Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C28: Fundamental processes in AMOLive
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Sponsoring Units: DAMOP Chair: Eduardo Ibarra Garcia Padilla, Rice Univ |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C28.00001: Broadband parametric downconversion: an analogy with Fano's theory of atomic autoionization Ryotatsu Yanagimoto, Edwin Ng, Marc P Jankowski, Tatsuhiro Onodera, Martin M Fejer, Hideo Mabuchi We develop a unified theoretical framework based on Fano’s theory for discrete-continuum interactions to analyze the dynamics of broadband parametric downconversion (PDC) in the few-pump-photon regime. Strong coupling of a discrete pump state to a continuum of signal states gives rise to several exotic dynamical features such as unit-efficiency PDC (i.e., complete pump depletion) and Rabi-like oscillations with subexponential decay. Our framework not only leads to fully analytic expressions for the PDC dynamics but also allows us to derive intuition via a direct analogy to Fano physics; e.g., unit-efficiency PDC is identified as analogous to atomic autoionization. As a demonstration of the utility of our framework, we investigate a pair of coupled nonlinear waveguides on which two discrete pump states are coupled to a common signal continuum, and destructive and constructive interferences between these two coupling paths critically control the PDC rate. In particular, perfect destructive interference leads to complete suppression of PDC, a quantum manifestation of a bound pump state in the continuum. Experimental numbers suggest these highly quantum dynamics may be relevant to dispersion-engineered nanophotonic platforms in the future. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C28.00002: Hydrogenic entanglement Sofia Qvarfort, Sougato Bose, Alessio Serafini Is there any entanglement in the simplest ubiquitous bound system? We study the solutions to the time-independent Schrödinger equation for a Hydrogenic system and devise two entanglement tests for free and localised states. For free Hydrogenic systems, we compute the Schmidt basis diagonalisation for general energy eigenstates, and for a Hydrogenic system localised to a three-dimensional Gaussian wavepacket, we demonstrate that measuring its second moments is sufficient for detecting entanglement. Our results apply to any system that exhibits Hydrogenic structure. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C28.00003: Less Probable Tunneling Takes Less Time David Spierings, Aephraim M Steinberg How much time does a tunneling particle spend in a barrier? A Larmor clock, one proposal to answer this question, measures the interaction between the particle and the barrier region using an auxiliary degree of freedom of the particle to clock the dwell time inside the barrier. We report on precise Larmor time measurements of an ultra-cold gas of 87Rb atoms tunneling through an optical barrier. The data capture distinctive features that confirm longstanding predictions of tunneling times. In particular, we demonstrate that atoms spend less time tunneling through higher barriers and that this time decreases for slower incident particles. For the lowest measured incident energy, at least 93(3)% of atoms tunneled through the barrier spending an average of 0.59(2)ms inside. This is 0.11(3)ms faster than atoms traversing the same barrier but with energy matching that of the barrier's peak and 0.21(3)ms faster than when the atoms traverse a barrier with 23% less energy. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C28.00004: Many-electron effects of strong-field ionization described in an exact one-electron theory Jakub Kocák, Axel Schild If we are interested in one-electron observables of a many-electron system, a many-electron dynamics can be represented exactly by a one-electron dynamics with effective potentials. This dimensionality reduction is achieved by the formalism of the Exact Electron Factorization (EEF). The study of the time-dependent features of the EEF potentials for a model of an atom ionized by an ultrastrong and ultrashort laser pulse sheds light upon how to construct computationally feasible approximations. The simplest approximation — the time-independent conditional amplitude (TICA) approximation — reproduces the exact dynamics for high laser field frequencies and is therefore a complementary method to single-active electron (SAE) approaches. For low frequencies there is excited state dynamics in the core region of the atom leading to a time-dependent ionization barrier in the EEF potential. Provided the core dynamics can be modeled successfully, a multi-state extention of the TICA approximation can correctly describe many-electron effects. