Pub Date : 2024-03-05DOI: 10.1088/2399-6528/ad2b8c
Yuma Hirakui, Takahiro Yajima
In this study, we discuss Jacobi stability in equilibrium and nonequilibrium regions for a first-order one-dimensional system using deviation curvatures. The deviation curvature is calculated using the Kosambi-Cartan-Chern theory, which is applied to second-order differential equations. The deviation curvatures of the first-order one-dimensional differential equations are calculated using two methods as follows. Method 1 is only differentiating both sides of the equation. Additionally, Method 2 is differentiating both sides of the equation and then substituting the original equation into the second-order system. From the general form of the deviation curvatures calculated using each method, the analytical results are obtained as (A), (B), and (C). (A) Equilibrium points are Jacobi unstable for both methods; however, the type of equilibrium points is different. In Method 1, the equilibrium point is a nonisolated fixed point. Conversely, the equilibrium point is a saddle point in Method 2. (B) When there is a Jacobi stable region, the size of the Jacobi stable region in the Method 1 is different from that in Method 2. Especially, the Jacobi stable region in Method 1 is always larger than that in Method 2. (C) When there are multiple equilibrium points, the Jacobi stable region always exists in the nonequilibrium region located between the equilibrium points. These results are confirmed numerically using specific dynamical systems, which are given by the logistic equation and its evolution equation with the Hill function. From the results of (A) and (B), differences in types of equilibrium points affect the size of the Jacobi stable region. From (C), the Jacobi stable regions appear as nonequilibrium regions where the equations cannot be linearized.
{"title":"Application of Jacobi stability analysis to a first-order dynamical system: relation between nonlinearizability of one-dimensional differential equation and Jacobi stable region","authors":"Yuma Hirakui, Takahiro Yajima","doi":"10.1088/2399-6528/ad2b8c","DOIUrl":"https://doi.org/10.1088/2399-6528/ad2b8c","url":null,"abstract":"In this study, we discuss Jacobi stability in equilibrium and nonequilibrium regions for a first-order one-dimensional system using deviation curvatures. The deviation curvature is calculated using the Kosambi-Cartan-Chern theory, which is applied to second-order differential equations. The deviation curvatures of the first-order one-dimensional differential equations are calculated using two methods as follows. Method 1 is only differentiating both sides of the equation. Additionally, Method 2 is differentiating both sides of the equation and then substituting the original equation into the second-order system. From the general form of the deviation curvatures calculated using each method, the analytical results are obtained as (A), (B), and (C). (A) Equilibrium points are Jacobi unstable for both methods; however, the type of equilibrium points is different. In Method 1, the equilibrium point is a nonisolated fixed point. Conversely, the equilibrium point is a saddle point in Method 2. (B) When there is a Jacobi stable region, the size of the Jacobi stable region in the Method 1 is different from that in Method 2. Especially, the Jacobi stable region in Method 1 is always larger than that in Method 2. (C) When there are multiple equilibrium points, the Jacobi stable region always exists in the nonequilibrium region located between the equilibrium points. These results are confirmed numerically using specific dynamical systems, which are given by the logistic equation and its evolution equation with the Hill function. From the results of (A) and (B), differences in types of equilibrium points affect the size of the Jacobi stable region. From (C), the Jacobi stable regions appear as nonequilibrium regions where the equations cannot be linearized.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140312030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-16DOI: 10.1088/2399-6528/ad2a41
Kevin Ndang Amassa, A. J. Etindele, D. H. Douma, S. Kenmoe, Chetty Nithaya
Based on density functional theory, we studied the effect of p- and n-type doping on the structural and electronic properties of MoO2 monolayers and bilayers. We used niobium (Nb) and nitrogen (N) as p-type dopants, and technetium (Tc) and fluorine (F) as n-type dopants through atomic substitutions. Our study shows that the presence of a substituent in the 4 × 4 supercell of MoO2 leads to a slight distortion and negligible modification of the lattice parameter. Both p- and n-type doped monolayers exhibit a metallic character. The bilayers obtained by vertically stacking n-p doped monolayers all exhibit a metallic character, as their band diagrams do not show a band gap. The study of their charge difference highlights a physisorption phenomenon. This type of material, which features a nucleophilic site in the p-doped region and an electrophilic site in the n-doped region, is a promising candidate for catalysis. When n-type and p-type doped monolayers are horizontally joined, the resulting stack exhibits a semi- conductor behavior.The special feature of this stacking is that we obtain a true pn junction, that is a space charge zone associated with a potential jump. For its application in infrared junction diodes, we have demonstrated both quantitatively and qualitatively the existence of a potential jump at the junction.
