Emanuele Tumbiolo, Simone Roncallo, Chiara Macchiavello, Lorenzo Maccone
{"title":"Quantum frequency resampling","authors":"Emanuele Tumbiolo, Simone Roncallo, Chiara Macchiavello, Lorenzo Maccone","doi":"10.1038/s41534-025-01076-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01076-z","url":null,"abstract":"<p>In signal processing, resampling algorithms can modify the number of resources encoding a collection of data points. Downsampling reduces the cost of storage and communication, while upsampling interpolates new data from limited one, e.g., when resizing a digital image. We present a toolset of quantum algorithms to resample data encoded in the probabilities of a quantum register, using the quantum Fourier transform to adjust the number of high-frequency encoding qubits. We discuss advantage over classical resampling algorithms.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"29 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Robust quantum control using reinforcement learning from demonstration","authors":"Shengyong Li, Yidian Fan, Xiang Li, Xinhui Ruan, Qianchuan Zhao, Zhihui Peng, Re-Bing Wu, Jing Zhang, Pengtao Song","doi":"10.1038/s41534-025-01065-2","DOIUrl":"https://doi.org/10.1038/s41534-025-01065-2","url":null,"abstract":"<p>Quantum control requires high-precision and robust control pulses to ensure optimal system performance. However, control sequences generated with a system model may suffer from model bias, leading to low fidelity. While model-free reinforcement learning (RL) methods have been developed to avoid such biases, training an RL agent from scratch can be time-consuming, often taking hours to gather enough samples for convergence. This challenge has hindered the broad application of RL techniques to larger and more complex quantum control issues, limiting their adaptability. In this work, we use Reinforcement Learning from Demonstration (RLfD) to leverage the control sequences generated with system models and further optimize them with RL to avoid model bias. By avoiding learning from scratch and starting with reasonable control pulse shapes, this approach can increase sample efficiency by reducing the number of samples, which can significantly reduce the training time. Thus, this method can effectively handle pulse shapes that are discretized into more than 1000 pieces without compromising final fidelity. We have simulated the preparation of several high-fidelity non-classical states using the RLfD method. We also find that the training process is more stable when using RLfD. In addition, this method is suitable for fast gate calibration using reinforcement learning.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"11 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144710627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Counterfactual communication not achieved yet – A Comment on Salih et al. (2022)","authors":"Sandu Popescu","doi":"10.1038/s41534-025-00975-5","DOIUrl":"https://doi.org/10.1038/s41534-025-00975-5","url":null,"abstract":"<p>In this comment I argue that there are two major issues with the protocol presented in “The laws of physics do not prohibit counterfactual communication”, Hatim Salih, Will McCutcheon, Jonte R. Hance and John Rarity, npj Quantum Information (2022) 8:60. One is an erroneous interpretation of the role of clicks in detector <i>D</i><sub>0</sub> and the second is the way in which post-selection is used. I argue that these invalidate the claims of that paper.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"12 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Alice Barthe, Michele Grossi, Sofia Vallecorsa, Jordi Tura, Vedran Dunjko
{"title":"Parameterized quantum circuits as universal generative models for continuous multivariate distributions","authors":"Alice Barthe, Michele Grossi, Sofia Vallecorsa, Jordi Tura, Vedran Dunjko","doi":"10.1038/s41534-025-01064-3","DOIUrl":"https://doi.org/10.1038/s41534-025-01064-3","url":null,"abstract":"<p>Parameterized quantum circuits are a key component of quantum machine learning models for regression, classification, and generative tasks. Quantum Circuit Born machines produce discrete distributions over bitstrings whose length is exactly the number of qubits. To allow for distributions on continuous variables, new models have been introduced where classical randomness is uploaded into quantum circuits and expectation values are returned with a dimensionality decoupled from qubit number. While these models have been explored experimentally, their expressivity remains underexplored. In this work, we formalize this family and establish its theoretical foundation. We prove the universality of several variational circuit architectures for generating continuous multivariate distributions and derive tight resource bounds to reach universality using tools related to the Holevo bound. Our results reveal a trade-off between the number of qubits and measurements. We further explore relaxed notions of universality and present a practical use case, outlining potential domains for quantum advantage.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"98 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144677385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Hamza Raniwala, Pratyush Anand, Stefan Krastanov, Matt Eichenfield, Matthew Trusheim, Dirk R. Englund
