Pub Date : 2024-07-10DOI: 10.1088/1367-2630/ad5df0
Yangzhe Guo, Jing Li and Yurui Fang
In recent years, research on the interaction between orbital angular momentum (OAM) of light and matter has shown a continuous influx of investigations. OAM possesses distinct properties, such as a degree of freedom with multiple states, vortex characteristics, and topological properties, which expand its applications in optical communication, optical sensing, and optical manipulation. We have observed different phenomena in the chiral metal windmill structure under excitation of spin angular momentum (SAM)-OAM beam generated by Q-plate than under SAM excitation. Fourier back focal plane (FBP) imaging under SAM beam excitation easily identifies the chirality and geometric properties of the structure. When the SAM-OAM beam excites the structure, FBP not only identifies its chirality and geometric properties but also distinguishes different OAM topological charges and signs, as well as the degree of elliptic polarization. The Stokes parametric FBP imaging reveals asymmetric polarization distribution resulting from the interaction between a vortex beam and the chiral structure. Moreover, it clearly reflects the conversion process of SAM to OAM. The experimental results match well with simulation results. These findings hold valuable insights for the advancement of optical information storage and communication using OAM, opening up new possibilities for further exploration in this field.
近年来，有关光的轨道角动量（OAM）与物质之间相互作用的研究不断涌现。轨道角动量具有多态自由度、涡旋特性和拓扑特性等独特性质，拓展了其在光通信、光传感和光操纵等领域的应用。我们观察到手性金属风车结构在 Q 板产生的自旋角动量（SAM）-OAM 光束激发下与 SAM 激发下的不同现象。在 SAM 光束激发下的傅立叶后焦平面（FBP）成像很容易识别结构的手性和几何特性。当 SAM-OAM 光束激发结构时，FBP 不仅能识别其手性和几何特性，还能区分不同的 OAM 拓扑电荷和符号以及椭圆极化程度。斯托克斯参数 FBP 成像揭示了涡流束与手性结构相互作用产生的不对称极化分布。此外，它还清楚地反映了从 SAM 到 OAM 的转换过程。实验结果与模拟结果非常吻合。这些发现为利用 OAM 推动光信息存储和通信提供了宝贵的见解，为这一领域的进一步探索开辟了新的可能性。
{"title":"Distinguishing the topological charge of vortex beam via Fourier back plane imaging with chiral windmill structure","authors":"Yangzhe Guo, Jing Li and Yurui Fang","doi":"10.1088/1367-2630/ad5df0","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5df0","url":null,"abstract":"In recent years, research on the interaction between orbital angular momentum (OAM) of light and matter has shown a continuous influx of investigations. OAM possesses distinct properties, such as a degree of freedom with multiple states, vortex characteristics, and topological properties, which expand its applications in optical communication, optical sensing, and optical manipulation. We have observed different phenomena in the chiral metal windmill structure under excitation of spin angular momentum (SAM)-OAM beam generated by Q-plate than under SAM excitation. Fourier back focal plane (FBP) imaging under SAM beam excitation easily identifies the chirality and geometric properties of the structure. When the SAM-OAM beam excites the structure, FBP not only identifies its chirality and geometric properties but also distinguishes different OAM topological charges and signs, as well as the degree of elliptic polarization. The Stokes parametric FBP imaging reveals asymmetric polarization distribution resulting from the interaction between a vortex beam and the chiral structure. Moreover, it clearly reflects the conversion process of SAM to OAM. The experimental results match well with simulation results. These findings hold valuable insights for the advancement of optical information storage and communication using OAM, opening up new possibilities for further exploration in this field.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"18 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141585943","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}
Pub Date : 2024-07-10DOI: 10.1088/1367-2630/ad5eb0
Jayanth Jayakumar, Monika E Mycroft, Marco Barbieri and Magdalena Stobińska
Accurate phase estimation in the presence of unknown phase diffusive noise is a crucial yet challenging task in noisy quantum metrology. This problem is particularly interesting due to the detrimental impact of the associated noise. Here, we investigate the joint estimation of phase and phase diffusion using generalized Holland–Burnett states, known for their experimental accessibility. These states provide performance close to the optimal state in single-parameter phase estimation, even in the presence of photon losses. We adopt a twofold approach by analyzing the joint information extraction through the double homodyne measurement and the joint information availability across all probe states. Through our analysis, we find that the highest sensitivities are obtained by using states created by directing all input photons into one port of a balanced beam splitter. Furthermore, we infer that good levels of sensitivity persist even in the presence of moderate photon losses, illustrating the remarkable resilience of our probe states under lossy conditions.
