Gelo Noel M Tabia, Alex Yueh-Ting Shih, Jin-Yuan Zheng and Yeong-Cherng Liang
{"title":"Almost device-independent calibration beyond Born’s rule: Bell tests for cross-talk detection","authors":"Gelo Noel M Tabia, Alex Yueh-Ting Shih, Jin-Yuan Zheng and Yeong-Cherng Liang","doi":"10.1088/2058-9565/ade911","DOIUrl":"https://doi.org/10.1088/2058-9565/ade911","url":null,"abstract":"In quantum information, device-independent (DI) protocols offer a new approach to information processing tasks, making minimal assumptions about the devices used. Typically, since these protocols draw conclusions directly from the data collected in a meaningful Bell test, the no-signaling conditions, and often even Born’s rule for local measurements, are taken as premises of the protocol. Here, we demonstrate how to test such premises in an (almost) DI setting, i.e. directly from the raw data and with minimal assumptions. In particular, for IBM’s quantum computing cloud services, we implement the prediction-based ratio protocol to characterize how well the qubits can be accessed locally and independently. More precisely, by performing a variety of Clauser–Horne–Shimony–Holt-type experiments on these systems and carrying out rigorous hypothesis tests on the collected data, we provide compelling evidence showing that some of these qubits suffer from measurement cross-talks, i.e. their measurement statistics are affected by the choice of measurement bases on another qubit. Unlike standard randomized benchmarking, our approach does not rely on assumptions such as gate-independent Markovian noise. Moreover, despite the relatively small number of experimental trials, the direction of ‘signaling’ may also be identified in some cases. Our approach thus serves as a complementary tool for benchmarking the local addressability of quantum computing devices.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"181 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144578118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wenlin Li, Paolo Piergentili, Francesco Marzioni, Michele Bonaldi, Antonio Borrielli, Enrico Serra, Francesco Marin, Francesco Marino, Nicola Malossi, Riccardo Natali, Giovanni Di Giuseppe and David Vitali
{"title":"Large amplitude mechanical coherent states and detection of weak nonlinearities in cavity optomechanics","authors":"Wenlin Li, Paolo Piergentili, Francesco Marzioni, Michele Bonaldi, Antonio Borrielli, Enrico Serra, Francesco Marin, Francesco Marino, Nicola Malossi, Riccardo Natali, Giovanni Di Giuseppe and David Vitali","doi":"10.1088/2058-9565/ade8a0","DOIUrl":"https://doi.org/10.1088/2058-9565/ade8a0","url":null,"abstract":"The generation of large-amplitude coherent states of a massive mechanical resonator, and their quantum-limited detection represent useful tools for quantum sensing and for testing fundamental physics theories. In fact, any weak perturbation may affect the coherent quantum evolution of the prepared state, providing a sensitive probe for such a perturbation. Here we consider a cavity optomechanical setup and the case of the detection of a weak mechanical nonlinearity. We consider different strategies, first focusing on the stationary dynamics in the presence of multiple tones driving the system, and then focusing on non-equilibrium dynamical strategies. These methods can be successfully applied for measuring Duffing-like material nonlinearities, or effective nonlinear corrections associated with quantum gravity theories.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"26 1","pages":"035055"},"PeriodicalIF":6.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144566007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jack Homans, Elliot Simcox, Jakub Wardak, Laura da Palma Barbara, Tim M Fuchs, Rafael Mufato, Florence Concepcion, Andrei Dragomir, Christian Vogt, Peter Nisbet-Jones, Christopher Bridges and Hendrik Ulbricht
{"title":"An experimental platform for levitated mechanics in space","authors":"Jack Homans, Elliot Simcox, Jakub Wardak, Laura da Palma Barbara, Tim M Fuchs, Rafael Mufato, Florence Concepcion, Andrei Dragomir, Christian Vogt, Peter Nisbet-Jones, Christopher Bridges and Hendrik Ulbricht","doi":"10.1088/2058-9565/ade624","DOIUrl":"https://doi.org/10.1088/2058-9565/ade624","url":null,"abstract":"Conducting experiments in extreme conditions has long been the aim of the levitated mechanics field, as it allows for the investigation of new fundamental physics phenomena. Sending these experiments into the micro-g environment of space has been one such milestone, with multiple proposals calling for such a platform. At the same time, levitated sensors have demonstrated a high sensitivity to external stimuli, such as electric, magnetic and gravitational forces, which will only improve in low-vibrational conditions. This paper describes the development of a technology demonstrator for optical and magnetic trapping experiments in space. Our payload represents the first concrete step towards future missions with aims of probing fundamental physical questions: matter-wave interferometry of nanoparticles to probe the limits of macroscopic quantum mechanics, detection of Dark Matter candidates and gravitational waves to test physics beyond the Standard Model, and accelerometry for Earth-observation.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"20 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144547065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ziqing Guo, Alex Khan, Victor S Sheng, Shabnam Jabeen and Ziwen Pan
