LPHYS'24. Plenary Speakers:
Time Reversed Quantum Metrology

Girish Agarwal
Texas A&M University, College Station, TX, USA
girish.agarwal@tamu.edu
Abstract:
It is well recognized that quantum physics can be used to build better sensors. Such sensors can be for parameters, like phases, forces, fields that correspond to the unitary evolution of the system or for parameters like absorption, scattering that require description in terms open system dynamics. The framework of the quantum Fisher information enables one to obtain best estimates of the parameters and then one can design experiments that can reach Cramer Rao bounds. I would highlight the importance of the quantum states used as probes, and the importance of the quantumness of the measurement schemes. It turns out that in many cases the schemes based on time reversed metrology saturate CramerRao bounds. I would discuss the importance of squeezed states of bosonic systems like photons, ions and cat states of qubits for metrological applications. I would present results on the quantized motion of trapped ions and on quantum advantage in the determination of phases, absorption and scattering parameters.

Random Lasers as platforms to study Universal Photonic PhaseTransitions

Cid B de Araújo
Universidade Federal of Pernambuco, Physics Department, Recife, PE, Brazil
cid@df.ufpe.br
Abstract:
Random Lasers (RLs) are light sources that operate due to the multiple scattering of light in disordered gain media that provide the feedback for laser action. No optical cavity of conventional mirrors contributes to the optical feedback. In this talk I will review advances in the RLs research with examples of systems operating in pulsed and continuouswave regimes. The mechanisms governing the behavior of RLs based on colloidalsuspensions of dielectric nanoparticles and luminescent dyes, powders consisting of nanocrystals doped with rareearth ions, and random fiber lasers, will be discussed. The contribution of wavemixing will be exemplified by the multiwavelength emission and tunable UVblue RL generation from neodymiumdoped nanocrystals. Wavemixing among lasing modes also influence the RLs intensity fluctuations. The observation of Lévy distribution of intensity fluctuations and the ReplicaSymmetryBreaking transition from the photonic paramagnetic phase to the photonic spinglass phase are interesting examples of the RLs complex behavior that will be also discussed.

Levitated Solids in the Quantum Regime

Markus Aspelmeyer
University of Vienna, Vienna, Austria
markus.aspelmeyer@univie.ac.at
Abstract:
The quantum optical control of solidstate mechanical devices, quantum optomechanics, has emerged as a new frontier of lightmatter interactions. Objects currently under investigation cover a mass range of more than 17 orders of magnitude – from nanomechanical waveguides to macroscopic, kilogramweight mirrors of gravitational wave detectors. Extending this approach to levitated solids opens up complete new ways of coherently controlling the motion of massive quantum objects in engineerable potential landscapes. I will discuss recent experimental advances in quantum controlling levitated solids, including demonstrations of the motional quantum ground state of optically trapped nanoparticles in a room temperature environment using either optical cavities or quantum Kalman filtering. I will also discuss the perspective to explore new regimes of macroscopic quantum physics, in particular ones that include quantum systems as sources of gravity.

Broadcasting singlequbit and multiqubitentangled states: authentication, cryptography, and distributed quantum computation

János A. Bergou
Department of Physics and Astronomy, Hunter College of the City University of New York, New York, NY, USA
Graduate Center of the City University of New York, New York, NY, USA
jbergou@hunter.cuny.edu
Abstract:
The nocloning theorem forbids the distribution of an unknown state to more than onereceiver. However, quantum entanglement assisted with measurements provides various pathways to communicate information to parties within a network. For example, if the sender knows the state, and the state is chosen from a restricted set of possibilities, a procedure known as remote state preparation can be used to broadcast a state. In this talk, we first examine a remote state preparation protocol that can be used to send the state of a qubit, confined to the equator of the Bloch sphere, to an arbitrary number of receivers [1]. The entanglement cost is less than that of using teleportation to accomplish the same task. We also present variations on this task: probabilistically sending an unknown qubit state to two receivers, sending different qubit states to two receivers, sending qutrit states to two receivers, and discuss some applications of these protocols. Next, we generalize the basic broadcasting protocol to broadcast product and multipartite entangled quantum states in a network where, in the latter case, the sender can remotely add phase gates or abort distributing the states [2]. The generalization allows for multiple receivers and senders, an arbitrary basis rotation, and adding and deleting senders from the network.
We also discuss the case where a phase to be applied to the broadcast states is not known in advance but is provided to a sender encoded in another quantum state. Applications of broadcasting product states include authentication and threestate quantum cryptography. We also study the distribution of a single multiqubit state shared among several receivers entangled with multi qubit phase gates, giving the graph states as an example. As an application, we discuss the distribution of the multiqubit GHZ state. We close with a discussion of the capabilities and limitations of implementations using linear optical quantum networks [3].
[1] Mark Hillery, János A Bergou, TzuChieh Wei, Siddhartha Santra and Vladimir Malinovsky, Phys. Rev. A 105, 042611 (2022)
[2] Hiroki Sukeno, TzuChieh Wei, Mark Hillery, János A Bergou, Dov Fields and Vladimir S Malinovsky, Phys. Rev. A 107, 062605 (2023)
[3] Dov Fields, János A Bergou, Mark Hillery, Siddhartha Santra, and Vladimir S Malinovsky, Phys. Rev. A 106, 023706 (2022)
High harmonic generation: the route towards bright sources in the soft Xray spectral range

