LPHYS'23.    Plenary Speakers:

  1. Quantum Optics Inspired Magnonic


    Quantum optical developments have seeded a number of developments in several fields, especially the condensed matter physics. For example, the cavity-produced strong coupling has led to similar studies with other systems like quantum dots, superconducting qubits, excitons, plasmons. In this talk, I would present applications of a number of ideas from quantum optics to the field of magnonics. These include use of quantum state transfer to prepare squeezed and entangled states of magnons; dispersive and dissipative magnon-magnon interactions; enhanced magnon response via the parametric interactions and many others.

  2. Structured Light Topology in Ultrafast Nonlinear Optics

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      Carlos Hernández-García

      Departamento de Física Aplicada, Universidad de Salamanca, Salamanca, Spain

    The development of structured ultrafast laser sources is a key ingredient to advance our knowledge about the fundamental dynamics of electronic and spin processes in matter. It has been widely recognized the relevance of ultrafast sources structured in their spin angular momentum (SAM, associated to the polarization of light) and orbital angular momentum (OAM, associated with the transverse phase profile, or vorticity of a light beam) to study chiral systems and magnetic materials in their fundamental temporal and spatial scales. In that scenario, structured coherent extreme-ultraviolet (EUV)/soft x-ray pulses are emerging thanks to the highly nonlinear process of high harmonic generation (HHG) [1-4].

    In this talk we will review several works that have triggered the field of ultrafast structured EUV pulses during the last decade. We will compare the interplay of light and matter topology in HHG in gases and in crystalline targets, paying special attention to the latter ones, which stand as particularly appealing targets in HHG due to their characteristic symmetries. In particular, we demonstrate that HHG in 2D materials allows for unprecedent study of the nonlinear dynamics through the study of light’s topology. This scenario opens the route towards high-order harmonic spectroscopy techniques based on the topology of the EUV/soft x-ray harmonic radiation [5].

    [1] L Rego, K Dorney, N Brooks, Q Nguyen, C Liao, J San Román, D Couch, A Liu, E Pisanty, M Lewenstein, L Plaja, H Kapteyn, M Murnane and C Hernández-García, Science 364, eaaw9486 (2019)
    [2] L Rego, N J Brooks, Q L D Nguyen, J San Román, I Binnie, L Plaja, H C Kapteyn, M M Murnane and C. Hernández-García, Sci. Adv. 8, eabj7380 (2022)
    [3] C Hernández-García, A Turpin, J San Román, A Picón, R Drevinskas, A Cerkauskaite, P G Kazansky, C G Durfee and I J Sola, Optica 4, 520 (2017)
    [4] A de las Heras, A Pandey, J San Román, J Serrano, E Baynard, G Dovillaire, M Pittman, C Durfee, L Plaja, S Kazamias, O Guilbaud and C Hernández-García, Optica 9, 71 (2022)
    [5] A García-Cabrera, R Boyero-García, Ó Zurrón-Cifuentes, J Serrano, J San Román, L Plaja and C Hernández-García, Interplay of crystal symmetries and light topology in high harmonic spectroscopy, Research Square (2022), preprint. DOI: 10.21203/rs.3.rs-2161917/v1

  3. From Precision Attosecond Physics at the Surface of a Needle Tip to a Lightfield-driven Logic Gate in Graphene


    Strongfield and attosecond physics at the surface of solids as well as inside of solids have made fantastic progress in recent years. I will discuss two examples from our group. In the first part of the talk I will show how two-color few-cycle laser fields allow us to get deep insights to the strongfield dynamics at the surface of metal needle tips. For example, we can now measure the electron emission time window to 710 attoseconds, with an error bar as small as 30 as, representing another example of what might be called precision attosecond physics. The second part of the talk will focus on strongly driven electrons inside of graphene and the graphene-gold interface. Some time ago, we could demonstrate Landau-Zener-Stückelberg-Majorana physics being responsible for current generation in graphene, so subsequent coherent Landau-Zener transitions. Just recently, we could combine these insights with new insights at the strongly driven graphene-gold interface to demonstrate the first logic gate with clock rates potentially approaching the petahertz range. We believe that these results might bring us a good step closer to lightwave electronics.

  4. Quantum Simulation of Spin-Charge Separation


    Models of quantum many-body phases of matter may be realized using fermionic ultracold atoms in place of the electrons, and engineered optical potentials to emulate a crystal lattice. Quantum simulation of this kind takes advantage of the capability to adhere to a theoretical model, while the tunability of model parameters enables quantitative comparison with theory.

    As an example, repulsively interacting spin-1/2 fermions confined to one-dimensional (1D) tubes, realize a Tomonaga-Luttinger liquid. The low energy excitations are collective, bosonic sound waves that correspond to either spin-density or charge-density waves that, remarkably, propagate at different speeds. Such a spin-charge 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 spin-wave dispersion arising from back-scattering, thus going beyond the Luttinger model. More recently, we explored the disruption of spin correlations with increasing temperature [2], an effect that destroys spin-charge separation. We are now working near a p-wave resonance with the goal of realizing p-wave pairs.