{"title":"Spin-optomechanical cavity interfaces by deep subwavelength phonon-photon confinement","authors":"Hamza Raniwala, Pratyush Anand, Stefan Krastanov, Matt Eichenfield, Matthew Trusheim, Dirk R. Englund","doi":"10.1038/s41534-025-00999-x","DOIUrl":"https://doi.org/10.1038/s41534-025-00999-x","url":null,"abstract":"<p>A central goal of quantum information science is transferring qubits between space, time, and modality. Spin-based systems in solids are promising quantum memories, but high-fidelity transfer of their quantum states to telecom optical fields remains challenging. Here, we introduce a phonon-mediated interface between spins in a diamond nanobeam optomechanical crystal and telecom optical fields by a simultaneous deep-subwavelength confinement of optical and acoustic fields with mode volumes <span>({V}_{{rm{mech}}}/{Lambda }_{{rm{p}}}^{3} sim 1{0}^{-5})</span> and <i>V</i><sub>opt</sub>/<i>λ</i><sup>3</sup> ~ 10<sup>−3</sup>, respectively. This confinement boosts the spin-mechanical coupling rate of Group-IV silicon vacancy (SiV<sup>−</sup>) centers by an order of magnitude to ~ 32 MHz while retaining high acousto-optical couplings. The optical cavity couples to the spin irrespective of the emitter’s native excited states, avoiding spectral diffusion. Using Quantum Monte Carlo simulations, we estimate heralded entanglement fidelities exceeding 0.96 between two such interfaces. We anticipate broad utility beyond diamond emitter-telecom systems to most solid-state quantum memories.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"93 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Zhenghao Li, Naomi R. Solomons, Jacob F. F. Bulmer, Raj B. Patel, Ian A. Walmsley
{"title":"A complexity transition in displaced Gaussian Boson sampling","authors":"Zhenghao Li, Naomi R. Solomons, Jacob F. F. Bulmer, Raj B. Patel, Ian A. Walmsley","doi":"10.1038/s41534-025-01062-5","DOIUrl":"https://doi.org/10.1038/s41534-025-01062-5","url":null,"abstract":"<p>Gaussian Boson Sampling (GBS) is the problem of sampling from the output of photon-number-resolving measurements of squeezed states input to a linear optical interferometer. For purposes of demonstrating quantum computational advantage as well as practical applications, a large photon number is often desirable. However, producing squeezed states with high photon numbers is experimentally challenging. In this work, we examine the computational complexity implications of increasing the photon number by introducing coherent states. This displaces the state in phase space and as such we call this modified problem <i>Displaced GBS</i>. By utilising a connection to the matching polynomial in graph theory, we first describe an efficient classical algorithm for Displaced GBS when displacement is high or when the output state is represented by a non-negative graph. Then we provide complexity theoretic arguments for the quantum advantage of the problem in the low-displacement regime and numerically quantify where the complexity transition occurs.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"693 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144594882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Jun Wu, Jin-Lei Wu, Fu-Qiang Guo, Bing-Bing Liu, Shi-Lei Su, Xue-Ke Song, Liu Ye, Dong Wang
{"title":"Quantum computation via Floquet tailored Rydberg interactions","authors":"Jun Wu, Jin-Lei Wu, Fu-Qiang Guo, Bing-Bing Liu, Shi-Lei Su, Xue-Ke Song, Liu Ye, Dong Wang","doi":"10.1038/s41534-025-01068-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01068-z","url":null,"abstract":"<p>Rydberg atoms have stood out as a highly promising platform for realizing quantum computation. Floquet frequency modulation (FFM), in Rydberg atom systems, provides a unique tool for achieving precise quantum control and uncovering exotic physical phenomena. This work introduces a method to realize controlled arbitrary phase gates in Rydberg atoms by manipulating system dynamics using FFM. Notably, the need for laser addressing of individual atoms is eliminated, enhancing convenience for practical applications. Furthermore, this approach is integrated with soft quantum control strategies to enhance the fidelity and robustness of the resultant controlled-phase gates. Finally, as an example, this methodology is applied in Grover-Long algorithm to search target items with zero failure rate, demonstrating its substantial significance for future quantum information processing applications. This work leveraging Rydberg atoms and FFM may herald a new era of scalable and reliable quantum computing.