September 11, 2026

Quantum-RAM Implementation Using Multiple Interacting Rydberg-Blockaded EIT SystemsTier 3

We propose a novel theoretical architecture for implementing a quantum random access memory (qRAM) based on quantum random walks in a Rydberg blockaded atomic ensemble utilizing multilevel Electromagnetically Induced Transparency (EIT). Unlike previous approaches that rely on geometric phase gates in solid-state or trapped ion systems, our scheme harnesses the strong, cohere...

The generalised semi-Clifford conjecture is falseTier 3

The Clifford hierarchy is a nested sequence of sets of quantum gates that can be fault-tolerantly performed using gate teleportation within standard quantum error correction schemes. The importance of these gates has motivated numerous studies of their structure. Zeng-Chen-Chuang conjectured in 2007 that all hierarchy gates are generalised semi-Clifford, i.e. take the form $...

Lifted surgery: Fast processing with QLDPC codesTier 3

Quantum low-density parity-check (QLDPC) codes are a leading candidate for achieving low-overhead fault-tolerant quantum computing. However, the time overhead of logical operations in QLDPC codes remains a key challenge. Code surgery, a space-efficient technique for fault-tolerant logical measurements, incurs this overhead through repeated rounds of syndrome measurement. We...

Quantum Random Access Memory Implementation Using Photon-Photon Interaction in Rydberg Atomic EnsembleTier 3

Quantum random access memory (qRAM) is crucial for overcoming data-loading bottlenecks in quantum machine learning; however, current physical implementations face severe scalability constraints. Traditional fanout designs demand exponential decoherence-prone gates, while bucket-brigade schemes require highly error-prone active switches. Motivated by these limitations, we pro...

Infleqtion and Cisco Collaborate on Quantum Networking ResearchTier 2

Previously: 2026-08-28, 2026-08-19, 2026-08-14

A Chip-scale Space-time Multiplexed Gaussian Boson Sampling Processor Beyond 10,000 PhotonsTier 3

Gaussian boson sampling (GBS) has emerged as a leading photonic paradigmfor demonstrating quantum computational advantage. Nevertheless, state-ofthe-art GBS setups face practical barriers including stringent optical alignment, phase instability, and limited programmability, which impede scalable engineering deployment. The chip-scale space-time multiplexed architecturepromis...

Heterogeneously Integrated Efficient and Widely Tunable Lasers at 795 nm for Rubidium-Based Quantum TechnologiesTier 3

Scaling quantum processors and optical atomic clocks fundamentally requires orders-of-magnitude reductions in the size, weight, power, and cost of optical control systems. Photonic integration of lasers is critical to fulfill these requirements. At the near-infrared wavelengths required for atomic clocks and quantum computing through manipulation of rubidium atoms, laser int...

Joint Mitigation of Algorithmic and Physical Errors in Noisy Hamiltonian SimulationTier 3

Product-formula Hamiltonian simulation is naturally suited to near-term quantum processors, but its accuracy is set by two competing errors: finite-step Trotter bias and physical hardware noise. We introduce a joint extrapolation strategy that ties the tunable per-layer noise strength to the Trotter step size, λ(s)=c(sT)^(p+1) for a p-th order product formula. Along this...

Self-guided certification of nonlocality in quantum networksTier 3

Bell's theorem shows that quantum theory is incompatible with local hidden-variable models. In recent years, research on nonlocality has moved beyond Bell's original scenario to quantum networks, where multiple independent sources distribute physical systems among distant parties, giving rise to correlations certified by nonlinear rather than standard Bell inequalities. Here...

Block entropy area based non-local fermionic mode optimization with gradient disentanglersTier 3

We introduce a systematic block entropy area based mode optimization algorithm for many-body quantum states of interacting fermions represented by matrix product states. From the gradient of a global cost function, the block entropy area, a long-ranged, non-interacting effective disentangler Hamiltonian is formed. We then simulate the time-dependent Schrödinger equation driv...

Learning structural balance of graphs from quantum spectral featuresTier 3

We develop a quantum approach to spectral feature extraction from the density of states (DOS) of a problem-dependent Hamiltonian, and apply it to machine learning on signed graphs. We propose to embed a signed graph as an Ising model instance with positive and negative interactions, and use the standardized moments of the Ising DOS as features for learning. We show that thes...

Certifying Adversarial Robustness of Quantum Classifiers under Known-Readout Query AccessTier 3

A quantum classifier assigns labels by evolving an input quantum state and measuring the output, so repeated executions reveal only a distribution over labels. We study certified adversarial robustness for such classifiers under known-readout query access (KRQA), where an evaluator can prepare inputs, knows the quantum measurement, and observes finite-shot outcomes but canno...