    [1] R Senaratne, D Cavazos-Cavazos, S Wang, F He, Y-T Chang, A Kafle, H Pu, X-W Guan and R G Hulet, Science 376, 1305 (2022)
    [2] D Cavazos-Cavazos, R Senaratne, A Kafle and R G Hulet, Nature Commun. 14, 3154 (2023)

  5. Quantum Computing with Trapped Atomic Ions


    Trapped atomic ions are a leading physical platform for networked quantum computers, featuring qubits with essentially infinite idle coherence times and the highest purity quantum gate operations. Such atomic clock qubits are controlled with laser beams, allowing densely-connected and reconfigurable universal gate sets. The path to scale involves concrete architectural paths based on well-established protocols, from shuttling ions between QPU cores to modular photonic interconnects between multiple QPUs. I will summarize the state-of-the-art in these quantum computers in both academic and industrial settings, for both scientific and commercial applications.

  6. Quantum Multidimensional Spectroscopies with X-ray Light, Entangled Photons, and in Optical Cavities

    Figure 1 (a) Setup of the nonlinear interferometer with the two nonlinear crystals PDC1/2, beamsplitters Bs/i and detectors D1-4. (b) Entangled photoelectron signal. (upper) Schematic of the setup and a comparison of the photoelectron signal with entangled and classical light fort the photodissociation of pyrrole. (c) Schematic of the setup of manipulating molecular charge migration in an optical cavity.
    Figure 2

    We present several novel femtosecond spectroscopic techniques that make use of the quantum nature of light and femtosecond X-ray pulses.

    The nonlinear interferometer setup of Fig. 1(a) can isolate exciton- scattering processes in the photosyetem II reaction center.

    The spectro-temporal correlation of time-energy entangled photon pairs was employed to overcome the Fourier limit of the temporal and spectral resolutions in conventional photoelectron signals of the photodissociation dynamics of pyrrole using the nonadiabatic wave packet simulations shown in Fig 1(b). The spectral resolution is achieved by electron detection and temporal resolution by a variable phase delay.

    The ultrafast electronic charge dynamics in molecules upon photoionization while the nuclear motions are frozen is known as charge migration. Quantum dynamics simulations of photoionized 5- Bromo-1-pentene shown in Fig. 1(c) and Fig. 2 reveal that the charge migration process can be enhanced by placing the molecule in an optical cavity and monitored by time-resolved photoelectron spectroscopy. Figure 2 shows the time-dependent polariton charge density differences (from the bare molecule) and the corresponding time-resolved photoelectron signals. The collective nature of the polaritonic charge migration process is examined. We find that molecular charge dynamics in a cavity is local and does not show many- molecule cooperativity. The same conclusion should apply to cavity polaritonic chemistry.

    [1] M Kizmann, H K Yadalam, V Y Chernyak and S Mukamel, Proc. Natl. Acad. Sci. USA (2023), in print
    [2] B Gu, S Sun, F Chen and S Mukamel, Proc. Natl. Acad. Sci. USA 120, e2300541120 (2023)
    [3] Y Gu, B Gu, S Sun, H Yong, V Y Chernyak and S Mukamel, (2023), under review

  7. Photonic Crystals in Chiral Space


    Two-dimensional photonic crystals that are extended and chirally twisted in the third dimension provide novel opportunities for controlling light, but are very difficult to realize using conventional planar techniques. Although arrays of individually chiral waveguides, formed by fs laser writing in bulk glass, have been employed to explore topological surface states, high waveguide loss restricts their usable length [1]. In contrast, low-loss chiral structures are straightforward to produce by drawing photonic crystal fibre from a spinning preform [2]. This has led to a series of novel experiments uncovering interesting and useful properties, for example, helical Bloch modes supported by chiral photonic crystal fibres with N-fold rotational symmetry are circularly and vortically birefringent, offering circular dichroism as well as robust preservation of polarization state and topological charge [3], and permitting enhanced control of nonlinear optical effects such as Raman and Brillouin scattering [4,5], four-wave-mixing [6], and supercontinuum generation [7]. A further intriguing effect is exponential localization of light in chiral arrays of exponentially coupled waveguides, e.g., coreless twisted photonic crystal fibre [8]. Indeed, localization of light in chiral PCF turns out to be a universal phenomenon, supporting whole families of helical Bloch modes, each with its own azimuthal and radial order [9].

    [1] M C Rechtsman, J M Zeuner, Y Plotnik, Y Lumer, D Podolsky, F Dreisow, S Nolte, M Segev and A Szameit, Nature 496, 196 (2013)
    [2] G K L Wong, M S Kang, H W Lee, F Biancalana, C Conti, T Weiss and P St J Russell, Science 337, 446 (2012)
    [3] P Roth, Y Chen, M C Günendi, R Beravat, N N Edavalath, M H Frosz, G Ahmed, G K L Wong and P St J Russell, Optica 5, 1315 (2018)
    [4] S Davtyan, Y Chen, M H Frosz, P St J Russell and D Novoa, Opt. Lett. 45, 1766 (2020)
    [5] X Zeng, P St J Russell, C Wolff, M H Frosz, G K L Wong and B Stiller, Sci. Adv. 8, eabq6064 (2022)
    [6] P Roth, P St J Russell, M H Frosz, Y Chen and G K L Wong, J. Lightwave Technol. 41, 2061 (2022)
    [7] R P Sopalla, G K L Wong, N Y Joly, M H Frosz, X Jiang, G Ahmed and P St J Russell, Opt. Lett. 44 (2019)
    [8] P Roth, G K L Wong, M H Frosz, G Ahmed and P St J Russell, Opt. Lett. 44, 5049 (2019)
    [9] P St J Russell and Y Chen, Laser Photonics Rev. 17, 2200570 (2022)

