Papers

We introduce an all-optical quantum-enhanced diagnostic for electric fields in low-temperature plasmas. Trace amounts of rubidium vapor, added to an argon plasma, allow us to employ spectrally narrow electric field-sensitive optical resonances via the quantum optical effect of Rydberg electromagnetically induced transparency. This non-invasive technique enables measurements of electric fields in plasma with a 1~V/cm precision and a 1.5~V/cm lower detection limit. By collecting the fluorescence from the illuminated region of interest, we reconstruct a 2D spatial profile of the electric field magnitude with $56~\mu$m resolution. As a proof-of-principle demonstration, we measured the changes in the electric field within the plasma sheath surrounding a biased Langmuir probe tip. This method holds significant potential for studying sheath structures in low-temperature plasmas.

Post-quantum cryptography (PQC) must secure large-scale communication systems against quantum adversaries where classical hardness alone is insufficient and purely quantum schemes remain impractical. Lattice-based key encapsulation mechanisms (KEMs) such as CRYSTALS-Kyber provide efficient quantum-resistant primitives but rely solely on computational hardness assumptions that are susceptible to hybrid classical-quantum attacks. To overcome this limitation, we introduce the first Clauser-Horne-Shimony-Holt (CHSH)-certified Kyber protocol, which embeds quantum non-locality verification directly within the key exchange phase. The proposed design integrates CHSH entanglement tests using Einstein-Podolsky-Rosen (EPR) pairs to yield measurable quantum advantage values exceeding classical correlation limits, thereby coupling information–theoretic quantum guarantees with lattice-based computational security. Formal reductions demonstrate that any polynomial-time adversary breaking the proposed KEM must either solve the Module Learning With Errors (Module-LWE) problem or a Quantum Merlin-Arthur (QMA)-complete instance of the 2-local Hamiltonian problem, under the standard complexity assumption QMA $\subset$ NP. The construction remains fully compatible with the Fujisaki-Okamoto (FO) transform, preserving chosen-ciphertext attack (CCA) security and Kyber's efficiency profile. The resulting CHSH-augmented Kyber scheme therefore establishes a mathematically rigorous, hybrid post-quantum framework that unifies lattice cryptography and quantum non-locality to achieve verifiable, composable, and forward-secure key agreement.

The scalability of current quantum networks is limited due to noisy quantum components and high implementation costs, thereby limiting the security advantages that quantum networks provide over their classical counterparts. Quantum Augmented Networks (QuANets) address this by integrating quantum components in classical network infrastructure to improve robustness and end-to-end security. To enable such integration, Quantum Anonymous Notification (QAN) is a method to anonymously inform a receiver of an incoming quantum communication. Therefore, several quantum primitives will serve as core tools, namely, quantum voting, quantum anonymous protocols, quantum secret sharing, etc. However, all current quantum protocols can be compromised in the presence of several common channel noises. In this work, we propose an improved quantum anonymous notification (QAN) protocol that utilizes rotation operations on shared GHZ states to produce an anonymous notification in an n-user quantum-augmented network. We study the behavior of this modified QAN protocol under the dephasing noise model and observe stronger resilience to false notifications than earlier QAN approaches. The QAN framework is also proposed to be integrated with a machine-learning classifier, an enhanced quantum-augmented network. Finally, we discuss how this notification layer integrates with QuANets so that receivers can allow switch-bypass handling of quantum payloads, reducing header-based information leakage and vulnerability to targeted interference at compromised switches.

Unlike QFT in Minkowski spacetime (QFTM), QFT in curved spacetime (QFTCS) suffers from a conceptual obscurity on the empirical (experimentally verifiable/falsifiable) laws. We propose to employ the notion of prior conditional probabilities to describe a part of the empirical laws of QFTCS. This is interpreted as a quantum conditional probability without no information on the initial state. Hence this notion is expected to be free from the inevitable vagueness of the empirical meaning of quantum states in QFTCS. More generally in quantum physics, this notion seems free from the conceptual problems on state reductions. We confine ourselves to the probabilistic laws of the free scalar fields (Klein-Gordon fields) in curved spacetime, which require some reconsideration on the empirical meaning of the canonical commutation relation (CCR). We give some examples of empirical laws in terms of prior conditional probabilities, concerning the CCR and the free scalar QFTCS.