Generative Replay Mitigates Sample Starvation in Quantum Architecture SearchTier 3

Reinforcement learning (RL) can automate quantum architecture search, but its scalability is limited when useful circuit trajectories become rare in the rapidly expanding search space. Existing replay mechanisms reuse observed transitions; the proposed learned model produces additional predicted one step transitions from real state-action seeds. Here we introduce GenQAS, a t...

Virtual quantum neural networksTier 3

Quantum neural networks are a prominent model of quantum machine learning. Their training consists in the minimization of a given loss function over a parametrized family of quantum circuits, mathematically described by unitary operators, or, more generally, completely positive linear maps. In this work, we extend the notion of quantum neural network, using random sampling a...

SI-Traceable Calibration and Performance Benchmarking of a Terahertz Photomixer Transmitter-Receiver System Using a Rydberg Atomic SensorTier 3

Accurate calibration of electromagnetic field strength in the terahertz (THz) frequency regime remains challenging due to the limited availability of SI-traceable field sensors. Here we demonstrate SI-traceable calibration and performance benchmarking of a commercial photomixer-based THz transmitter-receiver system operating near 204 GHz using Rydberg electric-field sensing...

An exchange-assisted entangling gate between 87Rb and 171Yb Rydberg atomsTier 3

Neutral-atom tweezer arrays support scalable quantum information processing. Dual-species ^(87)Rb--^(171)Yb arrays combine long-lived ytterbium nuclear-spin data qubits with fast, species-selective rubidium ancilla control and readout. However, realizing interspecies gates without inducing destructive Stark mixing in divalent atoms remains an outstandin...

Entanglement Meets Reality: A Network Engineering Assessment and Forecast of Rackable Entanglement SourcesTier 3

Quantum networks are transitioning from labo- ratory experiments to real-world deployments, with entangle- ment as their fundamental resource. Since an entanglement source effectively defines a quantum network, its performance directly impacts the reliability, scalability, and efficiency of future quantum communications. In this work, we investigate rack-mountable plug-and-p...

The cost of simulating classically tractable quantum circuits and dynamicsTier 3

Determining whether a quantum evolution can be efficiently simulated classically is central to understanding the boundary between classical and quantum computation. However, polynomial-time simulability is an asymptotic statement, and does not by itself determine whether the (quantum-inspired) classical simulation is actually practical. Indeed, different polynomial scalings...

Italy Courts IonQ as Rome Seeks Deeper U.S. Quantum TiesTier 2

Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber NetworkTier 3

Deploying quantum networks over existing network infrastructures requires the same engineering foundations that underpin classical communications: quantitative models of the channel's noise and of the impairments it imposes on the transmitted information. In this work, we build such a foundation on experimental measurements, grounding the quantum-network counterparts of the...

Quantifying Symmetry BreakingTier 3

Quantifying properties of quantum states through the limits of their manipulation is a central goal of quantum resource theories. For symmetry breaking, the quantum geometric tensor governs asymptotic pure-state conversion, but a complete characterization for general mixed states has remained elusive. Here we fully resolve this problem for finite-dimensional systems under co...

EFI Pairs Without One-Way Puzzles: Oracle Separations from Communication ComplexityTier 3

EFI pairs (Brakerski, Canetti, and Qian, ITCS 2023) and one-way puzzles (Khurana and Tomer, STOC 2024) are the leading candidates for the minimal assumption of quantum cryptography. The first are efficiently preparable quantum states, statistically far yet computationally indistinguishable; the second are classical puzzles, easy to sample and hard to solve. One-way puzzles i...

Taking Advantage of Noise in Distributed Random Quantum CircuitsTier 3

Adding noise can make a random quantum circuit look faster without making its unitary dynamics more random. This distinction is especially relevant in modular processors, where local gates randomize each core and scarce inter-core communication must spread that randomness across the full device. In this paper, we study this problem with a reduced second-moment transfer-matri...

Computational framework for quantum state tomography of spin ensemblesTier 3

We present Tomography-NMR, an open-source Python package that reconstructs quantum density matrices from spectroscopic measurement data. The package implements a complete analysis pipeline for two-qubit quantum state tomography based on the product operator formalism: raw time-domain signals are Fourier-transformed into frequency-domain spectra, spectral peak intensities are...

PureSuperQMA(exp) = BellPureSymQMA(poly) = QMA via Dimension-Free Bosonic ArgmaxTier 3

Pure-state consistency problems naturally lead to quantum proof systems in which a single pure witness must satisfy many acceptance constraints. The corresponding class PureSuperQMA was previously known to lie between QMA and QMA(2), and Kamminga and Rudolph (ITCS'26) conjectured that both containments are strict. In this paper, we prove the...

