Quantum Physics · Cross-listed from physics.atom-ph
Full-dimensional quantum scattering calculations of rovibrationally excited HD+HD collisions
Bikramaditya Mandal, Hubert Jóźwiak, Piotr Wcisło et al. (+1 more)
Full-dimensional
quantum scattering calculations are reported for ro-vibrational transitions in HD+HD collisions using a highly accurate interaction potential for the H$_2$-H$_2$ system. Several near-resonant ro-vibrational transitions are identified that conserve the overall rotational angular momentum and nearly conserve the internal energy of the collision partners. Key anisotropic terms that drive the rotational transitions and angular momentum partial waves that contribute to low energy resonant features in the energy dependence of the cross sections are identified. The computed results are in agreement with total cross sections reported in previous experimental results, including resonant features in the energy dependence of the cross section. In particular, low-energy cross sections show a strong resonant feature associated with an $l=3$ partial wave in the incident channel. Rate coefficients for several inelastic rotational and ro-vibrational transitions are reported for temperatures ranging from $0.1$ K to $200$ K and they display a maximum between $1$ K-$10$ K reflecting the important contributions from the $l=3$ shape resonance that occurs around 2.5 K.
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All authors Bikramaditya Mandal, Hubert Jóźwiak, Piotr Wcisło, Naduvalath Balakrishnan
Quantum Physics
Sequence and Image Transformations with Monarq: Quantum Implementations for NISQ Devices
Jan Balewski, Roel Van Beeumen, E. Wes Bethel et al. (+1 more)
We introduce Monarq, a unified
quantum data processing framework that combines QCrank encoding with the EHands protocol for
polynomial transformations, and demonstrate its implementation on noisy intermediate-scale
quantum (NISQ) hardware. This framework provides fundamental
quantum building blocks for signal and image processing tasks, including convolution, discrete-time
Fourier transform (DFT), squared gradient computation, and edge detection, serving as a reference for a broad class of data processing applications on near-term
quantum devices.
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All authors Jan Balewski, Roel Van Beeumen, E. Wes Bethel, Talita Perciano
Quantum Physics
Frequency-Time Multiplexing for Near-Deterministic Generation of n-Photon Frequency-Bin States
Alex Fischer, Nathan T. Arnold, Colin P. Lualdi et al. (+5 more)
One of the primary challenges of photonic
quantum information processing is the on-demand preparation of multiple single-
photon-level
quantum states from probabilistic
photon pair sources. Motivated by recent developments in frequency-bin-encoded photonic
quantum information processing, here we consider active time multiplexing to generate n-
photon states, where n single
photons with n distinct frequencies occupy the same spatiotemporal mode. We devise an approach that uses optical
quantum memories to manipulate the temporal mode of heralded single
photons and an array of fiber Bragg grating reflectors to jointly manipulate the frequency and temporal modes of the
photons, overlapping n
photons in n separate frequency bins into a single spatiotemporal mode. We calculate multiphoton state generation rates that, accounting for loss, are realistically achievable with commercially available hardware. Using only a single free-space switchable delay loop for an optical
quantum memory, this scheme could feasibly produce 8-
photon states at an average rate of 1 kHz.
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All authors Alex Fischer, Nathan T. Arnold, Colin P. Lualdi, Kelsey Ortiz, Michael Gehl, Paul Davids, Kai Shinbrough, Nils T. Otterstrom
Quantum Physics
Star-exponential for Fermi systems and the Feynman-Kac formula
J. Berra-Montiel, H. García-Compeán, A. Kafuri et al. (+1 more)
Inspired by the formalism that relates the
star-exponential with the
quantum propagator for bosonic systems, in this work we introduce the analogous extension for the fermionic case. In particular, we analyse the problem of calculating the
star-exponential (i.e., the symbol of the
evolution operator) for
Fermi systems within the deformation quantization program. Grassmann variables and coherent states are considered in order to obtain a closed-form expression for the fermionic
star-exponential in terms of its associated propagator. As a primary application, a fermionic version of the Feynman-Kac formula is derived within this formalism, thus allowing a straightforward calculation of the ground state energy in phase space. Finally, the method is validated by successfully applying it to the simple harmonic and driven
Fermi oscillators, for which the results developed here provide a powerful alternative computational tool for the study of fermionic systems.