We calculate separation-dependent Bell correlations for a fixed pair of Dirac electron wavepackets in a free, weakly relativistic packet model, treating the prepared joint wave as a physical wave–entity. Each station separation is sampled at the corresponding central packet arrival time. For the illustrated phase \(\chi=\pi/4\), the magnitude of the prescribed-setting Bell–CHSH response decreases and revives; optimizing the spin measurement directions retains the modulation. It occurs already at leading spin order, including for equal prepared branch weights. Interference between direct and exchanged assignments of the electron waves to the stations changes the relative weights and phases of the sampled spin amplitudes, thereby modulating the optimized response. Representative finite spatial and timing windows reduce visibility while retaining broader suppression and revival. This wave–entity account gives a quantitative, testable correlation pattern from prepared coherence, deterministic propagation, and local sampling, without postulating transmission between detectors.

Quantum computation departs from the classical paradigm of deterministic, bit-based processing by exploiting inherently quantum phenomena such as superposition and entanglement. We propose a framework for qubit realization based on skyrmionic states stabilized by the Dzyaloshinskii-Moriya interaction (DMI) in two-dimensional spin lattices. The model incorporates competing exchange interactions, perpendicular magnetic anisotropy, and Zeeman coupling, solved via exact diagonalization under periodic (PBC) and open boundary conditions (OBC). A quantum skyrmionic phase emerges for PBC within a parameter space defined by DMI, exchange, field, and anisotropy, while OBC favor classical-like, topologically protected skyrmions. Quantum logic gates (Pauli X, Y, Z, Hadamard) are implemented on both skyrmion types. Energy density and entanglement entropy analyses reveal that quantum skyrmions suffer from DMI-driven decoherence and reduced gate fidelity, whereas classical-like skyrmions maintain stability. Exact simulations of qubit dynamics, including drive effects and Lindblad decoherence, demonstrate tunable anharmonic energy levels and coherent Bloch-sphere manipulation, making these skyrmionic states promising candidates for qubit implementation. Overall, the Dzyaloshinskii-Moriya interaction plays a dual role-stabilizing skyrmionic qubits while simultaneously inducing decoherence during gate operations.

In this work, we investigate many-body phase transitions in a one-dimensional anisotropic XY model subject to a complex-valued transverse field. Within the biorthogonal framework, we calculate the ground-state correlation functions and entanglement entropy, confirming that their scaling behavior remains identical to that in the Hermitian XY model. The preservation of Hermitian phase transition features in the non-Hermitian setting is rooted in the persistence and emergence of symmetries and their breaking. Specifically, the ferromagnetic (FM) phase arises from the breaking of a $Z_2$ symmetry, while the Luttinger liquid (LL) phase is enabled by the emergence of a $U(1)$ symmetry together with the degeneracy of the real part of the energy spectrum. The nontrivial topology of the LL phase are characterized by the winding number around the exceptional point (EP). Given that non-Hermitian systems are inherently open, this research opens a new avenue for exploring conventional quantum phase transitions that are typically vulnerable to decoherence and environmental disruption in open quantum systems.

