arXiv subjects

Thibault Vogt

Publications and source records attributed to Thibault Vogt.

At least 19 recordsLinked to original sources

arXiv2025

Imaging a chain of strongly correlated Rydberg excitations enabled by Förster-resonance-enhanced interaction

Rydberg atoms are currently a very fast advancing quantum platform. For many interesting and demanding applications, including quantum computation, fast detection of a Rydberg excitation or a Rydberg qubit for information readout would be one of the most desirable developments. We demonstrate single-shot and \textit{in situ} absorption imaging of individual Rydberg excitations. This level of resolution is achieved using an electromagnetically induced transparency scheme involving a Rydberg energy level that is highly sensitive to the presence of Rydberg atoms due to Förster-resonance-enhanced dipole couplings. Spectroscopic measurements illustrate the existence of the Förster resonance and underscore the state-selectivity of the technique. With an imaging exposure time as short as 3 $μ$s, we successfully resolve linear chains of Rydberg excitations in a one-dimensional configuration. The extracted second-order correlation shows strong anti-bunching due to excitation blockade, and a Fourier analysis reveals the long-range order in the chains of Rydberg excitations. This imaging technique, with minimal destruction, will be of great interest for leveraging ensemble-encoded qubits in quantum computation and quantum simulation applications.

quant-ph↗

arXiv2024

Optimizing Four-Wave Mixing in Rydberg Atoms for Microwave-Optical Conversion

We perform a numerical and analytical investigation of microwave-to-optical conversion based on four-wave mixing in Rydberg atoms. Our work demonstrates that both all-resonant and off-resonant frequency-mixing configurations achieve near-unit photon conversion efficiencies. We review the conditions that can lead to the presence of two possible dark states. We find that for both configurations, one of the dark states can be detrimental at high microwave powers, and show that an additional limitation to all-resonant frequency mixing is microwave-induced fluorescence. Finally, we confirm that the off-resonant configuration is more appropriate as it allows for efficient photon conversion on a wider range of input microwave intensities with reduced total power of the auxiliary fields.

physics.atom-ph↗

arXiv2024

Hybrid atom-photon entangling gates via Gaussian soft control

Hybrid atom-photon gates play an important role for the realization of a quantum interface capable of mapping atomic states to photons for communication across quantum networks. Here, we propose a feasible theoretical scheme for implementing a hybrid atom-photon controlled-Z gate between an atom and a microwave photon in a superconducting coplanar waveguide resonator based on the Gaussian soft control technique. The gate protocol employs a classical auxiliary field that induces an atomic transition between one state of the atomic qubit and Rydberg states for obtaining strong coupling of the atom and microwave resonator. By tailoring the amplitude of this field with Gaussian temporal modulation, the gate performances are improved in various aspects. Numerical simulations demonstrate that the controlled-Z gate based on Gaussian soft control is resilient to the variation of the atom-photon coupling strength, deviation in the gate time, and less sensitive to the Rydberg level shifts caused by stray electric fields.

quant-ph↗

arXiv2023

Fast Single-shot Imaging of Individual Ions via Homodyne Detection of Rydberg-Blockade-Induced Absorption

We introduce well-separated $^{87}$Rb$^+$ ions into an atomic ensemble by microwave ionization of Rydberg excitations and realize single-shot imaging of the individual ions with an exposure time of 1 $μ$s. This imaging sensitivity is reached by using homodyne detection of ion-Rydberg-atom interaction induced absorption. We obtain an ion detection fidelity of (80 $\pm$ 5)\% from analyzing the absorption spots in acquired single-shot images. These \textit{in situ} images provide a direct visualization of the ion-Rydberg interaction blockade and reveal clear spatial correlations between Rydberg excitations. The capability of imaging individual ions in a single shot is of interest for investigating collisional dynamics in hybrid ion-atom systems and for exploring ions as a probe for measurements of quantum gases.

physics.atom-ph↗

arXiv2023

Ion Imaging via Long-Range Interaction with Rydberg Atoms

We demonstrate imaging of ions in an atomic gas with ion-Rydberg atom interaction induced absorption. This is made possible by utilizing a multi-photon electromagnetically induced transparency (EIT) scheme and the extremely large electric polarizability of a Rydberg state with high orbital angular momentum. We process the acquired images to obtain the distribution of ion clouds and to spectroscopically investigate the effect of the ions on the EIT resonance. Furthermore, we show that our method can be employed to image the dynamics of ions in a time resolved way. As an example, we map out the avalanche ionization of a gas of Rydberg atoms. The minimal disruption and the flexibility offered by this imaging technique make it ideally suited for the investigation of cold hybrid ion-atom systems.

