Z-boson Transverse-Momentum Resummation Improves PDF Precision

A new study has investigated the impact of small-transverse-momentum resummation for neutral-current Drell-Yan lepton-pair production on the determination of collinear parton distribution functions (PDFs). Researchers focused on measurements of the Z-boson transverse-momentum spectrum performed by the ATLAS and CMS collaborations at the LHC at centre-of-mass energies of 8 and 13 TeV, including them in PDF fits based on the NNPDF methodology. This analysis is crucial for refining our understanding of the internal structure of protons, a fundamental aspect for theoretical predictions in high-energy physics. Theoretical predictions were computed at next-to-next-to-leading order (NNLO) in perturbative quantum chromodynamics, supplemented with small-transverse-momentum resummation corrections at next-to-next-to-next-to-leading logarithmic accuracy obtained with the RadISH tool. Missing higher-order uncertainties were accounted for through a theory covariance matrix constructed from renormalisation and factorisation scale variations. The study revisited the treatment of 8 TeV data, replacing fixed-order predictions used in previous analyses with numerically stable NNLO calculations and removing additional numerical uncertainties introduced in earlier fits. The results indicate that resummation improves the description of Z boson transverse-momentum data and is essential for ensuring the overall consistency of PDF fits. Nevertheless, it does not conclusively support extending the fitted kinematic region to transverse momenta below a few tens of GeV. The impact of resummation on PDFs is moderate, primarily leading to a stabilisation of the gluon PDF in a kinematic region of relevance for LHC phenomenology. Furthermore, the study highlights that the treatment of correlations among theoretical uncertainties may play a central role in PDF fits to measurements with percent- and sub-percent-level precision.

Chiral-Interference Quantum Circuits for Benchmarking Composite Gates

Researchers have experimentally implemented compact quantum circuits that simulate the state-transfer interference underlying three- and four-level chiral-resolution protocols. These models, encoded in a two-qubit register, simulate the enantiomer-dependent sign of one of the couplings. In the four-level circuit, this is achieved by a conditional-phase operation, while in the three-level circuit, the sign of a final rotation is used. Experiments performed on an IBM quantum processor have shown that both circuits produce the expected enantiomer-dependent output states with probabilities of nearly 98%.

New Compiler Accelerates Large-Scale Quantum Circuit Simulation

Researchers have developed a new parallel compiler that enables more efficient simulation of large-scale quantum circuits. This tool addresses one of the main challenges in quantum computing development: the difficulty of testing and verifying complex quantum algorithms on classical simulators. The ability to simulate circuits with a larger number of qubits and logical gates is crucial for advancing the design and optimization of next-generation quantum hardware and algorithms. The compiler optimizes the execution of quantum circuits by reordering and merging operations, as well as by distributing the workload among multiple processors. This significantly reduces simulation time and memory requirements, making it possible to explore previously intractable circuits. Efficiency is achieved through advanced parallelization techniques and intelligent management of computational resources, making it a valuable tool for quantum computing research. This breakthrough has important implications for the quantum computing community. By facilitating the simulation of larger and more complex circuits, the compiler accelerates the design and debugging cycle of quantum algorithms. This is essential for identifying errors, evaluating the performance of different circuit architectures, and exploring new algorithmic ideas without relying solely on physical quantum hardware, which is still limited and error-prone. The tool also includes profiling capabilities that help developers better understand the behavior of their circuits and optimize them. While classical simulation of quantum systems will always have limits due to the inherent complexity of quantum mechanics, this compiler represents a significant step in extending those limits in the short to medium term. It allows researchers to validate concepts and algorithm prototypes in a controlled environment before their implementation on real quantum devices. This tool is expected to boost research and development of new quantum applications in fields such as quantum chemistry, materials science, and optimization.

Transversal Fault-Tolerant Distributed Quantum Computing Operations

Researchers have developed a new method for performing distributed quantum computing operations that are inherently fault-tolerant. This advance is crucial for building scalable quantum computers, as it addresses one of the biggest challenges in the field: the fragility of qubits and their susceptibility to errors. Fault tolerance is achieved through the use of quantum error correction codes, but their implementation in distributed systems, where qubits are physically separated, presents additional complexities. The new approach focuses on transversal operations, which apply identical transformations to each qubit in a code, simplifying error correction. The study proposes a framework for performing these transversal operations in a distributed environment, where communication between quantum nodes is a critical factor. The key lies in the ability to execute logical operations (on encoded qubits) without the need to decode and re-encode the information, which introduces fewer errors and is computationally more efficient. This method is applicable to various quantum computing architectures, including those based on ion traps, superconducting qubits, or photons, provided that reliable quantum communication channels can be established. The most significant implication of this work is that it brings closer the possibility of building a robust quantum internet and modular quantum computers. By allowing the connection of multiple smaller, fault-tolerant quantum processors, the limitation of building a single large-scale processor, which is extremely difficult due to coherence requirements, is overcome. This advance is not only relevant for quantum computing but also for secure quantum communication and distributed quantum metrology, opening new avenues for exploring large-scale quantum phenomena.

Topology of Bipartite Entangled Quantum States Unveiled

A recent study has explored the topology of the set of bipartite entangled states, $\mathsf E$, acting on the Hilbert space $\mathbb{C}^{n_1}\otimes\mathbb{C}^{n_2}$. Researchers have shown that this set is path-connected in all dimensions, and simply connected except for the specific two-qubit case. This advancement provides a deeper understanding of the mathematical structure of entanglement, a fundamental resource in quantum computing and information. For the exceptional two-qubit case, the set $\mathsf E$ is found to be homotopy equivalent to the set of maximally entangled states, which itself is homeomorphic to $\mathbb{RP}^3$. The authors have computed the complete homology of both the closure and the interior of $\mathsf E$ in this configuration. In larger dimensions, it has been shown that the homology and homotopy groups of $\mathsf E$ vanish in degrees $1\leq k\leq 2(n_1-1)(n_2-1)-2$, and all homology groups of degree $k\geq (n_1n_2)^2-3$ also vanish. This range is controlled by the space $\mathsf W$ of entanglement witnesses, which is shown to be highly connected beyond two qubits and homotopy equivalent to $\mathsf E$. Despite these vanishing results, the study reveals that $\mathsf E$ possesses non-trivial reduced homology over every field for all $n_1, n_2 \geq 2$. This was determined by computing the Euler characteristic using a torus-action fixed point argument, along with Alexander duality. These findings are crucial for understanding the complexity of quantum entanglement and could have implications for the development of future quantum technologies, by providing more robust mathematical tools for classifying and manipulating entangled states.

Pairing-induced phase transition in non-reciprocal Kitaev chain

Researchers have discovered a pairing-induced phase transition in a non-reciprocal Kitaev chain. This finding is significant because the Kitaev chain is a fundamental theoretical model in condensed matter physics, known for its ability to host Majorana fermions, which are particles that are their own antiparticle and are of great interest for fault-tolerant quantum computing. Non-reciprocity, where the interaction of A on B is not equal to that of B on A, adds a new layer of complexity and potential physical phenomena. The study focuses on how the introduction of a pairing term, representing the formation of particle pairs, can alter the topological properties of this chain. Traditionally, Kitaev chains have been studied in a reciprocal regime. The inclusion of non-reciprocal interactions opens the door to exploring exotic topological phases that have no analogues in reciprocal systems, offering new avenues for understanding and manipulating quantum states. The results suggest that this phase transition could be controllable, which would have important implications for the design of quantum devices. The ability to induce and control such transitions is crucial for engineering materials with specific topological properties that are robust against local perturbations. This advance contributes to the understanding of quantum systems out of equilibrium and could inspire new architectures for quantum computing.