Paolo A Carpeggiani
Technische Universität Wien, Institut für Photonik, Vienna, Austria
paolo.carpeggiani@tuwien.ac.at
Abstract:
With the process of High Harmonic Generation (HHG) in gases, the wavelength of a femtosecond (1 fs = 10^{–15} s) driving laser (from the UV to the midIR) can be upconverted to generate fully coherent, ultrashort pulses with spectra spanning through the extreme ultraviolet (XUV) and even into the soft Xrays. Not only can the emitted XUV pulses have durations in the order of attoseconds (1 as = 10^{–18} s), but they are also synchronized with the electric field of the driving laser within a very small fraction of the period of its carrier wavelength. Over the past 20 years, this has allowed researchers to perform experiments with temporal resolution on the order of a few attoseconds, i.e., a very small fraction of the typical optical period of the driver (e.g., 2.7 fs). The Nobel Prize in Physics 2023 was awarded for the experimental methods for the generation and characterization of attosecond pulses of light.
However, the main limitation of HHG is the extremely low efficiency of conversion, leading to low photon flux, especially at higher photon energies – in the hundreds of electronvolts, or few nanometer wavelengths. Significant effort is being put into the generation of soft Xray pulses with both extended spectral range and increased photon flux. Several solutions, based on driving pulses with either longer (midIR) or shorter (VIS, UV) wavelengths, or even by finely shaping the electric field of the driver, have been thoroughly investigated both theoretically and experimentally.
In the perspective of powerscaling HHG sources with extended spectral range, it is important to consider not only how the parameters of the driving pulse affect the HHG conversion process, but also how, and how efficiently, the driving pulses can be obtained – usually by frequencyshifting and nonlinear postcompression techniques applied to different laser sources.

The Wonderful World of Random Lasers and Random Fiber Lasers

Anderson S. L. Gomes
Universidade Federal of Pernambuco, Recife, Brazil
anderson@df.ufpe.br
Abstract:
Random Lasers (RLs) are coherent light sources whose feedback mechanism relies on light scattering in a strongly scattering media in the presence of a gain medium, instead of a pair of fixed mirrors. Upon appropriate pumping, inversion population and amplification precede the optical feedback such as the gain overcomes the loss as in conventional lasers. As reviewed in [1], where most of the historical background and theoretical/experimental developments until June 2021 can be read, RLs, as well as Random Fiber Lasers (RFLs) have become an important tool for photonic studies. As light sources, RLs and RFLs have been demonstrated in all 1D, 2D and 3D configurations, and well characterized regarding threshold, line narrowing/emitted intensity versus excitation intensity, polarization, spatial and temporal coherence, photon statistics (which has been shown to be Poissonian) and operation in the continuous wave or pulsed regime. Regarding RL materials, as long as there is a suitable gain medium (dye, rare earth doped glasses and crystals, semiconductors, quantum dots, etc.) and a scattering medium (which can be the same as the gain medium or external to it) a myriad of RLs/RFLs have been demonstrated [1]. As for RFLs, even the Rayleigh scattering in a few kms fiber length is enough to provide optical feedback, and intrinsic Raman or Brillouin processes provide the gain for laser action. Recently, we have demonstrated a transform limited modelocked random fiber laser [2]. Flexible RLs in 2D have also been exploited using biomaterials as hosts, and of course RFLs (1D) are intrinsically flexible by nature. Regarding applications, RLs and RFLS have been exploited for specklefree imaging, which is an important feature for diagnostic by imaging. A variety of sensing devices based on RLs/RFLs have been reported, including biosensors, powder delivery rate sensor, dopamine detection, among others. In optical communications, RFLs optical amplifiers have been demonstrated to perform better than conventional optical fiber amplifiers, as reviewed in [1] and refs therein. Finally, RLs and RFLs have been exploited as a photonic platform to study, by analogy, turbulence, photonic spin glass, Lévy statistics, Floquet states and extreme events. The connection between photonic turbulence and spin glass behavior of light has shown to bridge the two subjects and, through experiments using RFLs, have been highlighted in connection with the recently awarded 2021 Nobel Prize in Physics [3]. All these exciting features of the wonderful world of RLs and RFLs will be touched upon during this lecture.
[1] Anderson S L Gomes, André L Moura, Cid B de Araújo and Ernesto P Raposo, Prog. Quant. Electron. 78, 100343 (2021)
[2] Jean Pierre von der Weid, Marlon M. Correia, Pedro Tovar, Anderson S L Gomes and Walter Margulis, Nat. Commun. 15, 177 (2024)
[3] A S L Gomes, C B de Araújo, A M S Macêdo, I R R González, L de S Menezes, P I R Pincheira, R Kashyap, G L Vasconcelos and E P Raposo, Light Sci. Appl. 11, 104 (2022)
Quantum Simulation of ManyBody States of Matter with Ultracold Atoms