Quantum information science has been broadly explored in Einstein gravity and in various modified gravity theories; however, its extension to quantum gravity settings remains largely unexplored. Motivated by this gap, in this paper we investigate the degradation of quantum entanglement of scalar and Dirac fields in the third-type black hole geometry arising from effective quantum gravity, which incorporates generic quantum gravitational corrections beyond classical general relativity. This quantum corrected spacetime is free of a Cauchy horizon and can be cast into a Rindler form in the near-horizon regime, allowing a direct identification of vacuum modes and a clear correspondence with the framework developed for uniformly accelerated observers. Within this framework, we compute the quantum entanglement and mutual information of uniformly entangled detector pairs in terms of the quantum parameter $\tilde{\zeta}$, the mode frequency $\tilde{\omega}$, and Bob's radial position $R_0$. The quantum parameter $\tilde{\zeta}$ consistently weakens the horizon-induced loss of correlations. For scalar fields this effect is pronounced, producing clear departures from the classical behavior, whereas for Dirac fields the familiar correlation pattern remains intact but its degradation is noticeably reduced. Overall, $\tilde{\zeta}$ acts as a universal protective factor against gravitational suppression of quantum correlations. The third-type effective quantum black hole therefore provides a controlled and physically transparent arena for probing how quantum-gravity corrections influence relativistic quantum information.

Quantum coherence remains a fundamental challenge for advancing quantum technologies. Although dynamical decoupling can suppress decoherence noise, control errors can cause the overestimation of decoherence times. Here, we present Hadamard phase cycling, a scalable non-Markovian quantum error mitigation method using group-structured phase configurations to select target coherence pathways. Validated across molecular electron spins, nitrogen-vacancy centers in diamond, nuclear spins, trapped ions, and superconducting qubits, this technique enables accurate decoherence time characterization and enhanced state fidelity with linear complexity. Our results show that control-induced coherence-population mixing can substantially prolong measured echo decays in the systems studied. This mechanism provides grounds to question decoherence times obtained under comparable conditions when population-mediated contributions have not been excluded. By selecting target coherence pathways, Hadamard phase cycling establishes a robust framework for reliable quantum control, paving the way for reassessment and advancement of coherence benchmarks in the NISQ era.

We present a channel-constrained Markovian quantum diffusion (CCMQD) model that prepares quantum states by rigorously framing the generative process within the dynamics of open quantum systems. Our model interprets the forward diffusion process as natural decoherence using quantum master equations, whereas the reverse denoising is achieved by learning inverse quantum channels. Our core innovation is a comprehensive channel-constrained framework: we model the diffusion and denoising steps as quantum channels defined by Kraus operators, ensure their physical validity through optimization on the Stiefel manifold, and introduce tailored training strategies and loss functions that leverage this constrained structure for high-fidelity state reconstruction. Experimental validation on systems ranging from single qubits to entangled states $7$ -qubits demonstrates high-fidelity state generation, achieving fidelities exceeding $0.998$ under both random and depolarizing noise conditions. This work confirms that quantum diffusion can be characterized as a controlled Markov evolution, demonstrating that environmental interactions are not limited to being a source of decoherence but can also be utilized to achieve high-fidelity quantum state synthesis.

Charging optimization is a key challenge to the implementation of quantum batteries, particularly under inhomogeneity and partial observability. This paper employs reinforcement learning to optimize piecewise-constant charging policies for an inhomogeneous Dicke battery. We systematically compare policies across four observability regimes, from full-state access to experimentally accessible observables (energies of individual two-level systems (TLSs), first-order averages, and second-order correlations). Simulation results demonstrate that full observability yields near-optimal ergotropy with low variability, while under partial observability, access to only single-TLS energies or energies plus first-order averages lags behind the fully observed baseline. However, augmenting partial observations with second-order correlations recovers most of the gap, reaching 94%-98% of the full-state baseline. The learned schedules are nonmyopic, trading temporary plateaus or declines for superior terminal outcomes. These findings highlight a practical route to effective fast-charging protocols under realistic information constraints.