基于密度泛函理论，我们研究了p型和n型掺杂对二氧化硅单层和双层的结构和电子特性的影响。通过原子置换，我们使用铌（Nb）和氮（N）作为 p 型掺杂剂，使用锝（Tc）和氟（F）作为 n 型掺杂剂。我们的研究表明，在二氧化硅的 4 × 4 超胞中存在取代基会导致轻微的畸变，对晶格参数的改变可以忽略不计。p型和n型掺杂单层都表现出金属特性。通过垂直堆叠 n-p 掺杂单层获得的双层膜都表现出金属特性，因为它们的带图没有显示带隙。对其电荷差的研究凸显了一种物理吸附现象。这类材料在 p 掺杂区具有亲核位点，在 n 掺杂区具有亲电位点，是一种很有前景的催化候选材料。当 n 型和 p 型掺杂单层水平连接时，所产生的叠层表现出半导体行为。这种叠层的特殊之处在于我们获得了真正的 pn 结，即与电位跃迁相关的空间电荷区。为了将其应用于红外结二极管，我们从定量和定性两方面证明了结点处电位跃迁的存在。
{"title":"Ab initio study of p- and n-type doping of two-dimensional MoO2: investigation of a pn-homojunction","authors":"Kevin Ndang Amassa, A. J. Etindele, D. H. Douma, S. Kenmoe, Chetty Nithaya","doi":"10.1088/2399-6528/ad2a41","DOIUrl":"https://doi.org/10.1088/2399-6528/ad2a41","url":null,"abstract":"\u0000 Based on density functional theory, we studied the effect of p- and n-type doping on the structural and electronic properties of MoO2 monolayers and bilayers. We used niobium (Nb) and nitrogen (N) as p-type dopants, and technetium (Tc) and fluorine (F) as n-type dopants through atomic substitutions. Our study shows that the presence of a substituent in the 4 × 4 supercell of MoO2 leads to a slight distortion and negligible modification of the lattice parameter. Both p- and n-type doped monolayers exhibit a metallic character. The bilayers obtained by vertically stacking n-p doped monolayers all exhibit a metallic character, as their band diagrams do not show a band gap. The study of their charge difference highlights a physisorption phenomenon. This type of material, which features a nucleophilic site in the p-doped region and an electrophilic site in the n-doped region, is a promising candidate for catalysis. When n-type and p-type doped monolayers are horizontally joined, the resulting stack exhibits a semi- conductor behavior.The special feature of this stacking is that we obtain a true pn junction, that is a space charge zone associated with a potential jump. For its application in infrared junction diodes, we have demonstrated both quantitatively and qualitatively the existence of a potential jump at the junction.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139960341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-12DOI: 10.1088/2399-6528/ad246d
Nils Mengel, Marius Welzel, Woldemar Niedenthal, Markus Stein, Dominik Heider, Sangam Chatterjee
Handling and storing the immense amounts of data native to the information age is a major challenge in terms of technological sustainability and energy demand. To date, tape storage remains the most widespread method for data archiving, while DNA data storage appears to offer the best data density and long-term stability in the future. However, DNA data storage is still in its infancy primarily due to economic and accessibility challenges. This emphasizes the need for more practical and readily available alternatives. We present a method for data storage utilizing inkjet printable quantum dots on paper with photoluminescence (PL) readout. Our proof of principle study showcases the ability to print and stack multiple bits of data on a single spot by exploiting the unique PL properties of quantum dots. This approach utilizes easily accessible resources, including a consumer-grade printer and paper as the substrate. Additionally, we perform initial stability tests, investigate scalability by controlling emission intensity, and evaluate the potential data density achievable by our approach.