{"title":"Quantum-enhanced joint estimation of phase and phase diffusion","authors":"Jayanth Jayakumar, Monika E Mycroft, Marco Barbieri and Magdalena Stobińska","doi":"10.1088/1367-2630/ad5eb0","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5eb0","url":null,"abstract":"Accurate phase estimation in the presence of unknown phase diffusive noise is a crucial yet challenging task in noisy quantum metrology. This problem is particularly interesting due to the detrimental impact of the associated noise. Here, we investigate the joint estimation of phase and phase diffusion using generalized Holland–Burnett states, known for their experimental accessibility. These states provide performance close to the optimal state in single-parameter phase estimation, even in the presence of photon losses. We adopt a twofold approach by analyzing the joint information extraction through the double homodyne measurement and the joint information availability across all probe states. Through our analysis, we find that the highest sensitivities are obtained by using states created by directing all input photons into one port of a balanced beam splitter. Furthermore, we infer that good levels of sensitivity persist even in the presence of moderate photon losses, illustrating the remarkable resilience of our probe states under lossy conditions.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"17 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141585718","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}
Pub Date : 2024-07-10DOI: 10.1088/1367-2630/ad5df1
Vladlen Galetsky, Pol Julià Farré, Soham Ghosh, Christian Deppe and Roberto Ferrara
In this work, we present two new methods for variational quantum circuit (VQC) process tomography (PT) onto n qubits systems: unitary PT based on VQCs (PT_VQC) and unitary evolution-based variational quantum singular value decomposition (U-VQSVD). Compared to the state of the art, PT_VQC halves in each run the required amount of qubits for unitary PT and decreases the required state initializations from 4n to just 2n, all while ensuring high-fidelity reconstruction of the targeted unitary channel U. It is worth noting that, for a fixed reconstruction accuracy, PT_VQC achieves faster convergence per iteration step compared to quantum deep neural network and tensor network schemes. The novel U-VQSVD algorithm utilizes variational singular value decomposition to extract eigenvectors (up to a global phase) and their associated eigenvalues from an unknown unitary representing a universal channel. We assess the performance of U-VQSVD by executing an attack on a non-unitary channel quantum physical unclonable function. By using U-VQSVD we outperform an uninformed impersonation attack (using randomly generated input states) by a factor of 2 to 5, depending on the qubit dimension. For the two presented methods, we propose a new approach to calculate the complexity of the displayed VQC, based on what we denote as optimal depth.
{"title":"Optimal depth and a novel approach to variational unitary quantum process tomography","authors":"Vladlen Galetsky, Pol Julià Farré, Soham Ghosh, Christian Deppe and Roberto Ferrara","doi":"10.1088/1367-2630/ad5df1","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5df1","url":null,"abstract":"In this work, we present two new methods for variational quantum circuit (VQC) process tomography (PT) onto n qubits systems: unitary PT based on VQCs (PT_VQC) and unitary evolution-based variational quantum singular value decomposition (U-VQSVD). Compared to the state of the art, PT_VQC halves in each run the required amount of qubits for unitary PT and decreases the required state initializations from 4n to just 2n, all while ensuring high-fidelity reconstruction of the targeted unitary channel U. It is worth noting that, for a fixed reconstruction accuracy, PT_VQC achieves faster convergence per iteration step compared to quantum deep neural network and tensor network schemes. The novel U-VQSVD algorithm utilizes variational singular value decomposition to extract eigenvectors (up to a global phase) and their associated eigenvalues from an unknown unitary representing a universal channel. We assess the performance of U-VQSVD by executing an attack on a non-unitary channel quantum physical unclonable function. By using U-VQSVD we outperform an uninformed impersonation attack (using randomly generated input states) by a factor of 2 to 5, depending on the qubit dimension. For the two presented methods, we propose a new approach to calculate the complexity of the displayed VQC, based on what we denote as optimal depth.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"17 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141586282","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}