Quantum Spin Correlations to Search for Z' Bosons at Lepton Colliders

A theoretical study explores the potential of quantum spin correlations in top-antitop ($t\bar{t}$) pair production at future lepton colliders. The aim is to search for the existence of additional neutral gauge bosons, denoted $Z'$, which arise in extensions of the Standard Model with anomaly-free $U(1)$ symmetries. The research focuses on how the spin-density matrix, including the exchange of photons ($\gamma$), $Z$ bosons, and hypothetical $Z'$ bosons, as well as their interferences, can reveal the presence of these new particles. The researchers analyzed quantum-information observables such as the sufficient entanglement marker $\mathcal{D}_{\min}$, concurrence, purity, and the maximal Clauser-Horne-Shimony-Holt (CHSH) parameter. These were compared with information obtained from conventional production rates. Different charge assignments within the $U(1)_X$ framework were considered to investigate how chiral structures influence these observables, with particular emphasis on the $Z'$ resonance region and polarized $e^-e^+$ collisions. Electron-beam polarization provides a direct handle on the left- and right-handed lepton charges in various $U(1)_X$ scenarios. The results suggest that quantum spin observables provide information complementary to cross sections and angular distributions in searches for chiral neutral gauge interactions. This is crucial for identifying and characterizing potential $Z'$ bosons that could mediate fundamental forces yet unknown.

New Kinematic Dependencies in Collinear Scattering Amplitudes

Researchers have studied the spacelike-collinear limit of gauge-theory scattering amplitudes using the Method of Regions. They found that the resulting splitting amplitudes violate strict collinear factorization, showing a dependence on non-collinear partons. While the associated color dependence has long been known, starting at two loops, the splitting amplitude also acquires a dependence on the kinematics of these partons. This finding is crucial for understanding the complexity of particle interactions at high energies. The research reveals that this kinematic dependence originates from a unique hidden region, present in the asymptotic expansion of the five-point amplitude in the spacelike-collinear limit, but absent in the timelike limit. The authors propose that these hidden regions provide the mechanism by which crossing-related asymptotic limits cease to be analytically connected. They developed an algorithm for systematically identifying these hidden regions, applying it to the five-point amplitude in super Yang-Mills theory. By applying this algorithm, the scientists computed the hidden-region contributions to the complete set of basis integrals and recovered the exact kinematically dependent, factorization-violating splitting amplitude. In momentum space, the hidden region is characterized by soft and Glauber loop momenta. This discovery explains why the Wilson-line calculation captures the complete kinematic dependence, thereby accounting for the observed universality across gauge theories.

Supersymmetric μνSSM Model Impacts B Meson Decay

A theoretical study has investigated how new physics, specifically within the Supersymmetric Standard Model with neutrinos (μνSSM), influences the rare inclusive decay $B \to X_{\mathrm{s}} l^{+} l^{-}$. This decay is of particular interest because its rate and characteristics can be sensitive to particles and forces not accounted for in the Standard Model of particle physics. Researchers have identified the main contributions to the relevant Wilson coefficients, which are parameters describing the strength of interactions in the decay, and the particles associated with them within the μνSSM. The analysis focused on a systematic scan of the μνSSM parameter space, which allowed for the elucidation of the underlying physical mechanisms governing these dominant contributions. The obtained results are consistent with experimentally allowed regions, suggesting that the μνSSM could offer an explanation for potential future deviations observed in these decays. Experimental constraints from other relevant decays, such as $\bar{B} \to X_{\mathrm{s}}\gamma$, $B_{\mathrm{s}}^{0} \to \mu^{+} \mu^{-}$, and the 125 GeV Higgs boson mass, were also incorporated. A key part of the study was the systematic interference decomposition of the Wilson coefficient contributions to the forward-backward asymmetry (AFB). It was identified that the $C_7C_{10}$ and $C_9C_{10}$ interference terms are the dominant contributions governing the behavior of the AFB in both low- and high-$q^2$ (momentum transferred to the lepton pair) regions. Understanding these contributions is crucial for interpreting future measurements of the AFB, which is an observable sensitive to new physics and could reveal the existence of supersymmetric particles or other extensions of the Standard Model.

Quasi-solitons observed in Rydberg atom chains

Researchers have successfully observed the formation and propagation of quasi-solitons in one-dimensional chains of Rydberg atoms. This breakthrough marks the first detection of these collective excitations, which maintain their shape and velocity despite complex interactions, in a many-body quantum system. Solitons are waves that propagate without dispersion, and their observation in this context opens new avenues for studying quantum information dynamics and condensed matter. The experiment involved preparing a chain of laser-cooled rubidium atoms and exciting them to Rydberg states, where electrons occupy orbits far from the nucleus. The strong van der Waals interaction between these neighboring Rydberg atoms creates a blockade effect, preventing adjacent atoms from being simultaneously excited. This blockade is crucial for the formation of quasi-solitons, as it modulates the propagation of excitations along the chain. Scientists observed how these excitations moved coherently through the atomic chain, maintaining their integrity. The ability to generate and control these quasi-solitons in Rydberg chains could have significant implications. On one hand, it offers a novel platform for investigating coherent transport phenomena in quantum systems, which is fundamental to understanding conductivity in exotic materials or the mechanism of photosynthesis. On the other hand, the stability and coherence of solitons make them promising candidates for robust quantum information transport, a key aspect for the development of future quantum computing architectures and quantum communication networks. This work lays the groundwork for exploring quantum information manipulation through stable collective excitations.

NNLO QCD Corrections for Exclusive Drell-Yan Processes with Pions and Kaons

A new study has calculated the next-to-next-to-leading order (NNLO) quantum chromodynamics (QCD) corrections for exclusive Drell-Yan processes induced by pions and kaons. These processes, which correspond to inverse deeply virtual meson production, are crucial for future investigations at facilities like J-PARC. The calculations focus on the reactions $π^- p\to γ^*(\to l^+l^-) + n$ and $K^- p\to γ^*(\to l^+l^-) + Λ$, providing a more robust theoretical foundation for comparison with anticipated experimental data. The research was conducted within the generalized parton distribution (GPD) factorization framework, ensuring accuracy to leading twist in the generalized Bjorken limit ($Q^2\gg |t|,\,Λ_{\rm QCD}^2$). This approach is essential for describing the internal structure of hadrons, such as pions and kaons, in terms of their fundamental constituents (quarks and gluons). The ability to model these processes with high theoretical precision is fundamental for extracting detailed information about GPDs, which encode the three-dimensional distribution of partons within nucleons and mesons. The results indicate that the NNLO QCD corrections are substantial and positive. This means their inclusion is indispensable for obtaining reliable theoretical predictions that can be meaningfully confronted with experimental data generated in upcoming experiments. Omitting these corrections could lead to erroneous interpretations of data and an incomplete understanding of parton dynamics at high energies. This theoretical advancement sets the stage for a new era of precision in the study of hadronic structure.

New Radiative-Recoil Correction to Lamb Shift in Muonium Calculated

Scientists have calculated a new radiative-recoil contribution of order $Z^2\alpha(Z\alpha)^5(m/M)^2m$ to the Lamb shift in muonium. This correction arises from the insertion of radiative photons in the heavy line within two-photon exchange diagrams. This advance is crucial for precision physics, as the Lamb shift is one of the most sensitive quantities for testing quantum electrodynamics (QED) in bound systems. Muonium, an exotic atom composed of a muon and an electron, is an ideal system for these tests due to the simplicity of its components and the absence of internal structure in the muon, unlike the proton in hydrogen. The precision in determining the Lamb shift in muonium allows for the refinement of fundamental constants and interaction theories, especially in the low-energy regime. The newly calculated correction is particularly relevant given that current experiments are aiming for unprecedented accuracy in the $1S-2S$ and $2S-2P$ transitions of muonium. This calculation is inspired by a new round of high-precision muonium experiments currently in progress. The inclusion of this theoretical correction is fundamental for correctly interpreting experimental results and for ensuring that comparisons between theory and experiment are made with the highest possible accuracy. Improvements in theoretical precision are as important as experimental ones for revealing potential deviations from the Standard Model or for refining its parameters.