处理和存储信息时代的海量数据是技术可持续性和能源需求方面的一大挑战。迄今为止，磁带存储仍是最普遍的数据存档方法，而 DNA 数据存储似乎在未来能提供最佳的数据密度和长期稳定性。然而，DNA 数据存储仍处于起步阶段，这主要是由于经济和可访问性方面的挑战。因此，我们需要更实用、更容易获得的替代品。我们提出了一种在纸上利用可喷墨打印量子点和光致发光（PL）读出进行数据存储的方法。我们的原理验证研究展示了利用量子点独特的光致发光特性在一个点上打印和堆叠多比特数据的能力。这种方法利用了容易获得的资源，包括消费级打印机和作为基底的纸张。此外，我们还进行了初步的稳定性测试，通过控制发射强度研究了可扩展性，并评估了我们的方法所能达到的潜在数据密度。
{"title":"Inkjet-printed quantum dots on paper as concept towards high-density long-term data storage","authors":"Nils Mengel, Marius Welzel, Woldemar Niedenthal, Markus Stein, Dominik Heider, Sangam Chatterjee","doi":"10.1088/2399-6528/ad246d","DOIUrl":"https://doi.org/10.1088/2399-6528/ad246d","url":null,"abstract":"Handling and storing the immense amounts of data native to the information age is a major challenge in terms of technological sustainability and energy demand. To date, tape storage remains the most widespread method for data archiving, while DNA data storage appears to offer the best data density and long-term stability in the future. However, DNA data storage is still in its infancy primarily due to economic and accessibility challenges. This emphasizes the need for more practical and readily available alternatives. We present a method for data storage utilizing inkjet printable quantum dots on paper with photoluminescence (PL) readout. Our proof of principle study showcases the ability to print and stack multiple bits of data on a single spot by exploiting the unique PL properties of quantum dots. This approach utilizes easily accessible resources, including a consumer-grade printer and paper as the substrate. Additionally, we perform initial stability tests, investigate scalability by controlling emission intensity, and evaluate the potential data density achievable by our approach.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139767864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electron density of two-electron systems, He and H2, was analyzed when prolate spheroids with hard walls confine these systems. For this purpose, Hartree–Fock equations were solved using Roothaan's approach with a basis set defined in prolate spheroidal coordinates imposing Dirichlet boundary conditions. Total energy, its components, and orbital energies were analyzed for several confinements, and some of these results were compared with those reported by other authors to test the performance of the proposed approach. For both systems, the electron density exhibits a maximum value out of the nuclear region for extreme confinements. The chemical bond for H2 was analyzed through the concepts of the quantum theory of atoms in molecules, concluding that the chemical bond of this molecule disappears under extreme conditions. For this system, estimations of the correlation energy indicate that this is a small contribution to the total energy, and the Hartree–Fock method contains the necessary elements to describe the chemical bond for strong confinements.
{"title":"Electron density analysis of two-electron systems confined by prolate spheroids with hard walls","authors":"Heichi Yanajara-Parra, Adalberto Corella-Madueño, F Adrián Duarte-Alcaraz, Rubicelia Vargas, Jorge Garza","doi":"10.1088/2399-6528/ad246e","DOIUrl":"https://doi.org/10.1088/2399-6528/ad246e","url":null,"abstract":"The electron density of two-electron systems, He and H<sub>2</sub>, was analyzed when prolate spheroids with hard walls confine these systems. For this purpose, Hartree–Fock equations were solved using Roothaan's approach with a basis set defined in prolate spheroidal coordinates imposing Dirichlet boundary conditions. Total energy, its components, and orbital energies were analyzed for several confinements, and some of these results were compared with those reported by other authors to test the performance of the proposed approach. For both systems, the electron density exhibits a maximum value out of the nuclear region for extreme confinements. The chemical bond for H<sub>2</sub> was analyzed through the concepts of the quantum theory of atoms in molecules, concluding that the chemical bond of this molecule disappears under extreme conditions. For this system, estimations of the correlation energy indicate that this is a small contribution to the total energy, and the Hartree–Fock method contains the necessary elements to describe the chemical bond for strong confinements.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139767882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Artificial neural networks can be an important tool to improve the search for admissible string compactifications and characterize them. In this paper we construct the heterotic orbiencoder, a general deep autoencoder to study heterotic orbifold models arising from various Abelian orbifold geometries. Our neural network can be easily trained to successfully encode the large parameter space of many orbifold geometries simultaneously, independently of the statistical dissimilarities of their training features. In particular, we show that our autoencoder is capable of compressing with good accuracy the large parameter space of two promising orbifold geometries in just three parameters. Further, most orbifold models with phenomenologically appealing features appear in bounded regions of this small space. Our results hint towards a possible simplification of the classification of (promising) heterotic orbifold models.