{"title":"Quantum parallel information exchange (QPIE) hybrid network with transfer learning","authors":"Ziqing Guo, Alex Khan, Victor S Sheng, Shabnam Jabeen and Ziwen Pan","doi":"10.1088/2058-9565/ade89f","DOIUrl":"https://doi.org/10.1088/2058-9565/ade89f","url":null,"abstract":"Quantum machine learning (QML) has emerged as an innovative framework that has the potential to uncover complex patterns by leveraging the ability of quantum systems to simulate and exploit high-dimensional latent spaces, particularly in learning tasks. Quantum neural network frameworks are inherently sensitive to the precision of gradient calculations and the computational limitations of current quantum hardware, as unitary rotations introduce overhead from complex number computations, and quantum gate operation speed remains a bottleneck for practical implementations. In this study, we introduce a quantum parallel information exchange hybrid network, a new non-sequential hybrid classical quantum model architecture that leverages quantum transfer learning by feeding pre-trained parameters from classical neural networks into quantum circuits. This enables efficient pattern recognition and temporal series data prediction by utilizing non-Clifford parameterized quantum gates, thereby enhancing both learning efficiency and representational capacity. Additionally, we developed a dynamic gradient selection method that applies the parameter-shift rule to quantum processing units (QPUs) and adjoint differentiation to graphics processing units (GPUs). Our results demonstrate that the model performance exhibits higher accuracy in ad-hoc benchmarks, lowering approximately 88% convergence rate for extra stochasticity time-series data within 100 -steps, and showing a more unbiased eigenvalue spectrum of the Fisher information matrix on the CPU/GPU and IonQ QPU simulators.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"35 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144547483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruiyi Wang, Vincenzo Roberto Arezzo, Kiran Thengil, Giovanni Pecci and Giuseppe E Santoro
{"title":"From exponential to quadratic: optimal control for a frustrated Ising ring model","authors":"Ruiyi Wang, Vincenzo Roberto Arezzo, Kiran Thengil, Giovanni Pecci and Giuseppe E Santoro","doi":"10.1088/2058-9565/ade6a5","DOIUrl":"https://doi.org/10.1088/2058-9565/ade6a5","url":null,"abstract":"Exponentially small spectral gaps are known to be the crucial bottleneck for traditional Quantum Annealing (QA) based on interpolating between two Hamiltonians, a simple driving term and the complex problem to be solved, with a linear schedule in time. One of the simplest models exhibiting exponentially small spectral gaps is a ferromagnetic Ising ring with a single antiferromagnetic bond introducing frustration. Previous studies of this model have explored continuous-time diabatic QA, where optimized non-adiabatic annealing schedules provided good solutions, avoiding exponentially large annealing times. In our work, we move to a digital framework of Variational Quantum Algorithms, and present two main results: (1) we show that the model is digitally controllable with a scaling of resources that grows quadratically with the system size, achieving the exact solution using the Quantum Approximate Optimization Algorithm; (2) We combine a technique of quantum control—the Chopped RAndom Basis method—and digitized quantum annealing to construct smooth digital schedules yielding optimal solutions with very high accuracy.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"7 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144533272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adrià Labay-Mora, Eliana Fiorelli, Roberta Zambrini and Gian Luca Giorgi
{"title":"Theoretical framework for quantum associative memories","authors":"Adrià Labay-Mora, Eliana Fiorelli, Roberta Zambrini and Gian Luca Giorgi","doi":"10.1088/2058-9565/ade184","DOIUrl":"https://doi.org/10.1088/2058-9565/ade184","url":null,"abstract":"Associative memory (AM) refers to the ability to relate a memory with an input and targets the restoration of corrupted patterns. It has been intensively studied in classical physical systems, as in neural networks where an attractor dynamics settles on stable solutions. Several extensions to the quantum domain have been recently reported, displaying different features. In this work, we develop a comprehensive framework for a quantum AM (QAM) based on open quantum system dynamics, which allows us to compare existing models, identify the theoretical prerequisites for performing AM tasks, and extend it in different forms. The map that achieves an exponential increase in the number of stored patterns with respect to classical systems is derived. We establish the crucial role of symmetries and dissipation in the operation of QAM. Our theoretical analysis demonstrates the feasibility of addressing both quantum and classical patterns, orthogonal and non-orthogonal memories, stationary and metastable operating regimes, and measurement-based outputs. Finally, this opens up new avenues for practical applications in quantum computing and machine learning, such as quantum error correction or quantum memories.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"10 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144532959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the similarity of bandwidth-tuned quantum kernels and classical kernels","authors":"Roberto Flórez-Ablan, Marco Roth and Jan Schnabel","doi":"10.1088/2058-9565/ade7ad","DOIUrl":"https://doi.org/10.1088/2058-9565/ade7ad","url":null,"abstract":"Quantum kernels (QKs) are widely used in quantum machine learning applications; yet, their potential to surpass classical machine learning methods on classical datasets remains uncertain. This limitation can be attributed to the exponential concentration phenomenon, which can impair generalization. A common strategy to alleviate this is bandwidth tuning, which involves rescaling data points in the quantum model to improve generalization. In this work, we numerically demonstrate that optimal bandwidth tuning results in QKs that closely resemble radial basis function (RBF) kernels, leading to a lack of quantum advantage over classical methods. Moreover, we reveal that the size of optimal bandwidth tuning parameters further simplifies QKs, causing them to behave like polynomial kernels, corresponding to a low-order Taylor approximation of a RBF kernel. We thoroughly investigate this for fidelity quantum kernels and projected quantum kernels using various data encoding circuits across several classification datasets. We provide numerical evidence and derive a simple analytical model that elucidates how bandwidth tuning influences key quantities in classification tasks. Overall, our findings shed light on the mechanisms that render QK methods classically tractable.