LPHYS'25.    Plenary Speakers:

  1. Generalized Quantum Measurements - Cornerstones of Quantum Information Theory

    Abstract:

    Exploiting the potential of quantum systems for technological purposes is a major driving motivation in quantum information science. For advancing the capabilities of quantum systems the development of efficient and possibly even optimal procedures for measuring quantum systems is an important prerequisite. Generalized quantum measurements [1], i.e. positive operator valued measures (POVMs), represent the most general notion of measurement processes compatible with the laws of quantum theory, which allow to address such optimization issues in a systematic way.

    Starting from basic theoretical aspects of generalized quantum measurements, which particularly emphasize their significance for optimizing quantum measurements within the fundamental limits of quantum theory, in its second part this presentation focusses on current theoretical developments [2][3][4][5][6] aiming at unifying different types of recently discussed symmetric quantum measurement procedures, such as projective measurements involving mutually unbiased bases (MUBs), mutually unbiased measurements (MUMs), symmetric informationally complete measurements (SIC POVMs) or their generalizations, so-called GSIC POVMs. Possible applications of these generalized symmetric quantum measurements are discussed in the context of local bipartite entanglement detection [4], a measurement process of particular practical relevance for secure quantum key distribution.

    1. J A Bergou, M S Hillery, and M Saffman, Quantum Information Processing: Theory and Implementation (Springer, Cham, 2021). DOI: 10.1007/978-3-030-75436-5.
    2. K Siudzińska, Phys. Rev. A 105, 042209 (2022). DOI: 10.1103/PhysRevA.105.042209.
    3. M Schumacher and G Alber, Phys. Scr. 98, 115234 (2023). DOI: 10.1088/1402-4896/acfc7c.
    4. M Schumacher and G Alber, Phys. Rev. A 108, 042424 (2023). DOI: 10.1103/PhysRevA.108.042424.
    5. K Siudzińska, J. Phys. A: Math. Theor. 57, 355301 (2024). DOI: 10.1088/1751-8121/ad6cb8.
    6. M Schumacher and G Alber, Can. J. Phys. (2025). DOI: 10.1139/cjp-2023-0281.

  2. Relativistic Catoptrics

    Biography:

    Sergei Bulanov received his PhD in Theoretical Physics and Astrophysics from the Moscow Institute of Physics and Technology and a Doctor of Science degree in Plasma Physics from the A. M. Prokhorov Institute of General Physics, Russian Academy of Sciences. He has worked in the Department of Theoretical Physics at the P. N. Lebedev Institute of Physics and in the Plasma Physics Laboratory at the A. M. Prokhorov Institute of General Physics in Moscow. He was a full professor in Physics and Mathematics at the Moscow Institute of Physics and Technology. He later worked at the Kansai Photon Science Institute (JAERI, JAEA, and QST) in Japan. He is currently working at ELI-Beamlines in the Czech Republic.

    In these organisations, he has been engaged in the research on cosmic ray astrophysics and solar flare physics, plasma discharge physics, high-power microwave and laser radiation interaction with matter, controlled nuclear fusion, charged particle acceleration, and fundamental physics. For his achievements, he received the USSR State Prize, the Hannes Alfvén Medal and Award from the European Physical Society, and the Order of the Rising Sun, Gold Rays with Rosette, awarded by the Emperor of Japan.

    Abstract:

    With his colleagues, S. V. Bulanov formulated the concept of relativistic plasma mirrors, which can be called Relativistic Catoptrics (from Greek: κάτοπτρον katoptron, "mirror"). In the seminal paper published in 1905, A. Einstein used an example of the light reflection from a mirror moving with arbitrarily large velocity to illustrate the basic principles of the special theory of relativity. Nowadays, the electromagnetic field intensification and the frequency upshift during the light reflection from the relativistic mirror are attractive for research on the development of sources of high-brightness radiation with tunable parameters required by various applications, ranging from relatively moderate radiation intensity to those devoted to quantum field theory. In this regard, a question emerges on whether or not it is possible to prepare a relativistic mirror of high enough quality for efficient reflection of light, which can move with a velocity large enough for increasing the light frequency up to the level corresponding to photon energy in the x-ray range. We can find the answer to this question using knowledge in the physics of nonlinear processes in relativistic laser plasmas. Relativistic flying mirrors in laser plasmas are thin, dense electron or electron-ion layers accelerated by high-intensity laser pulses to velocities close to the speed of light. In the head-on-collision configuration, the reflection of the electromagnetic wave from the relativistic mirror leads to the frequency of the reflected wave multiplied by a factor proportional to the square of the mirror Lorentz factor. The expected radiation intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. In the co-propagating configuration, the radiation pressure of the electromagnetic wave transfers energy to the mirror, i.e., to the charged particles, providing a highly efficient acceleration mechanism. Here, we overview theoretical and experimental results obtained recently in studying the relativistic mirrors emerging in intense laser-plasma interactions.