Deep Thermalization and Quantum Non-Locality

A new study explores the nature of locality in the phenomenon of deep thermalization, where universal quantum state ensembles emerge in subsystems due to projective measurements on their complement. Researchers examined a subsystem partitioned into two disjoint subregions that remain causally disconnected under unitary dynamics. The work reveals that the onset of deep thermalization in this configuration is fundamentally bounded by measurement-induced entanglement teleportation between the subregions. Although measurements on the environment generate entanglement across the disconnected partitions, suggesting apparent non-locality, the study demonstrates that generic locally interacting systems exhibit emergent locality. Specifically, the timescales for both deep thermalization and entanglement teleportation scale logarithmically with the distance separating the subregions. This implies that, despite the quantum connection, the influence of measurements propagates in a way that respects a form of locality. Exceptions to this rule exist, such as certain special circuits where the randomness of measurement outcomes is perfectly transmitted to the subsystem's state ensemble, conditioned on those outcomes. In these particular cases, the timescale for deep thermalization is finite, leading to genuine non-locality. This finding underscores the complexity of quantum interactions and how locality can manifest or be circumvented in different thermalization scenarios.

Diagonal catalysts enhance quantum annealing

Researchers have developed a new technique to optimize quantum annealing, a computational method designed to solve complex optimization problems. The technique, dubbed "ZZ-catalysts," is based on manipulating the energy landscape of the problem, making state configurations far from the optimal solution less energetically favorable. This helps prevent the quantum system from getting trapped in local minima, a common obstacle that limits the efficiency of quantum annealing. Quantum annealing seeks to solve a problem by encoding its possible states as spin configurations in an energy landscape. The optimal solution corresponds to the global energy minimum. However, the presence of multiple local minima can trap the system, preventing it from reaching the true solution. The new methodology introduces a mathematical framework to understand the connection between energy and Hamming distance (the number of differing spins between configurations) in optimization problems. Using this framework, ZZ-catalysts are built from ground-state patterns of small, frustration-free subproblems. Experiments show that these catalysts multiply the probability of finding near-solutions in short sweeps for sparse problems. Furthermore, the gains persist on fully-connected models, and their effectiveness can be tuned via subproblem choice. This advancement could significantly improve the ability of quantum annealers to tackle large-scale optimization problems, with implications in fields such as logistics, materials design, and drug discovery, where finding optimal configurations is crucial.

Renormalizing two-photon contribution to K_L→μ⁺μ⁻ decay

A new study addresses the Standard Model prediction for the rare K_L→μ⁺μ⁻ decay, a process critically dependent on the long-distance contribution from the exchange of two photons. This calculation, fundamental for the precision of theoretical predictions, is typically performed using lattice quantum chromodynamics (lattice QCD) with an effective three-flavor theory (u, d, and s quarks), assuming that terms decaying as the inverse square of the charm quark mass (1/m_c²) are negligible. The challenge with this three-flavor approximation lies in the absence of the Glashow-Iliopoulos-Maiani (GIM) cancellation, which introduces additional low-energy constants that explicitly depend on the charm quark mass. The novelty of this work consists in demonstrating how these constants can be practically determined. To achieve this, the researchers propose a strategy involving a four-flavor lattice QCD simulation. This simulation is performed on a small volume and with u and d quark masses that are heavier than their physical values. The method allows for the renormalization of the two-photon contribution, improving the precision of the Standard Model prediction for this kaon decay. The ability to determine these low-energy constants from four-flavor lattice QCD calculations is a significant advancement for reducing theoretical uncertainties in particle physics.

AI-Assisted Formalization of Shor's Algorithm in Lean for Cryptanalysis

Scientists have successfully formalized the Shor's algorithm family within the Lean proof assistant, marking a significant milestone for machine-checked quantum cryptanalysis. This work employs an "agentic" approach, where software agents analyze sources, generate Lean code, and repair proofs, with human review of the scientific claims and machine verification of the resulting formal proofs. The formalization lays the mathematical foundations for analyzing quantum attacks in two key cryptographic settings: a 2048-bit modulus for RSA-2048 and the standardized elliptic curve over a 256-bit prime field (P-256). The formalization spans from quantum algorithms for order finding to reversible quantum circuits for modular and elliptic-curve arithmetic. Drawing upon previous work published in Quantum and ASIACRYPT, the team has formalized the logical resource estimates for RSA-2048 and P-256, respectively, and has provided additional estimates for the classical operations required. This advancement is crucial for understanding the computational requirements of quantum attacks on current cryptographic systems. This development represents an important step towards AI-assisted design and verification of quantum algorithms. The ability to rigorously formalize and verify quantum algorithms, especially those with security implications, is essential as quantum computing matures. These results are expected to pave the way for broader machine-checked quantum cryptanalysis, enhancing confidence in the security assessments of post-quantum cryptographic systems.

Fermilab and Qblox Commercialize QICK Platform for Quantum Control

The U.S. Department of Energy (DOE), Fermilab, and the company Qblox have formalized a collaboration for the commercialization of the QICK (Quantum Instrumentation Control Kit) platform. This agreement includes a commercial licensing structure to manage the manufacturing, supply chain, and distribution of the system developed by Fermilab. QICK is an open-source platform designed for the control and readout of superconducting qubits, which is crucial for the development of quantum computers. The initiative aims to accelerate the availability of high-performance quantum control hardware and reduce entry barriers for researchers and developers. The QICK platform enables more efficient integration between control software and experimental hardware, facilitating experimentation and innovation in the field of quantum computing. This step towards commercialization is fundamental for translating laboratory advances into practical applications and for standardizing certain components in the growing quantum industry. In addition to commercial distribution, the collaboration also aims to strengthen the quantum technology workforce. By making the QICK platform more accessible and supporting its use in academic and industrial settings, it is expected to foster the training of new talent and the creation of a broader community of quantum instrumentation experts. This focus on education and skill development is vital to sustain the rapid growth and complexity of quantum research and development.

New Quantum LDPC Codes Improve Error Correction

Researchers have developed new quantum low-density parity-check (LDPC) codes based on circulant permutation matrices (CPMs). These Calderbank-Shor-Steane (CSS) type codes are crucial for quantum computing, as they enable the protection of quantum information from errors inherent in qubits. The construction is parameterized by column weight J, row weight L, and prime lift size P, and uses an array of pair partitions to impose linear equations that ensure CSS orthogonality. Quantum LDPC codes are a promising avenue for quantum error correction due to their sparse structure, which facilitates decoding. Specific examples presented include a (J,L)=(4,12) code with a rate of 0.349 and a distance [[372,130,16]], and another (J,L)=(4,14) code with a rate of 0.440 and a distance [[518,228,16]]. Instances of (J,L)=(3,8) with distances [[472,122,14]] and [[488,126,14]] for lift sizes P=59 and P=61, respectively, are also reported. The distance of these codes has been established through exhaustive low-weight exclusion and the use of explicit non-stabilizer witnesses, ensuring their ability to detect and correct errors. The improvement in the coding rate and minimum distance of these new LDPC codes is a significant step towards the construction of fault-tolerant quantum computers, a fundamental requirement for the development of large-scale quantum computing.

Neutrino Day 2026: Exploring the Underground DUNE Experiment

Neutrino Day 2026 has highlighted the Deep Underground Neutrino Experiment (DUNE) from the Sanford Underground Research Facility (SURF) in Lead, South Dakota. This annual event, broadcast live from a mile underground, offers insight into the ambitious DUNE project, designed to study the fundamental properties of neutrinos and their role in the universe. During the broadcast, key figures such as Mike Headley, SURF laboratory director, and Dr. Sowjanya Gollapinni, senior scientist for the DUNE experiment, participated. Their interventions provided details on the progress and scientific objectives of DUNE, which seeks to understand neutrino oscillation, mass hierarchy, and potential CP violation in the leptonic sector, which could explain the matter-antimatter asymmetry in the universe.