Randall G. Hulet
Rice University, Houston, TX, USA
randy@rice.edu
Abstract:
Models of quantum manybody phases of matter have been realized using fermionic ultracold atoms instead of electrons and engineered optical potentials that emulate a crystal lattice. Quantum simulation of this kind takes advantage of the innate capability to adhere to a theoretical model, while the tunability of model parameters enables quantitative comparison with theory. For example, repulsively interacting spin1/2 fermions confined to onedimensional (1D) tubes realize a TomonagaLuttinger liquid. The lowenergy excitations are collective, bosonic sound waves that correspond to either spindensity or chargedensity waves that, remarkably, propagate at different speeds. Such a spincharge separation has been observed in electronic materials, but a quantitative analysis has proved challenging because of the complexity of the electronic structure and the unavoidable presence of impurities and defects in electronic materials. In collaboration with our theory colleagues, we made a direct theory/experiment comparison and found excellent agreement as a function of interaction strength [1]. It was necessary to include nonlinear corrections to the spinwave dispersion arising from backscattering, thus going beyond the Luttinger model. More recently, we explored the disruption of spin correlations with increasing temperature [2], an effect that destroys spincharge separation. We are now working near a pwave resonance to realize pwave pairs.
[1]Ruwan Senaratne, Danyel CavazosCavazos, Sheng Wang, Feng He, YaTing Chang, Aashish Kafle, Han Pu, XiWen Guan and Randall G Hulet, Science 376, 1305 (2022)
[2]Danyel CavazosCavazos, Ruwan Senaratne, Aashish Kafle and Randall G Hulet, Nat. Commun. 14, 3154 (2023)
Quantum entanglement and beyond

JianWei Pan
University of Science and Technology of China, Hefei, Anhui, China
pan@ustc.edu.cn
Abstract:
Quantum information science and technology are emerging and fascinating technologies formed by combining coherent manipulating of individual quantum systems and information technology, which enables secure quantum cryptography (quantum communication), superfast quantum computing (quantum computation), and improving measurement precision (quantum metrology) etc., to beat classical limits.
For fundamental aspect, one is led to the conception of quantum entanglement. The appeared ‘spooky action at a distance’ phenomena referred by Einstein, is often explained by seemingly reasonable assumptions of ”local realism”. The inequalities proposed by John Bell and others provide immediate tests for correctness of quantum mechanics. Many efforts are addressing loopholefree tests of Bell inequalities, which tries to close various loopholes, in which some of loopholes are still needed to be addressed including freedom of choice loophole, the collapse locality loophole. Well, the final test is ongoing, many developed groundbreaking technologies for coherent manipulation of quantum systems offers elegant and feasible solutions for satisfying increasing needs of computational power and information security.
Based on stateoftheart fiber technology and rich fiber resources, we have managed to achieve prevailing quantum communication with realistic devices in reallife situation. This constitutes demonstrations by developing decoy state scheme over 100 km firer, extending its employment in the metropolitan area network, as well as maintaining Measurement Device Independent QKD (MDIQKD) over 400 km. At the meantime, we are also developing practically useful quantum repeaters that combine entanglement swapping, entanglement purification, efficient and longlived quantum memory for the ultralong distance quantum communication. Another complementing route is to attain global quantum communication based on satellite. We have spent the past decade in performing systematic ground tests for satellitebased quantum communications. Our efforts finally ensure a successful launch of the Micius satellite. Three major scientific missions have been finished, which includes achieving QKD between satellite and ground station at thousand kilometer scale, achieving satellitebased entanglement distribution between two ground stations separated by a distance of 1200 km, achieving quantum teleportation from ground to satellite over 1400 km. Moreover, using Micius satellite as a trustful relay, the intercontinental QKD between Beijing and Vienna over a distance of 7600 km has also been realized.
Future Prospects include building a global quantum communication infrastructure with satellite and fiber networks, enormous spatial resolution and global precise timing information sharing networks with applications for the global quantum communication network, ultraprecise optical clocks in outer space to detect gravitational wave signal with lower frequency.