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All authors J. Berra-Montiel, H. García-Compeán, A. Kafuri, A. Molgado
Quantum Physics
Sleeping Beauty in One or Many Worlds: A Defense of the Halfer Position
Jiaxuan Zhang
The Sleeping Beauty Problem (SBP) is a long-standing puzzle in classical probability theory and has been used to challenge the Many-Worlds Interpretation (MWI) of
quantum mechanics, since both involve objective determinacy combined with subjective uncertainty about certain events. A common concern is that MWI yields a different answer to the
quantum version of SBP than the widely supported Thirder position in the classical case. We argue that this concern is unwarranted. We show that in both the
quantum and classical versions of SBP, the correct credence is given by the Halfer position. In the
quantum (MWI) SBP, we show that if no unjustified renormalization is introduced, the correct credence is 1/2. We then extend this result to the classical SBP by refuting four major arguments for 1/3. First, we reject the Proportion Argument by distinguishing event weight from probability. Second, we rebut Elga's Variant Argument by extending an earlier critique that identifies the implicit introduction of additional information; we further clarify this point by constructing a new variant and explaining why the Principle of Indifference is inapplicable, drawing an analogy with a mistake by d'Alembert in the history of probability theory. Third, we identify a flaw in the Technicolor Beauty Variant Argument, which arises from treating overlapping events as disjoint. Finally, we argue that causal decision theory is inappropriate for SBP, rendering the Thirders vulnerable to a Dutch Book. Our results support the consistency of MWI under the challenge posed by SBP and suggest that the dominant position on SBP needs careful reconsideration.
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Quantum Physics
Quantum Lego Power-up: Designing Transversal Gates with Tensor Networks
ChunJun Cao and Brad Lackey
Transversal gates are the simplest form of fault-tolerant gates and are relatively easy to implement in practice. Yet designing codes that support useful transversal operations – especially non-Clifford or addressable gates – remains difficult within the stabilizer formalism or CSS constructions alone. We show that these limitations can be overcome using tensor-network frameworks such as the
quantum lego formalism, where transversal gates naturally appear as global or localized
symmetries. Within the
quantum lego formalism, small codes carrying desirable
symmetries can be "glued" into larger ones, with operator-flow rules guiding how logical
symmetries are preserved. This approach enables the systematic construction of codes with addressable transversal single- and multi-
qubit gates targeting specific logical
qubits regardless of whether the gate is Clifford or not. As a proof of principle, we build new finite-rate code families that support strongly transversal $T$, $CCZ$, $SH$, and Gottesman's $K_3$ gates, structures that are challenging to realize with conventional methods. We further construct
holographic and fractal-like codes that admit addressable transversal inter-, meso-, and intra-block $T$, $CS$, and $C^\ell Z$ gates. As a corollary, we demonstrate that the heterogeneous
holographic Steane-Reed-Muller black hole code also supports fully addressable transversal inter- and intra-block $CZ$ gates, significantly lowering the overhead for universal fault-tolerant computation.
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Quantum Physics · Cross-listed from gr-qc
Analogue Hawking radiation in nonlinear quantum optics
Isaac Bernal, Miguel A. Cortés-Ortiz and David Bermudez
The Hawking effect can be understood as a broad kinematic phenomenon associated with mode behavior near a horizon. While astrophysical black holes produce one specific realization of this radiation, this perspective inspires extensive theoretical and experimental efforts to create event horizons in diverse physical systems to observe the resulting analogue Hawking emission. One of the most successful realizations is the fiber-optical analogue, based on nonlinear
quantum optics. In these notes, we introduce and motivate this system while outlining the theoretical concepts underlying the gravitational analogy. Finally, we review key experiments and discuss their impact on the field.
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Quantum Physics
Adversarial Learning Game for Intrusion Detection in Quantum Key Distribution
Noureldin Mohamed and Saif Al-Kuwari
While
Quantum Key Distribution (QKD) provides information-theoretic security, the transition from theory to physical hardware introduces side-channel vulnerabilities that traditional error metrics often fail to characterize. This paper presents a high-fidelity simulation framework for intrusion detection in decoy-state QKD, modeled as a minimax game between a learning-based defender and a physically constrained, adaptive adversary. The defender utilizes block-level telemetry (comprising decoy-state residuals, timing-histogram moments, and detector imbalances) to trigger alarms that gate key
distillation . Unlike heuristic thresholds, our optimization objective is strictly operational: missed detections are penalized based on the resulting degradation of the finite-key secret fraction calculated via three-intensity decoy
estimators and
entropy-accumulation (EAT) penalties. The emulated adversary performs an automated search over time-shift, detector-blinding,
photon number splitting (PNS), and Trojan-horse families, subject to hardware-limited feasibility bands. Concurrently, the defender co-trains one-class and temporal detectors (LSTM/TCN) using hard-negative mining to minimize the missed-attack rate at a calibrated false-alarm rate ($\text{FAR}$). Under adaptive attack scenarios, the system preserves $82\text{--}92\%$ of the honest finite-key rate while discarding only approximately $1.2\%$ of traffic, representing a net gain of $+20\text{--}35$ percentage points in usable secret bits over non-
adversarial baselines. These results demonstrate that optimizing detection directly for secret-bit retention provides a robust, physically grounded layer of defense against adaptive side-channel strategies in practical QKD deployments.
