interacting many-body systems. Reducing these circuits while retaining high fidelity is therefore crucial for TFD-state preparation on noisy quantum processors. We study this problem by applying the multi-angle quantum approximate optimization algorithm (ma-QAOA) to...

Phonon-limited detection thresholds for genetically encoded fluorescent-protein spin-qubit relaxometry of neural radicalsTier 3

The demonstration that enhanced yellow fluorescent protein hosts an optically addressable spin-1 qubit in its metastable triplet state raises the prospect of genetically encoded quantum sensing at molecular length scales. We develop a detection-limit theory for using this fluorescent-protein spin qubit (FPSQ) to sense paramagnetic neural signaling radicals by spin relaxometr...

Efficient Simulation of Nonreciprocal Many-body Physics via Quantum FeedbackTier 3

We present a scheme to efficiently simulate nonreciprocal many-body spin models using a non-Markovian open system. Our scheme utilizes a single quantum emitter coupled to a waveguide mode that is fed back to the same emitter after a time delay. With this coherent delayed feedback, an effective nonreciprocal interaction can be engineered, wherein the emitter at earlier times...

A Recursive Module-Coupling Algorithm for Computing Low-Energy EigenstatesTier 3

Finding the eigenstates of a many-body Hamiltonian is a fundamental challenge in physics and computational science. Since the search space grows exponentially with system size, numerous classical and quantum algorithms have been developed to address this problem. A practical strategy is to identify a physics-informed low-dimensional subspace that effectively accommodates the...

Quantum MeanFlow: single-shot generative sampling on NISQ hardwareTier 3

Quantum generative models offer a promising framework for exploring whether quantum computation can enhance generative machine learning. Flow matching is a generative method in which samples are generated by transporting a simple, known distribution to the target data distribution with a learned velocity field. Its quantum counterpart, known as quantum flow matching (QFM), w...

A variational quantum eigensolver-based cutting plane framework for semidefinite programming problemsTier 3

Semidefinite programming plays a key role in optimization, with broad impact across control theory, machine learning, and combinatorial optimization. Although semidefinite programs are polynomially solvable, several commonly used algorithms rest on a linear-algebraic step whose running time grows cubically with the matrix dimension and which requires the matrix itself to be...

Computational methods for photoionization of H_2 molecules: a comparative studyTier 3

Single-photon ionization cross sections of molecular hydrogen in the electric dipole limit have been computed. Both time-dependent and -independent approaches within the clamped-nuclei approximation at equilibrium internuclear distance are employed, featuring the explicit time-propagation of the time-dependent Schrödinger equation and newly implemented multi-channel configur...

IBM Ventures Invests in BQP as Quantum-Algorithm Physics Acceleration Reaches ProductionTier 2

IBM’s Nighthawk r2 Quantum Processor Targets a 25-Fold Increase in Circuit SpeedTier 2

QuNorth Clears Facility Milestone for MAGNE Quantum ComputerTier 2

Long-lived telecom-heralded single-photon storage in an absorptive spin-rephased quantum memoryTier 3

Long-lived storage of single photons under the form of atomic excitations is at the foundation of long-distance entanglement distribution in quantum networks. To mitigate decoherence effects induced by the environment, rephasing of the hyperfine coherences using microwave pulses have been implemented in a variety of single-emitter and ensemble-based solid-state systems. Howe...

A proposal for a hybrid free-space optical quantum communication network with hexagonal boron nitride-based single photon sourcesTier 3

Hexagonal boron nitride (hBN) is known as a promising solid-state platform to host room temperature quantum emitters that produce high purity single photons. The bright and spectrally adaptable hBN emitters are space-compatible, making hBN well-suited for satellite-based free-space optical (FSO) quantum key distribution (QKD) at wavelengths where the atmospheric background i...

A quantum oracle separation between QMA(2) and QMATier 3

We find a quantum oracle relative to which QMA ≠QMA(2). As a consequence, we resolve the no-disentanglers conjecture of Watrous: for every ε+δ<1, any (ε,δ)-disentangler requires input size exponential in the number of output qubits. Our proof combines the unitarily invariant polynomial method of She and Yuen (ITCS '23) with a new construction base...

Previously: 2026-08-13

Effective Sub-Quantum Readout for Non-Monochromatic Axion Signals in High-Q HaloscopesTier 3

The search for wave-like dark matter using microwave cavity haloscopes is constrained by the Standard Quantum Limit, which dictates that phase-preserving linear amplification results in a minimum of one quantum of total system noise for a narrow-band signal. We demonstrate that this limit is effectively halved for a non-monochromatic axion signal coupled to a high-Q cavity...

Model-level synthetic-flux control of hyperchaos order and matched-resource sensing in dissipative optomechanicsTier 3

Within a normalised six-dimensional model of dissipative optomechanics (one cavity + two mechanical resonators), a synthetic-flux phase Φ_(rmsyn) selects the \emph{order} of a drive- and coupling-gated hyperchaos transition---up to four simultaneously unstable Lyapunov directions, beyond any reported single-mode benchmark---while the same matched-resource force-sensing p...

