物理与天体物理最新文献

{"title":"On the average-case complexity of learning output distributions of quantum circuits","authors":"Alexander Nietner, Marios Ioannou, Ryan Sweke, Richard Kueng, Jens Eisert, Marcel Hinsche, Jonas Haferkamp","doi":"10.22331/q-2025-10-13-1883","DOIUrl":"https://doi.org/10.22331/q-2025-10-13-1883","url":null,"abstract":"In this work, we show that learning the output distributions of brickwork random quantum circuits is average-case hard in the statistical query model. This learning model is widely used as an abstract computational model for most generic learning algorithms. In particular, for brickwork random quantum circuits on $n$ qubits of depth $d$, we show three main results:<br/> – At super logarithmic circuit depth $d=omega(log(n))$, any learning algorithm requires super polynomially many queries to achieve a constant probability of success over the randomly drawn instance.<br/> – There exists a $d=O(n)$, such that any learning algorithm requires $Omega(2^n)$ queries to achieve a $O(2^{-n})$ probability of success over the randomly drawn instance.<br/> – At infinite circuit depth $dtoinfty$, any learning algorithm requires $2^{2^{Omega(n)}}$ many queries to achieve a $2^{-2^{Omega(n)}}$ probability of success over the randomly drawn instance.<br/> As an auxiliary result of independent interest, we show that the output distribution of a brickwork random quantum circuit is constantly far from any fixed distribution in total variation distance with probability $1-O(2^{-n})$, which confirms a variant of a conjecture by Aaronson and Chen.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"7 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277499","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":"Deep-Circuit QAOA","authors":"Gereon Koßmann, Lennart Binkowski, Lauritz van Luijk, Timo Ziegler, René Schwonnek","doi":"10.22331/q-2025-10-13-1882","DOIUrl":"https://doi.org/10.22331/q-2025-10-13-1882","url":null,"abstract":"Despite its popularity, several empirical and theoretical studies suggest that the quantum approximate optimization algorithm (QAOA) has persistent issues in providing a substantial practical advantage. Numerical results for few qubits and shallow circuits are, at best, ambiguous, and the well-studied barren plateau phenomenon draws a rather sobering picture for deeper circuits. However, as more and more sophisticated strategies are proposed to circumvent barren plateaus, it stands to reason which issues are actually fundamental and which merely constitute – admittedly difficult – engineering tasks. By shifting the scope from the usually considered parameter landscape to the quantum state space's geometry we can distinguish between problems that are fundamentally difficult to solve, independently of the parameterization, and those for which there could at least exist a favorable parameterization. Here, we find clear evidence for a 'no free lunch'-behavior of QAOA on a general optimization task with no further structure; individual cases have, however, to be analyzed more carefully.<br/> Based on our analysis, we propose and justify a performance indicator for the deep-circuit QAOA that can be accessed by solely evaluating statistical properties of the classical objective function. We further discuss the various favorable properties a generic QAOA instance has in the asymptotic regime of infinitely many gates, and elaborate on the immanent drawbacks of finite circuits. We provide several numerical examples of a deep-circuit QAOA method based on local search strategies and find that – in alignment with our performance indicator – some special function classes, like QUBOs, indeed admit a favorable optimization landscape.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"116 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277428","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":"The SOFIA Massive (SOMA) star formation Q-band follow-up","authors":"Prasanta Gorai, Kotomi Taniguchi, Jonathan C. Tan, Miguel Gómez-Garrido, Viviana Rosero, Izaskun Jiménez-Serra, Yichen Zhang, Giuliana Cosentino, Chi-Yan Law, Rubén Fedriani, Gemma Busquet, Brandt A. L. Gaches, Maryam Saberi, Ankan Das","doi":"10.1051/0004-6361/202556220","DOIUrl":"https://doi.org/10.1051/0004-6361/202556220","url":null,"abstract":"<i>Context<i/>. Hydrogen recombination lines (HRLs) are valuable diagnostics of the physical conditions in ionized regions surrounding high-mass stars. Understanding these lines, including broadening mechanisms and intensity trends, can provide insights into HII region densities, temperatures, and kinematics.<i>Aims<i/>. This study aims to investigate the physical properties of ionized gas around massive protostars by analysing the HRLs (H<i>α<i/> and H<i>β<i/>) in the Q band.