Multimode phonon laser with levitated optomechanics

Researchers have developed a novel multimode phonon laser that utilizes an optically levitated silica sphere as a resonator. This innovative system allows for the generation and control of coherent acoustic vibrations (phonons) in multiple modes simultaneously, opening new avenues for information manipulation through mechanical vibrations. The key to this advancement lies in the combination of levitated optomechanics, which minimizes damping losses, with thermomechanical coupling that enables phonon amplification. The phonon laser operates based on the interaction between light and the mechanical vibrations of the sphere. By illuminating the sphere with a laser, radiation pressure and thermomechanical effects induce a self-amplified oscillation of the sphere at specific frequencies, generating coherent phonons. Unlike conventional phonon lasers, which typically operate in a single mode, this new design demonstrates the ability to excite and stabilize multiple vibrational modes, each with its own frequency and spatial pattern. This is achieved through precise control of the optical cavity and the environmental temperature. This development has significant implications for quantum computing and precision sensing. The ability to generate and control phonons in multiple modes could be fundamental for the development of new types of phonon-based quantum processors, as well as for ultra-sensitive sensors that leverage mechanical coherence. Furthermore, the levitated optomechanics platform offers a low-noise, high-mechanical-quality environment, ideal for exploring fundamental quantum phenomena and for designing devices that operate at room temperature.

New calculation of the hadronic contribution to the anomalous magnetic moment of the muon

A team of researchers has published a new calculation of the leading-order hadronic vacuum polarization (HVP) contribution to the anomalous magnetic moment of the muon, $a_\mu$. This result, obtained using functional quantum chromodynamics (QCD) methods based on the Dyson-Schwinger and Bethe-Salpeter equations, is crucial for resolving the persistent discrepancy between theoretical predictions and experimental measurements of $a_\mu$. The study incorporates complex effects such as pion back-reaction and a dynamically generated $\rho$-meson resonance structure in the quark-photon vertex, in addition to self-consistently treating strong and electromagnetic isospin breaking at the quark level. The central value obtained for the $u, d, s, c$ quark contribution with isospin breaking (ISB) is $a_\mu^{\mathrm{HVP,LO}}(u+d+s+c)|_{\mathrm{ISB}} = 709.7 \times 10^{-10}$. This result shows good agreement with recent lattice-QCD determinations, bolstering confidence in the methodology. Furthermore, the study quantifies the impact of isospin breaking, finding a shift of $\Delta a_\mu^{\mathrm{HVP,LO}} = 4.5 \times 10^{-10}$, which represents $0.6\%$ of the total value. Although modest, these effects prove not to be negligible and must be considered in precision calculations. Including the bottom-quark contribution and an indicative estimate of systematic uncertainties, the final result is established as $a_\mu^{\mathrm{HVP,LO}}(u+d+s+c+b)|_{\mathrm{ISB}} = (710.0 \pm 14.5) \times 10^{-10}$. This advance is significant because the HVP contribution is one of the largest sources of uncertainty in the theoretical prediction of $a_\mu$. The improved precision and robustness of this calculation help to narrow down the muon anomaly, a potential hint of new physics beyond the Standard Model.

1-Form Symmetric Projected Entangled-Pair States

Researchers have introduced a new class of quantum states, termed 1-form symmetric projected entangled-pair states (PEPS). These states represent a generalization of traditional PEPS, incorporating a global symmetry that acts on the boundaries of the system in a specific manner. 1-form symmetry is a concept that has gained relevance in theoretical physics, especially in the study of topological phases of matter and in field theories, and its application to PEPS opens new avenues for understanding and classifying complex quantum states. The relevance of this proposal lies in its potential to describe phases of matter with non-trivial topological orders, which are of great interest in condensed matter physics. PEPS are a powerful tool for simulating two-dimensional many-body quantum systems, and the addition of 1-form symmetry allows for capturing properties that were previously inaccessible or difficult to characterize. This advance could facilitate the identification and study of new topological phases, as well as the understanding of their fundamental properties, such as the degeneracy of their ground states and the existence of excitations with anomalous statistics. The construction of these 1-form symmetric PEPS involves a modification of the tensors that define the state, ensuring that the action of the symmetry is preserved at a local level. This approach offers a unified framework for describing a variety of quantum phenomena, from long-range entanglement to boundary properties in topological systems. It is expected that this new formulation will boost both theoretical research and numerical simulations, providing more precise tools to explore the vast landscape of many-body quantum states.

New Method for Calculating P-wave Quarkonium Decays

A new theoretical framework combining lattice Quantum Chromodynamics (lattice QCD) with potential Non-Relativistic QCD (pNRQCD) has enabled the calculation of inclusive hadronic decay widths for P-wave quarkonia. This advance addresses a long-standing challenge in first-principles QCD, where precise prediction of these decays has been particularly complex. The methodology focuses on heavy quarkonia, which are bound states of a heavy quark and antiquark, such as charmonium and bottomonium. At leading order in the velocity expansion, all non-perturbative effects, apart from the square of the derivative of the wavefunction at the origin, are encoded in a single universal moment of the two-point chromoelectric correlator. This correlator has been determined for the first time from a quenched lattice QCD calculation, matched to the $\overline{\mathrm{MS}}$ scheme via the gradient flow. This approach allows for a rigorous description of the strong interactions governing these decays. By combining this result with perturbative short-distance coefficients and the square of the derivative of the wavefunction at the origin, the framework reproduces the observed widths for the $\chi_{cJ}(1P)$ states. Furthermore, it provides predictions for the widths of the $\chi_{bJ}(nP)$ states, which have not yet been experimentally measured. This new method not only validates predictions against existing data but also opens the door to exploring inclusive decays and production of ordinary and exotic hadrons, extending its applicability to a broader range of phenomena in particle physics.

New Cryogenic Neutral-Atom Platform Enhances Qubit Lifetime

Scientists have developed a new neutral-atom platform that achieves trapping lifetimes of up to two hours for single strontium-88 ($^{88}\mathrm{Sr}$) atoms in an optical tweezer array. This breakthrough is significant for the development of large-scale quantum processors, as it addresses the limitation of current platforms that must compromise between optical accessibility and atom storage time. The platform combines a simplified cryogenic design with full optical access, a feature that has previously been challenging to achieve simultaneously. The system allows atoms to be held in optical traps for exceptionally long periods, which is crucial for qubit coherence and manipulation in quantum computing. The ability to preserve optical access is fundamental for reading and writing quantum information. This achievement is an important step towards building arrays of tens of thousands of sorted atoms, which would enable the realization of more complex quantum algorithms and quantum simulation experiments on an unprecedented scale. The architecture is adaptable to other atomic species, suggesting a viable path for scalability and versatility in the field of neutral-atom quantum computing.

Universal Energy-Space Localization in Stable Quantum Phases

Researchers have discovered a new principle of universal energy-space localization that allows quantum phases to remain stable against time-dependent perturbations. This finding is significant because it addresses one of the biggest challenges in quantum physics: the fragility of quantum systems to interactions with their environment. The ability to maintain quantum coherence in the presence of noise is crucial for the development of robust quantum technologies, such as quantum computing and high-precision quantum sensing. This principle is based on the observation that, under certain conditions, quantum systems can self-organize in such a way that their energy and spatial distribution become localized, making them intrinsically more resilient to external fluctuations. This contrasts with the traditional view that time-dependent perturbations always lead to decoherence and the loss of quantum properties. The study proposes a theoretical framework that explains how this localization emerges and how it can be leveraged to design more stable quantum systems. The results of this research have profound implications for the fundamental understanding of quantum mechanics and for the engineering of quantum devices. By providing a mechanism to protect quantum phases from time-induced decoherence, this work opens new avenues for the creation of more durable qubits and more sensitive quantum sensors. Experimental validation of this principle could significantly accelerate progress in the field of quantum information and quantum metrology.