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C28.00005: On the early-time behaviour of quantum subharmonic generation Yunjin Choi, Boerge Hemmerling, Shan-Wen Tsai, Allen P Mills A few years ago, the exponential growth rate of the stimulated annihilation photons from a singlet positronium Bose-Einstein condensate should be proportional to the square root of the positronium number density [Avetissian et al., Phys. Rev. Lett. 113, 23904 (2014)], not to the number density itself as had previously been assumed by many authors. Here we consider a quantum analysis of stimulated emission by modeling the conversion of k-ordered initial quanta of in a first oscillator to l-ordered final quanta of in a second oscillator. Our result shows that nonlinearities of this type are not unique to positronium and in fact are encountered in many systems that can be modeled as nonlinearly coupled quantum oscillators. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C28.00006: Radiative Auger process in the single-photon limit Matthias Löbl, Clemens Spinnler, Alisa Javadi, Liang Zhai, Giang Nguyen, Julian Ritzmann, Leonardo Midolo, Peter Lodahl, Andreas D. Wieck, Arne Ludwig, Richard J. Warburton An excited electron can relax by emitting a photon. In a radiative Auger process, this optical decay leads to the simultaneous excitation of another particle. On a single quantum emitter, radiative Auger has not been observed. Here, we report radiative Auger for trions in individual quantum dots. For the trion, just one electron is left after the optical recombination. The radiative Auger process promotes this Auger electron to a higher shell of the quantum dot, and the emitted photon is red-shifted. We show that the energy splitting between this red-shifted photon and the resonance fluorescence directly measures the single-particle splittings of the quantum dot [1], energies which are otherwise difficult to acquire. We prove the radiative Auger mechanism by measuring the photon statistics and the magnetic field dispersion of the emission. Going beyond the original work in the X-ray spectrum of atoms, we apply quantum optics techniques to the radiative Auger photons. This gives access to the single-electron dynamics, notably the relaxation and tunneling rates. All these properties of radiative Auger can be exploited on other semiconductor nanostructures and quantum emitters in the solid-state. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C28.00007: Suppression of Penning ionization by orbital angular momentum conservation Tobias Sixt, Jiwen Guan, Jonas Grzesiak, Markus Debatin, Frank Stienkemeier, Katrin Dulitz In our experiment, we study quantum-state-controlled Penning collisions between lithium atoms (Li) and metastable helium atoms (He*) to investigate new ways of controlling the outcome of Penning-ionizing collisions. For this, we have combined a supersonic beam source for He* atoms with a magneto-optical trap (MOT) for Li atoms. In order to get full quantum-state control of the reaction partners, the Li atoms are optically pumped into selected electronic hyperfine and magnetic substates. Additionally, we produce a pure beam of He(23S1) by the optical depletion of the He(21S0) state using a novel excitation scheme. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C28.00008: The Free Electron Gas in Cavity QED Vasil Rokaj, Michael Ruggenthaler, Florian G Eich, Angel Rubio Cavity modification of materials is a novel research field motivated by the advances in light-matter interactions. Despite this progress, exact solutions for extended macroscopic systems strongly coupled to the photon field are not available. Therefore a paradigmatic example of an exactly solvable extended system in a cavity is highly desireable. To fill this gap we revisit Sommerfeld's theory of the free electron gas in cavity quantum electrodynamics (QED). We solve this system analytically in the long-wavelength limit and we show that the electron-photon ground state is a Fermi liquid which contains virtual photons. In contrast to models of finite systems, no ground state exists if the diamagentic A2 term is omitted. Further, the cavity field modifies the conductive properties of the electron gas. Our exact solution allows to consider the thermodynamic/continuum limit for both electrons and photons by constructing an effective quantum field theory, in which the continuum of modes leads to a many-body renormalization of the electron mass, modifies the quasiparticle excitations of the Fermi liquid, and introduces dissipation into the system. |
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