{"title":"An autoencoder for heterotic orbifolds with arbitrary geometry","authors":"Enrique Escalante–Notario, Ignacio Portillo–Castillo, Saúl Ramos–Sánchez","doi":"10.1088/2399-6528/ad246f","DOIUrl":"https://doi.org/10.1088/2399-6528/ad246f","url":null,"abstract":"Artificial neural networks can be an important tool to improve the search for admissible string compactifications and characterize them. In this paper we construct the <monospace>heterotic orbiencoder</monospace>, a general deep autoencoder to study heterotic orbifold models arising from various Abelian orbifold geometries. Our neural network can be easily trained to successfully encode the large parameter space of many orbifold geometries simultaneously, independently of the statistical dissimilarities of their training features. In particular, we show that our autoencoder is capable of compressing with good accuracy the large parameter space of two promising orbifold geometries in just three parameters. Further, most orbifold models with phenomenologically appealing features appear in bounded regions of this small space. Our results hint towards a possible simplification of the classification of (promising) heterotic orbifold models.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139767861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-09DOI: 10.1088/2399-6528/ad27e0
M. Krzystyniak, Giovanni Romanelli, Beata Grabowska, Felix Fernandez-Alonso
This work provides a current, critical view of the application of MAss- selective Neutron SpEctroscopy (MANSE) to nanocomposite materials. MANSE is a unique technique made possible owing to the existence of the pulsed neutron sources. At present, the only operating MANSE spectrometer in the world, VESUVIO, is located at the ISIS Neutron and Muon Source in the UK. We start by providing a brief description of the neutron Compton scattering, the anatomy of a mass-selective neutron spectrometer, and the experimental data treatment. We continue by briefly outlining the main quantum mechanical concepts, models and approximations relevant both to the ab initio prediction and experimental measurement of main MANSE observables. Next, we present several recent exemplars chosen to highlight the use of MANSE in the field of nanocomposites. Our examples include, in chronological order, encapsulated nanoparticles in amorphous silica gel, bioactive glass-ionomer cement, Cu-Ti-C composites, and sodium carboxymethyl starch-based binders in the presence of a mineral matrix. We close by providing our view of the ongoing and future challenges and opportunities in the mass-selective neutron investigation of NQEs in nanocomposite materials.
{"title":"Nanocomposite materials as observed by mass-selective neutron spectroscopy","authors":"M. Krzystyniak, Giovanni Romanelli, Beata Grabowska, Felix Fernandez-Alonso","doi":"10.1088/2399-6528/ad27e0","DOIUrl":"https://doi.org/10.1088/2399-6528/ad27e0","url":null,"abstract":"\u0000 This work provides a current, critical view of the application of MAss- selective Neutron SpEctroscopy (MANSE) to nanocomposite materials. MANSE is a unique technique made possible owing to the existence of the pulsed neutron sources. At present, the only operating MANSE spectrometer in the world, VESUVIO, is located at the ISIS Neutron and Muon Source in the UK. We start by providing a brief description of the neutron Compton scattering, the anatomy of a mass-selective neutron spectrometer, and the experimental data treatment. We continue by briefly outlining the main quantum mechanical concepts, models and approximations relevant both to the ab initio prediction and experimental measurement of main MANSE observables. Next, we present several recent exemplars chosen to highlight the use of MANSE in the field of nanocomposites. Our examples include, in chronological order, encapsulated nanoparticles in amorphous silica gel, bioactive glass-ionomer cement, Cu-Ti-C composites, and sodium carboxymethyl starch-based binders in the presence of a mineral matrix. We close by providing our view of the ongoing and future challenges and opportunities in the mass-selective neutron investigation of NQEs in nanocomposite materials.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139788111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-09DOI: 10.1088/2399-6528/ad27e0
M. Krzystyniak, Giovanni Romanelli, Beata Grabowska, Felix Fernandez-Alonso
This work provides a current, critical view of the application of MAss- selective Neutron SpEctroscopy (MANSE) to nanocomposite materials. MANSE is a unique technique made possible owing to the existence of the pulsed neutron sources. At present, the only operating MANSE spectrometer in the world, VESUVIO, is located at the ISIS Neutron and Muon Source in the UK. We start by providing a brief description of the neutron Compton scattering, the anatomy of a mass-selective neutron spectrometer, and the experimental data treatment. We continue by briefly outlining the main quantum mechanical concepts, models and approximations relevant both to the ab initio prediction and experimental measurement of main MANSE observables. Next, we present several recent exemplars chosen to highlight the use of MANSE in the field of nanocomposites. Our examples include, in chronological order, encapsulated nanoparticles in amorphous silica gel, bioactive glass-ionomer cement, Cu-Ti-C composites, and sodium carboxymethyl starch-based binders in the presence of a mineral matrix. We close by providing our view of the ongoing and future challenges and opportunities in the mass-selective neutron investigation of NQEs in nanocomposite materials.