New Algorithm Reduces Trotter Error in Quantum Simulations

Researchers have developed a high-order nested-commutator compensation (HNCC) algorithm that significantly improves the precision of Hamiltonian simulations using product formulas. This method addresses the limitation of traditional product formulas, whose circuit size scales polynomially with inverse precision, by achieving polylogarithmic precision dependence in circuit size. The key innovation lies in HNCC's ability to maintain the advantages of product formulas, such as requiring no ancillary qubits, while drastically reducing computational requirements for high precision. The HNCC algorithm employs a truncated Baker-Campbell-Hausdorff expansion to represent high-order Trotter errors as products of nested commutators. These errors are compensated at the superoperator level through randomly sampled Pauli-rotation channels, thus avoiding the need for Hadamard tests and ancillary qubits. For a K-th order product formula applied to a k-local Hamiltonian on N qubits with Γ Pauli terms and local interaction strength g₀, HNCC estimates the trace of Oe^(-i tH)ρe^(i tH) to an additive precision ε||O||. This is achieved using O(ε⁻²) repetitions and a maximum gate count per circuit of O(N^(2/(2K+1)) (k g₀ t log(1/ε))^(1+1/(2K+1)) k(Γ+log(1/ε))). The resulting time dependence of the algorithm matches that of a product formula of order 2K+1. Finite-size resource estimates for the periodic Heisenberg chain indicate that HNCC achieves the lowest CNOT and T-gate counts per circuit among the product-formula-based methods considered. This advancement is crucial for the feasibility of complex quantum simulations, where error reduction and resource optimization are decisive factors in achieving quantum advantage.

D-meson decays: CP asymmetry in the Standard Model

A new analysis has explored the decays of the D⁰ meson into pions and kaons, processes that are Cabibbo-suppressed. Researchers used factorization and isospin symmetry to quantify non-factorizable effects and the U-spin symmetry breaking required to explain the observed decay rates. This approach has established that corrections of the order of 50% are sufficient to describe these decays, a significant but not unexpected value in the realm of hadronic charm decays. The study focused on the $D^0\to \pi^-\pi^+$, $D^0\to K^-K^+$ and $D^0\to K_{\rm S}^0K_{\rm S}^0$ decays. From the constraints imposed by the measured branching fractions, Standard Model (SM) predictions for the direct CP asymmetry in the $D^0\to K_{\rm S}^0K_{\rm S}^0$ decay have been derived. The results indicate that this asymmetry is, at most, at the per-mille level in the proposed benchmark scenario. This prediction of a very small CP asymmetry in $D^0\to K_{\rm S}^0K_{\rm S}^0$ is crucial, as it provides clear motivation for future precision measurements. Detecting a CP asymmetry significantly larger than this per-mille level could signal the existence of new physics beyond the Standard Model, opening a window to as-yet unknown phenomena in particle physics.

Nonlinear tripartite coupling of trapped electrons and magnons in a hybrid system

Scientists have achieved a nonlinear tripartite coupling between trapped electrons and magnons in a hybrid quantum system. This breakthrough is significant because it enables coherent interaction between two types of quantum excitations (electrons and magnons) via a mediator, opening new avenues for quantum information manipulation and the development of hybrid devices. The novelty lies in demonstrating a nonlinear coupling that overcomes the limitations of linear interactions, which are often weak or require more restrictive experimental conditions. The experiment was conducted using a hybrid system combining a single electron trapped in a Penning trap with a microwave resonator containing a ferromagnetic material, where magnons reside. Magnons are quasi-particles representing collective excitations of electron spins in a magnetic material. The coupling was achieved through the interaction of the electron with the resonator's electromagnetic field, which in turn interacted with the magnons. This approach provides an interface between quantum matter systems (electrons) and collective excitations (magnons) via a mediating field. The importance of this work lies in its potential for quantum computing and sensing. By coherently and nonlinearly coupling electrons and magnons, the door is opened to creating hybrid quantum memories or quantum information transducers that could operate at higher temperatures or with greater efficiency. Furthermore, this type of coupling could enable the development of ultra-sensitive quantum sensors that leverage the unique properties of magnons. This study lays a foundation for future research into manipulating quantum states in complex hybrid systems.

Fermionic parton theory for Rydberg Z2 quantum spin liquids

Researchers have developed a fermionic parton theory to describe Z2 quantum spin liquids (QSLs) in Rydberg atom systems. QSLs are exotic states of matter exhibiting long-range quantum entanglement and lacking conventional magnetic order, making them a highly active area in condensed matter physics. The new theory provides a framework for understanding the fundamental properties of these states in promising experimental platforms. The proposed theory specifically addresses Z2-type QSLs, characterized by elementary excitations that are Majorana fermions and gauge bosons. These systems are relevant for fault-tolerant quantum computing, as Majorana excitations can be used to robustly encode quantum information. The study focuses on how these properties emerge in Rydberg atom systems, which are atoms excited to high-energy states with electrons in very large orbits. These atoms interact strongly with each other and can be precisely controlled, making them an ideal platform for simulating QSLs. The work provides a detailed description of the Z2 spin liquid phases and their phase transitions, including the identification of topological orders and the characterization of low-energy excitations. The theory predicts how the properties of these QSLs can be tuned by varying experimental parameters, opening avenues for the observation and manipulation of these exotic states. Although the article does not detail experimental methods, the theoretical formulation is crucial for guiding future experiments in the search for QSLs in Rydberg systems.

Kirkwood-Dirac Negativity Bounded for Gaussian Processes

Scientists have successfully established an upper bound for the negativity of the Kirkwood-Dirac (KD) quasiprobability in quantum states subjected to Gaussian processes. The KD negativity is a fundamental measure of a quantum state's nonclassicality, and its extremal value in the general case has remained unknown until now. This breakthrough provides a deeper understanding of the nonclassical properties of quantum systems under transformations that are ubiquitous in experimental physics. The Kirkwood-Dirac quasiprobability offers an operational representation of a quantum state. Its negativity is a key indicator that a system cannot be described by classical physics, analogous to the negativity of the Wigner function. The study focused on arbitrary quantum states interacting with Gaussian processes, which are transformations that preserve the Gaussian character of input states, such as displacement or squeezing operations in quantum optics. The team derived an upper bound for this negativity applicable to any number of modes and measurements. For the specific case of a single mode and two measurements, they showed that the eigenstates of the quadrature operators (such as Fock states or squeezed states) saturate this upper bound. Conversely, pure Gaussian states, which are the most classical among quantum states, achieve a nontrivial minimum of negativity. These results suggest that Gaussian states are sufficient to achieve extreme values of nonclassicality, which is relevant for quantum computing and metrology.

Scientific judgment more crucial than ever in the age of AI

Nicole Sharp, in a recent article, emphasizes the growing importance of scientific judgment in the era of artificial intelligence. She argues that as AI tools become more ubiquitous and sophisticated in research, the human ability to critically evaluate results, design meaningful experiments, and formulate pertinent questions becomes an indispensable asset. AI can process and generate data on an unprecedented scale, but it lacks the intuition, contextual understanding, and discernment that define scientific expertise. The author stresses that over-reliance on AI without a robust framework of human judgment could lead to uncritical acceptance of erroneous results or the loss of opportunities for genuine discoveries. Instead of viewing AI as a replacement, Sharp positions it as a powerful tool that amplifies the need for fundamental skills such as critical thinking, hypothesis formulation, data interpretation, and effective communication. These skills are what allow scientists to navigate complexity, identify significant patterns, and distinguish between correlation and causation, aspects that AI alone cannot yet replicate with the same depth. This approach highlights the complementarity between artificial intelligence and human intelligence in the scientific domain. AI can automate repetitive tasks and analyze vast datasets, freeing researchers to focus on the more creative and conceptual aspects of their work. However, the direction of research, the validation of AI models, and the final interpretation of their results require a solid foundation of scientific judgment. Therefore, training in these skills must not only be maintained but actively reinforced in future generations of scientists.

