Rydberg atoms have shown significant promise as the basis for highly sensitive detectors of continuous radio-frequency (RF) E-fields. Here, we study their time-dependent response to pulse-modulated RF E-fields at 19.4 GHz using a cesium vapour cell at room temperature. We use density matrix simulations to explain the time scales that shape the transient atomic response under different laser conditions, finding them to be limited by dephasing mechanisms including transit time broadening, Rydberg-Rydberg collisions, and ionization. Using a matched filter, we demonstrate the detection of individual pulses with durations from 10 $μ$s down to 50 ns and amplitudes from 15000 $μ$V cm$^{-1}$ down to ~170 $μ$V cm$^{-1}$, corresponding to a sensitivity of ~240 nV cm$^{-1}$ Hz$^{-1/2}$. Finally, we highlight the potential of a Rydberg vapour cell as a receiver by detecting pulse trains from a rotating emitter on a simulated passing aircraft.
We present the experimental realization and characterization of a Ramsey interferometer based on optically trapped ultracold potassium atoms, where one state is continuously coupled by an off-resonant laser field to a highly-excited Rydberg state. We show that the observed interference signals can be used to precisely measure the Rydberg atom-light coupling strength as well as the population and coherence decay rates of the Rydberg-dressed states with sub-kilohertz accuracy and for Rydberg state fractions as small as one part in $10^{6}$. We also demonstrate an application for measuring small,…
The highly sensitive, phase- and frequency-resolved detection of microwave electric fields is of central importance for diverse fields ranging from astronomy, remote sensing, communication and microwave quantum technology. However, present quantum sensing of microwave electric fields primarily relies on atom-based electrometers only enabling amplitude measurement. Moreover, the best sensitivity of atom-based electrometers is limited by photon shot noise to few $μ$Vcm$^{-1}$Hz$^{-1/2}$: While going beyond is in principle possible by using squeezed light or Schrödinger-cat state, the former is v…
The non-linear and non-local effects in atomic Rydberg media under electromagnetically induced transparency (EIT) make it a versatile platform for fundamental studies and applications in quantum information. In this paper, we study the dynamics of a Rydberg-EIT system in an ensemble that allows for more than one Rydberg excitation in the propagation direction. The density of two-level atoms is such that transient superradiant effects occur. We experimentally observe a cross-over between coherent collective emission (`flash') of two-level atoms to a Rydberg dressed regime ('dressed flash') unde…
Using ab-initio non-Born-Oppenheimer simulations, we demonstrate amplification of XUV radiation in a high-harmonic generation type process using the example of the hydrogen molecular ion. A small fraction of the molecules is pumped to a dissociative Rydberg state from which IR-assisted XUV amplification is observed. We show that starting at sufficiently high IR driving field intensities the ground state molecules become quasi-transparent for XUV radiation, while due to stabilization gain from Rydberg states is maintained, thus leading to lasing from strongly driven Rydberg states. Further incr…
We present an object-oriented Python library for computation of properties of highly-excited Rydberg states of alkali atoms. These include single-body effects such as dipole matrix elements, excited-state lifetimes (radiative and black-body limited) and Stark maps of atoms in external electric fields, as well as two-atom interaction potentials accounting for dipole and quadrupole coupling effects valid at both long and short range for arbitrary placement of the atomic dipoles. The package is cross-referenced to precise measurements of atomic energy levels and features extensive documentation t…
We study the photon statistics of weak coherent pulses propagating through a cold Rydberg atomic ensemble in the regime of Rydberg electromagnetically induced transparency. We show experimentally that the value of the second-order autocorrelation function of the transmitted light strongly depends on the position within the pulse and heavily varies during the transients of the pulse. In particular, we show that the falling edge of the transmitted pulse displays much lower values than the rest of the pulse. We derive a theoretical model that quantitatively predicts our results and explains the p…
Electrometry near a dielectric surface is performed using Rydberg electromagnetically induced transparency (EIT). The large polarizability of high n-state Rydberg atoms gives this method extreme sensitivity. We show that adsorbates on the dielectric surface produce a significant electric field that responds to an applied field with a time constant of order one second. For transient applied fields (with a time scale of < 1 s) we observe good agreement with calculations based on numerical solutions of Laplace's equation using an effective dielectric constant to simulate the bulk dielectric.