Superfluid Quantum Gases on a Shell

Hélène Perrin
Université Sorbonne Paris Nord, Laboratoire de physique des lasers, Paris, France
helene.perrin@univ.paris13.fr
Abstract:
Quantum gases offer an exquisite playground for the study of superfluid dynamics. Superfluids are characterized by a bunch of fascinating properties, including the absence of viscosity, the possibility of persistent flows in an annular trap or the irrotational character of a superfluid flow.
When submitted to a large enough forced rotation, trapped superfluid develop a number of quantum vortices of quantized circulation that arrange at very low temperature in a regular triangular lattice, known as the Abrikosov lattice. As temperature increases, however, the Abrikosov lattice is expected to be gradually destroyed, by displacement of the vortex centers and eventually strong phase fluctuations. In our experiment, we rotate a quasi twodimensional quantum gas in a very smooth, shellshaped, adiabatic potential and produce vortex lattices at the bottom of the shell. We characterize the vortex phase by computing the position and angular correlations in the lattice for increasing rotation frequency. We observe the melting of the vortex lattice at large rotation frequency and finite temperature.
In the regime where the quantum gas rotates even faster, the centrifugal force pushes the atoms outwards, up along the shell, resulting in a central hole. The angular momentum per particle reaches several hundreds and the gas forms the precursor of a giant vortex, with a superfluid flowing at speeds strongly exceeding the speed of sound in the gas. We observe a strong deformation of the shape of the annulus when applying a resonant elliptical deformation.
Finally, we compensate the effect of gravity on the shell to populate a large fraction of the surface. In this low gravity limit, the shape of the cloud is dominated by small energy differences on the surface, in particular zeropoint energy of the transverse confinement, which results again in the formation on an annular quantum gas.

Quantum Optics Meets Attosecond Science: Novel Regimes of Coherent Xray Generation with Strong Electron Correlation Dynamics and Attosecond Rabi Oscillations