  3. Attosecond Chronoscopy: From Atoms to Condensed Matter

    Biography:

    Joachim Burgdörfer received his PhD degree in theoretical physics from the Free University of Berlin (Germany) in 1982. After a postdoctoral appointment at Oak Ridge National Laboratory (ORNL) from 1982 to 1983, he was appointed Assistant Professor in 1984, Associate Professor in 1987, and Full Professor in 1988 at the University of Tennessee at Knoxville (UTK) and concurrently held a research staff position at ORNL. In 1995, he was named Distinguished Service Professor of Physics at UTK. In 1997, he accepted a chair in theoretical physics at the Vienna University of Technology (TUW), where he served as the director of the Institute of Theoretical Physics from 2004 to 2016 and as the dean of the Faculty of Physics from 2016 to 2021.

    His research work addresses the interaction of ultrashort electromagnetic pulses with atoms, molecules, and solids, attosecond physics, charged-particle interactions with surfaces, time-dependent many-body systems, and quantum chaos. He was elected Fellow of the American Physical Society in 1993 and became a member of the Austrian Academy of Sciences in 2005. He received the RIKEN Eminent Scientist Award (Japan) in 2005. He has been an honorary member of the Hungarian Academy of Sciences since 2010 and of the Eötvös Physical Society since 2011. He was awarded an honorary professorship at Shenzhen University in 2022 and was elected member of the European Academy of Arts and Sciences in 2023.

    Abstract:

    Observing and clocking non-equilibrium electronic dynamics in real time has developed into one of the key areas of attosecond physics . Attosecond chronoscopy holds the promise to provide novel information on many-electron systems complementary to conventional spectroscopy. The timing of the photoelectric effect represents one of the first breakthroughs of attosecond chronoscopy . Its extension to condensed matter opens up new opportunities to explore electronic band structures and topology, electron transport, and decoherence. We will illustrate the timing of electronic processes with the help of a few recent prototypical examples. They include the Eisenbud-Wigner-Smith (EWS) time delays in atoms and molecules and transport time delay in layered materials , the influence of the collective screening response on electron timing, the quest for identifying the speed limit of optoelectronics, and timing of valleytronics in graphene.

  4. Intense Infrared Lasers for Driving Attosecond X-ray Sources

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      Zenghu Chang


      Laboratory for Infrared-driven Intense-field Science (IRIS), University of Ottawa, Ottawa, ON, Canada
    Abstract:

    Attosecond extreme ultraviolet sources based on high harmonic generation (HHG) in gases driven by Ti:Sapphire lasers centered at 800 nm have been the workhorse for studying electron dynamics since 2001. However, the photon energy range with sufficient flux for time-resolved experiments has been limited < 130 eV. It was predicted that the cutoff photon energy of the phase-matched HHG can be extended by increasing the driving laser wavelengths. Significant progress has been made in developing few-cycle, carrier-envelope phase stabilized, high peak-power lasers in the 1.6 to 2 micron that has laid the foundation for tabletop attosecond X-ray sources in the water window (282 – 533 eV), which covers the atomic K-shell excitation of carbon and oxygen. Breakthroughs in ultrafast mid-wave infrared light sources have been made in recent years. Chirped pulse amplifiers centered at 2.5 and 4.1 micron based on Cr:ZnSe and Fe:ZnSe have been developed. In addition, chirped pulse optical parametric amplifiers using ZnGeP2 pumped by 2-micron lasers with high conversion efficiency has been demonstrated. They are emerging as powerful tools for studying wavelength scaling laws in strong-field atomic, molecular, and plasma physics.