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Quantum Physics
Observation of Improved Accuracy over Classical Sparse Ground-State Solvers using a Quantum Computer
William Kirby, Bibek Pokharel, Javier Robledo Moreno et al. (+25 more)
Demonstrating
quantum advantage over classical
algorithms for ground state energy problems is an outstanding open problem in
quantum computation. We experimentally demonstrate that a
quantum algorithm can outperform classical selected configuration interaction (SCI) methods, a key family of techniques used in computational chemistry and condensed matter physics. We construct a class of local
Hamiltonian problems with sparse ground states, and show that SCI fails to find the ground state of a 49-
qubit instance. We then show that sample-based Krylov
quantum diagonalization, run on an IBM Heron R3 processor, succeeds at the same task. While the problem is solvable classically using iterative solvers designed to target our
Hamiltonian construction, this work resolves the question of whether a sample-based
quantum diagonalization
algorithm can outperform standard SCI heuristics.
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All authors William Kirby, Bibek Pokharel, Javier Robledo Moreno, Kevin C. Smith, Sergey Bravyi, Abhinav Deshpande, Constantinos Evangelinos, Bryce Fuller, James R. Garrison, Ben Jaderberg, Caleb Johnson, Petar Jurcevic, Su-un Lee, Simon Martiel, Mario Motta, Seetharami Seelam, Oles Shtanko, Kevin J. Sung, Minh Tran, Vinay Tripathi, Kazuhiro Seki, Kazuya Shinjo, Han Xu, Lukas Broers, Tomonori Shirakawa, Seiji Yunoki, Kunal Sharma, Antonio Mezzacapo
Quantum Physics
Spectral statistics and localization properties of a $C_3$-symmetric billiard
Matic Orel and Marko Robnik
We revisit the spectral statistics of the C$_3$–symmetric billiard introduced by Dembowski [Phys. Rev. E, R4516 (2000)], which exhibits both GOE and GUE statistics depending on the
symmetry block. Using high–precision Beyn's contour–integral method for the nonlinear Fredholm
eigenvalue problem with built-in separation of irreducible subspaces, we compute 2.8x10$^5$
eigenvalues in each
symmetry subspace, enabling statistically meaningful comparisons with random
matrix theory. The improved spectra reveal clear GOE–GUE correspondence and resolve previously observed deviations in long–range spectral correlations. Furthermore, we analyze phase–space eigenstate localization through the distribution of
entropy localization measures, which, for chaotic states follow a Beta distribution whose standard deviation decays as a power–law with energy, consistent with the onset of
quantum ergodicity as described by Schnirelman's
theorem.
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Quantum Physics · Cross-listed from cond-mat.str-el
Mixed-state Phases from Higher-order SSPTs with Kramers-Wannier Symmetry
Aswin Parayil Mana, Zijian Song, Fei Yan et al. (+1 more)
Mixed-state phases have recently attracted significant
attention as a generalization beyond their pure-state counterparts. Prominent examples include mixed-state
symmetry-protected topological (mSPT) phases and the strong-to-weak
symmetry breaking (SWSSB) phases. It has been shown recently that mSPT phases admit a
holographic dual description in terms of higher-order subsystem SPT phases. In this work, we investigate the mixed-state phases obtained by tracing out the bulk degrees of freedom of higher-order subsystem SPT phases protected by non-invertible
symmetries. We find that the resulting mixed states exhibit the coexistence of the
symmetry-protected topological order and SWSSB. We also use the interface as a probe to characterize the mixed state phases, and specifically, when there is no local modification to preserve the
symmetries across the interface, the two sides of the interface are in distinct phases.