physics.atom-ph↗

arXiv2020

Directional THz generation in hot Rb vapor excited to a Rydberg state

We optically excite $^{85}$Rb atoms in a heated vapor cell to a low-lying Rydberg state 10D$_{5/2}$ and observe directional terahertz (THz) beams at 3.3 THz and 7.8 THz. These THz fields are generated by amplified spontaneous emission from the 10D$_{5/2}$ state to the 11P$_{3/2}$ and 8F$_{7/2}$ states, respectively. In addition, we observe ultraviolet (UV) light produced by four-wave mixing of optical pump lasers and the 3.3 THz field. We characterize the generated THz power over the detuning and power of pump lasers, and identify experimental conditions favoring THz and UV generation, respectively. Our scheme paves a new pathway towards generating high-power narrow-band THz radiation.

physics.atom-ph↗

arXiv2019

Collimated UV light generation by two-photon excitation to a Rydberg state in Rb vapor

We use two continuous-wave (CW) laser beams of 780 nm and 515 nm to optically drive $^{85}$Rb atoms in a heated vapor cell to a low-lying Rydberg state 10D$_{5/2}$. We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the 11P$_{3/2}$ state to the 5S$_{1/2}$ state. This indicates the presence of a coherent four-wave mixing process, built up by two input laser fields as well as a terahertz (THz) radiation of 3.28 THz that is generated by amplified spontaneous emission between the 10D$_{5/2}$ and the 11P$_{3/2}$ states. We characterize the 311 nm UV light generation and its dependence on various physical parameters. This scheme could open up a new possibility for generating narrow-band THz waves as well as deep UV radiation.

physics.atom-ph↗

arXiv2018

Efficient microwave-to-optical conversion using Rydberg atoms

We demonstrate microwave-to-optical conversion using six-wave mixing in $^{87}$Rb atoms where the microwave field couples to two atomic Rydberg states, and propagates collinearly with the converted optical field. We achieve a photon conversion efficiency of ~5% in the linear regime of the converter. In addition, we theoretically investigate all-resonant six-wave mixing and outline a realistic experimental scheme for reaching efficiencies greater than 60%.

physics.atom-ph↗

arXiv2018

Microwave-assisted Rydberg Electromagnetically induced transparency

We demonstrate electromagnetically induced transparency (EIT) in a four-level cascade-like system, where the two upper levels are Rydberg states coupled by a microwave field. A two-photon transition consisting of an off-resonant microwave field and an off-resonant optical field forms an effective coupling field to induce transparency of the probe light. We characterize the Rabi frequency of the effective coupling field, as well as the EIT microwave spectra. The results show that microwave assisted EIT allows us to efficiently access Rydberg states with relatively high orbital angular momentum $\ell=3$, which is promising for the study of exotic Rydberg molecular states.

physics.atom-ph↗

arXiv2018

Lévy statistics of interacting Rydberg gases

A statistical analysis of the laser excitation of cold and randomly distributed atoms to Rydberg states is developed. We first demonstrate with a hard ball model that the distribution of energy level shifts in an interacting gas obeys Lévy statistics, in any dimension $d$ and for any interaction $-C_p/R^p$ under the condition $d/p<1$. This result is confirmed with a Monte Carlo rate equations simulation of the actual laser excitation in the particular case $p=6$ and $d=3$. With this finding, we develop a statistical approach for the modeling of probe light transmission through a cold atom gas driven under conditions of electromagnetically induced transparency involving a Rydberg state. The simulated results are in good agreement with experiment.

physics.atom-ph↗

arXiv2018

Coherent microwave-to-optical conversion via six-wave mixing in Rydberg atoms

We present an experimental demonstration of converting a microwave field to an optical field via frequency mixing in a cloud of cold $^{87}$Rb atoms, where the microwave field strongly couples to an electric dipole transition between Rydberg states. We show that the conversion allows the phase information of the microwave field to be coherently transferred to the optical field. With the current energy level scheme and experimental geometry, we achieve a photon conversion efficiency of ~0.3% at low microwave intensities and a broad conversion bandwidth of more than 4 MHz. Theoretical simulations agree well with the experimental data, and indicate that near-unit efficiency is possible in future experiments.