  5. High-field Terahertz Pulse Sources and their Applications

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      János Hebling


      Institute of Physics, University of Pécs, Pécs, Hungary
      Szentágothai Research Centre, University of Pécs, Pécs, Hungary
    Biography:

    János Hebling received M.S. and Ph.D. degrees in physics from the JATE University, Szeged, Hungary, in 1978 and 1982, respectively. For twenty years, he was at JATE University. During this period, he was a visiting researcher at the Max-Planck Institute for Solid State Research, Stuttgart, Germany, for over six years. Now, he is with the University of Pécs, Hungary, where he was the Head of the Experimental Physics Department from 1999 to 2010 and the Director of the Institute of Physic from 2008 to 2018. From 2006 to 2008, he was with the Massachusetts Institute of Technology, Cambridge. In 2012, he founded, and until 2020, he led the MTA-PTE High-Field Terahertz Research Group. He is a Doctor of the Hungarian Academy of Sciences. In 2002 he invented the tilted-pulse-front velocity-matching technique revolutizing the high energy terahertz pulse generation. He is the author of over 140 research articles and holds over 20 patents in laser physics and particle acceleration.

    Prof. Hebling is the Fellow of the OPTICA (previously OSA). He was a topical editor of the JOSA B. He is the recipient of the Pál Selényi, the Denis Gábor, the Széchenyi, and the Ányos Jedlik Awards.

    Abstract:

    Femtosecond laser-based THz pulse generation and detection methods make it possible to measure easily the temporal shape of the field of the generated and transmitted or reflected THz pulses, and in this way, performing time-domain-terahertz spectroscopy (TDTS). TDTS measurements use THz pulses with only 10 fJ energy and 100 V/cm field, yet can, for example, simultaneously result in both absorption- and index of refraction spectrum. However, it does not make it possible to follow ultrafast changes.

    The invention of tilted-pulse-front velocity-matching first made it possible to generate THz pulses with energy on the µJ and field on the 100 kV/cm level [1][2], suitable for following the ultrafast dynamics of electrons and lattice excitations (applying THz pump-probe and other nonlinear optical techniques) [3], controlling material excitations [4], and material structure [5].

    Existing and foreseen THz pulse sources generate pulses with a few mJ energy and tens of MV/cm field strength [6]. Such powerful pulses could boost the energy of THz-driven ultrashort electron bunches from 10 keV to above 1 MeV [7][8].

    This talk will comprehensively overview the high-field THz generation methods, explicitly focusing on setups using tilted-pulse-front velocity-matching. It will also overview the already demonstrated and expected applications of THz pulses with high and extremely high field strength.

    1. J Hebling, G Almási, I Z Kozma, and J Kuhl, Opt. Express 10, 1161 (2002). https://opg.optica.org/abstract.cfm?uri=oe-10-21-1161.
    2. J Hebling, K L Yeh, M C Hoffmann, B Bartal, and K A Nelson, JOSA B 25, B6 (2008). https://opg.optica.org/abstract.cfm?uri=josab-25-7-B6.
    3. M C Hoffmann, J Hebling, H Y Hwang, K L Yeh, and K A Nelson, Phys. Rev. B 79, 161201 (2009). DOI: 10.1103/PhysRevB.79.161201.
    4. P Salén, M Basini, S Bonetti, J Hebling, M Krasilnikov, T Tanaka, G Mourou, and T Tajima, Phys. Rep. 836–837, 1 (2019). DOI: 10.1016/j.physrep.2019.09.002.
    5. X Li, T Qiu, J Zhang, E Baldini, J Lu, A M Rappe, and K A Nelson, Science 364, 1079 (2019). DOI: 10.1126/science.aaw4913.
    6. Gy Tóth, L Kocsis, I Juhász, Á Andrási, P Simon, A Hoffmann, M C Hoffmann, K Varjú, J Hebling, and Z Ollmann, Light: Sci. Appl. 12, 256 (2023). DOI: 10.1038/s41377-023-01293-1.
    7. J Ying, et al., Nat. Photonics 18, 758 (2024). DOI: 10.1038/s41566-024-01441-y.
    8. Sz Turnár, B Sarkadi, S W Jolly, J Hebling, and Z Tibai, Appl. Phys. B 130, 24 (2024). DOI: 10.1007/s00340-023-08157-x.