PPT states of almost maximal Schmidt numberTier 3

We construct PPT states on C^m ⊗C^n that have Schmidt number asymptotically approaching the smaller local dimension. More specifically, we construct a PPT state with Schmidt number at least lceil(m + n - ((m - n)^2 + 4(m + n - 1))^(1/2))/2 rceil. In the case of equal local dimensions (m = n), this becomes n - lfloor(2n...

Oracle Separations in the Fourier HierarchyTier 3

The Fourier hierarchy FH_0⊆FH_1⊆FH_2⊆⋯, introduced by Shi (TCS 2005), measures a quantum computation by the number of Hadamard layers it uses. Between two layers the circuit may permute basis states and attach phases, but it may not create superposition; the layers are its only source of interference. The first level...

Strong Converse for Quantum Capacity via a Fully Quantum Blowing-Up LemmaTier 3

We prove an exponential strong converse for quantum communication through every finite-dimensional memoryless channel: at any fixed rate above the quantum capacity, the entanglement-transmission fidelity of every code decays exponentially with the number of channel uses. The proof has two main ingredients. First, a fully quantum blowing-up lemma converts a low-fidelity code...

Quantum transport along a tight-binding chain connected to Markovian reservoirsTier 3

We consider quantum transport of non-interacting particles in a tight-binding chain coupled to Markovian reservoirs at its boundaries and subject to uniform on-site dephasing. Using the masterequation approach, we derived the exact analytic solution for the mean current along the chain. This analytic solution is obtained in the framework of single-particle quantum mechanics...

Hilbert-space selected switch of helical edges in an artificial quantum Hall insulatorTier 3

Quantum Hall effects (QHE) host one-dimensional topologically-protected edge channels, which can serve as an essential ingredient in exotic quantum electronic systems. Yet the manual reconstruction of Landau-level topology, by electrostatic confinement or symmetry breaking, remains experimentally challenging. Here, we show that interfacial charge transfer in between CrOCl an...

Bridging steady-state and time-domain descriptions of molecular electron transportTier 3

Electron transmission from an input electrode, through a molecular system, to an output electrode has been widely studied using the steady-state non-equilibrium Green's function (NEGF) method. Recently, the wave packet method, which provides access to the transient dynamics of electrons as well as internal molecular degrees of freedom, has been employed to investigate enanti...

Nonlinear dynamics and mechanical frequency combs with a Meissner-levitated micromagnetTier 3

Nonlinearities in multimode mechanical systems can give rise to rich dynamical phenomena with great potential for sensing applications and for future quantum experiments. We demonstrate that the coupled center-of-mass and rotational motion of a Meissner-levitated micromagnet offer a promising platform for nonlinear dynamics, combining low dissipation, magnetic tunability, st...

A Near-Quartic Separation Between Certificate Complexity and Quantum Query ComplexityTier 3

We construct a total Boolean function f for which Q(f) = O(√([)4]C(f)), where Q(f) denotes the bounded-error quantum query complexity and C(f) denotes the certificate complexity. This resolves a longstanding open question and is tight up to logarithmic factors.

Quantum-hardware spectral co-design framework for multifrequency Rydberg electrometryTier 3

Engineering electromagnetic hardware to satisfy discrete quantum-defined spectral constraints constitutes a general spectral co-design problem for quantum systems. Here we address this challenge in multifrequency Rydberg electrometry by directly coupling a fabrication-constrained simultaneous perturbation stochastic approximation (SPSA)--Adam optimizer to full-wave finite-el...

Quantum models of interaction Hamiltonian and their paradoxesTier 3

In quantum physics it is commonplace to model the interaction of remote systems with a many-body Hamiltonian. Taking such an action-at-a-distance description {\it à la lettre} leads to various paradoxes related to faster-than-light communication and apparent inconsistencies in local energy accounting. It also neglects residual effects, such as entanglement between the remote...

Dissipative Quantum Battery from Many-Body ScarsTier 3

We propose an autonomous quantum-battery protocol based on dissipatively selected quantum many-body scars. Using an embedding-type spin chain with an exact scar tower and a generalized interacting J_1--J_2 chain, we show that engineered local bond dissipation can drive the system from a passive state into a high-energy scar-supported manifold with large extractable work....

Finite-time effects in periodically kicked systemsTier 3

In this work, we study finite-time effects in ultracold atomic systems by considering time-dependent modulations with variable waveforms and durations. These two characteristics can be controlled by adjusting only a single parameter. For arbitrarily short pulses, our model recovers the paradigmatic kicked rotor while maintaining the impulse transmitted per period and unit am...

Impossible to conjugate an unknown quantum state via a unitary evolutionTier 3

The no-cloning theorem, the no-deleting theorem, the no-hiding theorem, the no-flip theorem, and the no-broadcasting play a crucial role in quantum mechanics and quantum information. In this paper, we propose the no-conjugating theorem which states that it is impossible to conjugate an unknown arbitrary quantum state via a universal physical device or linear/unitary operation.