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"49 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144533271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bounding fidelity in quantum feedback control: theory and applications to Dicke state preparation","authors":"Eoin O’Connor, Hailan Ma and Marco G Genoni","doi":"10.1088/2058-9565/ade55f","DOIUrl":"https://doi.org/10.1088/2058-9565/ade55f","url":null,"abstract":"Achieving unit fidelity in quantum state preparation is often impossible in the presence of environmental decoherence. While continuous monitoring and feedback control can improve fidelity, perfect state preparation remains elusive in many scenarios. Inspired by quantum speed limits, we derive a fundamental bound on the steady-state average fidelity achievable via continuous monitoring and feedback control. This bound depends only on the unconditional Lindblad dynamics, the Hamiltonian variance, and the target state. We also adapt the bound to the case of Markovian feedback strategies. We then focus on preparing Dicke states in an atomic ensemble subject to collective damping and dispersive coupling. By imposing additional constraints on control Hamiltonians and monitoring strategies, we derive tighter fidelity bounds. Finally, we propose specific control strategies and validate them using reinforcement learning. Benchmarking their performance against our theoretical bounds highlights the relevance and usefulness of these bounds in characterizing quantum feedback control strategies.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"19 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144516122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andrea De Girolamo, Giuseppe Magnifico and Cosmo Lupo
{"title":"Percolation thresholds and connectivity in quantum networks","authors":"Andrea De Girolamo, Giuseppe Magnifico and Cosmo Lupo","doi":"10.1088/2058-9565/ade55e","DOIUrl":"https://doi.org/10.1088/2058-9565/ade55e","url":null,"abstract":"We study entanglement percolation in qubit-based planar quantum network models of arbitrary topology, where neighboring nodes are initially connected by pure states with quenched disorder in their entanglement. To address this, we develop a physics-informed heuristic algorithm designed to find a sequence of entanglement swapping and distillation operations to connect any pair of distant nodes. The algorithm combines locally optimal percolation strategies between nodes at a maximum distance of one swapping operation. If this fails to produce a maximally entangled state, it looks for alternative paths surrounding intermediate states within the process. We analytically find and numerically verify thresholds in quantum percolation, which depend on the initial network configuration and entanglement, and are associated with specific percolation strategies. We classify these strategies based on the connectivity, a quantity that relates the entanglement in the final state and the level of integrity of the network at the end of the process. We find distinct regimes of quantum percolation, which are clearly separated by the percolation thresholds of the employed strategies and vastly vary according to the network topology.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144488447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Coherence of quantum non-Gaussian states via nonlinear absorption of quanta","authors":"Kingshuk Adhikary, Darren W Moore and Radim Filip","doi":"10.1088/2058-9565/ade334","DOIUrl":"https://doi.org/10.1088/2058-9565/ade334","url":null,"abstract":"The linear and phase insensitive absorption of a single quanta via coherent interactions with a saturable system, even a single ground state qubit, is sufficient to deterministically generate quantum non-Gaussian states in an oscillator, even stimulated merely by increasing thermal oscillator energy. However, the resultant states only approach Fock states and therefore do not exhibit quantum coherence. Here we overcome this limitation using a minimal step: a nonlinear phase-insensitive absorption process added to the linear one. The coherent addition of such individually passive processes allows coherence to emerge and increase in phase space without an external drive and with minimal interaction requirements. The coherence of quantum non-Gaussian states emerges because the linear and nonlinear absorption processes are not mutually passive. In the simplest case rotationally symmetric Wigner functions of the oscillator Fock states convert their many negative regions to an extremely complex asymmetric structure in sharp contrast to the rotational symmetry of those obtained by the individual interactions. We extend this case to include an unsaturable absorber (oscillator) and analyse switching between linear and nonlinear absorptions, suitable for broad classes of experiments.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"46 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144488446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}