  6. Quantum Nanoplasmonic Coherent Perfect Absorption: A Route to Room-Temperature Quantum Networks

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      Ortwin Hess


      School of Physics and CRANN Institute, Trinity College Dublin, The University of Dublin, Dublin, Ireland
    Biography:

    Ortwin Hess holds the Chair Professorship of Quantum Nanophotonics and an SFI Research Professorship at the School of Physics and the CRANN Institute, Trinity College Dublin, The University of Dublin, Ireland. He currently serves as Editor-in-Chief of the gold open-access journal APL Quantum. Ortwin has been elected a Member of the Royal Irish Academy, a Fellow of the Institute of Physics (FInstP), a Fellow of Optica (formerly OSA), and a Professorial Fellow of Trinity College Dublin. Previously, he held the Leverhulme Chair in Metamaterials at the Blackett Laboratory, Imperial College London, UK, and held visiting professorships at Stanford University, USA, and Ludwig-Maximilians University Munich, Germany.

    Ortwin's research bridges quantum nanophotonics, semiconductor and metamaterials physics, laser science, and biomedical photonics. He discovered the 'trapped-rainbow' principle, introduced the concept of stopped-light lasing, and made seminal contributions to the spatio-temporal dynamics of semiconductor lasers, ultraslow light in metamaterials, complex quantum-dot photonics, photonic crystals, and strong coupling phenomena in nanoplasmonics. Ortwin pioneered active quantum nanoplasmonics and optical metamaterials with quantum gain, achievements recognized by the Royal Society through the Rumford Medal. Awarded since 1800, this medal honors outstanding contributions to physics, with previous recipients including Michael Faraday, James Clerk Maxwell, Gustav Kirchhoff, Heinrich Hertz, and Dennis Gabor.

    Abstract:

    Plasmonic nanoresonators uniquely confine light into deeply sub-wavelength volumes, significantly enhancing local fields via resonant surface plasmon modes. These properties enable strong light-matter interactions and extreme nano-optical phenomena fundamental to quantum dynamics. Nanoplasmonic strong coupling, recently demonstrated at room temperature using ultrathin (~1 nm) plasmonic cavities [1] and nano-slit resonators [2] with single molecules and quantum dots, generates plasmon-exciton polaritons crucial for advanced quantum operations [3]. However, rapid decay of plasmon modes severely limits the temporal coherence of these states under ambient conditions.

    This talk introduces quantum nanoplasmonic coherent perfect absorption (qnCPA) [4] as a transformative strategy for overcoming such limitations. By selectively exciting and dynamically stabilizing plasmon-exciton polariton states through coherent, non-perturbative waveguide feeding, qnCPA effectively compensates intrinsic plasmonic losses, ensuring robust quantum coherence even at room temperature. This approach challenges conventional quantum state preservation methods that typically require cryogenic cooling.

    Additionally, we discuss non-Markovian collective plasmon-polariton dynamics in slow-wave nanoplasmonic waveguides with spatially separated quantum emitters [5]. Such systems exhibit sustained collective dynamics and suppressed emission, suggesting the potential for quantum nanoplasmonic memory applications and scalable quantum networks.

    By addressing plasmonic loss through qnCPA and leveraging strong coupling, this work advances practical, room-temperature quantum nanophotonics, paving the way for integrated quantum information processing and photonic quantum technologies.