Non-Hermitian cavity magnomechanics (CMM), which incorporates the magnon-photon and magnon-phonon interactions simultaneously, enables rich physical phenomena, including exceptional-point-enhanced sensing, and offers pathways toward topological transitions and nonreciprocal quantum transformation. These interactions exert a pivotal influence on the optical response of a weak probe field and pave the way for novel applications in quantum technologies. In this work, we consider a yttrium-iron-garnet (YIG) sphere coupled to a microwave cavity. The magnon mode of the YIG sphere is directly excited through microwave field coupling, whereas the cavity mode is probed via a weak-field interrogation scheme. The direct interaction of a traveling field with the magnon mode induces gain in the system, thereby establishing non-Hermitian dynamics. The parity-time (PT)-symmetric behavior of a hybrid non-Hermitian CMM is designed and investigated. Eigenvalue spectrum analysis demonstrates that a third-order exceptional point (EP_3) emerges under tunable effective magnon-photon coupling when the traveling field is oriented at an angle of \pi/2 relative to the cavity's x-axis. The photonic spin Hall effect (PSHE) in a reflected probe field is subsequently examined in such a system. Under balanced gain and loss conditions and in the presence of effective magnon-phonon coupling, tunable effective magnon-photon coupling enables coherent control of the PSHE across the broken PT-symmetric phase, at the EP_3, and in the PT-symmetric phase. Investigation reveals that the PSHE can be significantly enhanced or suppressed via effective magnon-photon coupling. The influence of intracavity length on the PSHE is further explored, providing an additional parameter for fine-tuning the transverse shift. These findings establish a direct correspondence between the PSHE and the underlying non-Hermitian eigenvalue spectrum.

In this paper, we focus on the task of optimizing the parameters in Parametrized Quantum Circuits (PQCs). While popular algorithms, such as Simultaneous Perturbation Stochastic Approximation (SPSA), limit the number of circuit-execution to two per iteration, irrespective of the number of parameters in the circuit, they have their own challenges. These methods use central-differences to calculate biased estimates of directional derivatives. We show, both theoretically and numerically, that this may lead to instabilities in training the PQCs. To remedy this, we propose Stochastic Shadow Descent (SSD), which uses random-projections (or shadows) of the gradient to update the parameters iteratively. We eliminate the bias in directional derivatives by employing the Parameter-Shift Rule, along with techniques from Quantum Signal Processing, to construct a quantum circuit that parsimoniously computes unbiased estimates of directional derivatives. Finally, we prove the convergence of the SSD algorithm, provide worst-case bounds on the number of iterations, and numerically demonstrate its efficacy.

High-Q optical microresonators combine low losses and high optical energy concentration in a small effective mode volume, making them an attractive platform for optical sensors. While light is confined in the microresonator by total internal reflection, a portion of the optical field, known as the evanescent field, extends outside. This makes the mode's resonant frequency sensitive to changes in the surrounding environment. In this work, we explore the quantum sensitivity limits of this type of sensors. We show that using the intracavity squeezing of the light in the microresonator, it is possible to suppress the influence of the optical losses and cancel the undesirable self phase modulation effect, originating from the cubic non-linearity of the microresonators media. As a result, the sensitivity surpassing the shot noise limit can be achieved. An additional sensitivity gain can be obtained by preparing the input light in a squeezed quantum state.

Quantum batteries have attracted significant attention as efficient quantum energy storage devices.In this work, we propose a nonlinear two-photon driving quantum battery model featuring nonreciprocal dynamics that enables a highly efficient unidirectional charging mechanism through environmental engineering. Using a Markovian master-equation approach, we derive analytical solutions for the system dynamics and identify the parameter regime required for dynamical equilibration. Our results reveal that increasing the driving strength enhances both energy conversion and storage efficiency, albeit at the cost of longer equilibration times. Compared with single-photon driving, the two-photon process exhibits a pronounced advantage in energy capacity and entropy regulation, which becomes more prominent under stronger driving. Under asymmetric dissipation, optimizing the system-bath coupling can further improve performance. The proposed model is experimentally feasible and can be implemented across multiple quantum platforms, including photonic systems, superconducting circuits, and magnonic devices.