Tenio Popmintchev
University of California San Diego, Physics Department, La Jolla, CA, USA
Vienna University of Technology, Photonics Institute, Vienna, Austria
tenio.popmintchev@physics.ucsd.edu
Biography:
Prof. Tenio Popmintchev is an Assistant Professor in the Physics Department and the Center for Advanced Nanoscience at the University of California San Diego, as well as at the TU Wien, Vienna, Austria. He received his PhD in Atomic, Molecular, and Optical Physics from the JILA Institute and University of Colorado Boulder in 2010, where he conducted pioneering research on ultrashortpulse lasers and bright coherent Xray generation using laboratory scale apparatus with designer classical and quantum properties. Prof. Popmintchev is an internationally recognized leader in the field of Attosecond and Xray Science. Some of his honors include the Sloan Research Fellowship, European Research Council Starting Grant, Science News USA 10 Outstanding Young Scientist Award, Presidential Medal for Pioneering Contribution to Science and Technology, Bulgaria. Prof. Popmintchev led groundbreaking work on scaling EUV attosecond pulses towards generating attosecondtozeptosecond Xrays in the keV regime  the shortest events ever created in a laboratory. His research on developing bright coherent EUV and Xray light with tunable spectral, spatial, and temporal shape, and tunable angular momentum, has been enabling new capabilities for ultrafast multidimensional imaging and spectroscopies at the spacetime resolution extreme. Some of his current research directions expand towards novel quantum regimes of Xray generation, merging quantum optics and strong field physics.
Abstract:
Ultrafast imaging and spectroscopies using coherent EUV – Xray light based on the nonlinear process of high harmonic generation are already addressing grand challenges in complex molecular systems, plasmas, and advanced nanomaterials. The exquisite quantum control of the attosecond dynamics of the rescattering electrons in this extreme frequency upconversion makes it possible to sculpt the classical and quantum properties of the light with unprecedented tunability of the spectral, spatial, temporal shape, and spin and orbital angular momentum state. The superb coherence of this unique light allows for multidimensional imaging at the spacetime extreme with 4D resolution of nanometers and femtoseconds, including access to an effective 5th dimension – the periodic table of elements – due to the Xray absorption fingerprinting with elemental and chemical specificity.
In this talk, I will present two novel quantum regimes of coherent Xray generation where the design of the light properties is dominated by the dynamics of the strongly correlated electrons in a simple He atomic system. Interestingly, the physics of these regimes extends beyond the wellestablished threestep high harmonic model.
In the first regime, using strong UV laser fields, the entangled electron dynamics yield a characteristic secondary plateau in the Xray spectral region, extending well beyond the conventional cutoff. This is due to simultaneous double electron recombination where a single highenergy Xray photon is emitted only in atomic systems with strongly correlated electrons. This low probability phenomenon paves a way to a sensitive attosecond spectroscopy as a probe of highly correlated interactions. Similar physics of high harmonics from solids might be able to characterize electron correlations in phase transition materials and nanosystems of relevance to quantum computing and superconductivity.
In the second extreme regime, using intense EUV driving fields tuned to a resonance frequency of He can result in very bright harmonic emission in the Xray regime. Favorable quantum dynamics of the electron wavepackets, and phase and group velocity matching of the light fields enhance the Xray yield. Furthermore, recordfast attosecond Rabi oscillations are predicted to suppress the depletion of the ground state, which otherwise terminates the emission of Xray photons.
These new advances in quantum control over the coherent Xray emission enable new insights into complex entangled electron dynamics and applications in nanoscience and quantum technology.

Quantum Light: Coherence, Photon Statistics and Phase Space

Luis L SánchezSoto
Complutense University of Madrid, Department of Optics, Madrid, Spain
lsanchez@ucm.es
Abstract:
The three topics coherence, photon statistics and phase space distribution are intimately related and closely connected to the properties of the quantum vacuum. Here we will pick three different scenarios which underline this relation: two experimental results and one speculative consideration. The first one [1] is about the nature of spontaneous emission. Wigner and Weisskopf treated spontaneous emission perturbatively as an irreversible process, which raises the question whether or not there coherence between the light emitted by a single atom spontaneously into different direction: the experiment gives the answer. The second scenario [2] is a simultaneous measurement of the phase space distribution function and the intensity correlation in a light field which can be tuned between from a squeezed state to a thermal State. The intensity correlation is determined in two different ways and the results are compared: one way is to measure the intensity correlation directly and the other way is to calculate the intensity correlation from the measured Wigner function. We focus on weak squeezing for which the g(2) function diverges. The third scenario, the speculative consideration [3] is to treat the modern vacuum as a dielectric and show that this provides a phenomenological approach to determining the speed of light, the permittivitty of the vacuum and the fine structure constant.
[1] Gerd Leuchs, Luis L SánchezSoto, Martin Fischer, Markus Sondermann and Ralf Menzel, to be published
[2] Gerd Leuchs, Luis L SánchezSoto, Hanna Le Jeannic, Kun Huang, Julien Laurat and Mojdeh Shikhali Najafabadi, to be published
[3] Gerd Leuchs, Margaret Hawton and Luis L SánchezSoto, Physics 5, 179 (2023)
LandauZener transitions, Hawking radiation and number theory

Wolfgang P. Schleich
Institute for Quantum Physics, Ulm University, Ulm, Germany
wolfgang.schleich@uniulm.de
Abstract:
Landau–Zenertransitions are an essential tool in atom optics, and in particular, in accelerated optical lattices. It is amazing that despite its simplicity, the derivation of the wellknown LandauZenerformula for the transition probability amplitude is rather involved, independent of the approach pursued. In the present talk, we employ the Markov approximation and the wellknown Fresnelintegral to derive [1] in ‘’oneline” the familiar expression for the LandauZenerformula. Moreover, we provide numerical as well as analytical justifications for our approach, and identify three characteristic motions of the probability amplitude in the complex plane. In addition, we make the connection to Hawking radiation [2] and number theory, in particular, the Riemann hypothesis [3].
[1] Eric P Glasbrenner and Wolfgang P Schleich, J. Phys. B  At. Mol. Opt., 56, 104001 (2023)
[2] Marlan O Scully, Stephen Fulling, David M Lee and Anatoly A Svidzinsky, Proc. Natl. Acad. Sci. USA, 115 8131 (2018)
[3] Michael E N Tschaffon, Iva Tkáčová, Helmut Maier and Wolfgang P Schleich, in: Roberta Citro, Maciej Lewenstein, Angel Rubio, Wolfgang P Schleich, James D Wells and Gary P Zank (Eds.), Sketches of Physics, Lecture Notes in Physics 1000, Springer Heidelberg, 2023, p. 191
Novel Phase Transitions in Disordered Quantum Systems