Spin squeezing by geometric focusing in vacuum Rabi oscillationsTier 3

We show that vacuum Rabi oscillations can directly generate spin squeezing through geometric focusing on the Bloch sphere. Starting from a coherent spin state resonantly coupled to a cavity initially in the vacuum state, quantum fluctuations are focused by the curvature of the Bloch sphere as the collective spin approaches the atomic ground state, producing squeezing transve...

QArray+: A physics-informed GPU-accelerated simulator for quantum dot arraysTier 3

Semiconductor quantum-dot arrays are a compelling platform for scalable quantum technologies, yet their practical operation is hindered by the complexity of tuning large-scale devices. Existing automation tools rely on simplified physical models---such as constant-capacitance approximations and equilibrium Hubbard models---which assume instantaneous relaxation to a steady st...

Effective quasiparticle conserving Lindbladians in the thermodynamic limitTier 3

Open quantum many-body systems are commonly described by Lindblad master equations, yet the treatment of Lindbladian operators in the thermodynamic limit remains a major challenge. We develop a framework for constructing effective quasiparticle-conserving Lindbladian operators directly in the thermodynamic limit. Our approach extends continuous similarity transformations to...

Quantum Meta-Complexity Is All You Need: Characterizing One-Way Puzzles via Time-Bounded Kolmogorov ComplexityTier 3

We initiate the time-bounded meta-complexity program for quantum cryptography. Recent work characterizes one-way puzzles, the minimal search primitive of quantum cryptography without one-way functions, by the average-case hardness of approximating the plain, uncomputable Kolmogorov complexity over quantumly samplable distributions; the classical program of Liu and Pass, by c...

Heuristically optimizing, synthesizing, and prioritizing measurement settings for quantum state tomographyTier 3

A key task in many quantum-computing applications, e.g., quantum simulation and quantum state tomography (QST), is to partition an arbitrary set of operators into mutually commuting subsets for efficient measurements. However, brute-force approaches to this task quickly become intractable as the number and dimensionality of operators grow. Here, we reformulate operator parti...

The advantages of extended nonreciprocal quantum batteriesTier 3

This study investigates the performance of extended nonreciprocal quantum batteries (QBs), as well as its advantages in energy storage and energy transfer compared to reciprocal charging and the original nonreciprocal batteries. After analyzing the detuning between the charging system and the external pump, we discover that resonance is a key factor in maintaining high-energ...

Thouless pumping and generation of squeezed Fock-state superpositions in a Fock-state latticeTier 3

In this paper, Thouless pumping in a one-dimensional semi-infinite Fock-state lattice is investigated. A distinctive feature of such lattices is the intrinsic √n-dependent coupling arising from the bosonic mode, which leads to spatially nonuniform hopping amplitudes. In the dimer limit, the topological invariants and the quantized transport dynamics in the Fock-state...

Combinatorial optimization of connected UAV communication bridges for emergency responseTier 3

We present a combinatorial optimization problem for the strategic deployment of UAVs equipped with 5G antennas to assist rescue operations in regions hit by natural disasters. Our goal is to optimize the placement of UAVs to provide coverage in flying ad-hoc networks among given candidate sites. Our formulation aims to maximize signal coverage and minimize interference while...

Experimental Evaluation of Passive Polarization Compensation Techniques for Fiber-Distributed Polarization-Entangled PhotonsTier 3

Entanglement distribution through optical fibers is essential for quantum communication networks; however, fiber transmission can alter photon polarization and modify the observed correlations of polarization-entangled states, necessitating polarization compensation to recover the desired entangled state in the measurement basis. Here, we experimentally evaluate two passive...

Branching stochastic mechanics. II. Relative localization and collective poles from Bohm/Fisher feedbackTier 3

Paper I introduced branching stochastic mechanics (BSM) by lifting the Schrödinger-Nagasawa pair to reciprocal forward and backward branching fields. Their centered connected kernel C_(rmFB)=E_ω[ψ_Fψ_B] carries the organized reciprocal sector, where E_ω denotes expectation over branching-noise realizations, with ρ_(rmBSM)=-C_(rmFB)(x,x) on the ant...

Engineering of Non-Hermitian Trajectories and Phase Structure in an Open Bose-Hubbard Model via Rate Operator TransformationsTier 3

Non-Hermitian evolution can be realized through post-selection on stochastic pure-state trajectories arising in continuously monitored open quantum systems. The rate operator formalism provides a versatile and systematic framework for unraveling a master equation into stochastic pure-state evolutions, offering enhanced control over the resulting non-Hermitian dynamics. In th...

Precise spectral asymptotics, exponential localization, and spectral gap estimates for the three-boson lattice Schrödinger operatorTier 3

We study the three-boson Schrodinger operator on the two-dimensional integer lattice with pairwise contact interactions. First, we obtain precise asymptotics of the two bound states below the essential spectrum at zero total quasimomentum in the strong-coupling limit mu to infinity: the ground state energy is -3 mu + 6 + O(1/mu), and the first excited state energy is - mu +...