Switchable nonreciprocal entanglement via magnon squeezing in optomagnomechanical cavities

Researchers have proposed a theoretical scheme to generate switchable bipartite and tripartite quantum entanglement in a ring-cavity optomagnomechanical system. This advance relies on exploiting phase-controlled magnon squeezing, which allows for modulating the entanglement response. The proposed system involves two spatially separated ferrimagnetic YIG (yttrium iron garnet) microbridges, which become entangled through their magnetostriction-mediated coupling to mechanical motion and a common cavity field via radiation-pressure interaction. The squeezing process introduces two phase-dependent contributions to the magnon response: an effective detuning shift, Δ_{θ_j}, and a quadrature-damping contribution, κ_{θ_j}. Both reverse sign upon a π phase shift, providing in situ control to switch the entanglement response. Nonreciprocal entanglement is operationally defined by the asymmetric entanglement response under phase reversal θ_j → θ_j + π, quantified by normalized contrast ratios C_E and C_R, which measure the relative difference between the entanglement obtained at θ_j and in the phase-reversed configuration θ_j+π. This phase-tuning method offers a flexible and robust route to achieve high-contrast bipartite and tripartite entanglement within stable parameter regions. The work establishes magnon squeezing as a practical quantum resource for switchable quantum correlations in hybrid platforms. This type of control over entanglement is crucial for the development of future quantum technologies, such as quantum computing and communication, by allowing more precise and dynamic manipulation of quantum states.

Gapless fracton quantum spin liquid and emergent photons found in 2D spin-1 model

Researchers have discovered a new type of quantum spin liquid, dubbed a gapless fracton quantum spin liquid, in a theoretical two-dimensional spin-1 model. This finding is significant because quantum spin liquids are exotic states of matter that do not order their spins in a conventional way, but instead exhibit long-range quantum entanglement. The particularity of this new state is its "gapless" nature, meaning there is no minimum energy to excite the system, and the emergence of "photons" as low-energy excitations, which distinguishes it from other known spin liquids. The concept of fractons, which are excitations with restricted mobility, has been an area of intense research in condensed matter physics. Until now, studied fracton spin liquids typically had an energy gap (gapped), meaning they required a minimum energy to generate excitations. The identification of a gapless fracton state in two dimensions, and the association of its excitations with particles that behave like photons, opens new avenues for understanding the interplay between topology and quantum dynamics in many-body systems. This theoretical model could serve as a basis for the design of new quantum materials with exotic properties. This advance is based on a spin-1 model, more complex than the commonly studied spin-1/2 models, allowing for a greater richness of quantum phenomena. The emergence of photons in this context does not refer to actual light particles, but to collective excitations of the system that exhibit photon-like properties, such as being massless and propagating at a constant speed. Understanding these exotic states is crucial for the development of future quantum technologies, including fault-tolerant quantum computing and high-precision quantum sensing, as the stability of quantum information often depends on the topological nature of the ground state.

Optimal Transport for Monte Carlo Event Weights at the LHC

Researchers have developed a new technique based on optimal transport to manage event weights generated by Monte Carlo simulations at the Large Hadron Collider (LHC). These weights, which can be negative or pathologically large, pose a significant computational challenge for experiments. The new approach uses cell resampling algorithms to locally redistribute event weights among nearby events in a metric space, improving the efficiency and accuracy of simulations. The study focuses on the performance of metrics defined in terms of optimal transport, specifically the Energy Mover's Distance and a spectral variant. These metrics are particularly useful because they are insensitive to the addition of soft and collinear radiation, allowing them to be applied directly to particles at any stage of event generation. This contrasts with previous methods that might require specific adjustments for different simulation phases. When this methodology was applied to samples simulated at next-to-leading-order in quantum chromodynamics, a significant reduction in bias was observed compared to other cell resampling techniques found in the literature. Furthermore, the researchers introduced the Cross-Section Mover's Distance as a general, unbinned figure of merit for quantifying the bias introduced by any full-phase-space reweighting. This advance is crucial for refining theoretical predictions and interpreting experimental data at the LHC, where precision is fundamental for discoveries in particle physics.

Heavy Quark Coalescence: Potential Influences Probability

A recent study has investigated the role of the interaction potential between heavy quarks in the coalescence process, a crucial phenomenon in hadron formation. Heavy quark coalescence, which is expected to have a probability close to unity at low momenta, is influenced by the nature of this potential. The research developed a phenomenological model for the heavy quark potential that successfully reproduces the vacuum masses of pseudoscalar and vector heavy mesons, providing a solid basis for the analysis. Using this potential, the researchers demonstrated that its inclusion enhances the coalescence probability. Furthermore, the study examined how medium-induced modifications of the heavy quark potential in the quark-gluon plasma (QGP) affect the coalescence process. The QGP is a state of matter that briefly existed in the early universe and is recreated in heavy-ion collision experiments, such as those at the LHC. The results indicate that the coalescence probability remains close to unity as long as the modification of the potential in the QGP is sufficiently moderate. This suggests that, even under extreme conditions like those in the QGP, hadron formation from heavy quarks remains an efficient process, provided that the interactions are not drastically altered. This finding is relevant for a deeper understanding of quantum chromodynamics and the formation of hadronic matter in high-energy environments.

Analysis of Pion Nuclear Fragmentation Functions to Understand Hadronization

A new quantum chromodynamics (QCD) analysis has allowed the extraction of pion nuclear fragmentation functions (nFFs), which describe how hadronization is modified in high-energy nuclear collisions. This study, which simultaneously considers vacuum fragmentation functions and their nuclear modifications, is crucial for understanding the fundamental processes by which quarks and gluons transform into composite particles (hadrons) within a nuclear environment. Nuclear effects have been parameterized as functions of the nuclear mass number ($A$), the energy of the fragmenting parton in the target rest frame ($\nu$), and the hadron energy fraction ($z$). This parameterization has allowed the quantification of the dependence of these effects on these variables. The analysis incorporated semi-inclusive deep-inelastic scattering data on nuclear targets, applying specific kinematic cuts to ensure the applicability of perturbative QCD and collinear factorization. The resulting fit provides a good description of most datasets, with nFFs well constrained in the energy fraction range $z \in [0.2, 0.7]$. With these new nuclear fragmentation functions, next-to-leading order (NLO) predictions have been made for proton-proton ($pp$) and proton-nucleus ($pA$) collisions. These predictions show reasonable agreement with experimental data from the ALICE experiment, within current experimental uncertainties. This advance is significant for high-energy physics, as it provides a more precise tool for interpreting results from accelerator experiments like the LHC, where the properties of matter under extreme conditions are studied.

Variational Gibbs State Preparation on Trapped-Ion Devices

Researchers have demonstrated a method for preparing variational Gibbs states on a trapped-ion device. This advancement is crucial for the quantum simulation of thermodynamic systems, as Gibbs states are fundamental for describing thermal equilibrium. The ability to efficiently generate these states on quantum hardware opens new avenues for exploring condensed matter phenomena and quantum chemistry at finite temperatures. The method employed uses a variational quantum algorithm, which combines classical optimization with execution on a quantum processor. In this case, it was applied to a system of Yb+ ions in a radiofrequency trap. Preparing Gibbs states is inherently complex due to the non-unitary nature of thermal evolution, making it difficult to implement directly in unitary quantum circuits. The variational approach circumvents this difficulty by searching for a state that minimizes a cost function related to the Helmholtz free energy. This work represents a significant step towards quantum simulation of open systems and quantum thermodynamics. The ability to prepare Gibbs states in a controlled manner on noisy intermediate-scale quantum (NISQ) platforms is a prerequisite for studying material properties at non-zero temperatures, such as phase transitions or transport properties. The obtained results validate the feasibility of these approaches on real hardware and suggest future applications in the design of new materials and the study of complex chemical reactions.

Leptogenesis Viable with Very Low Reheating Temperatures

A new study explores the possibility of generating the observed baryon asymmetry in the universe through leptogenesis, even with very low cosmic reheating temperatures, close to the Big Bang Nucleosynthesis (BBN) bound of approximately 4 MeV. Traditionally, leptogenesis requires significantly higher reheating temperatures. This work focuses on the canonical type-I seesaw framework, where the dominant production of right-handed neutrinos (RHN) is non-thermal, originating from inflaton decays (φ → NN). The research reveals that, while matter-like reheating (with an equation of state parameter w_φ=0) is incompatible with standard leptogenesis at very low temperatures, the situation changes drastically for generalized Starobinsky potentials, approximated by V(φ)∝φ^k with k≥4. In these scenarios, the observed baryon asymmetry can be readily obtained. A particular case studied in detail is radiation-like reheating (w_φ=1/3, k=4), where the evolving effective mass of the inflaton condensate leads to a kinematic shutoff of the φ → NN channel, qualitatively altering the leptogenesis dynamics. The authors include a detailed treatment of the effects of inflaton condensate fragmentation. Interestingly, the final baryon asymmetry primarily depends on only two parameters: the inflaton-RHN coupling (y_φNN) and the CP-violating parameter (|ε|). A key finding is that the final asymmetry is largely insensitive to the RHN mass, the reheating temperature, and the RHN decay rate. Although the study focuses on fermionic reheating, it is shown that the general features of these results also hold for bosonic reheating to scalars.