Georgy V. Shlyapnikov
Laboratoire de Physique Théorique et Modèles Statistiques, Orsay, France
georgy.shlyapnikov@upsud.fr
Abstract:
I first give a brief overview of the studies of cold atoms in disorder. Then I discuss a singleparticle problem and consider a rotational excitation in the system of polar molecules randomly spaced in an optical lattice. It will be shown that in three dimensions all states are extended, but some of them are nonergodic so that there are novel ergodicnonergodic transitions. I then turn to manybody problems and consider a onedimensional Hubbard model for spin1/2 fermions with onsite disorder and finite onsite interactions. The key issue here is the presence of a variety of ergodicnonergodic phase transitions. For lowenergy states this is established by DMRG in systems as large as several hundred lattice sites.

Everything You Always Wanted to Know About Atom Tunneling & Photon Propagation but Were Afraid to Ask

Aephraim M Steinberg
University of Toronto, Department of Physics, Toronto, ON, Canada
steinberg@physics.utoronto.ca
Abstract:
If there are two problems you would think quantum mechanicists & opticians had beaten to death, they might be quantum tunneling and the propagation of photons through a cloud of atoms.
And yet when you look more deeply – and ask "where are the atoms while they’re tunneling through the forbidden region, and how much time do they spend there?” or “how do photons get slowed down, and where is the energy spending its time?" – the answers are not so simple.
This is related to a simple reality: one of the most famous tidbits of received wisdom about quantum mechanics is that one "cannot ask" how a particle got to where it was finally observed, e.g., which path of an interferometer a photon took before it reached the screen. What, then, do present observations tell us about the state of the world in the past? I will describe two experiments looking into aspects of this "quantum retrodiction." In the first, we measure how long Bosecondensed atoms spend inside a potential barrier (created by a fardetuned laser beam focused to 1 micron) before being transmitted; I will also talk about some predictions regarding what insidious effects actually observing a particle in the barrier could have. In the second, we measure the amount of time atoms spend in the excited state when a resonant photon is not absorbed by those atoms, but propagates clear through. We find, surprisingly, that the answer need not even be a positive number. I will connect this to betterknown aspects of optical propagation.
I will also describe the observation of (initially) surprising "spin textures" in the tunneling cloud that illuminate novel features of coldatom magnetohydrodynamics; and planned experiments to study the timescales relevant to quantum measurement in a tunneling scenario.
[1] R Ramos, D Spierings, I Racicot and A M Steinberg, Nature 583, 529 (2020)
[2] D C Spierings and A M Steinberg, Phys. Rev. Lett. 127, 133001 (2021)
[3] D C Spierings, J H Thywissen and A M Steinberg, Phys. Rev. Lett. 132, 173401 (2024)
[4] J Sinclair, D Angulo, K Thompson, K BonsmaFisher, A Brodutch and A M Steinberg, PRX Quantum 3, 010314 (2022)
[5] K Thompson, K Li, D Angulo, VM Nixon, J Sinclair, A V Sivakumar, H M Wiseman and A M Steinberg, arXiv:2310.00432v1 [quantph] (2023)
Frequency Comb Spectroscopy from 1 THz to 1 PHz