    1. R Chikkaraddy, B de Nijs, F Benz, S J Barrow, O A Scherman, E Rosta, A Demetriadou, P Fox, O Hess, and J J Baumberg, Nature 535, 127–130 (2016). DOI: 10.1038/nature17974.
    2. H Groß, J M Hamm, T Tufarelli, O Hess, and B Hecht, Sci. Adv. 4, eaar4906 (2018). DOI: 10.1126/sciadv.aar4906.
    3. X Xiong, N Kongsuwan, Y Lai, C E Png, L Wu, and O Hess, Appl. Phys. Lett. 118, 130501 (2021). DOI: 10.1063/5.0032013.
    4. Y Lai, D D A Clarke, P Grimm, A Devi, D Wigger, T Helbig, T Hofmann, R Thomale, J S Huang, B Hecht, and O Hess, Nat. Commun. 15, 6324 (2024). DOI: 10.1038/s41467-024-50574-9.
    5. Z Jalali-Mola, S Asgarnezhad-Zorgabad, and O Hess, APL Quantum 1, 046104 (2024). DOI: 10.1063/5.0217702.

  7. Structured Quantum Waves

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      Ebrahim Karimi


      University of Ottawa, Department of Physics and Max Planck Centre for Extreme and Quantum Photonics, Ottawa, ON, Canada
    Biography:

    Professor Ebrahim Karimi is a Tier 1 Canada Research Chair in Structured Waves and Quantum Communication and co-director of the University of Ottawa Quantum Institute (NexQT). He has authored over 180 publications and holds 3 patents, exploring the quantum properties of electrons and photons. He has received recognition from Optica, the Global Young Academy, and the Royal Society of Canada, and is a fellow of the National Research Council Canada and Max Planck Institute for the Science of Light in Germany. He has been awarded the Ontario Early Researcher Award, uOttawa Early Career Researcher of the Year Award, Herzberg Medal, NSERC Arthur B. McDonald Fellowship, and Rutherford Memorial Medal.

    Abstract:

    In quantum mechanics, the wavefunction is a mathematical representation that defines the quantum state of a system. Both photons, the particles of light, and electrons, the carriers of charge, exhibit wavefunctions characterised by various quantum numbers, including frequency/energy, polarisation/spin, as well as spatial and temporal modes. The ability to generate, manipulate, and measure quantum wavefunctions in different regimes is fundamental to quantum information processing. For instance, precise control over photon states is essential for tasks such as quantum key establishment, quantum state determination (tomography), and quantum simulation of complex systems. Similarly, massive quantum objects, like electrons, play a crucial role in quantum imaging and quantum sensing applications, such as detecting objects or measuring magnetic fields. These research areas fall under the broader study of structured quantum waves.

    In my talk, I will present an overview of techniques for engineering the quantum states of photons and electrons, demonstrating how structured quantum waves can provide insights into fundamental questions. Moreover, I will highlight their applications in quantum key establishment, quantum simulators, and quantum microscopy.

  8. An Operational Distinction Between Quantum Entanglement and Classical Non-Separability

    Biography:

    Gerd Leuchs studied physics at the Universities of Cologne and Munich. His Ph.D. thesis dealt with the fine structure splitting of sodium Rydberg atoms. He received the Habilitation degree at the University of Munich on multiphoton processes in atoms. After staying in the USA and Switzerland, Gerd Leuchs became a full professor of physics at the University Erlangen-Nuremberg in Germany. Since 2009, he has been a director at the Max Planck Institute for the Science of Light, and since 2011, he has been a professor adjunct at the University of Ottawa. He is a member of the German and the Russian Academy of Sciences and holds honorary degrees from Danish Technical University and St. Petersburg State University. He won the 2005 Quantum Electronics and Optics Prize of the European Physical Society and the 2018 Herbert Walther Prize, a joint award by Optica (formerly OSA) and DPG. He is a fellow of the European Optical Society, Optica, and the Chinese Optical Society. In 2012, he was awarded the Cross of Merit of the Federal Republic of Germany, and in 2018, he was appointed a member of Bavaria’s Maximilian Order. He is the 2024 president of Optica. His research spans the whole range from classical to quantum optics, with emphasis on the limits of focusing, photon-atom-coupling and quantum noise reduction of light.

    Abstract:

    Quantum entanglement describes superposition states in multi-dimensional systems, at least two partite, which cannot be factorized and are thus non-separable. Non-separable states also exist in classical theories involving vector spaces. In both cases, it is possible to violate a Bell-like inequality. This has led to controversial discussions, which were resolved by identifying an operational distinction between the classical and quantum cases [1].

    1. N V Korolkova, L Sanchez-Soto, and G Leuchs, Phil. Trans. R. Soc. A 382, 20230342 (2024). DOI: 10.1098/rsta.2023.0342.