Pub Date : 2024-07-10DOI: 10.1088/1367-2630/ad5d84
M Sauppe, T Bischoff, C Bomme, C Bostedt, A Colombo, B Erk, T Feigl, L Flückiger, T Gorkhover, A Heilrath, K Kolatzki, Y Kumagai, B Langbehn, J P Müller, C Passow, D Ramm, D Rolles, D Rompotis, J Schäfer-Zimmermann, B Senfftleben, R Treusch, A Ulmer, J Zimbalski, T Möller and D Rupp
Because of their high photon flux, x-ray free-electron lasers (FEL) allow to resolve the structure of individual nanoparticles via coherent diffractive imaging (CDI) within a single x-ray pulse. Since the inevitable rapid destruction of the sample limits the achievable resolution, a thorough understanding of the spatiotemporal evolution of matter on the nanoscale following the irradiation is crucial. We present a technique to track x-ray induced structural changes in time and space by recording two consecutive diffraction patterns of the same single, free-flying nanoparticle, acquired separately on two large-area detectors opposite to each other, thus examining both the initial and evolved particle structure. We demonstrate the method at the extreme ultraviolet (XUV) and soft x-ray Free-electron LASer in Hamburg (FLASH), investigating xenon clusters as model systems. By splitting a single XUV pulse, two diffraction patterns from the same particle can be obtained. For focus intensities of about W cm−2 we observe still largely intact clusters even at the longest delays of up to 650 picoseconds of the second pulse, indicating that in the highly absorbing systems the damage remains confined to one side of the cluster. Instead, in case of five times higher flux, the diffraction patterns show clear signatures of disintegration, namely increased diameters and density fluctuations in the fragmenting clusters. Future improvements to the accessible range of dynamics and time resolution of the approach are discussed.
由于 X 射线自由电子激光器（FEL）具有高光子通量，因此可以在单个 X 射线脉冲内通过相干衍射成像（CDI）解析单个纳米粒子的结构。由于样品不可避免的快速破坏限制了可实现的分辨率，因此透彻了解辐照后纳米尺度物质的时空演变至关重要。我们提出了一种在时间和空间上跟踪 X 射线诱导的结构变化的技术，即在两个相对的大面积探测器上分别记录同一单个自由飞行纳米粒子的两个连续衍射图样，从而检查粒子的初始结构和演变结构。我们在汉堡的极紫外（XUV）和软 X 射线自由电子激光仪（FLASH）上演示了这种方法，并将氙簇作为模型系统进行了研究。通过分离单个 XUV 脉冲，可以获得同一粒子的两种衍射图样。在聚焦强度约为 W cm-2 的情况下，即使第二个脉冲的延迟时间最长达 650 皮秒，我们也能观察到基本完好无损的星团，这表明在高吸收系统中，损伤仍局限于星团的一侧。相反，在通量高出五倍的情况下，衍射图样显示出明显的解体特征，即直径增大和碎片星团的密度波动。本文讨论了该方法在动态范围和时间分辨率方面的未来改进。
{"title":"Double diffraction imaging of x-ray induced structural dynamics in single free nanoparticles","authors":"M Sauppe, T Bischoff, C Bomme, C Bostedt, A Colombo, B Erk, T Feigl, L Flückiger, T Gorkhover, A Heilrath, K Kolatzki, Y Kumagai, B Langbehn, J P Müller, C Passow, D Ramm, D Rolles, D Rompotis, J Schäfer-Zimmermann, B Senfftleben, R Treusch, A Ulmer, J Zimbalski, T Möller and D Rupp","doi":"10.1088/1367-2630/ad5d84","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5d84","url":null,"abstract":"Because of their high photon flux, x-ray free-electron lasers (FEL) allow to resolve the structure of individual nanoparticles via coherent diffractive imaging (CDI) within a single x-ray pulse. Since the inevitable rapid destruction of the sample limits the achievable resolution, a thorough understanding of the spatiotemporal evolution of matter on the nanoscale following the irradiation is crucial. We present a technique to track x-ray induced structural changes in time and space by recording two consecutive diffraction patterns of the same single, free-flying nanoparticle, acquired separately on two large-area detectors opposite to each other, thus examining both the initial and evolved particle structure. We demonstrate the method at the extreme ultraviolet (XUV) and soft x-ray Free-electron LASer in Hamburg (FLASH), investigating xenon clusters as model systems. By splitting a single XUV pulse, two diffraction patterns from the same particle can be obtained. For focus intensities of about W cm−2 we observe still largely intact clusters even at the longest delays of up to 650 picoseconds of the second pulse, indicating that in the highly absorbing systems the damage remains confined to one side of the cluster. Instead, in case of five times higher flux, the diffraction patterns show clear signatures of disintegration, namely increased diameters and density fluctuations in the fragmenting clusters. Future improvements to the accessible range of dynamics and time resolution of the approach are discussed.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"78 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141585717","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}