physics.atom-ph↗

arXiv2016

Spectral shift and dephasing of electromagnetically induced transparency in an interacting Rydberg gas

We perform spectroscopic measurements of electromagnetically induced transparency (EIT) in a strongly interacting Rydberg gas, and observe a significant spectral shift of the transparency from the single-atom EIT resonance as well as a spectral dephasing of the same order. We characterize the shift and dephasing as a function of atomic density, probe Rabi frequency, and principal quantum number of Rydberg states, and demonstrate that the observed spectral shift and dephasing are reduced if the size of a Gaussian atomic cloud is increased. We simulate our experiment with a semi-analytical model, which gives results in good agreement with our experimental data.

physics.atom-ph↗

arXiv2015

Lensing effect of electromagnetically induced transparency involving a Rydberg state

We study the lensing effect experienced by a weak probe field under conditions of electromagnetically induced transparency (EIT) involving a Rydberg state. A Gaussian coupling beam tightly focused on a laser-cooled atomic cloud produces an inhomogeneity in the coupling Rabi frequency along the transverse direction and makes the EIT area acting like a gradient-index medium. We image the probe beam at the position where it exits the atomic cloud, and observe that a red-detuned probe light is strongly focused with a greatly enhanced intensity whereas a blue-detuned one is de-focused with a reduced intensity. Our experimental results agree very well with the numerical solutions of Maxwell-Bloch equations.

quant-ph↗

arXiv2011

Cooperative scattering measurement of coherence in a spatially modulated Bose gas

Correlations of a Bose gas released from an optical lattice are measured using superradiant scattering. Conditions are chosen so that after initial incident light pumping at the Bragg angle for diffraction, due to matter wave amplification and mode competition, superradiant scattering into the Bragg diffracted mode is preponderant. A temporal analysis of the superradiant scattering gain reveals periodical oscillations and damping due to the initial lack of coherence between lattice sites. Such damping is used for characterizing first order spatial correlations in our system with a precision of one lattice period.

cond-mat.quant-gas↗

arXiv2011

Exploring multi-band excitations of interacting Bose gases in a 1D optical lattice by coherent scattering

We use a coherent Bragg diffraction method to impart an external momentum to ultracold bosonic atoms trapped in a one-dimensional optical lattice. This method is based on the application of a single light pulse, with conditions where scattering of photons can be resonantly amplified by the atomic density grating. An oscillatory behavior of the momentum distribution resulting from the time evolution in the lattice potential is then observed. By measuring the oscillating frequencies, we extract multi-band energy structures of single-particle excitations with zero pseudo-momentum transfer for a wide range of lattice depths. The excitation energy structures reveal the interaction effect through the whole range of lattice depth.

cond-mat.quant-gas↗

arXiv2011

Mode competition in superradiant scattering of matter waves

Superradiant Rayleigh scattering in a Bose gas released from an optical lattice is analyzed with incident light pumping at the Bragg angle for resonant light diffraction. We show competition between superradiance scattering into the Bragg mode and into end-fire modes clearly leads to suppression of the latter at even relatively low lattice depths. A quantum light-matter interaction model is proposed for qualitatively explaining this result.

cond-mat.quant-gas↗

arXiv2011

Laser driving of Superradiant scattering at variable incidence angle

We study superradiant scattering from a Bose-Einstein condensate using a pump laser incident at variable angle and show the presence of asymmetrically populated scattering modes. Experimental data reveal that the direction of the pump laser plays a significant role in the formation of this asymmetry, result which is in good agreement with numerical simulations based on coupled Maxwell-Schrödinger equations. Our study complements the gap of previous work in which the pump laser was only applied along the short axis or the long axis of a condensate, and extends our knowledge about cooperative scattering processes.

cond-mat.quant-gas↗

arXiv2011

Rapid non-adiabatic loading in an optical lattice

We present a scheme for non-adiabatically loading a Bose-Einstein condensate into the ground state of a one dimensional optical lattice within a few tens of microseconds typically, i.e. in less than half the Talbot period. This technique of coherent control is based on sequences of pulsed perturbations and experimental results demonstrate its feasibility and effectiveness. As the loading process is much shorter than the traditional adiabatic loading timescale, this method may find many applications.

cond-mat.quant-gas↗