  9. Semiconductor Nanolasers

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      Jesper Mørk


      Technical University of Denmark, Department of Photonics Engineering, Denmark
    Abstract:

    The talk will discuss recent progress on semiconductor nanolasers. Besides their interesting physics, such lasers may be applied in future on-chip optical interconnects. Three topics will be covered: electrically-injected lasers with sub-microampere threshold current; lasers exploiting cavities with deep sub-wavelength light confinement for enhanced light-matter interaction; and Fano lasers exploiting strong cavity dispersion for linewidth reduction and enhancement of modulation speed.

  10. Subwavelength-Scale Lasing: Physics and Technology of Nanolasers

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      Cun-Zheng Ning


      Shenzhen Technology University, College of Integrated Circuits and Optoelectronic Chips, Shenzhen, Guangdong, China
    Biography:

    Cun-Zheng Ning obtained his PhD in physics from the University of Stuttgart under Hermann Haken. He went to the University of Arizona as a postdoctoral researcher in 1994. He was then a senior scientist, group leader, and Nanotechnology Task Manager at NASA Ames Research Centre for the next 10 years. He was subsequently a full professor of electrical engineering at Arizona State University for 15 years and a Thousand-Talent Professor at Tsinghua University for 8 years, where he was a founding director of the Tsinghua International Centre for Nano-Optoelectronics. In 2022, he was appointed Dean and Chair Professor to establish a new College of Integrated Circuits and Optoelectronic Chips at Shenzhen Tech University.

    Dr Ning's early research in Stuttgart involved laser instabilities, two-photon lasers, the geometric phase, and noise-related phenomena. While studying laser instabilities, he discovered the first example of the Berry phase in a nonlinear dissipative system. His collaboration with others has led to the discovery of a noise-induced oscillation that becomes more coherent with increasing noise, a phenomenon now called coherence resonance that finds applications in numerous systems. His main research activities over the last 20 years involve nanolasers. His group demonstrated various nanowire lasers, including the first dual-colour lasers and the first monolithic white laser. In collaboration with Martin Hill, they demonstrated the first plasmonic nanolaser in 2009 (simultaneously with two other US teams), under electrical injection. Later, in 2013, his group achieved the first room-temperature continuous-wave operation of a nanolaser under electrical injection. For various research accomplishments, he was awarded several international awards, including IEEE Distinguished Lecturer, Best Engineering Invention of the Year by Popular Science, and the Humboldt Research Award. Dr Ning is a fellow of OSA (Optica), IEEE, and the Electromagnetic Academy.

    Abstract:

    Sixty-five years of laser research and applications have pushed the limits of almost all laser parameters to their extremes: from wavelengths, pulse width, and size of a laser, to output power. This talk focuses on recent efforts to shrink the size of a laser down to the smallest limit, at sub-wavelength scales. The question of how small a laser can be made is important both for fundamental laser physics and for many technological applications. The quest for the ultimate size limit of a laser has led to various ideas for confining photons to the smallest possible scales using mechanisms such as surface plasmons. Understanding the behaviour of nanolasers has also led to a re-examination of basic issues in laser physics, such as linewidth, quantum fluctuation, laser threshold, etc. Technologically, nanolasers are expected to become important light sources for future photonic chips or to serve as strongly localised nanoprobes for biomedical or biomolecular applications. The history, current status, and future prospects of many aspects of nanolasers will be discussed in detail.

  11. Recent Advances on Modeling Pair Showers and Avalanches in the Laboratory

    Biography:

    Caterina Riconda obtained her PhD in 1996 at the Massachusetts Institute of Technology. After a one-year fellowship at the Joint European Torus, UK, she was at École Polytechnique, France, with a TMR Marie Curie grant, and at CEA, Saclay. She is currently a full professor at the Laboratory for the Use of Intense Lasers (LULI) in Sorbonne University in Paris and group leader of the Theory group Theory, Interpretation, Plasmas and Simulations (TIPS).

    Her main research interests are the theory and simulation of laser-created plasma, high-field plasmonics, plasma optics, and strong-field QED and pair creation. She was nominated Jubilee Professor of Chalmers University, Sweden, in 2023 and an APS Fellow the same year.