We investigate the transient optical response property of an electromagnetically induced transparency (EIT) in a cold Rydberg atomic gas. We show that both the transient behavior and the steady-state EIT spectrum of the system depend strongly on Rydberg interaction. Especially, the response speed of the Rydberg-EIT can be five-times faster (and even higher) than the conventional EIT without the Rydberg interaction. For comparison, two different theoretical approaches (i.e. two-atom model and many-atom model) are considered, revealing that Rydberg blockade effect plays a significant role for in…
We investigate the phenomenon of bistability in a thermal gas of cesium atoms excited to Rydberg states. We present both measurements and a numerical model of the phenomena based on collisions. By directly measuring the plasma frequency, we show that the origin of the bistable behavior lies in the creation of a plasma formed by ionized Rydberg atoms. Recombination of ions and electrons manifests as fluorescence which allows us to characterize the plasma properties and study the transient dynamics of the hysteresis that occurs. We determine scaling parameters for the point of plasma formation, …
When Rydberg states are excited in a dense atomic gas the mean number of excited atoms reaches a stationary value after an initial transient period. We shed light on the origin of this steady state that emerges from a purely coherent evolution of a closed system. To this end we consider a one-dimensional ring lattice, and employ the perfect blockade model, i.e. the simultaneous excitation of Rydberg atoms occupying neighboring sites is forbidden. We derive an equation of motion which governs the system's evolution in excitation number space. This equation possesses a steady state which is stro…
The observation of the Stark-tuned Förster resonances between Rydberg atoms excited by narrowband cw laser radiation requires usage of a Stark-switching technique in order to excite the atoms first in a fixed electric field and then to induce the interactions in a varied electric field, which is scanned across the Förster resonance. In our experiments with a few cold Rb Rydberg atoms we have found that the transients at the edges of the electric pulses strongly affect the line shapes of the Förster resonances, since the population transfer at the resonances occurs on a time scale of $\sim$100 …
The dynamics of autoionizing Rydberg states of oxygen are studied using attosecond transient absorption technique, where extreme ultraviolet (XUV) initiates molecular polarization and near infrared (NIR) pulse perturbs its evolution. Transient absorption spectra show positive optical density (OD) change in the case of $nsσ_g$ and $ndπ_g$ autoionizing states of oxygen and negative OD change for $ndσ_g$ states. Multiconfiguration time-dependent Hartree-Fock (MCTDHF) calculation are used to simulate the transient absorption spectra and their results agree with experimental observations. The time …
Rydberg-assisted atomic electrometry using alkali-metal atoms contained inside a vacuum environment for detecting external electric fields (E-fields) at frequencies $<$ a few kHz has been quite challenging due to the low-frequency E-field screening effect that is caused by the alkali-metal atoms adsorbed on the inner surface of the container. We report a very slow E-field screening phenomenon with a time scale up to $\sim$ second on a rubidium (Rb) vapor cell that is made of monocrystalline sapphire. Using this sapphire-made Rb vapor cell with optically induced, internal bias E-field, we demon…
Exploring controllable interactions lies at the heart of quantum science. Neutral Rydberg atoms provide a versatile route toward flexible interactions between single quanta. Previous efforts mainly focused on the excitation annihilation~(EA) effect of the Rydberg blockade due to its robustness against interaction fluctuation. We study another effect of the Rydberg blockade, namely, the transition slow-down~(TSD). In TSD, a ground-Rydberg cycling in one atom slows down a Rydberg-involved state transition of a nearby atom, which is in contrast to EA that annihilates a presumed state transition. …
Non-destructive optical read-out and manipulation of circular Rydberg atoms
Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-Université PSL, Sorbonne Université（卡斯特尔-布罗塞尔实验室，法兰西公学院，法国国家科学研究中心，巴黎高等师范学院-巴黎文理研究大学，索邦大学）；Institut Universitaire de France（法兰西学院）
We study transient charges formed in methane clusters following ionization by intense near-infrared laser pulses. Cluster ionization by 400 fs ($I=1 \times 10^{14}$ W/cm$^2$) pulses is highly efficient, resulting in the observation of a dominant C$^{3+}$ ion contribution. The C$^{4+}$ ion yield is very small, but is strongly enhanced by applying a time-delayed weak near-infrared pulse. We conclude that most of the valence electrons are removed from their atoms during the laser-cluster interaction, and that electrons from the nanoplasma recombine with ions and populate Rydberg states when the c…
In any atomic species, the spherically symmetric potential originating from the charged nucleus results in fundamental symmetry properties governing the structure of atomic states and transition rules between them. If atoms are exposed to external electric fields, these properties are modified giving rise to energy shifts such as the AC Stark-effect in varying fields and, contrary to this in a constant (DC) electric field for high enough field strengths, the breaking of the atomic symmetry which causes fundamental changes in the atom's properties. This has already been observed for atomic Rydb…