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"10 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144586944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Excessive precision compromises accuracy even with unlimited resources due to the trade-off in quantum metrology","authors":"Cong-Gang Song, Qing-yu Cai","doi":"10.1038/s41534-025-01071-4","DOIUrl":"https://doi.org/10.1038/s41534-025-01071-4","url":null,"abstract":"<p>This paper provides a unified definition of precision and accuracy from the perspective of distinguishing neighboring quantum states. We find that the conventional quantum Cramér–Rao bound underestimates the effect of statistical noise, because the biases of parameters were inappropriately ignored. Given that probability estimation is unbiased, defining precision based on probability distributions provides a more accurate approach. This leads to a correction of factor 2 to the traditional precision lower bound. The trade-off between precision and accuracy shows that precision can be further improved by sacrificing accuracy, while it should be restricted by the inherent precision limit determined by the number of samples. The inherent precision limit can reach the Heisenberg scaling even without entanglement resources, which, however, comes at the cost of significantly reduced accuracy. We show that increasing sampling may decrease accuracy when one pursues excessive precision, which indicates that the trade-off should be considered even with unlimited resources.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"9 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144578329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"High dimensional counterdiabatic quantum computing","authors":"Diego Tancara, Francisco Albarrán-Arriagada","doi":"10.1038/s41534-025-01070-5","DOIUrl":"https://doi.org/10.1038/s41534-025-01070-5","url":null,"abstract":"<p>The digital version of adiabatic quantum computing enhanced by counterdiabatic driving, known as digitized counterdiabatic quantum computing, has emerged as a paradigm that opens the door to fast and low-depth algorithms. In this work, we explore the extension of this paradigm to high-dimensional systems. Specifically, we consider qutrits in the context of quadratic problems, obtaining the qutrit Hamiltonian codifications and the counterdiabatic drivings. Our findings show that qutrits can improve the solution quality up to 90 times compared to the qubit counterpart. We tested our proposal on 1000 random instances of the multiway number partitioning, max 3-cut, and portfolio optimization problems, demonstrating that, in general, without prior knowledge, it is better to use qutrits and, apparently, high-dimensional systems in general instead of qubits. Finally, considering the state-of-the-art quantum platforms, we show the experimental feasibility of our high-dimensional counterdiabatic quantum algorithms at least in a fully digital form. This work paves the way for the efficient codification of optimization problems in high-dimensional spaces and their efficient implementation using counterdiabatic quantum computing.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"17 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144578328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Thuy Dung Tran, Daniel Babjak, Artem Kovalenko, Kratveer Singh, Tuan Minh Pham, Petr Obšil, Adam Lešundák, Ondřej Číp, Lukáš Slodička
{"title":"Coherent enhancement of collection of light from linear ion crystals","authors":"Thuy Dung Tran, Daniel Babjak, Artem Kovalenko, Kratveer Singh, Tuan Minh Pham, Petr Obšil, Adam Lešundák, Ondřej Číp, Lukáš Slodička","doi":"10.1038/s41534-025-01058-1","DOIUrl":"https://doi.org/10.1038/s41534-025-01058-1","url":null,"abstract":"<p>The efficient detection of light from trapped ions in free space is paramount for most of their applications. We propose a scheme to enhance the photon collection from linear ion strings. It employs the constructive interference of light scattered from ions along the axial direction in linear Paul traps. The coherent enhancement of photon collection is numerically optimized for a range of feasible spatial angles and realistic ion positions in a single harmonic Coulomb potential. Despite the large mutual distance of scatterers on the order of many wavelengths of scattered light, the experimental tests presented confirm the feasibility of enhancements by a factor of 3.05 ± 0.09 with a crystal of nine <sup>40</sup>Ca<sup>+</sup> ions. The proposed collection geometry is intrinsic to diverse linear ion trap designs, and the methodology can be directly applied to an observation of scattering from ion crystals prepared in collective electronic excitations.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"11 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144586945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}