    Abstract:

    Quantum electrodynamic (QED) plasmas, composed of electrons and positrons coupled to photons, play an important role in the physics of the exteriors of neutron stars and black holes, where extreme electromagnetic fields exist. While reproducing such conditions in a laboratory is exceptionally challenging, recent advances on multi-PW lasers allow to envisage in the near future laboratory experiments where abundant pairs will be created.

    In this talk I will focus on recent predictions of pair creation via the Inverse Compton Scattering and the Breit-Wheeler mechanisms in two regimes, the so-called shower regime and the avalanche regime. The shower regime is attained when an electron beam or a gamma flash interacts with an ultra-intense laser: in this case the process will go on until the available energy in the seed beam or flash is exhausted. In the avalanche regime instead the pair creation is self-sustained, extracting energy for the background electromagnetic field rather than the seed particles, which results in an exponential growth of the number of pairs and photons.

    In the first part of the talk the kinetic structure of electron-seeded showers in a crossed field and its temporal evolution will be discussed as a function the initial shower quantum parameter and radiation time. Explicit solutions for the shower multiplicity (the number of pairs produced per seed electron) and the emitted photon spectrum will be given for timescales below and above the radiation time [1]. Some result of relevance for near future experiment in laser beam interaction will be also discussed, complementing the multiplicity calculation with extensive studies with the PIC code Smilei and an analysis of the impact on pair production of the laser spatio-temporal shape, as well as the difference in the interaction with electron or photon beams [2].

    In the second part of the talk, a general analytical solution for the cascade growth rate will be presented as a function of the local values of a general time- and space-dependent electromagnetic field. Our model, benchmarked with 3D simulations, explains and extends many results previously accessible only numerically. It allows to identify the avalanche onset threshold and shows that at high fields the solution for the cascade growth rate converges to a simpler and universal form [3].

    This new framework is useful in optimizing conditions for producing avalanches and dense QED plasmas in future experiments with high intensity lasers and can be embedded in studies of plasma dynamics in interactions with extreme laser or stellar fields.

    1. M Pouyez, T Grismayer, M Grech, and C Riconda, arXiv: 2411.03377.
    2. M Pouyez, T Grismayer, M Grech, and C Riconda, Phys. Rev. E 110, 065208 (2024). DOI: 10.1103/PhysRevE.110.065208.
    3. A Mercuri-Baron, A A Mironov, C Riconda, A Grassi, and M Grech, arXiv: 2402.04225, accepted in Phys. Rev. X (2025).

  12. The Birth of Modern Quantum Mechanics

    Biography:

    Wolfgang P. Schleich is engaged in research on quantum optics ranging from the foundations of quantum physics via general relativity to number theory. He was educated at the Ludwig Maximilians-Universität (LMU) in Munich and studied with Marlan O. Scully at the University of New Mexico, Albuquerque, and the Max-Planck Institute for Quantum Optics, Garching. Moreover, he was also a post doctoral fellow with John Archibald Wheeler at the University of Texas at Austin. Professor Schleich is a member of several national and international academies and has received numerous prizes and honors for his scientific work such as the Gottfried Wilhelm Leibniz Prize, the Max Planck Research Award, the Willis E. Lamb Award for Laser Science and Quantum Optics, and the Herbert Walther Award. He is also a Faculty Fellow at the Hagler Institute for Advanced Study at Texas A&M University. His textbook, Quantum Optics in Phase Space, has been translated into Russian and a Chinese edition was published in 2010.

    Abstract:

    The year 1925 was remarkable – it brought us, courtesy of Werner Heisenberg and Erwin Schrödinger, matrix mechanics as well as wave mechanics. Initially, there was quite a rivalry between the followers of both schools, until it was discovered that the two approaches are identical. Today, wave mechanics dominates. In this talk, we provide a historical perspective on the development of quantum mechanics in this particular year and provide new insight into the Schrödinger equation.