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All authors Aswin Parayil Mana, Zijian Song, Fei Yan, Tzu-Chieh Wei
Quantum Physics
Multi-Parameter Multi-Critical Metrology of the Dicke Model
Luca Previdi, Yilun Xu, Qiongyi He et al. (+1 more)
Critical
quantum metrology exploits the hypersensitivity of
quantum systems near phase transitions to achieve enhanced precision in parameter estimation. While single-parameter estimation near critical points is well established, the simultaneous estimation of multiple parameters, which is essential for practical sensing applications, remains challenging. This difficulty arises from sloppiness, a phenomenon that typically renders the
quantum Fisher information
matrix (QFIM) singular or nearly singular. In this work, we demonstrate that multiparameter critical metrology is not only feasible but can also retain divergent precision scaling, provided one accepts a trade-off in the scaling exponent. Using the ground state of the single-cavity Dicke model (DM), we show that two
Hamiltonian parameters can be simultaneously estimated with a scalar variance bound scaling as the square root of the critical parameter. This overcomes the inherent sloppiness by leveraging higher-order contributions to the QFIM. To recover the optimal quadratic scaling, we introduce the Dicke dimer (DD) with
photon hopping. In this extended model, a triple point in the phase diagram enables the simultaneous closure of two excitation gaps, which effectively increases the rank of the QFIM and restores the ideal single-parameter scaling for specific parameter pairs. Furthermore, we extend our analysis to dissipative settings subject to
photon loss. Finally, we establish a connection between the derived critical scalings and the fundamental state preparation time, providing a unified framework to operationally compare different sensing strategies. Our results demonstrate that critical
quantum metrology can be made robust against dissipation and scalable to multiparameter scenarios, paving the way for practical
quantum sensors operating near phase transitions.
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All authors Luca Previdi, Yilun Xu, Qiongyi He, Matteo G. A. Paris
Quantum Physics
Phase-space complexity of discrete-variable quantum states and operations
Siting Tang, Shunlong Luo and Matteo G. A. Paris
We introduce a quantifier of phase-space complexity for discrete-variable (DV)
quantum systems. Motivated by a recent framework developed for continuous-variable systems, we construct a complexity measure of
quantum states based on the Husimi Q-function defined over
spin coherent states. The quantifier combines into a single scalar quantity two complementary information-theoretic quantities, the Wehrl
entropy, which captures phase-space spread, and the Fisher information, which captures localization. We derive fundamental properties of this measure, including its invariance under SU(2) displacements. The complexity is normalized such that coherent states have unit complexity, while the completely mixed state has zero complexity, a feature distinct from the continuous-variable case. We provide analytic expressions for several relevant families of states, including Gibbs and Dicke states, and perform a numerical analysis of
spin-squeezed states, NOON states, and randomly generated states. Numerical results reveal a monotonic, but not deterministic, relationship between complexity and purity, leading us to
conjecture that maximal complexity is attained by pure states, thereby connecting the problem to the optimization of Wehrl
entropy via Majorana constellations. Finally, we extend the framework to
quantum channels, defining measures for both the generation and breaking of complexity. We analyze the performance of common
unitary gates and the amplitude damping channel, showing that while low-dimensional systems can achieve maximal complexity via
spin squeezing or NOON states, this becomes impossible in higher dimensions. These results highlight dimension-dependent limitations in the generation of phase-space complexity and establish a unified phase-space approach to complexity across both continuous and discrete variable regimes.
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Quantum Physics
Photonic hyperentanglement in polarisation and frequency via joint spectrum shaping
Tommaso Faleo, Fabian Steinhauser, Gregor Weihs et al. (+2 more)
Hyperentanglement offers enhanced capacity for
quantum information processing and communication protocols, especially in combination with robust high-dimensional degrees of freedom such as frequency-bin encoding. Here, we present a single-pass, unfiltered, down-conversion source of hyperentangled
photon pairs in polarisation and frequency-bin degrees of freedom with dynamically tunable state dimension and composition at telecom wavelengths. We achieve this by optimal tailoring of the
photons' joint spectral amplitude via pump and nonlinearity shaping. Using polarisation-resolved time-of-flight spectrometry and Hong-Ou-Mandel interference, we characterise the hyperentangled states and demonstrate for the polarisation component fidelities exceeding 99% averaged over frequency bins and concurrences above 98%. The degree of spectral
entanglement, quantified by the Hong-Ou-Mandel visibility, is measured as 90%, well in line with numerical simulations. This approach provides a scalable route toward high-dimensional
quantum states for
quantum communication and computing applications.