New State of Matter Discovered: The Time Crystal

Scientists have successfully created and observed a time crystal, a new state of matter that challenges the laws of thermodynamics as we know them. Unlike spatial crystals, which have a repetitive atomic structure in space, time crystals exhibit a structure that repeats periodically in time. This breakthrough represents a milestone in condensed matter physics and opens new avenues for fundamental research. The concept of a time crystal was first proposed in 2012 by Nobel laureate Frank Wilczek, who suggested that a system could exhibit periodic motion in its lowest energy state, the ground state. However, subsequent studies showed that equilibrium time crystals could not exist. The key to their realization has been the creation of a non-equilibrium system, one driven by laser pulses that maintain it in a dynamic yet stable state. The experiment was conducted using a chain of ytterbium ions, which were manipulated with laser pulses. Researchers observed that the ions oscillated with a period that was twice the period of the laser pulses, a clear signature of a time crystal. This anomalous behavior, where the system does not absorb energy from the environment despite its perpetual motion, is what distinguishes it from other periodic systems. This discovery has profound implications for our understanding of matter and energy. It could lead to the development of new technologies, such as ultra-precise atomic clocks or more robust quantum information storage devices. Furthermore, it offers a unique platform for exploring out-of-equilibrium quantum phenomena and could shed light on the nature of decoherence and stability in complex quantum systems. The scientific community now anticipates replicating and expanding these results in different systems to confirm the universality of this new state of matter.

Spatially Dependent Optical Behavior in Quantum Dot Molecules

A recent study has explored the optical behavior of quantum dot molecule (QDM) systems with unprecedented spatial resolution. QDMs are semiconductor nanostructures formed by two coupled quantum dots, exhibiting unique quantum properties due to exciton confinement. Understanding how these properties vary spatially within a QDM is crucial for their application in quantum technologies, such as quantum computing and high-precision sensing. This work has revealed significant variations in optical responses, suggesting an intrinsic heterogeneity in the structure and coupling of these systems. Researchers employed advanced near-field optical microscopy techniques to probe individual QDMs. This allowed them to map photoluminescent emission and absorption with nanometer resolution, overcoming the limitations of far-field techniques that average the properties of multiple QDMs or larger regions. The methodology focused on analyzing how the intensity and spectrum of emitted and absorbed light changed when scanning different points within the quantum dot molecule, providing a detailed insight into the spatial distribution of excitonic states and coupling interactions. The results showed that optical properties, such as exciton energy and emission efficiency, are not uniform throughout the quantum dot molecule. Regions with different spectral and intensity characteristics were observed, indicating local variations in the size, composition, or strain of the individual quantum dots, as well as in the strength of their coupling. This spatial heterogeneity is a critical factor to consider in the design and fabrication of QDM-based quantum devices, as it can directly influence their performance and reliability. The study underscores the importance of nanoscale characterization to optimize these materials and advance the development of quantum technologies.

Robust Quantum Key Distribution Demonstrated with High-Dimensional Photons

Researchers have experimentally demonstrated a robust one-sided device-independent quantum key distribution (1sDI-QKD) protocol using photons entangled in their transverse-spatial degree-of-freedom. This advancement addresses practical limitations of QKD, including susceptibility to noise and losses in communication. The proposed protocol relies on high-dimensional entanglement and leverages quantum steering to certify security, enabling positive secret key rates even under adverse conditions. The study develops a systematic security analysis for high-dimensional 1sDI-QKD protocols, evaluating achievable secret key rates for different measurement configurations and system dimensions. Theoretical results indicate that increasing the dimension significantly enhances the protocol's robustness against both noise and loss. For the experimental implementation, the team developed a high-quality source of high-dimensional photonic entanglement and a fully programmable, multi-outcome measurement device capable of operating up to 11 dimensions. These components allowed for positive key rates across all investigated dimensions, with the highest rates achieved for dimension d=7, under the fair-sampling assumption. This work represents a crucial step towards the practical implementation of QKD with information-theoretic security. The ability to operate in high dimensions confers greater resilience to device imperfections and noisy or lossy communication channel conditions. Although the current demonstration relies on the fair-sampling assumption, the authors discuss the steps required for a loophole-free implementation in realistic regimes of loss and noise, paving the way for future applications in secure quantum communications.

Plaquette: A Platform for Designing Fault-Tolerant Quantum Computers

Researchers have developed Plaquette, a theoretical and software platform designed to evaluate the logical performance of fault-tolerant quantum computing (FTQC) architectures based on the physical imperfections of devices. This tool addresses a critical need in the development of quantum computers, where error suppression is fundamental. Plaquette enables hardware teams to make informed decisions about which imperfections to mitigate, offering a precise view of how actual hardware noise affects the logical performance of an FTQC. Unlike stochastic Pauli models used by scalable stabilizer simulators, Plaquette considers a broader range of noise sources common in physical qubits. This includes leakage out of the computational subspace in superconducting qubits, scattering through intermediate states in neutral atoms, heating in trapped ions due to phonon absorption, and coherent errors from miscalibrated controls. The platform allows hardware error models to be specified using Kraus operators, Hamiltonian-Lindblad dynamics, or experimentally reconstructed quantum channels, automatically compiling them for different classes of samplers. Plaquette incorporates samplers such as stabilizer sampling for Pauli noise, the new XPauli sampler for leakage and environment sectors, near-Clifford samplers for coherent errors, and full-state simulation for exact reference calculations. Validation of the XPauli and near-Clifford samplers against full-state simulation has demonstrated their accuracy, matching within statistical uncertainty, while Pauli twirling can fall short depending on the error model. The tool has been demonstrated on three specific error models: leakage in superconducting qubits, intermediate-state scattering in neutral atoms, and heating in trapped ions. The discrepancy between Plaquette simulations and Clifford-only simulations varies with platform and noise process. This highlights the importance of using the most accurate simulation available to obtain reliable thresholds, error budgets, and overhead estimates. Plaquette provides a direct path from the open-system physics of a device to the evaluation of the logical performance of the FTQC built upon it, facilitating progress towards robust and functional quantum computers.

Probability of Quantum Steering in Two-Qubit States

Researchers have quantified the probability of observing quantum steering in generic two-qubit states. Steering is a manifestation of entanglement where measurements performed by one party influence the conditional states of another, without the correlations being explainable by a local hidden state model. This study addresses the question of how common this behavior is in quantum systems, which is crucial for the development of quantum information technologies. The team derived analytical expressions for the steering probability ($\mathcal{P}_S$) in Werner states for two- and three-setting scenarios, restricting the latter case to coplanar projective measurements on the Bloch sphere. For a larger number of settings and various random state ensembles, numerical analyses showed that $\mathcal{P}_S$ systematically increases with the number of measurements. Furthermore, this probability substantially exceeds the probabilities associated with Bell nonlocality. The results indicate that random states with minimal environmental coupling exhibit a high probability of steering for a finite number of measurements ($m$), approaching genuine typicality, where $\mathcal{P}_S = 100\%$, as the number of settings increases. The study provides a detailed characterization of $\mathcal{P}_S$ across different state ensembles and specific families, such as Werner and Bell-diagonal states, identifying those with the greatest non-classical potential and highlighting their relevance for protocols where steering serves as a key resource in quantum communication and computation.

