We demonstrate a physical quantum simulator of ultrafast phenomena, in which
time-varying forces on neutral atoms in a tunable optical trap emulate the
electric fields of a pulsed laser acting on electrons or nuclei in a binding
potential. The simulator operates in regimes equivalent to those of ultrafast
and strong-field pulsed-laser experiments, opening up a hitherto unexplored
application of quantum simulation techniques and a complementary path towards
investigating open questions in ultrafast science. Counter-intuitively, this
approach emulates some of the fastest processes in atomic physics with some of
the slowest, giving rise to a temporal magnification factor of up to twelve
orders of magnitude which greatly simplifies experimental access to the
dynamics. The correspondence with ultrafast science is demonstrated by a
sequence of experiments: we perform nonlinear spectroscopy of a many-body bound
state, control the excitation spectrum by shaping the potential, observe
sub-cycle unbinding dynamics during strong few-cycle pulses, and directly
measure carrier-envelope phase dependence of the response to an
ultrafast-equivalent pulse.
We demonstrate a physical quantum simulator of ultrafast phenomena, in which
time-varying forces on neutral atoms in a tunable optical trap emulate the
electric fields of a pulsed laser acting on electrons or nuclei in a binding
potential. The simulator operates in regimes equivalent to those of ultrafast
and strong-field pulsed-laser experiments, opening up a hitherto unexplored
application of quantum simulation techniques and a complementary path towards
investigating open questions in ultrafast science. Counter-intuitively, this
approach emulates some of the fastest processes in atomic physics with some of
the slowest, giving rise to a temporal magnification factor of up to twelve
orders of magnitude which greatly simplifies experimental access to the
dynamics. The correspondence with ultrafast science is demonstrated by a
sequence of experiments: we perform nonlinear spectroscopy of a many-body bound
state, control the excitation spectrum by shaping the potential, observe
sub-cycle unbinding dynamics during strong few-cycle pulses, and directly
measure carrier-envelope phase dependence of the response to an
ultrafast-equivalent pulse.
Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.
Abstract Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.
The demanding experimental access to the ultrafast dynamics of materials challenges our understanding of their electronic response to applied strong laser fields. For this purpose, trapped ultracold atoms with highly controllable potentials have become an enabling tool to describe phenomena in a scenario in which some effects are more easily accessible and 12 orders of magnitude slower. In this work, we introduce a mapping between the parameters of attoscience platforms and atomic cloud simulators and propose an experimental protocol to access the emission spectrum of high-harmonic generation, a regime that has so far been elusive to cold-atom simulation. As we illustrate, the benchmark offered by these simulators can provide new insights into the conversion efficiency of extended and short nuclear potentials, as well as the response to applied elliptical polarized fields or ultrashort few-cycle pulses. Published by the American Physical Society 2024
Weakly-interacting atoms in a Bose-Einstein condensate coherently occupy the ground-state of their container. This phenomenon, coupled with the technical ability to produce precise, isolated and dynamically-tunable trapping potentials, makes ultracold atoms a versatile platform for simulating quantum mechanical systems. This thesis details the construction of two apparatus at the University of California, Santa Barbara for the production of Bose-Einstein condensates of lithium and strontium atoms respectively. Results of the first experiment performed on the strontium apparatus, a quantum simulation of ultrafast dynamics, are presented. In this experiment, driven cold atoms simulate ultrafast ionization dynamics in attosecond laser pulses, counter-intuitively emulating some of the fastest processes in atomic physics with some of the slowest. A sequence of experiments which demonstrate the correspondence with ultrafast science are described, including the direct observation of carrier-envelope-phase dependent sub-cycle unbinding dynamics. Preliminary results from a second experiment, studying phasonic excitations in a quasiperiodic lattice, are also discussed.
For decades, ultrafast light-matter interactions have provided a powerful means to observe electrons in motion across a wide range of physical systems. This dissertation builds new theoretical frameworks to make sense of the emergent phenomena that arise when light drives matter into the strong-field regime, spanning atomic, molecular, and condensed-matter systems. The resulting dynamics leave their fingerprints on a variety of observables, such as photoionization spectra, high-harmonic generation, and nonlinear spectroscopic signals, each of which provides a different window onto the underlying electronic motion. The work is organized into two parts.The first part focuses on the electric-field observables of nonlinear optical signals. Because both the amplitude and phase of the emitted field are experimentally accessible through techniques such as spectral interferometry and electro-optic sampling, the full field itself serves as a rich observable for characterizing nonlinear responses in atomic, molecular, and condensed-matter systems. Leveraging this, the simulations presented here uncover novel and largely unexplored physical phenomena encoded in these field observables. The second part turns to optical spectroscopy with quantum light. Although nonlinear optical processes are conventionally modeled within a semiclassical framework, treating the matter quantum mechanically while the driving ultrafast fields remain classical, the resulting signals can nonetheless exhibit intrinsically non-classical properties. Building on this insight, a framework for interpreting experimental data is introduced and used to show that four-wave mixing driven by ultrafast femtosecond laser pulses generates bright squeezed light. Beyond squeezed light, strong field-matter interactions can also produce attosecond entangled photons, a distinct form of quantum light. Several strategies are proposed to enhance the efficiency of their generation, with the developed theory predicting rates of energy-time entangled biphoton production orders of magnitude beyond those achievable with conventional spontaneous parametric down-conversion (SPDC) sources. The studies presented here are initial steps toward investigating quantum properties of these systems through quantum phynonlinear spectroscopy, which is not achievable with classical light.
The recent development of laser cooling and trapping techniques has made possible the controlled realization of dense and cold atomic samples, thus opening the way for spectroscopic investigations in the low and ultra-low temperature regimes not accessible with conventional techniques. In our lab, an apparatus for laser cooling and Bose-Einstein condensation of rubidium atoms is in operation, producing a sample large enough to perform reliable investigations by absorption or emission techniques. Moving from previous photoionization experiments of laser-cooled atoms in a magneto-optical trap irradiated by cw-laser radiation [1] and stimulated by the interest grown recently on ultra-cold plasma [2], we have started a series of experiments aimed at investigating the interaction of intense laser pulses with the ultra-cold neutral sample, boty aboeand below the condensation temperature. Radiation from an excimer-pumped dye laser was used at a wavelength close to 594 nm, corresponding to the ionization threshold of rubidium for two photon non-resonant absorption from the ground state, with intensities in the tens of MW/cm^2 range and a pulse duration of 16 ns. Preliminary results, attained through the dynamical analysis (atom number, temperature) of the cold atom sample after the arrival of the laser pulse, suggest the occurrence of different processes, initiated by multi-photon ionization, involving collisions between cold electrons and ultra-cold neutrals, recombination at low temperatures and collective processes in the weak and cold plasma. Interpretation of those results demonstrates that this class of experiments, based on a variety of topics typical of atomic, plasma and statistical physics, can open the way for novel and intriguing investigations of laser-matter interaction. Further experimental developments will include duplication of the laser pulse frequency and one photon ionization of ground state rubidium laser-cooled atoms. [1] O. Maragò et al., Phys. Rev. A 57 R4110 (1998); E., Arimondo et al., Appl. Surf. Sci. 154-155 527 (2000); F. Fuso et al., Opt. Commun. 173 223 (2000). [2] T.C. Killian et al., Phys. Rev. Lett. 83 4776 (1999); S. Kulin et al., Phys. Rev. Lett. 85 318 (2000).