Ground-state estimation lies at the heart of a broad range of quantum simulations. Most near-term approaches are cast as variational energy minimization and thus inherit the challenges of problem-specific energy landscapes. We develop the quantum amplitude-amplification eigensolver (QAAE), which departs from the variational paradigm and instead coherently drives a trial state toward the ground state via quantum amplitude amplification. Each amplitude-amplification round interleaves a reflection about the learned trial state with a controlled short-time evolution under a normalized Hamiltonian; an ancilla readout yields an amplitude-amplified pure target state that a state-learning step then re-encodes into an ansatz circuit for the next round – without evaluating the energy gradients. Under standard assumptions (normalized $\hat{H}$, a nondegenerate ground-state, and a learning update), the ground-state overlap increases monotonically per round and the procedure converges; here, a per-round depth bound in terms of the ansatz depth and Hamiltonian-simulation cost establishes hardware compatibility. Cloud experiments on IBMQ processor verify our amplification mechanism on a two-level Hamiltonian and a two-qubit Ising model, and numerical benchmarks on $\mathrm{H}_2$, $\mathrm{LiH}$, and a $10$-qubit longitudinal-and-transverse-field Ising model show that QAAE integrates with chemistry-inspired and hardware-efficient circuits and can surpass gradient-based VQE in accuracy and stability. These results position QAAE as a variational-free and hardware-compatible route to ground-state estimation for near-term quantum simulation.

In this paper, we develop a framework for designing arbitrary high order low-rank schemes for the Lindblad equation with time-dependent Hamiltonians. Our approach is based on nested Picard iterative integrators (NPI) and results in schemes in Kraus form that are completely positive and trace preserving (CPTP). The schemes are amenable to low rank formulations, making them suitable for problems where the matrix rank of the density matrix is small.

We demonstrate that the ground state of a spin-1 $XXZ$ chain with uniaxial anisotropies, single-ion anisotropy $D$ and Ising-like anisotropy $J$, within the Haldane phase can serve as a resource state for measurement-based quantum computation implementing single-qubit gates. The gate fidelity of both elementary rotation gates and general single-qubit unitary gates composed of rotations about the $x$, $y$, and $z$ axes is evaluated, and is found to exceed 0.99 when $D$ or $J$ is appropriately tuned. Furthermore, we derive an analytic expression for the rotation-gate fidelity under the assumption that the state lies within the $\mathbb Z_2\times \mathbb Z_2$-protected Haldane phase, showing that it is determined by the postmeasurement spin-spin correlation function and the failure probability. The observed enhancement of gate fidelity in the spin-1 $XXZ$ chain originates from the strengthening of antiferromagnetic (AFM) correlations near the AFM phase, which effectively suppresses failure states.

We report a new oscillatory form in the two coupled dissipative Rydberg atomic chains by modulating its spacing. Such oscillation has $\pi$-phase difference between two neighboring sites, which distinguishes itself from antiferromagnetic-type synchronization in the previous studies. Theoretically, we find a phase with coexisting two types of continuous time crystals, and recognize that the transition belongs to Hopf and pitchfork bifurcation. Furthermore, we generalize the conclusion to multiple chains and verify the uniqueness of the new synchronization mode. We also discuss its experimental feasibility.

Classical computational methods, such as molecular dynamics and Monte Carlo simulations, have long been the standard for modeling viral structure and function. However, these approaches may overlook crucial quantum phenomena that operate at the nanoscale, particularly within the highly-compacted genetic material of the viral capsid. The confined, high-density environment of genetic material within the capsid strongly suggests that quantum confinement effects play a significant, yet unexplored, role in viral processes. This study introduces a novel quantum approach using Supersymmetric Quantum Mechanics (SQM) to investigate the quantum confinement effects on viruses. In this paper, the viral capsid environment is modeled using the Pariacoto virus, a model system well-suited for this analysis due to its specific structural properties. The findings reveal that quantum effects are not merely marginal but essential for understanding key processes inside the capsid, providing new insights beyond the scope of classical physics.