  13. From Sub-keV to Multi-GeV: Progress and the State-of-the-Art of Laser Plasma Electron Acceleration Research

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      Csaba Tóth


      BELLA Center, Accelerator Technology and Applied Physics Division – ATAP, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA, USA
    Biography:

    Dr. Csaba Tóth received his PhD in Optics & Quantumelectronics at the Eötvös University, Budapest, Hungary in 1987. From 1983 he was a scientific coworker in the Research Institute for Solid State Physics, Budapest, Hungary (predecessor of the present Wigner Institute of HUN-REN), studying multiphoton electron emission processes from metals and in general nonlinear optics and ultrafast laser technology. In 1993 and in the period of 1995-97 he was a visiting scholar at Rice University, Houston, TX, USA, developing ionic excimer lasers and VUV imaging techniques. Then, from 1997 until 2000, he was a project scientist at the University of California, San Diego, CA, developing femtosecond CPA lasers and applying them for ultrafast diffraction studies of non-thermal melting in solids, and studying inner-shell excitation-based X-ray lasers. In 2000 he joined the Lawrence Berkeley National Laboratory (LBNL), Berkeley, California, as a staff physicist, where he was responsible for the laser systems and experimental activities of the l'OASIS (‘Lasers, Optical Accelerators System Integrated Studies’) Group. Since 2000 his research has been focused on acceleration of electrons and other charged particles by high power laser pulses and plasma waves, and on the design and development of multi-terawatt and PW chirped pulse amplification (CPA) laser systems. The l'OASIS group evolved to the current BELLA Center, where he was a key contributor and co-leader in the design, commissioning and operation of the BELLA PetaWatt (PW) laser, a pioneering 1 Hz rep-rate PW laser system at LBNL, and its recent upgrades. He is currently a Retiree Affiliate of the BELLA Center, LBNL, focusing on transferring his experience in ultrafast laser science & technology, laser based particle accelerators, secondary source development, and their applications and operational safety to the younger generations of scientists. His honors include the John Dawson Award for Excellence in Plasma Physics Research by APS (2010), and the Department of Energy Secretary’s Achievement Award (2014) for the BELLA Project. Dr. Csaba Tóth is a Senior Member of OPTICA (previously OSA), member of the Hungarian and the American Physical Societies (ELFT, APS), and the Society for Photo-Optical Instrumentation and Engineering (SPIE).

    Abstract:

    The acceleration of particles to multi-GeV energies in short distances by the extremely strong local gradients achievable in plasmas via laser excitation became the topic of intensive experimental and theoretical research worldwide in the last four decades. After several laser installations and upgrades from the TW to multi-hundred TW level in LBNL, the BELLA (Berkeley Lab Laser Accelerator) system with its PW peak-power, 1 Hz repetition rate, and ~35 fs pulses was designed and developed into a uniquely dedicated laser plasma acceleration (LPA) research tool. The ‘BELLA-PW’ is a Chirped Pulse Amplification laser system (a.k.a. CPA, – see Nobel Prize in Physics - 2018), and it is used for studying laser-plasma interactions occurring at extreme high laser intensities. The peak intensity of the focused femtosecond laser beam reaches the relativistic photon-electron interaction regime, allowing electron acceleration experiments involving gas jets, gas cells, and capillary discharges as primary plasma sources.

    The latest two upgrades of the BELLA laser were recently completed and are now producing new experimental results. The first upgrade is the so-called “Second Beamline” (PW-2BL), where the fully amplified, still stretched pulses of the laser are split before compression, allowing two independently adjustable high intensity pulses to interact with a variety of target arrangements with up to ~40 J total energy. The new BELLA PW 2BL allows to conduct the next generation of LPA experiments, such as staging, laser-driven waveguides for increased electron energy, and positron acceleration. The other upgrade is labeled as “Interaction Point #2” (PW-iP2), in which setup the already compressed PW laser pulses of the original beamline are transported to a new target chamber equipped with a short focal length (0.5 m) optic, resulting in a small focal spot in the order of ~3 μm and very high laser intensity of >5×1021 W/cm2. An overview of the special considerations, planning, and implementation processes related to radiation shielding, laser and radiation interlock systems required for the safe and efficient operation of the new BELLA PW beamlines and the conduction of the ongoing experiments will also be presented. In addition to the latest results, emerging applications of laser-based particle acceleration will also be discussed.