Pub Date : 2024-07-09DOI: 10.1088/1367-2630/ad5756
Bharti Bhoy, Paul Stevenson
This study presents a simulated quantum computing approach for the investigation into the shell-model energy levels of 58Ni through the application of the variational quantum eigensolver (VQE) method in combination with a problem-specific ansatz. The primary objective is to achieve a fully accurate low-lying energy spectrum of 58Ni. The chosen isotope, 58Ni is particularly interesting in nuclear physics through its role in astrophysical reactions while also being a simple but non-trivial nucleus for shell-model study, it being two particles outside a closed shell. Our ansatz, along with the VQE method are shown to be able to reproduce exact energy values for the ground state and first and second excited states. We compare a classical shell model code, the values obtained by diagonalization of the Hamiltonian after qubit mapping, and a noiseless simulated ansatz+VQE simulation. The exact agreement between classical and qubit-mapped diagonalization shows the correctness of our method, and the high accuracy of the simulation means that the ansatz is suitable to allow a full reconstruction of the full nuclear wave function.
{"title":"Shell-model study of 58Ni using quantum computing algorithm","authors":"Bharti Bhoy, Paul Stevenson","doi":"10.1088/1367-2630/ad5756","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5756","url":null,"abstract":"This study presents a simulated quantum computing approach for the investigation into the shell-model energy levels of <sup>58</sup>Ni through the application of the variational quantum eigensolver (VQE) method in combination with a problem-specific ansatz. The primary objective is to achieve a fully accurate low-lying energy spectrum of <sup>58</sup>Ni. The chosen isotope, <sup>58</sup>Ni is particularly interesting in nuclear physics through its role in astrophysical reactions while also being a simple but non-trivial nucleus for shell-model study, it being two particles outside a closed shell. Our ansatz, along with the VQE method are shown to be able to reproduce exact energy values for the ground state and first and second excited states. We compare a classical shell model code, the values obtained by diagonalization of the Hamiltonian after qubit mapping, and a noiseless simulated ansatz+VQE simulation. The exact agreement between classical and qubit-mapped diagonalization shows the correctness of our method, and the high accuracy of the simulation means that the ansatz is suitable to allow a full reconstruction of the full nuclear wave function.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"18 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568044","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}
Pub Date : 2024-07-09DOI: 10.1088/1367-2630/ad5b13
Raja Yehia, Matteo Schiavon, Valentina Marulanda Acosta, Tim Coopmans, Iordanis Kerenidis, David Elkouss, Eleni Diamanti
We present and analyze an architecture for a European-scale quantum network using satellite links to connect Quantum Cities, which are metropolitan quantum networks with minimal hardware requirements for the end users. Using NetSquid, a quantum network simulation tool based on discrete events, we assess and benchmark the performance of such a network linking distant locations in Europe in terms of quantum key distribution rates, considering realistic parameters for currently available or near-term technology. Our results highlight the key parameters and the limits of current satellite quantum communication links and can be used to assist the design of future missions. We also discuss the possibility of using high-altitude balloons as an alternative to satellites.