Konstantin L Vodopyanov
University of Central Florida, College of Optics & Photonics, Orlando, FL, USA
vodopyanov@creol.ucf.edu
Abstract:
Frequency comb spectroscopy across terahertz to UV has evolved into a powerful technique that simultaneously provides broad spectral coverage, high spectral resolution, high data acquisition rates, and an absolute frequency referencing to an atomic clock, and provides unique insights into the structure of matter with applications ranging from testing fundamental laws of nature to chemical analysis, trace gas sensing, astronomical observations, and biomedical applications [1].
I will present our results on highresolution dual comb spectroscopy (DCS) based on a new laser platform with unprecedented spectral coverage. We start from two mutually coherent frequency combs based on modelocked Cr:ZnS lasers with center wavelength 2.35 µm. For producing MIRTHz frequency combs we use subharmonic optical parametric oscillation [2] or optical rectification combined with electrooptic sampling [3], and for the UVvisible combs generation we use high harmonics of the driving laser [4].
The low intensity and phase noise of our dualcomb system allows us to capture a large amount of spectral information (e.g. 240,000 combmoderesolved spectral lines, Fig. 1a) in the MIR at up to a video rate [5]. Fig. 1b, on the other hand, shows a combmode resolved spectrum of the UV comb containing some million comb teeth.
Overall, our approach provides the basis for highresolution (down to <1 MHz with spectral interleaving) highly precise spectroscopic measurements with frequency coverage from 1 THz to 1 PHz. This opens new avenues for fundamental spectroscopy and for generating spectral line lists for various molecules to help characterize exoplanetary atmospheres and study the interstellar and circumstellar environment.
[1] N Picqué and T W Hänsch, Nat. Photonics 13, 146 (2019)
[2] A V Muraviev, V O Smolski, Z E Loparo and K L Vodopyanov, Nat. Photonics 12, 209 (2018)
[3] S Vasilyev, A Muraviev, D Konnov, M Mirov, V Smolski, I Moskalev, S Mirov and K L Vodopyanov, Opt. Lett. 48, 2273 (2023)
[4] A Muraviev, D Konnov, V Smirnov, S Vasilyev and K L Vodopyanov, in: Conference on Lasers and ElectroOptics (CLEO'2024), Charlotte NC, USA, May 510, 2024, paper SF3O.2
[5] D Konnov, D Muraviev, S Vasilyev and K L Vodopyanov, APL Photonics 8, 110801 (2023)

Observing the quantum topology of light

DaWei Wang
Zhejiang University, School of Physics, Hangzhou, China
dwwang@zju.edu.cn
Abstract:
Topological photonics provides a powerful platform to explore topological physics beyond traditional electronic materials and shows promising applications in light transport and lasers. Classical degrees of freedom are routinely used to construct topological light modes in real or synthetic dimensions. Beyond the classical topology, the inherent quantum nature of light provides a wealth of fundamentally distinct topological states. In this talk I will introduce the experiment on topological states of quantized light in a superconducting circuit, with which one and twodimensional Fockstate lattices are constructed. We realize rich topological physics including topological zeroenergy states of the SuSchriefferHeeger model, straininduced pseudoLandau levels, valley Hall effect, and Haldane chiral edge currents. Our study extends the topological states of light to the quantum regime, bridging topological phases of condensedmatter physics with circuit quantum electrodynamics, and offers a freedom in controlling the quantum states of multiple resonators.

Embracing the Potential of Nonlinear Integrated Photonics Beyond Silicon: Advantages and Limitations

Gustavo Wiederhecker
Universidade Estadual de Campinas, Department of Applied Physics, Campinas, SP, Brazil
gustavo@ifi.unicamp.br
Abstract:
Nonlinear integrated photonics is a rapidly evolving field that offers exciting opportunities for novel devices and applications, promising a realm of possibilities beyond traditional silicononly approaches. In this presentation, we journey through some recent results in this field, uncovering both its inherent advantages and the challenges it presents. From the interplay of light and matter on the nanoscale to 2 the practical applications in sensing, communication, and computation, we delve deep into the potential and flaws that nonlinear integrated photonics bring in.

Seeing Life in a New Light: from Simple Classical Physics to QuantumEnhanced Imaging