We introduce a multicomponent unitary coupled cluster framework for quantum simulations of molecular systems that incorporate both electronic and nuclear quantum effects beyond the Born-Oppenheimer approximation. Using the nuclear-electronic orbital formalism, we construct mcUCC ansätze for positronium hydride and molecular hydrogen with a quantum proton, and analyze hardware requirements for different excitation truncations. To further reduce resource costs effectively, we employ the local unitary cluster Jastrow ansatz and implement it experimentally on IBM Q's Heron superconducting hardware. With the Physics-Inspired Extrapolation error mitigation protocol, the computed ground-state energies remain within chemical accuracy, consistent with the stated uncertainty level. These results provide the first demonstration of error-mitigated multicomponent correlated simulations on quantum hardware and outline a path toward scalable algorithms unifying electronic and nuclear degrees of freedom.

We present a non-perturbative Hamiltonian mapping method for quantum systems strongly coupled to a quantized field mode (cavity), yielding compact closed-form representations of hybrid light-matter systems. The mapping method builds on an entangling transformation of photonic and atomic degrees of freedom. By truncating the resulting cavity-dressed Hamiltonian (CDH) to successively larger excitation sectors, we construct a series of compact models that converge to the exact limit, outpacing conventional approaches even in the challenging resonant and ultrastrong light-matter regime. The mapping principle also applies to multimode cavities coupled to matter through noncommuting operators and to leaky cavities. We benchmark the CDH framework on the quantum Rabi model, demonstrating accurate spectral predictions in both weak and strong coupling regimes, together with converging ground-state and thermal observables. We study the Dicke-Heisenberg lattice model and determine its phase diagram under resonant and strong light-matter coupling, achieving significant computational savings over brute-force simulations and identifying cavity-mediated spin correlations both analytically and numerically. The closed-form and compactness of the CDH provide both physical insight and enhanced computational efficiency, facilitating studies of strongly coupled hybrid light-matter systems.

We derive relativistic Maxwell-Bloch equations for potential applications in astronomical environments, where various radiative processes are known to occur, including the maser action and Dicke's superradiance. We show that for both phenomena a radiating system's response is preserved at different relative velocities between the system's rest frame and the observer, while the relevant timescales and the radiation intensity transform as expected from relativistic considerations. We verify that the level of coherence between groups of emitters travelling at different speeds is unchanged in all reference frames. We also derive relativistic versions of the maser equations applicable in the steady-state regime.

Quantum computers can efficiently sample from probability distributions that are believed to be classically intractable, providing a foundation for quantum generative modeling. However, practical training of such models remains challenging, as gradient evaluation via the parameter-shift rule scales linearly with the number of parameters and requires repeated expectation-value estimation under finite-shot noise. We introduce a training framework that extends the principle of contrastive divergence to quantum models. By deriving the circuit structure and providing a general recipe for constructing it, we obtain quantum circuits that generate the samples required for parameter updates, yielding constant scaling with respect to the cost of a forward pass, analogous to backpropagation in classical neural networks. Numerical results demonstrate that it attains comparable accuracy to likelihood-based optimization while requiring substantially fewer samples. The framework thereby establishes a scalable route to training expressive quantum generative models directly on quantum hardware.

This report synthesizes the outcomes of a two-day workshop held in Washington, D.C. in May, 2025 that convened researchers, industry representatives, and government stakeholders to examine the current state and future directions of quantum diamond technologies. The workshop's goals were to assess the most promising use cases, to identify the key technical and structural challenges limiting adoption, and to chart potential pathways for aligning application needs with diamond material and device development. Through a series of technical presentations and open discussions, participants explored both near-term demonstrations and long-term infrastructure needs, highlighting the critical role of coordination between material suppliers, device engineers, and end users. The goal of this report is to distill those insights into a coherent set of cross-cutting themes, challenges, and strategic actions that can guide government, industry, and academic efforts to accelerate the maturation and commercialization of quantum diamond technologies.

