IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-10-13 DOI: 10.22331/q-2025-10-13-1880

David Schmid, John H. Selby, Vinicius P. Rossi, Roberto D. Baldijão, Ana Belén Sainz

{"title":"Shadows and subsystems of generalized probabilistic theories: when tomographic incompleteness is not a loophole for contextuality proofs","authors":"David Schmid, John H. Selby, Vinicius P. Rossi, Roberto D. Baldijão, Ana Belén Sainz","doi":"10.22331/q-2025-10-13-1880","DOIUrl":"https://doi.org/10.22331/q-2025-10-13-1880","url":null,"abstract":"It is commonly believed that failures of tomographic completeness undermine assessments of nonclassicality in noncontextuality experiments. In this work, we study how such failures can indeed lead to mistaken assessments of nonclassicality. We then show that proofs of the failure of noncontextuality are robust to a very broad class of failures of tomographic completeness, including the kinds of failures that are likely to occur in real experiments. We do so by showing that such proofs actually rely on a much weaker assumption that we term $textit{relative tomographic completeness}$: namely, that one's experimental procedures are tomographic $textit{for each other}$. Thus, the failure of noncontextuality can be established even with coarse-grained, effective, emergent, or virtual degrees of freedom. This also implies that the existence of a deeper theory of nature (beyond that being probed in one's experiment) does not in and of itself pose any challenge to proofs of nonclassicality. To prove these results, we first introduce a number of useful new concepts within the framework of generalized probabilistic theories (GPTs). Most notably, we introduce the notion of a GPT $subsystem$, generalizing a range of preexisting notions of subsystems (including those arising from tensor products, direct sums, decoherence processes, virtual encodings, and more). We also introduce the notion of a $shadow$ of a GPT fragment, which captures the information lost when one's states and effects are unknowingly not tomographic for one another.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"10 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277424","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}

引用次数: 0

Spin–orbit torque control via distinct exchange-coupling interfaces 通过不同的交换耦合接口控制自旋轨道转矩

IF 4 2区物理与天体物理

Applied Physics Letters Pub Date : 2025-10-13 DOI: 10.1063/5.0293687

Mingming Tian, Qian Chen, Wei Jiang, Hainan Mao, Ruobai Liu, Qingjie Guo, Jun Du, Zhongming Zeng, Zhaocong Huang, Ya Zhai

{"title":"Spin–orbit torque control via distinct exchange-coupling interfaces","authors":"Mingming Tian, Qian Chen, Wei Jiang, Hainan Mao, Ruobai Liu, Qingjie Guo, Jun Du, Zhongming Zeng, Zhaocong Huang, Ya Zhai","doi":"10.1063/5.0293687","DOIUrl":"https://doi.org/10.1063/5.0293687","url":null,"abstract":"Efficient manipulation of magneto-dynamics is critical for advancing nonvolatile spin memory devices, and high spin–orbit torque (SOT) efficiency enables rapid and energy-efficient magnetization switching. One promising strategy to enhance SOT efficiency involves interface engineering, where spin transmission is modulated through interfacial exchange coupling in magnetic heterostructures. Here, we construct two distinct types of exchange-coupling interfaces: a self-assembled antiferromagnetic coupling (AFC) interface (Py/Ho) and an intrinsic exchange-coupled AFC interface (Py/FeMn), to systematically investigate their influences on SOT efficiency. Both spin dynamic damping and SOT efficiency are significantly enhanced in Py/X (X = Ho, FeMn) compared to their Cu spacer counterparts, Py/Cu/X (X= Ho, FeMn), highlighting the key contribution of AFC interface in facilitating efficient spin transmission. Notably, the Py/Ho interface enables the generation of spin currents with out-of-plane spin polarization—an effect absent in the Py/FeMn system. Moreover, the SOT efficiency in the Py/Ho system, modulated by the self-assembled AFC interface, exhibits pronounced frequency dependence, whereas the exchange-coupled AFC in Py/FeMn leads to a nearly frequency-independent behavior. This frequency-dependent behavior is likely attributed to magnon coupling at the Py/Ho interface, where the low-energy self-assembled AFC state allows dynamic coupling with the adjacent Py layer. These findings highlight the critical role of exchange-coupling interfaces in governing spin transmission and SOT behavior, enabling the design of low-power spintronic devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"39 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282928","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}

引用次数: 0

Signatures of Einstein-Maxwell dilaton-axion gravity from the observed quasi-periodic oscillations in black holes 黑洞中观测到的准周期振荡的爱因斯坦-麦克斯韦膨胀-轴子引力特征

IF 6.4 2区物理与天体物理

Journal of Cosmology and Astroparticle Physics Pub Date : 2025-10-13 DOI: 10.1088/1475-7516/2025/10/054