{"title":"Nanocomposite materials as observed by mass-selective neutron spectroscopy","authors":"M. Krzystyniak, Giovanni Romanelli, Beata Grabowska, Felix Fernandez-Alonso","doi":"10.1088/2399-6528/ad27e0","DOIUrl":"https://doi.org/10.1088/2399-6528/ad27e0","url":null,"abstract":"\u0000 This work provides a current, critical view of the application of MAss- selective Neutron SpEctroscopy (MANSE) to nanocomposite materials. MANSE is a unique technique made possible owing to the existence of the pulsed neutron sources. At present, the only operating MANSE spectrometer in the world, VESUVIO, is located at the ISIS Neutron and Muon Source in the UK. We start by providing a brief description of the neutron Compton scattering, the anatomy of a mass-selective neutron spectrometer, and the experimental data treatment. We continue by briefly outlining the main quantum mechanical concepts, models and approximations relevant both to the ab initio prediction and experimental measurement of main MANSE observables. Next, we present several recent exemplars chosen to highlight the use of MANSE in the field of nanocomposites. Our examples include, in chronological order, encapsulated nanoparticles in amorphous silica gel, bioactive glass-ionomer cement, Cu-Ti-C composites, and sodium carboxymethyl starch-based binders in the presence of a mineral matrix. We close by providing our view of the ongoing and future challenges and opportunities in the mass-selective neutron investigation of NQEs in nanocomposite materials.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139848158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-08DOI: 10.1088/2399-6528/ad22e5
Yunwei Lu, Sandeep Joshi, Vinh San Dinh, Jens Koch
Gradient Ascent Pulse Engineering (GRAPE) is a popular technique in quantum optimal control, and can be combined with automatic differentiation (AD) to facilitate on-the-fly evaluation of cost-function gradients. We illustrate that the convenience of AD comes at a significant memory cost due to the cumulative storage of a large number of states and propagators. For quantum systems of increasing Hilbert space size, this imposes a significant bottleneck. We revisit the strategy of hard-coding gradients in a scheme that fully avoids propagator storage and significantly reduces memory requirements. Separately, we present improvements to numerical state propagation to enhance runtime performance. We benchmark runtime and memory usage and compare this approach to AD-based implementations, with a focus on pushing towards larger Hilbert space sizes. The results confirm that the AD-free approach facilitates the application of optimal control for large quantum systems which would otherwise be difficult to tackle.