We study the localization problem in quantum stochastic mechanics. We start from the Edwards model for a particle in a bath of scattering centers and prove static localization of the ground state wavefunction of the particle in a one dimensional square well coupled to Dirac delta like scattering centers in arbitrary but fixed positions. We see how the localization increases for increasing coupling $g$ and increasing number of scattering centers at constant density. Then we choose the scattering centers positions as pseudo random numbers with a uniform probability distribution and observe an increase in the localization of the average of the ground state over the many positions realizations. We discuss how this averaging procedure is consistent with a picture of a particle in a Bose-Einstein condensate of of non interacting boson scattering centers interacting with the particle with Dirac delta functions pair potential. We then study the dynamics of the ground state wave function. We conclude with a discussion of the affine quantization version of the Lax model which reduces to a system of contiguous square wells with walls in arbitrary positions independently of the coupling constant $g$.

We demonstrate $4\pi$-steradian vector magnetic field sensing using an ensemble of nitrogen-vacancy (NV) centers in a single-crystal diamond coupled to a microwave (MW) cavity. The MW cavity enhances the spin-photon coupling which enables efficient, high-contrast spin-state readout via MW interrogation and removes the need for bulky optical collection components. An applied AC bias magnetic field lifts the zero-field degeneracy of the four crystallographic NV orientations, allowing each orientation to be individually addressed and used for vector reconstruction of the magnetic field. The resulting magnetometer has a 40% contrast (20x higher than typical for optical spin-ensemble readout) and achieves a single-axis sensitivity of 250 pT/$\sqrt{\mathrm{Hz}}$ which is flat from DC to 1 kHz. Noise models of the composite spin-cavity system establish MW amplitude noise as the dominant noise source and predict a thermal noise limit of 2 pT/$\sqrt{\mathrm{Hz}}$.

We present an approach to compute time-optimal control of a quantum system which combines quantum brachistochrone and Lax pair techniques and enables efficient investigation of large-scale quantum systems. We illustrate our method by finding the quantum speed limit for a single-particle excitation in a nearest-neighbor-coupled qubit lattice with switchable couplings and fixed sum of their squares. We obtain the solution for a finite system with up to 10 000 qubits and for the effectively infinite lattice closed into ring. As another application of our method, we derive the quantum speed limit for a lattice with time-independent couplings.

Analogous to Coulomb blockade for electrons, photon blockade is a key quantum optical effect in which the presence of one photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest, photon and multi-photon blockade are actively studied as mechanisms for generating technologically-relevant quantum states of light. Although photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a quantum resonator that embeds a two-photon-coupled ensemble of emitters, combining an approximate analytical approach with full quantum numerical simulations. We show that when light and matter are coupled via a two-photon interaction, both single- and multi-photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-photon couplings are a powerful mechanism for realizing photon blockade even in platforms where individual strong coupling is not achievable.

Spins in semiconductor quantum dots offer a scalable approach to quantum computing; however, precise control and efficient readout of large quantum dot arrays remain challenging, mainly due to the hyperdimensional voltage space required for tuning multiple gates per dot. To automate this process, large datasets are required for testing and training autotuning algorithms. To address the demand for such large datasets, we introduce RF-Squad, a physics-based simulator designed to realistically replicate radiofrequency (RF) reflectometry measurements of quantum dot arrays, with the ability to go beyond the Constant Interaction Model (CIM) and simulate physical phenomena such as tunnel coupling, tunnel rates, and quantum confinement. Implemented in JAX, an accelerated linear algebra library, RF-Squad achieves high computational speed, enabling the simulation of a 100x100 pixel charge stability diagram of a double quantum dot (DQD) in 52.1 $\pm$0.2 milliseconds at the CIM level. Using optimization algorithms, combined with it's layered architecture, RF-Squad allows users to balance physical accuracy with computational speed, scaling from simple to highly detailed models.