Anirban Dasgupta, Nishant Tiwari and Indrani Banerjee

{"title":"Signatures of Einstein-Maxwell dilaton-axion gravity from the observed quasi-periodic oscillations in black holes","authors":"Anirban Dasgupta, Nishant Tiwari and Indrani Banerjee","doi":"10.1088/1475-7516/2025/10/054","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/10/054","url":null,"abstract":"String-inspired models are often believed to provide an interesting framework for quantum gravity and force unification with promising prospects to resolve issues like dark matter and dark energy, which cannot be satisfactorily incorporated within the framework of general relativity (GR). The goal of the present work is to investigate the role of the Einstein-Maxwell dilaton-axion (EMDA) gravity arising in the low-energy effective action of the heterotic string theory in explaining astrophysical observations, in particular, the high-frequency quasi-periodic oscillations (HFQPOs) observed in the power spectrum of black holes. EMDA gravity has interesting cosmological implications, and hence it is worthwhile to explore the footprints of such a theory in available astrophysical observations. This requires one to study the stationary, axi-symmetric black hole solution in EMDA gravity, which corresponds to the Kerr-Sen spacetime. Such black holes are endowed with a dilatonic charge while the rotation is sourced from the axionic field. We investigate the orbital and epicyclic frequencies of matter rotating in the Kerr-Sen spacetime and consider eleven well-studied QPO models in this work. We compare the model-dependent QPO frequencies with the available observations of five BH sources, namely, XTE J1550-564, GRS 1915+105, H 143+322, GRO J1655-40 and Sgr A*. Our analysis provides constraints on the spins of the aforesaid black holes which, when compared with previous estimates, enables us to understand the observationally favored QPO models for each of these sources. Further, from the current data, the EMDA scenario cannot be ruled out in favor of general relativity. We comment on the implications and limitations of our findings and how the present constrains compare with the existing literature.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282939","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}

引用次数: 0

Issue Information: Ann. Phys. 10/2025 发布信息：Ann。理论物理的10/2025

IF 2.5 4区物理与天体物理

Annalen der Physik Pub Date : 2025-10-13 DOI: 10.1002/andp.70073

引用次数: 0

Room-Temperature Nanosecond Amplified Spontaneous Emission from Tin Iodide Perovskite Nanostructures 室温纳秒级放大的碘化锡钙钛矿纳米结构自发辐射

IF 7 1区物理与天体物理

ACS Photonics Pub Date : 2025-10-13 DOI: 10.1021/acsphotonics.5c01400

Andreas Manoli, Modestos Athanasiou, Paris Papagiorgis, Kushagra Gahlot, Loredana Protesescu, Grigorios Itskos

{"title":"Room-Temperature Nanosecond Amplified Spontaneous Emission from Tin Iodide Perovskite Nanostructures","authors":"Andreas Manoli, Modestos Athanasiou, Paris Papagiorgis, Kushagra Gahlot, Loredana Protesescu, Grigorios Itskos","doi":"10.1021/acsphotonics.5c01400","DOIUrl":"https://doi.org/10.1021/acsphotonics.5c01400","url":null,"abstract":"Lead halide perovskite nanocrystals (NCs) exhibit remarkable stimulated emission properties, facilitating efficient optically pumped lasing across the visible spectrum. While their tin-based counterparts do not match such achievements yet, they offer the prospect of a greener, lead-free alternative, also extending access to the important near-infrared region. In this study, we exploit recent advances in the synthesis of colloidal tin halide perovskite nanostructures to fabricate robust layer-by-layer heterostructures composed of CsSnI3 nanocrystals (NCs) and the eco-friendly polymer cellulose acetate (CA). The engineered structures support nanosecond-pumped amplified spontaneous emission (ASE), exhibiting a threshold as low as 870 μJ/cm2 and a net modal gain of up to 25 cm–1. The alternating NC–polymer film architecture not only enhances optical waveguiding within the high-refractive-index CsSnI3 layers, but also enables uniform active layer formation through sequential thin-film deposition, in contrast to disordered thick NC films that sustain ASE only at cryogenic temperatures. This approach presents a promising pathway toward the realization of practical, lead-free perovskite-based laser technologies.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"94 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145283818","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}

引用次数: 0

On the average-case complexity of learning output distributions of quantum circuits 量子电路学习输出分布的平均情况复杂度

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-10-13 DOI: 10.22331/q-2025-10-13-1883

Alexander Nietner, Marios Ioannou, Ryan Sweke, Richard Kueng, Jens Eisert, Marcel Hinsche, Jonas Haferkamp

{"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: – 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. – 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. – 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. 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}