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All authors Tommaso Faleo, Fabian Steinhauser, Gregor Weihs, Stefan Frick, Robert Keil
Quantum Physics
Bayesian post-correction of non-Markovian errors in bosonic lattice gravimetry
Bharath Hebbe Madhusudhana, Andrew Harter and Avadh Saxena
We study gravimetry with bosonic trapped atoms in the presence of random spatial inhomogeneity. The errors resulting from a random, shot-to-shot fluctuating spatial inhomogeneity are
quantum non-Markovian. We show that in a system with $L>2$ modes (i.e., trapping sites), these errors can be post-corrected using a
Bayesian inference. The post-correction is done via in situ measurements of the errors and refining the data-processing according to the measured error. We define an effective Fisher information $F_{\text{eff}}$ for such measurements with a
Bayesian post-correction and show that the Cramer-Rao bound for the final precision is $\frac{1}{\sqrt{F_{\text{eff}}}}$. Exploring the scaling of the effective Fisher information with the number of atoms $N$, we show that it saturates to a constant when there are too many sources of error and too few modes. That is, with $\ell$ independent sources of error, we show that the effective Fisher information scales as $F_{\text{eff}} \sim \frac{N^2}{a+bN^2}$ for constants $a, b>0$ when the number of modes is small: $L<\ell+2$, even after maximization over the
Hilbert space. With larger number of modes, $L\geq \ell+2$, we show that the effective Fisher information has a Heisenberg scaling $F_{\text{eff}}= O(N^2)$ when optimized over the
Hilbert space. Finally, we study the density of the effective Fisher information in the
Hilbert space and show that when $L\geq \ell+2$, almost any Haar random state has a Heisenberg scaling, i.e., $F_{\text{eff}}=O(N^2)$. Based on these results, we develop a Loschmidt echo-like experimental sequence for error mitigated gravimetry and gradiometry and discuss potential implementations. Finally, we argue that the effective Fisher information can be interpreted as the Fisher information corresponding to an equivalent non-Hertimitian
evolution.
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Quantum Physics · Cross-listed from cond-mat.mtrl-sci
Quantum Theory of Functionally Graded Materials
Michael J. Landry, Ryotaro Okabe, Chuliang Fu et al. (+1 more)
Functionally graded materials (FGMs) are composites whose composition or microstructure varies continuously in space, producing position-dependent mechanical and functional properties. In recent years, FGMs have gained significant
attention due to advances in additive manufacturing, which enable precise spatial control of composition and orientation. However, their graded, aperiodic structure breaks the assumptions of Bloch's
theorem, making first-principles electronic and electromagnetic calculations challenging. Here we develop an ab initio
quantum theoretical framework for the electromagnetic properties of FGMs. Using a non-interacting electron model, we formulate a theory of modulated Bloch states, derive effective field equations, and solve them by proposing a generalized WKB (GWKB) method, an effective mass approximation, the Boltzmann equation, and numerical approaches. Our GWKB solution is not semiclassical but remains valid in the fully
quantum regime. We show that effective observables such as conductivity,
magnetic permeability, and electric permittivity generally do not admit a tensorial description in graded media, and that engineered orientational gradients enable precise control of Landau quantization. As a device example, we further develop a theory of graded p-n junctions with enhanced electronic tunability. This framework lays the
quantum foundation for predictive design of graded composite materials, enabling AI-accelerated discovery of next-generation functional architectures.
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All authors Michael J. Landry, Ryotaro Okabe, Chuliang Fu, Mingda Li
Quantum Physics
Generalised All-Optical Cat Correction
Ari John Boon, Olivier Landon-Cardinal and Nicolás Quesada
We have generalised an all-optical telecorrection protocol for the higher orders of the cat code, and show that with these higher orders we can achieve target performance at substantially reduced iteration counts at the cost of a higher mean
photon-number. We also introduce a probabilistic scheme for correcting deformation of the state, which highlights two interesting abilities of telecorrection: to encode new sets of transformations, and to change the basis of the code. We find that for a target channel fidelity of $99.9\%$ over a channel with $1\text{ dB}$ of loss, a third-order cat code requires $70$ times fewer telecorrection iterations than a first-order one, at a cost of a $3.6$-fold increase in mean
photon-number.
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Quantum Physics · Cross-listed from cond-mat.mes-hall
Anomalous Klein tunnelling with magnetic barriers in strained graphene
Edgardo Marin-Colli, Tonatiuh Gómez-Ramírez, O-Excell Gutierrez et al. (+3 more)
We study electron transport in a strained
graphene sheet subjected to a sequence of $N$ electrostatic and
magnetic barriers. Employing a modified and improved transfer-
matrix framework, we examine how the transmission and reflection coefficients evolve with variations in uniaxial strain and in the number of barriers. The interplay of mechanical deformation and external
magnetic fields is found to generate an anomalous Klein tunnelling, allowing the conductance to be effectively modulated through strain and barrier configurations. These findings highlight the role of strain engineering and
magnetic field modulation as powerful tools for tailoring charge transport in two-dimensional materials. More broadly, they underscore how mechanical and electromagnetic control can be used to design next-generation solid-state devices with tunable electronic properties.