Vladislav V Yakovlev
Texas A&M University, Affiliated Faculty, Physics, College Station, TX, USA
yakovlev@tamu.edu
Abstract:
The progress of biomedical sciences depends on the availability of advanced instrumentation and imaging tools capable of attaining the state of biological systems in vivo without using exogenous markers. Mechanical forces and local elasticity play a central role in understanding physical interactions in all living systems. We demonstrate a novel way to image microscopic viscoelastic properties of biological systems using Brillouin microspectroscopy [1]. In my talk, I will discuss the ways how an old spectroscopic tool can be used for real time microscopic imaging [23] and provide possible solutions to long standing problems in Life Sciences and Medicine [46] while advancing instrumentation beyond classical limits [7].
[1] Z Meng, A J Traverso, C W Ballmann, M A TroyanovaWood and V V Yakovlev, Adv. Opt. Photon. 8, 300 (2016)
[2] Z N Coker, M TroyanovaWood, Z A Steelman, B L Ibey, J N Bixler, M O Scully and V V Yakovlev, PhotoniX 5, 9 (2024)
[3] C W Ballmann, Z Meng, A J Traverso, M O Scully and V V Yakovlev, Optica 4, 124 (2017)
[4] Z Meng, T Thakur, C Chitrakar, M K Jaiswal, A K Gaharwar and V V Yakovlev, ACS Nano 11, 7690 (2017)
[5] M TroyanovaWood, Z Meng and V V Yakovlev, Biomed. Opt. Express 10, 1774 (2019)
[6] D Akilbekova, V Ogay, T Yakupov, M Sarsenova, B Umbayev, A Nurakhmetov, K Tazhin, V Yakovlev and Z Utegulov, J. Biomed. Opt. 23, 097004 (2018)
[7] T Li, F Li, X Liu, V V Yakovlev and G S Agarwal, Optica 9, 9594 (2022)
Explore Exceptional Points in Optical Microresonators: Fundamentals and Applications

Lan Yang
Washington University in St. Louis, Department of Electrical & Systems Engineering, St. Louis, MO, USA
yang@seas.wustl.edu
Abstract:
Exceptional points (EPs) are nonHermitian degeneracies featured by the coalescence of eigenvalues and corresponding eigenstates when the parameters of a dissipative system are tuned appropriately. EPs universally occur in all open physical systems and have a significant impact on their behavior, leading to counterintuitive phenomena such as lossinduced lasing, unidirectional invisibility, and enhanced sensors. We have adopted whisperinggallerymode (WGM) resonators as a platform to showcase the impact of nonHermitian physics and EPs on physical systems and devices. HighQ WGM microresonators have a superior capability to trap light in a highly confined volume, enabling strong lightmatter interactions, which can be utilized to investigate various interesting phenomena and applications, such as lasing, nonlinear optics, optomechanics, and sensing, etc. We will review our recent study in nonHermitian physics and EPs that have unraveled innovative strategies to achieve a new generation of optical systems enabling unconventional control of light flow, such as loss engineering in a lasing system, directional lasing emission, and EPs enhanced sensing. We will also present a new finding regarding EPenhanced sensing that can expand this approach to a wide range of optical sensor systems. Our research discoveries provide a glimpse of the potential of EPs in photonic resonators. There are many exciting opportunities to be explored in various physical systems by leveraging the interesting features associated with EPs.

Nonlinear optics of stochastic field waveforms

Aleksey M. Zheltikov
Texas A&M University, College Station, TX, USA
zheltikov@physics.tamu.edu
Biography:
Aleksei Zheltikov received his PhD and Doctor of Science degrees from M.V. Lomonosov Moscow State University. He has been a full professor at M.V. Lomonosov Moscow State University since 2000 until 2022. He served as a group leader at the Russian Quantum Center, head of the Laboratory of Neurophotonics at Kurchatov Institute, and head of the Laboratory of Fiber Optics for Quantum Technologies at A.N. Tupolev Kazan Technical University. Since 2010, he is a professor at Texas A&M University. His research is focused on ultrafast nonlinear optics, quantum physics, and biophotonics.
Abstract:
Methods of statistical analysis offer new insights into a nonlinear dynamics of stochastic optical field waveforms, providing a framework that helps understand supercontinuum generation driven by stochastic laser pulses, as well as dynamic instabilities and filamentation of stochastic laser beams. Unlike deterministic selffocusing, whose criterion is expressed in terms of a welldefined selffocusing threshold, its stochastic counterpart is a probabilistic process whose combined probability for a sample of N laser pulses builds up as a function of N. We show that the ratio 𝑃/𝑃_{cr} of the laser peak power 𝑃 to the critical power of selffocusing 𝑃_{cr}, which plays a central role in deterministic selffocusing, keeps its status as a key governing parameter in stochastic selffocusing. However, in contrast to its deterministic counterpart, the 𝑃/𝑃_{cr} ratio of a stochastic laser beam is no longer an indicator of whether selffocusing will occur, but is, rather, a predictor of when the selffocusing is expected, in the sense of the first passage time, given the statistics of the laser field. We will also examine supercontinuum generation driven by stochastic laser pulses. The statistics of extreme bandwidths emerging from such a process is shown to converge, in the largesamplesize limit, to a generalized Poisson distribution whose mean is given by the exponent of the respective extremeevent statistics.