{"title":"Connecting quantum cities: simulation of a satellite-based quantum network","authors":"Raja Yehia, Matteo Schiavon, Valentina Marulanda Acosta, Tim Coopmans, Iordanis Kerenidis, David Elkouss, Eleni Diamanti","doi":"10.1088/1367-2630/ad5b13","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5b13","url":null,"abstract":"We present and analyze an architecture for a European-scale quantum network using satellite links to connect Quantum Cities, which are metropolitan quantum networks with minimal hardware requirements for the end users. Using NetSquid, a quantum network simulation tool based on discrete events, we assess and benchmark the performance of such a network linking distant locations in Europe in terms of quantum key distribution rates, considering realistic parameters for currently available or near-term technology. Our results highlight the key parameters and the limits of current satellite quantum communication links and can be used to assist the design of future missions. We also discuss the possibility of using high-altitude balloons as an alternative to satellites.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"21 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568045","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}
Pub Date : 2024-07-08DOI: 10.1088/1367-2630/ad5bf9
C A Downing, L Martín-Moreno, O I R Fox
Some popular mechanisms for restricting the diffusion of waves include introducing disorder (to provoke Anderson localization) and engineering topologically non-trivial phases (to allow for topological edge states to form). However, other methods for inducing somewhat localized states in elementary lattice models have been historically much less studied. Here we show how edge states can emerge within a simple two-leg ladder of coupled harmonic oscillators, where it is important to include interactions beyond those at the nearest neighbor range. Remarkably, depending upon the interplay between the coupling strength along the rungs of the ladder and the next-nearest neighbor coupling strength along one side of the ladder, edge states can indeed appear at particular energies. In a wonderful manifestation of a type of bulk-edge correspondence, these edge state energies correspond to the quantum number for which additional stationary points appear in the continuum bandstructure of the equivalent problem studied with periodic boundary conditions. Our theoretical results are relevant to a swathe of classical or quantum lattice model simulators, such that the proposed edge states may be useful for applications including waveguiding in metamaterials and quantum transport.
{"title":"Unconventional edge states in a two-leg ladder","authors":"C A Downing, L Martín-Moreno, O I R Fox","doi":"10.1088/1367-2630/ad5bf9","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5bf9","url":null,"abstract":"Some popular mechanisms for restricting the diffusion of waves include introducing disorder (to provoke Anderson localization) and engineering topologically non-trivial phases (to allow for topological edge states to form). However, other methods for inducing somewhat localized states in elementary lattice models have been historically much less studied. Here we show how edge states can emerge within a simple two-leg ladder of coupled harmonic oscillators, where it is important to include interactions beyond those at the nearest neighbor range. Remarkably, depending upon the interplay between the coupling strength along the rungs of the ladder and the next-nearest neighbor coupling strength along one side of the ladder, edge states can indeed appear at particular energies. In a wonderful manifestation of a type of bulk-edge correspondence, these edge state energies correspond to the quantum number for which additional stationary points appear in the continuum bandstructure of the equivalent problem studied with periodic boundary conditions. Our theoretical results are relevant to a swathe of classical or quantum lattice model simulators, such that the proposed edge states may be useful for applications including waveguiding in metamaterials and quantum transport.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"46 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568046","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}
Pub Date : 2024-07-08DOI: 10.1088/1367-2630/ad5bfa
Margarita Khokhlova, Vasily Strelkov
The production of brighter coherent XUV radiation by intense laser pulses through the process of high-harmonic generation (HHG) is one of the central challenges in contemporary nonlinear optics. We study the generation and spatial propagation of high harmonics analytically and via ab initio simulations. We focus on the length scales defining the growth of the harmonic signal with propagation distance and show that the well-known coherence length limits HHG only for relatively low driving intensities. For higher intensities, the photoionisation of the medium, naturally accompanying HHG, leads to essentially transient phase matching and laser frequency blue shift. By systematically taking both of these factors into account, we demonstrate that the behaviour of the harmonic signal at higher intensities is defined by another length scale—the blue-shift length. In this generation regime the XUV intensity at a given frequency first grows quadratically and then saturates passing the blue-shift length, but the total harmonic efficiency continues growing linearly due to the linear increase of the harmonic line bandwidth. The changeover to this generation regime takes place for all harmonic orders roughly simultaneously. The rate of the efficiency growth is maximal if the atomic dispersion is compensated by photoelectrons near the centre of the laser pulse. Our theory offers a robust way to choose the generation conditions that optimise the growth of the harmonic signal with propagation.