Fermilab installs first component for new PIP-II accelerator

Fermilab has reached a significant milestone in its neutrino research program with the installation of the first beamline component for the new PIP-II linear accelerator. This accelerator, once completed, will be fundamental in powering future neutrino experiments, solidifying Fermilab's position as a leading center in particle physics. The PIP-II (Proton Improvement Plan-II) is designed to be a state-of-the-art particle accelerator, capable of producing a high-intensity and high-energy proton beam. This beam will be crucial for generating more powerful neutrino fluxes, allowing scientists to study the fundamental properties of these elusive particles with greater precision. The installation of this first component marks the beginning of the assembly phase in the tunnel that will house the accelerator.

Re-evaluating Supersymmetry Limits with LHC Data

A new study has re-examined the constraints imposed by the Large Hadron Collider (LHC) on supersymmetry (SUSY), focusing on the electroweak-ino sector. Using public data from ATLAS Run 2 searches, researchers employed the SModelS v3.0 tool to reproduce and extend the original analysis, also incorporating results from the CMS experiment. This work is crucial for understanding which regions of the vast SUSY parameter space remain unexplored or are compatible with current observations. The ATLAS collaboration recently published an extensive scan of the phenomenological Minimal Supersymmetric Standard Model (pMSSM), with a particular focus on electroweak-inos, which are the supersymmetric partners of gauge and Higgs bosons. This scan aimed to determine how searches for electroweak production of SUSY particles in LHC Run 2 constrained this model. The simulation data (SLHA files) and the constraints from eight individual searches were made publicly available, allowing other research groups to validate and expand upon the results. The research team used this data to evaluate the capability of SModelS v3.0 to replicate the ATLAS constraints. Furthermore, they explored how the inclusion of CMS results alters the picture and what benefits are gained from the statistical combination of analyses from both experiments. The results underscore the need for a broad, multifaceted approach to maximize sensitivity and close loopholes in the extensive SUSY parameter space. The study also discusses the part of the parameter space with light electroweak-inos that remains valid despite the stringent LHC limits, indicating that supersymmetry is not ruled out, but its manifestations might be more subtle than anticipated.

Scotogenic Models Predict New Asymmetries in Lepton Decays

Researchers have re-evaluated a specific class of scotogenic models, known as "T1-2-A", which aim to simultaneously explain neutrino oscillation data and propose a viable dark matter candidate. The study focused on charged lepton flavor violating (cLFV) decays, particularly in rare muon transitions. The results suggest that these models can predict significant rates for cLFV observables, opening new avenues for experimental detection. The work explores in detail the model's parameter space, identifying regions where cLFV rates are appreciable. Furthermore, the scientists have considered the role of parity and time-reversal asymmetries in three-body lepton decays, specifically in processes like $\ell_\alpha^+ \to \ell_\beta^+ \ell_\gamma^+ \ell_\delta^-$. These asymmetries could be experimentally investigated in association with polarized muon and tau decays. The inclusion of these new observables offers complementary information on the "T1-2-A" scotogenic model, providing additional means to test its validity. If these asymmetries or the predicted cLFV rates were detected, it would strengthen the hypothesis that these models can describe phenomena beyond the Standard Model, such as the nature of dark matter and the origin of neutrino masses.

Quantum Reservoir Networks Enhance Chaotic System Prediction

Researchers have developed a hybrid method that improves the prediction of high-dimensional chaotic systems using quantum reservoir networks (QRNs). The approach combines classical machine learning techniques with quantum metrology to model the one-dimensional Kuramoto-Sivashinsky (KS) system, a paradigmatic example of a chaotic partial differential equation. This advancement is significant given the growing capabilities of low-error quantum computers and robust simulation tools. The proposed method utilizes a classical autoencoder to process latent space representations of the KS system. The key to the improvement lies in the preparation of "metrologically useful" quantum states via a specific unitary operation within the QRN. These states, optimized for precision measurements, allow the quantum network to capture complex dynamics with higher fidelity. Rigorous simulations have demonstrated that this configuration outperforms other QRN implementations that do not employ this state preparation, as well as classical echo-state networks when weight regularization is not applied. This work not only presents a more powerful tool for simulating chaotic systems but also highlights the importance of integrating quantum metrology principles into the design of quantum machine learning algorithms. Furthermore, the authors point out potential challenges that arise when incorporating autoencoders into QRN workflows, suggesting areas for future research. The results open new avenues for the application of quantum computing in the prediction and control of complex phenomena in physics and other sciences.

Nearby Materials Can Steal Energy from Superconducting Qubits

A new study has revealed that the proximity of dielectric and semiconductor materials can induce significant energy losses in superconducting qubits, affecting their coherence. This finding is crucial for the development of quantum computing, as decoherence is one of the biggest obstacles to building reliable and scalable quantum computers. The research details how interaction with these materials can generate two-level states (TLS) that act as energy sinks. Superconducting qubits are promising due to their scalability and relatively long coherence times, but their performance is limited by interaction with the environment. Until now, attention had primarily focused on intrinsic losses of the superconducting material or at interfaces. This work expands understanding by demonstrating that adjacent materials, even if not an active part of the qubit, can be a dominant source of decoherence. Experiments were conducted by varying the distance between qubits and different types of materials, measuring how this affected relaxation and coherence times. The results show that dielectric and semiconductor materials, such as silicon oxide or silicon, can drastically reduce qubit coherence times. A clear distance dependence was observed, suggesting that the qubit's electromagnetic field interacts with excitations in these materials. This interaction induces TLS, which absorb energy from the qubit, shortening its lifespan. Identifying these loss mechanisms is a fundamental step towards designing more robust qubits. This discovery has direct implications for the design of future quantum processors. Engineers will now need to consider not only the quality of the qubit material but also the composition and spacing of surrounding materials on the chip. Mitigating these losses could be achieved by using materials with a lower density of TLS or by a design that minimizes qubit exposure to nearby fields. This paves the way for qubits with longer coherence times, an indispensable requirement for fault-tolerant quantum computing.

New Predictions for b-Baryon Lifetimes

Researchers have updated predictions for the total decay rates and lifetimes of b-baryons, as well as their lifetime ratios relative to the B^0_d meson. This work, conducted within the framework of the heavy quark expansion (HQE), incorporates for the first time next-to-next-to-leading-order (NNLO) quantum chromodynamics (QCD) corrections for the free b-quark decay. The inclusion of these NNLO corrections significantly reduces theoretical uncertainties in the total decay rates, enhancing model precision. In addition to the NNLO corrections for the free b-quark, the study also includes, for the first time, complete next-to-leading-order (NLO) QCD corrections to dimension-five contributions. While these latter corrections have a minor effect on the total decay rates, they induce a noticeable shift in the lifetime ratios. This improvement is crucial as it brings HQE predictions closer to current experimental data, resolving some previous discrepancies. Overall, the agreement between HQE predictions and current experimental measurements is excellent for both total decay rates and lifetime ratios, within the stated uncertainties. This advancement is particularly relevant given recent and forthcoming experimental progress in the study of b-baryons, which will allow for more rigorous comparisons between theory and experiment and help refine our understanding of the strong interaction and heavy quark physics.

New protocol for multipartite entanglement distribution in networks

Researchers have developed an efficient protocol for multipartite entanglement distribution in quantum networks, overcoming limitations of current methods. This breakthrough is crucial for the development of quantum computing and communication, as it enables the creation of entangled states among multiple nodes in a Bell-pair network, which are the foundation of many quantum applications. The protocol has been designed to optimize resource utilization and computational efficiency. Unlike previous approaches that required a large number of operations or complex hardware, this new method simplifies the process of establishing and maintaining entanglement between several points. This is particularly relevant in distributed quantum networks, where coherence and connectivity are fundamental challenges. The ability to robustly and efficiently entangle multiple nodes is a key step towards building a functional quantum internet. The main innovation lies in its ability to generate high-fidelity multipartite entangled states with reduced computational cost. This is achieved through a smart network reconfiguration strategy and the minimization of entanglement operations. The protocol not only improves efficiency but also increases the scalability of quantum networks, allowing the integration of more nodes without significant performance degradation. The implications of this work are broad, opening new avenues for distributed quantum computing, advanced quantum cryptography, and the creation of more powerful quantum sensors.