<i>Methods<i/>. We carried out observations using the Yebes 40m radio telescope in the Q band (30.5–50 GHz) towards six high-mass protostars selected from the SOMA Survey (G45.12+0.13, G45.47+0.05, G28.20−0.05, G35.20−0.74, G19.08−0.29, and G31.28+0.06). The observed line profiles were analysed to assess broadening mechanisms, and electron densities and temperatures were derived. The results were compared with available Q-band data from the TianMa 65-m Radio Telescope (TMRT) that have been reported in the literature, and ALMA Band 1 (35–50 GHz) Science Verification observations towards Orion KL, analysed in this study.<i>Results<i/>. A total of eight H<i>α<i/> (n = 51 to 58) and ten H<i>β<i/> (n = 64 to 73) lines were detected towards G45.12+0.13, G45.47+0.05, and G28.20−0.05; there were no detections in other sources. We derived electron densities of ~1−5 × 10<sup>6<sup/> cm<sup>−3<sup/> and temperatures of 8000–10 000 K for the sources. However, for Orion KL, we obtained an electron density one order of magnitude lower, while its temperature was found to be more similar. Interestingly, G45.12 and G28.20 show an increasing intensity trend with frequency for both H<i>α<i/> and H<i>β<i/> transitions, contrary to the decreasing trend observed in Orion KL.<i>Conclusions<i/>. The line widths of the detected HRLs indicate contributions from both thermal and dynamical broadening, suggesting the presence of high-temperature ionized gas that is likely kinematically broadened (e.g. due to turbulence, outflows, rapid rotation, or stellar winds). Pressure broadening caused by electron density may also have a minor effect. We discuss different scenarios to explain the measured line widths of the HRLs. The contrasting intensity trends between the sources may reflect variations in local physical conditions or radiative transfer effects, highlighting the need for further investigation through higher-resolution observations and detailed modelling.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"86 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277460","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":"Rotational modulation and long-term evolution of the small-scale magnetic fields of M dwarfs observed with SPIRou","authors":"P. I. Cristofari, J.-F. Donati, S. Bellotti, É. Artigau, A. Carmona, C. Moutou, X. Delfosse, P. Petit, B. Finociety, J. Dias do Nascimento","doi":"10.1051/0004-6361/202554902","DOIUrl":"https://doi.org/10.1051/0004-6361/202554902","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. M dwarfs are known to host magnetic fields, impacting exoplanet studies and playing a key role in stellar and planetary formation and evolution. Observational constraints are essential to guide theories of dynamo processes believed to be at the origin of those fields, in particular for fully convective stars whose internal structure differs from that of partially convective stars. Observations reveal long-term evolution of the large-scale magnetic field reconstructed with Zeeman-Doppler imaging, and a diversity of their topologies. These large-scale magnetic fields, however, only account for a small amount of the unsigned magnetic flux at the stellar surface that can be probed by directly modeling the Zeeman broadening of spectral lines in unpolarized spectra.&lt;i&gt;Aims&lt;i/&gt;. We aim to investigate the long-term behavior of the average small-scale magnetic field of fully convective and partially convective M dwarfs with time, and assess our ability to detect rotational modulation and retrieve rotation periods from time series of field measurements derived from unpolarized spectra.&lt;i&gt;Methods&lt;i/&gt;. We performed fits of synthetic spectra computed with ZeeTurbo to near-infrared high-resolution spectra recorded with SPIRou between 2019 and 2024 in the context of the SLS and SPICE large programs. The analysis was performed on the spectra of two partially convective (AD Leo and DS Leo) and three fully convective (PM J18482+0741, CN Leo, and Barnard’s star) M dwarfs, along with EV Lac, whose mass is close to the fully convective limit. Our analysis provides measurements of the average small-scale magnetic field, which are compared to longitudinal magnetic field and temperature variation measurements (d&lt;i&gt;Temp&lt;i/&gt;) obtained from the same data.&lt;i&gt;Results&lt;i/&gt;. We detected the rotation period in the small-scale magnetic field series for four of the 6 stars in our sample. We find that the average magnetic field can vary by up to 0.3 kG throughout the year (e.g., CN Leo), or of up to 1 kG across rotation phases (e.g., EV Lac). The rotation periods retrieved from longitudinal and small-scale magnetic fields are found to agree within error bars. The d&lt;i&gt;Temp&lt;i/&gt; measurements are found to anti-correlate with small-scale magnetic field measurements for three stars (EV Lac, DS Leo, and Barnard’s star).