梯度上升脉冲工程（GRAPE）是量子优化控制领域的一种流行技术，它可以与自动微分（AD）相结合，以方便对代价函数梯度进行即时评估。我们的研究表明，自动微分的便利性需要付出巨大的内存代价，因为需要累积存储大量的状态和传播者。对于希尔伯特空间大小不断增大的量子系统来说，这是一个显著的瓶颈。我们重新审视了硬编码梯度的策略，该方案完全避免了传播者的存储，并显著降低了内存需求。另外，我们对数值状态传播进行了改进，以提高运行时性能。我们对运行时间和内存使用情况进行了基准测试，并将这种方法与基于 AD 的实现方法进行了比较，重点是向更大的希尔伯特空间尺寸推进。结果证实，无 AD 方法促进了大型量子系统最优控制的应用，否则很难解决这些问题。
{"title":"Optimal control of large quantum systems: assessing memory and runtime performance of GRAPE","authors":"Yunwei Lu, Sandeep Joshi, Vinh San Dinh, Jens Koch","doi":"10.1088/2399-6528/ad22e5","DOIUrl":"https://doi.org/10.1088/2399-6528/ad22e5","url":null,"abstract":"Gradient Ascent Pulse Engineering (GRAPE) is a popular technique in quantum optimal control, and can be combined with automatic differentiation (AD) to facilitate on-the-fly evaluation of cost-function gradients. We illustrate that the convenience of AD comes at a significant memory cost due to the cumulative storage of a large number of states and propagators. For quantum systems of increasing Hilbert space size, this imposes a significant bottleneck. We revisit the strategy of hard-coding gradients in a scheme that fully avoids propagator storage and significantly reduces memory requirements. Separately, we present improvements to numerical state propagation to enhance runtime performance. We benchmark runtime and memory usage and compare this approach to AD-based implementations, with a focus on pushing towards larger Hilbert space sizes. The results confirm that the AD-free approach facilitates the application of optimal control for large quantum systems which would otherwise be difficult to tackle.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139767880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-07DOI: 10.1088/2399-6528/ad1f73
Eemeli A Eronen, Anton Vladyka, Florent Gerbon, Christoph J Sahle, Johannes Niskanen
We apply a recently developed technique utilizing machine learning for statistical analysis of computational nitrogen K-edge spectra of aqueous triglycine. This method, the emulator-based component analysis, identifies spectrally relevant structural degrees of freedom from a data set filtering irrelevant ones out. Thus tremendous reduction in the dimensionality of the ill-posed nonlinear inverse problem of spectrum interpretation is achieved. Structural and spectral variation across the sampled phase space is notable. Using these data, we train a neural network to predict the intensities of spectral regions of interest from the structure. These regions are defined by the temperature-difference profile of the simulated spectra, and the analysis yields a structural interpretation for their behavior. Even though the utilized local many-body tensor representation implicitly encodes the secondary structure of the peptide, our approach proves that this information is irrecoverable from the spectra. A hard x-ray Raman scattering experiment confirms the overall sensibility of the simulated spectra, but the predicted temperature-dependent effects therein remain beyond the achieved statistical confidence level.
我们将最近开发的机器学习技术应用于三甘氨酸水溶液的计算氮 K 边光谱的统计分析。这种基于仿真器的成分分析方法能从数据集中识别出与光谱相关的结构自由度，过滤掉不相关的自由度。这样就大大降低了光谱解释的非线性逆问题的维度。整个采样相空间的结构和频谱变化非常明显。利用这些数据，我们训练了一个神经网络，以从结构中预测感兴趣光谱区域的强度。这些区域是由模拟光谱的温差曲线定义的，分析得出了对其行为的结构解释。尽管所利用的局部多体张量表示法隐含了多肽的二级结构，但我们的方法证明了这一信息是无法从光谱中恢复的。硬 X 射线拉曼散射实验证实了模拟光谱的整体灵敏度，但其中预测的温度效应仍然超出了统计置信水平。
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Pub Date : 2024-02-02DOI: 10.1088/2399-6528/ad2560
R. Rajaram, N. Ritchey, Brian C. Castellani
The current paper is part of a series exploring how to link diversity measures (e.g., Gini-Simpson index, Shannon entropy, Hill numbers) to a distribution's original shape and to compare parts of a distribution, in terms of diversity, with the whole. This linkage is crucial to understanding the exact relationship between the density of an original probability distribution, denoted by $p(x)$, and the diversity $D$ in non-uniform distributions, both within parts of a distribution and the whole. This linkage is empirically useful because most real-world systems have unequal distributions and consist of multiple diversity types with unknown and changing frequencies at different levels of scale (e.g., income diversity, economic complexity indices, rankings). To date, we have proven our results for discrete distributions. Our focus here is continuous distributions. In both instances, we do so by linking case-based entropy, a diversity approach we developed, to a probability distribution’s shape for continuous distributions. This allows us to demonstrate that the original probability distribution $g_1$, the case-based entropy curve $g_2$, and the slope of diversity $g_3$ ($c_{(a,x)}$ versus the $c_{(a,x)}* ln A_{(a,x)}$ curve) are one-to-one (or injective). In other words, a different probability distribution $g_1$, results in different curves for $g_2$, and $g_3$. Therefore, a different permutation of the original probability distribution (resulting in a different shape) will uniquely determine the graphs $g_2$ and $g_3$. By proving our approach’s injective nature for continuous distributions, we establish a unique method to measure the degree of uniformity as measured by $D/c$ and show a unique way to compute $D/c$ for various shapes of the original continuous distribution to compare different distributions and their parts.
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