Circuit-Level Loss Performance of FFCC and RHG Codes in a Compound Photon-Atom Quantum ArchitectureTier 3

We compare the Raussendorf-Harrington-Goyal (RHG) code, the Foliated Floquet Color Code (FFCC), and the reduced FFCC in a compound photon-atom architecture that directly generates measurement-based quantum computation (MBQC) resources with near-deterministic photon-atom CZ gates. RHG serves as a natural benchmark, while the FFCC variants allow us to study whether reduced gra...

DMRG using Belief PropagationTier 3

Tensor networks have attracted much attention as a powerful tool for modeling quantum many-body systems. Their contraction is a significant challenge, however, especially in highly connected networks, as memory requirements become prohibitive and the optimal contraction order is increasingly hard to find. The belief propagation (BP) algorithm has emerged as an alternative to...

Unfolded Krylov complexity: universal chaotic dynamics without false positivesTier 3

A central challenge in diagnosing quantum chaos is to distinguish genuine many-body scrambling from kinematic effects of the spectrum. Krylov state complexity, or spread complexity, has emerged as a powerful diagnostic, with its characteristic growth, peak, and relaxation often taken as signatures of chaos. However, previous work has shown that this criterion can give false...

Renormalization group and long-range conditional mutual information in hierarchical modelsTier 3

A departure of a mixed quantum state from a local Gibbs description is generally invisible to local observables but can be detected by the conditional mutual information (CMI). Here we study the relationship between the renormalization group (RG) and CMI, and in particular, how RG constrains CMI. We first show that the CMI between nonadjacent regions A and C, conditioned...

Laser-induced phase shift of swift electronsTier 3

We revisit the calculation of the phase shift experienced by swift electrons on passing through the electromagnetic field of a laser. Such phase shifts are now utilized in the form of `laser phase plates' in transmission electron microscopes (TEMs), for example. We calculate the phase shift using three different methods, namely, perturbation theory applied to the Dirac equat...

A Quantum Algorithm for the Radical of a Lie Algebra: Kernel Projection and ConditioningTier 3

Every finite-dimensional real or complex Lie algebra has a largest solvable ideal, its radical. In the compact dynamical Lie algebra (DLA) of a closed quantum system, this radical is the center; projecting onto it isolates directions that commute with the supplied algebra. With sparse Lie-bracket data and a known spectral gap, we construct a quantum circuit that approximatel...

Analytic Maximal Violation of Extended MABK Inequalities for Generalized GHZ StatesTier 3

We analytically characterize the maximal quantum violation of the extended Mermin-Ardehali-Belinskii-Klyshko (EMABK) family of inequalities by n-qubit generalized Greenberger-Horne-Zeilinger (GHZ) states. We develop a correlation-tensor approach in which the Bell value is expressed as the Frobenius inner product of the quantum correlation tensor and an effective coefficien...

A generalized harmonic oscillator problem for a spin-1/2 fermionTier 3

The exact bound-state wavefunctions and the corresponding energy equation are calculated for a new generalized harmonic oscillator problem describing a spin-1/2 fermion in 3+1-dimensions, involving scalar, vector, and tensor couplings acting simultaneously within a particular plane of motion. For the scalar and vector coupling, singular harmonic oscillator shapes are conside...

Bell inequality violation with momentum-entangled massive particlesTier 3

Bell's theorem revealed the fundamental incompatibility between the predictions of quantum mechanics and local realism. Bell inequality violations have since demonstrated quantum nonlocality using photons and internal states of massive particles, but never using their motional states. Here we report the first Bell inequality violation in the motional states of massive partic...

Contrasting Effects of Control on Fidelity and Fidelity Deviation in Controlled TeleportationTier 3

Teleportation performance is commonly characterized by the average teleportation fidelity, while its variation over input states provides additional information captured by the fidelity deviation. In controlled teleportation, the controller's measurement introduces an additional source of fidelity variation through its measurement outcomes. We investigate the fidelity deviat...

Generalized Foldy-Wouthuysen approach for the derivation of non-relativistic effective field theoriesTier 3

Effective field theories (EFTs) are a powerful framework for performing high-precision calculations at reduced complexity compared to their fundamental counterparts. A particularly important class of EFTs arises in the non-relativistic (NR) regime. Their construction relies on a different realization of the underlying symmetries, since Lorentz invariance is no longer manifes...

Maximal-velocity deficit under a finite-support constraint in hard-wall half-line continuous-time quantum walkTier 3

Continuous-time quantum walks on a lattice spread ballistically and converge to a limiting distribution for the rescaled position. On the hard-wall half line the boundary reflects the walker but does not change the bulk dispersion, so the ballistic front remains set by the maximal group velocity. We ask how close one can get to this front when the initial state is constraine...

Quobly and TNO Partner on Silicon Spin Qubit DevelopmentTier 2

Pasqal and True Nexus Apply Quantum Computing to Protein GelationTier 2

Previously: 2026-06-12, 2026-05-20, 2026-05-19

Cyprus and Greece Establish Quantum-Secure Satellite LinkTier 2

Scientists Observe Einstein’s Gravity in The Quantum WorldTier 2