Birth and Death of Entanglement in Hamiltonian-Driven Quantum Games under DecoherenceTier 3

Quantum game theory investigates the influence of quantum resources on strategic decision-making. In this work, two-player quantum games based on the Transverse Field Ising Model(TFIM) are investigated under amplitude-damping decoherence. The TFIM Hamiltonian naturally produces a family of entangling gates, enabling a physically motivated implementation of quantum games. The...

One-clean-qubit spectroscopy of simulated Kitaev chainsTier 3

Spin qubits in gate-defined quantum dots provide a highly programmable platform for simulating condensed-matter phenomena. In this work, we introduce a digital-analog quantum simulation protocol for extracting the single-particle spectrum of a Kitaev chain. The Kitaev chain is mapped onto qubits via the standard Jordan-Wigner transformation and implemented as a drive-enginee...

Statistical Symmetry Release for Equivariant Quantum LearningTier 3

Hard symmetry constraints reduce model complexity, but can also erase label information. Statistical symmetry release determines when finite data and quantum measurements justify relaxing such a constraint, which directions to open, and how far to move. We connect global signal detection to local, loss-dependent improvement. A two-copy twirl--swap gate estimates task informa...

The Quantum Plumber's ProblemTier 3

Recent work quantified the notion of quantum counterfactual gain for an extended Elitzur-Vaidman bomb test style scenario, through a connection to the negativity of the Kirkwood-Dirac quasiprobability distribution. We here extend this work to identifying quantum advantage in a new scenario, which we term the ``Quantum Plumber's Problem''. In this scenario, we imagine a ``qua...

Rare-History Transitions in Temporally Random Integrable Quantum CircuitsTier 3

We study current fluctuations in a temporally random integrable quantum circuit. Commutativity reduces every drive history exactly to its layer composition, turning annealed fluctuations into a competition between current gain and the large-deviation cost of rare compositions. For each fixed composition, homogeneous thermodynamic Bethe ansatz dressing supplemented by ballist...

The Quantum Composition ParadoxTier 3

Quantum theory does not generally permit the probability laws obtained from individual unitary steps by the Born rule to be sewn into a consistent genealogy; we classify the exceptions and show that faithful composition can hold from an initial boundary yet fail after an internal restart. For finite-dimensional, composition-closed unitary families, universal composition hold...

Microwave-controlled interactions and stripe formation of static-field-shielded polar moleculesTier 3

We study polar molecules where short-range losses are suppressed by a shielding scheme involving a static electric field and an elliptically polarized microwave field. Using perturbation theory, we derive the effective interaction potential and validate it against coupled channel calculations. We identify a parameter regime where two-body losses are strongly suppressed and t...

Optimizing quantum encodings for analog simulation through dynamical algebra reachabilityTier 3

Analog quantum computers provides direct access to continuous many-body dynamics, but their native control Hamiltonians generate only a restricted operator space. Consequently, the fidelity with which they can reproduce a target Hamiltonian's dynamics depends not only on spectral agreement but on whether the physical controls can actually generate the required evolution. We...

From Analytic Structure to Quantum Complexity: Walsh-Pauli Representations of Continuum OperatorsTier 3

How does continuum operator structure appear in a finite qubit register? We address this question for analytic functions of diagonal operators represented in a binary basis, focusing on the Jordan--Lee--Preskill (JLP) momentum operator, by developing an operator-level generating-function framework for their Walsh-Pauli spectra. The construction determines the spectrum analyt...

Enhancing charge stability of Ge quantum well heterostructures via SiGe layer composition engineeringTier 3

Composition modulation is a powerful technique for designing materials with tailored properties, fueling the development of advanced semiconductor devices. In this work, we have implemented this technique into Ge quantum well heterostructures, offering a promising avenue to address the critical challenge of charge stability in spin qubit devices. Harnessing the atomic-scale...

Researchers Send Twin Photons 7 Kilometers Across Brazil’s Guanabara BayTier 2

Researchers And AI Agents Cut Estimated Quantum Cost of Attacking Bitcoin Encryption by 86%Tier 2

Cal State East Bay Opens Pathways to Careers in Quantum TechnologyTier 2

Chalmers Researchers Make Bosonic Quantum Operations More Than 1,000 Times FasterTier 2

Steve Hoffman Discusses Quantum Technology Adoption in U.S. DefenseTier 2

A Geometric Theory of Quantum EntanglementTier 3

Entanglement Distance (ED) was originally proposed as a geometric measure of entanglement derived from the Fubini-Study metric on the projective Hilbert space. Independently, the Meyer-Wallach and Scott measures quantify multipartite entanglement via linear entropy. In this work, we demonstrate that these two seemingly distinct frameworks are mathematically identical for pur...