{"title":"Role of blue-shift length in macroscopic properties of high-harmonic generation","authors":"Margarita Khokhlova, Vasily Strelkov","doi":"10.1088/1367-2630/ad5bfa","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5bfa","url":null,"abstract":"The production of brighter coherent XUV radiation by intense laser pulses through the process of high-harmonic generation (HHG) is one of the central challenges in contemporary nonlinear optics. We study the generation and spatial propagation of high harmonics analytically and via <italic toggle=\"yes\">ab initio</italic> simulations. We focus on the length scales defining the growth of the harmonic signal with propagation distance and show that the well-known coherence length limits HHG only for relatively low driving intensities. For higher intensities, the photoionisation of the medium, naturally accompanying HHG, leads to essentially transient phase matching and laser frequency blue shift. By systematically taking both of these factors into account, we demonstrate that the behaviour of the harmonic signal at higher intensities is defined by another length scale—the blue-shift length. In this generation regime the XUV intensity at a given frequency first grows quadratically and then saturates passing the blue-shift length, but the total harmonic efficiency continues growing linearly due to the linear increase of the harmonic line bandwidth. The changeover to this generation regime takes place for all harmonic orders roughly simultaneously. The rate of the efficiency growth is maximal if the atomic dispersion is compensated by photoelectrons near the centre of the laser pulse. Our theory offers a robust way to choose the generation conditions that optimise the growth of the harmonic signal with propagation.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"25 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568104","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}
Pub Date : 2024-07-04DOI: 10.1088/1367-2630/ad5a32
Jana Bender, Patrick Mischke, Tanita Klas, Florian Binoth, Hani Naim, Herwig Ott and Thomas Niederprüm
We experimentally study the level mixing, splitting and repulsion of an optically driven atomic multi-level system under two competing interactions. The strength of the optical coupling is increased until it surpasses the atomic hyperfine interaction responsible for mixing the magnetic substates. Due to the multi-level character of the coupled state space, the level shifts exhibit complex behavior reminiscent of the Paschen–Back effect. Our results show that multi-level effects can have significant influence for strong external drive, differing from a simple model of effective non-interacting two-level systems. These results highlight the relevance of imperfections of the light polarization or initial state preparation in strongly optically driven systems.
{"title":"Competing interactions in strongly driven multi-level systems","authors":"Jana Bender, Patrick Mischke, Tanita Klas, Florian Binoth, Hani Naim, Herwig Ott and Thomas Niederprüm","doi":"10.1088/1367-2630/ad5a32","DOIUrl":"https://doi.org/10.1088/1367-2630/ad5a32","url":null,"abstract":"We experimentally study the level mixing, splitting and repulsion of an optically driven atomic multi-level system under two competing interactions. The strength of the optical coupling is increased until it surpasses the atomic hyperfine interaction responsible for mixing the magnetic substates. Due to the multi-level character of the coupled state space, the level shifts exhibit complex behavior reminiscent of the Paschen–Back effect. Our results show that multi-level effects can have significant influence for strong external drive, differing from a simple model of effective non-interacting two-level systems. These results highlight the relevance of imperfections of the light polarization or initial state preparation in strongly optically driven systems.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"43 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141550478","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}
Pub Date : 2024-07-03DOI: 10.1088/1367-2630/ad5b14
Di Zhou
Particle-hole symmetry and chiral symmetry play a pivotal role in multiple areas of physics, yet they remain unstudied in systems with nonlinear interactions whose nonlinear normal modes do not exhibit -gauge symmetry. In this work, we establish particle-hole symmetry and chiral symmetry in such systems. Chiral symmetry ensures the quantization of the Berry phase of nonlinear normal modes and categorizes the topological phases of nonlinear dynamics. We show topologically protected static boundary modes in chiral-symmetric nonlinear systems. Furthermore, we demonstrate amplitude-induced nonlinear topological phase transition in chiral-symmetric nonlinear dynamics. Our theoretical framework extends particle-hole and chiral symmetries to nonlinear dynamics, whose nonlinear modes do not necessarily yield -gauge symmetry.
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