引用次数: 0

Cosmological consequences of varying couplings in gravity action 引力作用中不同耦合的宇宙学结果

IF 6.4 2区物理与天体物理

Journal of Cosmology and Astroparticle Physics Pub Date : 2025-10-13 DOI: 10.1088/1475-7516/2025/10/048

Sandipan Sengupta

引用次数: 0

From kinetic gases to an exponentially expanding universe — the Finsler-Friedmann equation 从动能气体到指数膨胀的宇宙——芬斯勒-弗里德曼方程

IF 6.4 2区物理与天体物理

Journal of Cosmology and Astroparticle Physics Pub Date : 2025-10-13 DOI: 10.1088/1475-7516/2025/10/050

Christian Pfeifer, Nicoleta Voicu, Annamária Friedl-Szász and Elena Popovici-Popescu

{"title":"From kinetic gases to an exponentially expanding universe — the Finsler-Friedmann equation","authors":"Christian Pfeifer, Nicoleta Voicu, Annamária Friedl-Szász and Elena Popovici-Popescu","doi":"10.1088/1475-7516/2025/10/050","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/10/050","url":null,"abstract":"We investigate the gravitational field of a kinetic gas beyond its standard derivation from the second moment of the one-particle distribution function (1PDF), which typically serves as the energy-momentum tensor in the Einstein equations. This standard procedure raises an important question: why do the other moments of the 1PDF (which are needed to fully characterize the kinematical properties of the gas) not contribute to the gravitational field? Moreover, could these moments be relevant in addressing the dark energy problem? Using the canonical coupling of the full 1PDF to Finsler spacetime geometry via the Finsler gravity equation, we show that in general all moments contribute non-trivially. We derive the Finsler gravity equation in homogeneous and isotropic symmetry in conformal time — dubbed the Finsler-Friedmann equation — which determines both the scale factor and the causal structure dynamically. Remarkably, this equation naturally admits a vacuum solution describing an exponentially expanding spacetime, without requiring a cosmological constant or any additional quantities. The resulting causal structure is a mild deformation of the one of Friedmann-Lemaître-Robertson-Walker (FLRW) geometry; close to the rest frame defined by cosmological time (i.e. for slowly moving objects), the causal structures of the two geometries are nearly indistinguishable.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"11 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282902","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}

引用次数: 0

Tuning exciton binding and photoabsorption in vacancy-ordered halide double perovskites Rb2ZrX6 (X = Cl, Br, I) 空位有序卤化物双钙钛矿Rb2ZrX6 （X = Cl, Br， I）的激子结合和光吸收调谐

IF 4 2区物理与天体物理

Applied Physics Letters Pub Date : 2025-10-13 DOI: 10.1063/5.0281038

Il-Chol Ri, Myong Choe, Suk-Gyong Hwang, Chol-Jun Yu

{"title":"Tuning exciton binding and photoabsorption in vacancy-ordered halide double perovskites Rb2ZrX6 (X = Cl, Br, I)","authors":"Il-Chol Ri, Myong Choe, Suk-Gyong Hwang, Chol-Jun Yu","doi":"10.1063/5.0281038","DOIUrl":"https://doi.org/10.1063/5.0281038","url":null,"abstract":"Vacancy-ordered halide double perovskites (VHDPs) have emerged as a promising candidate for broadband luminescence, but the underlying mechanism remains obscure. Here, we report a study of quasiparticle band structures and excitonic properties under the lattice strain of Rb2ZrX6 (X = Cl, Br, I) using G0W0 plus the Bethe–Salpeter equation calculations. Our calculations demonstrate that cubic Rb2ZrX6 have direct bandgaps and large effective masses of electrons and holes, which become smaller for larger halogens. Through the analysis of the photoabsorption spectra, we identify bright and dark excitons blueshifted for smaller halogens, finding a bright exciton at 4.96 eV in agreement with the experimental optical bandgap for Rb2ZrCl6. We find an extremely large exciton binding energy of 1.17 eV for chloride but a much smaller value of 0.22 eV for iodide. Furthermore, compressive strain reduces bandgaps, effective masses, and exciton binding energies, but tensile strain causes an inverse effect, while both strains enhance photoabsorption. Our work highlights an important role of halogen substitution and lattice strain in tuning the optoelectronic properties of VHDPs.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"22 11 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282921","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}

引用次数: 0

Deep-Circuit QAOA Deep-Circuit QAOA

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-10-13 DOI: 10.22331/q-2025-10-13-1882

Gereon Koßmann, Lennart Binkowski, Lauritz van Luijk, Timo Ziegler, René Schwonnek

{"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. 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}

引用次数: 0

物理与天体物理最新文献