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All authors Edgardo Marin-Colli, Tonatiuh Gómez-Ramírez, O-Excell Gutierrez, Yonatan Betancur-Ocampo, Alfredo Raya, Erik Díaz-Bautista
Quantum Physics
Multiparty Quantum Key Agreement: Architectures, State-of-the-art, and Open Problems
Malik Mouaji and Saif Al-Kuwari
Multiparty
quantum key agreement (MQKA) enables $n \geq 3$ mutually distrustful users to establish a shared secret key through collaborative
quantum protocols. In this paper, we provide a comprehensive review where we argue that MQKA is best understood as a design space organized along three orthogonal but tightly coupled axes: (1) network architecture, which determines how
quantum states flow between participants; (2)
quantum resources, which encode the physical degrees of freedom used for implementation; and (3) security model, which defines trust assumptions about devices and infrastructure. Rather than treating MQKA as a linear sequence of isolated protocols, we develop this three-axis perspective to reveal recurrent patterns, sharp trade-offs, and unexplored design spaces. We classify MQKA protocols into structural families, map them to underlying
quantum resources, and analyze how different security models shape
fairness and collusion resistance. We further identify open challenges in composable security frameworks, network native integration, device-independent implementations, and propose a research roadmap toward hybrid-resource, bosonic-code-encoded, and
fairness-aware MQKA suitable for the future
quantum internet deployments in the post-NISQ era.
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Quantum Physics
Recovery-Induced Erasure Attack on QKD Systems
Hashir Kuniyil, Asad Ali, Syed M. Arslan et al. (+3 more)
Detector dead time is typically treated as a fixed parameter in
quantum key distribution (QKD) security analyses. In practice, however, the effective recovery time of single-
photon avalanche photodiodes (SPADs) depends on the incident count rate. In this work, we demonstrate that this count-rate-dependent recovery nonlinearity constitutes a distinct attack primitive. We experimentally characterize the dead time shift of a free-running SPAD under controlled broadband loading and observe a substantial increase in effective recovery time as the detected rate rises into the high
photon count regime. We show that recovery-induced availability reduction can be modeled as an
adversarial erasure channel and derive a conservative bound on the signal detection probability under loading. Unlike previously studied detector-control or efficiency mismatch attacks, the proposed mechanism does not rely on deterministic blinding or timing discrimination. Instead, count-rate-dependent recovery asymmetry induces basis-dependent suppression of detection probabilities ($p_\perp<p_\parallel$), converting mismatch-induced errors into loss. Particularly, we show in active-basis BBM92 systems, this effect reduces the observed
quantum bit error rate (QBER) below the abort threshold while increasing erasure probability. Using experimentally measured detector recovery data, we quantify the parameter regime in which such stealth suppression is achievable. These results establish count-rate-dependent detector recovery as a security-relevant vulnerability and show that countermeasures designed for timing-based efficiency mismatch do not directly address recovery-induced erasure (RIE) attack. Our findings underscore the need to incorporate detector recovery dynamics explicitly into practical QKD security models.
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All authors Hashir Kuniyil, Asad Ali, Syed M. Arslan, Muhammad Talha Rahim, Artur Czerwinski, Saif Al Kuwari
Quantum Physics · Cross-listed from cond-mat.mes-hall
Simultaneous anti-bunched and super-bunched photons from a GaAs Quantum dot in a dielectric metasurface
Sanghyeok Park, Oleg Mitrofanov, Kusal M. Abeywickrama et al. (+9 more)
Semiconductor quantum dots host a rich
manifold of excitonic complexes, including neutral
excitons that emit anti-bunched single
photons and charged
exciton complexes capable of producing super-bunched
photons via cascade emission. Accessing both emission regimes from a single emitter would open routes to novel
quantum protocols, including advanced
quantum imaging. In practice, however, emission from charged
exciton complexes is intrinsically weak, often orders of magnitude dimmer than neutral
excitons, placing simultaneous dual-mode operation out of reach. Here, we overcome this limitation by
embedding the
quantum dot in a dielectric Mie-resonant metasurface that provides order-of-magnitude photoluminescence enhancement across both neutral and charged
exciton transitions of a single GaAs
quantum dot. Under identical non-resonant pumping conditions, the emission from the neutral
exciton yields anti-bunched emission ($g^{(2)}(0) < 0.5$) and the emission from positively charged
exciton complexes shows super-bunched emission ($g^{(2)}(0) > 3.5$) with comparable count rates (~12 kHz). Crucially, super-bunching emerges only when charged
exciton emission spectrally overlaps with the Mie resonances and vanishes in un-patterned slabs, demonstrating that photonic engineering, is essential for accessing these weak
quantum light states. These results demonstrate a scalable, position-tolerant platform for harnessing the full excitonic structure of solid-state emitters.