&lt;i&gt;Conclusions&lt;i/&gt;. The results demonstrate our ability to measure rotation periods from high-resolution data through small-scale magnetic field measurements, provided that the inclination of the observed targets is sufficiently large. We observe long-term fluctuations of the average magnetic field that could indicate magnetic cycles in the parent dynamo processes. These long-term variations appear mainly uncorrelated with large-scale magnetic field variations probed through longitudinal field measurements. Large variations in the amplitude of the rotationally modulated signals, in particular, hint towards a change in the distribution of the surface inhomoge","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"124 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277461","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":"Post‐Processing‐Free Orbital Angular Momentum Holographic Encryption","authors":"Chaoxu Chen, Yuan Wei, Haoyu Zhang, Fang Dong, Ziwei Li, Chao Shen, Nan Chi, Haiwen Cai, Junwen Zhang, Jianyang Shi","doi":"10.1002/lpor.202501835","DOIUrl":"https://doi.org/10.1002/lpor.202501835","url":null,"abstract":"Orbital angular momentum (OAM) holography provides a promising degree of freedom for optical encryption. However, conventional schemes often rely on discrete vortex sampling, leading to visible concentric ring patterns under direct detection. To conceal such leakage, spatial filter arrays are typically used, but they introduce complexity and remain vulnerable to partial information exposure. A post‐processing‐free OAM holographic encryption scheme based on symmetric grating phase sampling is presented. A pair of complementary pseudo‐orthogonal gratings modulates a single OAM mode into two holographic channels: one encoding the target information and the other carrying structured noise. These channels are coherently multiplexed into a single phase‐only hologram. Upon direct detection, mutual interference conceals the information, which is only revealed when the correct decryption beam collapses the field into a Gaussian‐like mode. It is experimentally validated this approach in both static and dynamic scenarios. Under brute‐force decryption, the recognition accuracy remains below 10%, while correct decryption achieves over 99.8% accuracy. In multi‐frame video experiments, pre‐decryption recognition drops to 5.6%, confirming strong concealment. This compact and filter‐free scheme enables real‐time, high‐security optical encryption, offering a scalable platform for secure imaging, data protection, and photonic communication systems.","PeriodicalId":204,"journal":{"name":"Laser & Photonics Reviews","volume":"137 1","pages":""},"PeriodicalIF":11.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277430","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":"Anisotropy‐Engineered Ultrabroadband Anti‐BIC Polarizer Based on Thin‐Film Lithium Niobate","authors":"Weixi Liu, Jiahao Wu, Boyu Pu, Jintao Song, Chengfeng Wen, Lijia Song, Huan Li, Daoxin Dai, Yaocheng Shi","doi":"10.1002/lpor.202501419","DOIUrl":"https://doi.org/10.1002/lpor.202501419","url":null,"abstract":"Thin‐film lithium niobate (TFLN) has emerged as a revolutionary platform for photonic integrated circuits due to its outstanding electro‐optic efficiency, strong nonlinearity, and low loss. However, polarization crosstalk in TFLN PIC remains a critical challenge. Conventional polarizers cannot simultaneously achieve both low insertion loss (&lt;0.5 dB) and large operational bandwidth (&gt;300 nm). In this work, a waveguide orientation‐engineering strategy that manipulates the coupling between TM bound mode and TE continuous modes in the anisotropic TFLN platform is proposed and demonstrated. By aligning the extraordinary optical axis parallel to the waveguide direction, an ultrabroadband polarizer with enhanced anti bound state in the continuum has been achieved. The device achieves an insertion loss below 0.18 dB and an extinction ratio exceeding 17 dB across 1.24–1.7 µm wavelength range.","PeriodicalId":204,"journal":{"name":"Laser & Photonics Reviews","volume":"29 1","pages":""},"PeriodicalIF":11.