  8. The Thorium Isomer 229mTh: From the Atomic to the Nuclear Clock


    In recent years the possibility to realize a so-called Nuclear Clock has attracted increasing attention, as today’s most precise timekeeping devices, based on optical atomic clocks, could be challenged in performance by a nuclear clock, based on a nuclear transition instead of an atomic shell transition.

    Such a nuclear clock promises intriguing applications in applied as well as fundamental physics, ranging from geodesy and seismology to the investigation of possible time variations of fundamental constants and the search for Dark Matter [1,2].

    Only one nuclear state is known so far that could drive a nuclear clock: the ‘Thorium Isomer 229mTh’, i.e. the isomeric first excited state of 229Th, representing the lowest nuclear excitation so far reported in the whole landscape of nuclear isotopes. Since its first direct detection in 2016 [3], considerable progress could be achieved in characterizing the properties and decay parameters of this elusive nuclear excitation: the half-life of the neutral isomer was determined [4], the hyperfine structure was measured via collinear laser spectroscopy, providing information on nuclear moments and the nuclear charge radius [5] and also the excitation energy of the isomer could be directly determined 8.28(17) eV [6]. In a recent experiment at CERN’s ISOLDE facility, the long-sought radiative decay of the Thorium isomer could be observed for the first time via implantation of (β decaying) 229Ac into a VUV transparent crystal and subsequent fluorescence detection in a VUV spectrometer. Thus, the excitation energy of 229mTh could be determined with unprecedented precision to 8.338(24) eV, corresponding to a wavelength of 148.71(42) nm [7]. Moreover, the observation of the radiative decay lays the foundation for a future solid-state based nuclear clock as a promising alternative to an ion-trap based configuration.

    This recent breakthrough opens the door towards a laser-driven control of the isomeric transition and thus to the development of an ultra-precise nuclear frequency standard. The talk will review the present status together with recently completed, ongoing and planned activities towards the realization of a first nuclear clock.

    [1] E Peik, T Schumm, M S Safronova, A Pálffy, J Weitenberg and P G Thirolf, Quantum Sci. Technol. 6, 034002 (2021)
    [2] P G Thirolf, B Seiferle and L von der Wense, Ann. Phys. 531, 1800391 (2019)
    [3] L von der Wense, B Seiferle, M Laatiaoui, J B Neumayr, H-J Maier, H-F Wirth, C Mokry, J Runke, K Eberhardt, C E Düllmann, N G Trautmann and P G Thirolf, Nature 533, 47 (2016)
    [4] B Seiferle, L von der Wense and P G Thirolf, Phys. Rev. Lett. 118, 042501 (2017)
    [5] J Thielking, M V Okhapkin, P Głowacki, D M Meier, L von der Wense, B Seiferle, C E Düllmann, P G Thirolf and E Peik, Nature 556, 321 (2018)
    [6] B Seiferle, L von der Wense, P V Bilous, I Amersdorffer, C Lemell, F Libisch, S Stellmer, T Schumm, C E Düllmann, A Pálffy and P G Thirolf, Nature 573, 243 (2019)
    [7] S Kraemer, J Moens, M Athanasakis-Kaklamanakis et al., arXiv:2209:10276 (2022) and Nature (2023), in press

  9. Quantum matter, clocks, and fundamental physics

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      Jun Ye

      JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO, USA

    Precise quantum state engineering, many-body physics, and innovative laser technology are revolutionizing the performance of atomic clocks and metrology, providing opportunities to explore emerging phenomena and probe fundamental physics. Recent advances include precise control of many-body interactions to achieve high accuracy, measurement of gravitation time dilation across a few hundred micrometers, and employment of spin squeezing for clock comparison.

  10. Analog Quantum Machine Learning


    Quantum neuromorphic computing is a subfield of quantum machine learning that capitalizes on inherent system dynamics. As a result, it can run on contemporary, noisy quantum hardware and is poised to realize challenging algorithms in the near term. I will show how a present-day programmable quantum simulator has all the features to allow the learning of several cognitive tasks, such as multitasking, decision-making, and memory, by taking advantage of several key features of such a platform. One key element yet to be added to such modes is the characterization of the requisite dynamics for universal quantum neuromorphic computations. We address this issue by proposing a quantum perceptron, a simple mathematical model for a neuron that is the building block of various machine learning architectures and demonstrate that it can realize universal quantum computations. The effectiveness of this architecture can then also be shown by applying it to, e.g., calculating the inner products between quantum states, energy measurement, and quantum metrology.