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All authors Sanghyeok Park, Oleg Mitrofanov, Kusal M. Abeywickrama, Samuel Prescott, Jaeyeon Yu, Stephanie C Malek, Hyunseung Jung, Emma Renteria, Sadhvikas Addamane, Alisa Javadi, Igal Brener, Prasad P Iyer
Quantum Physics
Witnesses of non-Gaussian features as lower bounds of stellar rank
Jan Provazník, Šimon Bräuer, Vojtěch Kala et al. (+2 more)
Quantum non-Gaussian states and operations serve as fundamental resources for universal
quantum computation, error correction, and high-precision metrology, extending beyond the Gaussian limits. While the
stellar rank provides a rigorous hierarchical measure of non-Gaussianity, it remains challenging to determine experimentally. Conversely, witnesses of non-Gaussian features, based on the expectation values and variances of measurable observables, offer an accessible method for certifying non-Gaussian behavior but lack a direct connection to
stellar rank. In this work, we establish a quantitative connection between these witnesses and
stellar rank, demonstrating that the former can provide certifiable lower bounds on
stellar rank. We introduce normalized expectation value and variance-based quantifiers and show that these witnesses form a consistent hierarchy of thresholds corresponding to
stellar rank. Our results bridge the gap between abstract hierarchical measures and experimentally accessible quantifiers, enabling scalable certification of non-Gaussian states.
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All authors Jan Provazník, Šimon Bräuer, Vojtěch Kala, Jaromír Fiurášek, Petr Marek
Quantum Physics
Entanglement-Assisted Codes Outside the Stabilizer Framework
Jaszmine DeFranco and Andrew Nemec
We show how
entanglement-assisted codes can be constructed from arbitrary
quantum codes by associating them with
quantum codes for erasure channels. If a subset of physical
qubits is correctable for an erasure error, then it naturally forms the receiver's share of a bipartite state that can be used for
entanglement-assisted communications, both in the noiseless and noisy ebit error models. In the case of degenerate codes, we show that the receiver's share of the bipartite state can sometimes be compressed, at the cost of potentially reduced error-correction ability in the noisy ebit error model. We also give examples of permutation-invariant and XP-stabilizer
entanglement-assisted codes, the first outside of the stabilizer and codeword-stabilized frameworks.
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Quantum Physics
Achieving speedup in Dark Matter search experiments with a transmon-based NISQ algorithm
Roberto Moretti, Pietro Campana, Rodolfo Carobene et al. (+9 more)
Coherent detection of ultralight bosonic dark matter can be achieved by monitoring slow Rabi oscillations in superconducting
qubits. We introduce an ancilla-assisted, gate-based protocol that enhances sensitivity to the hidden
photon kinetic mixing parameter $\epsilon$ using a single two-
qubit gate, bypassing the need to maintain long-lived multi-
qubit entangled states and remaining compatible with the limitations of modern
quantum hardware. We characterized the increase in sensitivity accounting for decoherence, thermal occupation, errors in readout and reset, indicating up to a ten-fold reduction in the required integration time to reach the same exclusion limit on $\epsilon$ achievable via Rabi-sampling experiments. Under plausible hardware assumptions and three years of data taking, the projected $95\%$ C.L. exclusion limit on the hidden
photon mixing parameter reaches $\epsilon\approx 1\times 10^{-14}$ across $2.5$-$6.0$ GHz ($10$-$25$ \textmu eV).
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All authors Roberto Moretti, Pietro Campana, Rodolfo Carobene, Alessandro Cattaneo, Marco Gobbo, Danilo Labranca, Matteo Borghesi, Marco Faverzani, Elena Ferri, Sara Gamba, Angelo Nucciotti, Andrea Giachero
Quantum Physics
Efficient Image Reconstruction Architecture for Neutral Atom Quantum Computing
Jonas Winklmann, Yian Yu, Xiaorang Guo et al. (+2 more)
In recent years, neutral atom
quantum computers (NAQCs) have attracted a lot of
attention, primarily due to their long coherence times and good scalability. One of their main drawbacks is their comparatively time-consuming control overhead, with one of the main contributing procedures being the detection of individual atoms and measurement of their states, each occurring at least once per compute cycle and requiring fluorescence imaging and subsequent image analysis. To reduce the required time budget, we propose a highly-parallel atom-detection accelerator for tweezer-based NAQCs. Building on an existing solution, our design combines
algorithm-level optimization with a field-programmable gate array (FPGA) implementation to maximize parallelism and reduce the run time of the image analysis process. Our design can analyze a 256$\times$256-pixel image representing a 10$\times$10 atom array in just 115 $\mu$s on a Xilinx UltraScale+ FPGA. Compared to the original CPU baseline and our optimized CPU version, we achieve about 34.9$\times$ and 6.3$\times$ speedup of the reconstruction time, respectively. Moreover, this work also contributes to the ongoing efforts toward fully integrated FPGA-based control systems for NAQCs.