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277444","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":"Prospects for quantum process tomography at high energies","authors":"Clelia Altomonte, Alan J Barr, Michał Eckstein, Paweł Horodecki and Kazuki Sakurai","doi":"10.1088/2058-9565/ae0af1","DOIUrl":"https://doi.org/10.1088/2058-9565/ae0af1","url":null,"abstract":"In quantum information theory, the evolution of an open quantum system—a unitary evolution followed by a measurement—is described by a quantum channel or, more generally, a quantum instrument. In this work, we formulate spin and flavour measurements in collider experiments as quantum instruments. We demonstrate that the Choi matrix, which completely determines input-output transitions, can be both theoretically computed from a given model and experimentally reconstructed from a set of final state measurements (quantum state tomography) using varied input states. The experimental reconstruction of the Choi matrix, known as quantum process tomography, offers a powerful new approach for probing potential extensions of the Standard Model, which predict different input-output transitions. In addition, the methodology constitutes a new foundational test of quantum mechanics itself. As an example, we outline the quantum process tomography approach applied to the process at a polarised lepton collider.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"22 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277425","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":"Timelike boundary and corner terms in the causal set action","authors":"Fay Dowker, Roger Liu and Daniel Lloyd-Jones","doi":"10.1088/1361-6382/ae0be5","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0be5","url":null,"abstract":"The causal set action of dimension d is investigated for causal sets that are Poisson sprinklings into manifolds that are regions of d-dimensional Minkowski space. Evidence, both analytic and numerical, is provided for the conjecture that as the discreteness length l tends to zero, the mean of the causal set action over Poisson sprinklings into a manifold with a timelike boundary, is dominated by a term proportional to the volume of the timelike boundary and diverges like l−1. A novel conjecture for the contribution to the causal set action from co-dimension two corners, also known as joints, is proposed and justified.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"124 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Sourced metric perturbations of Kerr spacetime in Lorenz gauge","authors":"Barry Wardell, Chris Kavanagh and Sam R Dolan","doi":"10.1088/1361-6382/ae0918","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0918","url":null,"abstract":"We derive a formalism for solving the Lorenz gauge equations for metric perturbations of Kerr spacetime sourced by an arbitrary stress-energy tensor. The metric perturbation is obtained as a sum of differential operators acting on a set of six scalars, with two of spin-weight ±2, two of spin-weight ±1, and two of spin-weight 0. We derive the sourced Teukolsky equations satisfied by these scalars, with the sources given in terms of differential operators acting on the stress-energy tensor. The method can be used to obtain both linear and higher-order nonlinear metric perturbations, and it fully determines the metric perturbation up to a time integral, omitting only static contributions which must be handled separately.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"117 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Gravitational waves decohere quantum superpositions","authors":"Flynn Linton and Shubhanshu Tiwari","doi":"10.1088/1361-6382/ae0d27","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0d27","url":null,"abstract":"Understanding the interplay between quantum mechanical systems and gravity is a crucial step towards unifying these two fundamental ideas. Recent theoretical developments have explored how global properties of spacetime would cause a quantum spatial superposition to lose coherence. In particular, this loss of coherence is closely related to the memory effect, which is a prominent feature of gravitational radiation. In this work, we explore how a burst of gravitational radiation from a far-away source would decohere a quantum superposition. We identify the individual contributions to the decoherence from the memory and oscillatory components of the gravitational wave source, corresponding to hard and soft graviton emissions, respectively. In general, the memory contributions dominate, while the oscillatory component of the decoherence is strongly dependent on the phase of the burst when it is switched off. This work demonstrates how quantum systems can lose coherence from interactions with a classical gravitational field. We also comment on the electromagnetic analogue of this effect and discuss its correspondence to the gravitational case.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"53 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}