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All authors Jonas Winklmann, Yian Yu, Xiaorang Guo, Korbinian Staudacher, Martin Schulz
Quantum Physics
Quantum-Inspired Hamiltonian Feature Extraction for ADMET Prediction: A Simulation Study
B. Maurice Benson, Kendall Byler, Anna Petroff et al. (+2 more)
Predicting absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties remains a critical bottleneck in drug discovery. While molecular fingerprints effectively capture local structural features, they struggle to represent higher-order correlations among molecular substructures. We present a
quantum-inspired feature extraction method that encodes molecular fingerprints into a parameterized
Hamiltonian, using mutual information (MI) to guide
entanglement structure. By simulating
quantum evolution on GPU-accelerated backends, we extract expectation values that capture pairwise and triadic correlations among fingerprint bits. On ten Therapeutic Data Commons (TDC) ADMET
benchmarks, our method achieves state-of-the-art performance on CYP3A4 substrate prediction (AUROC 0.673 0.004) and improves over classical baselines on 8/10 tasks. SHAP (SHapley Additive exPlanations) analysis reveals that
quantum-derived features contribute up to 33% of model importance despite comprising only 1.6% of features, demonstrating that
Hamiltonian encoding concentrates predictive signal. This simulation study establishes the foundation for hardware validation on near-term
quantum devices.
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All authors B. Maurice Benson, Kendall Byler, Anna Petroff, Shahar Keinan, William J Shipman
Quantum Physics · Cross-listed from cond-mat.stat-mech
Tripartite information of free fermions: a universal entanglement coefficient from the sine kernel
Aleksandrs Sokolovs
We study the tripartite information I_3 of free
fermions on two-dimensional
lattices partitioned into three adjacent strips of width w. Translation invariance yields the exact decomposition I_3 = \sum_{k_y} g(k_F(k_y) w), where g(z) is a universal function of the scaling variable z = k_F w, determined by the spectrum of the sine-kernel (Slepian) integral operator. We find that g(z) has a unique zero at z* = 1.329 +/- 0.001: modes with k_F w < z* violate monogamy of mutual information (g > 0), while modes with k_F w > z* satisfy it (g < 0). The central analytical result is g(z) = cz + O(z^3 ln z) with c = 3 ln(4/3)/pi ~ 0.2747, derived from the rank-1 limit of the sine kernel. Two exact cancellations – of the z ln z area-law terms and of the z^2 terms – are intrinsic to the I_3 combination. The coefficient c generalizes to n-partite information: c_n = (n/pi) ln R_n with R_n a rational number from binomial combinatorics. For Renyi
entropy of index alpha, we show that g_alpha(z) ~ z^alpha for alpha < 2 and g_2(z) = -(8/pi^3)z^3: von Neumann
entropy (alpha = 1) uniquely gives linear sensitivity to Lifshitz transitions, while Renyi-2 gives only cubic sensitivity. We verify all predictions on square, triangular, and cubic
lattices. DMRG calculations on the interacting t-V model provide evidence that the linear coefficient is independent of the Luttinger parameter K.
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Quantum Physics
From Reachability to Learnability: Geometric Design Principles for Quantum Neural Networks
Vishal S. Ngairangbam and Michael Spannowsky
Classical deep networks are effective because depth enables adaptive
geometric deformation of data representations. In
quantum neural networks (QNNs), however, depth or state reachability alone does not guarantee this feature-learning capability. We study this question in the pure-state setting by viewing encoded data as an embedded
manifold in $\mathbb{C}P^{2^n-1}$ and analysing infinitesimal
unitary actions through Lie-
algebra directions. We introduce Classical-to-Lie-
algebra (CLA) maps and the criterion of almost Complete Local Selectivity (aCLS), which combines directional completeness with data-dependent local selectivity. Within this framework, we show that data-independent trainable
unitaries are complete but non-selective, i.e. learnable rigid reorientations, whereas pure data encodings are selective but non-tunable, i.e. fixed deformations. Hence,
geometric flexibility requires a non-trivial joint dependence on data and trainable weights. We further show that accessing high-dimensional deformations of many-
qubit state
manifolds requires parametrised entangling directions; fixed entanglers such as CNOT alone do not provide adaptive
geometric control. Numerical examples validate that aCLS-satisfying data re-uploading models outperform non-tunable schemes while requiring only a quarter of the gate operations. Thus, the resulting picture reframes QNN design from state reachability to controllable geometry of hidden
quantum representations.
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