arXiv subjects

G. Raithel

Publications and source records attributed to G. Raithel.

At least 19 recordsLinked to original sources

arXiv2021

Tractor Atom Interferometry

We propose a tractor atom interferometer (TAI) based on three-dimensional (3D) confinement and transport of split atomic wavefunction components in potential wells that follow programmed paths. The paths are programmed to split and recombine atomic wavefunctions at well-defined space-time points, guaranteeing closure of the interferometer. Uninterrupted 3D confinement of the interfering wavefunction components in the tractor wells eliminates coherence loss due to wavepacket dispersion. Using Crank-Nicolson simulation of the time-dependent Schrödinger equation, we compute the quantum evolution of scalar and spinor wavefunctions in several TAI sample scenarios. The interferometric phases extracted from the wavefunctions allow us to quantify gravimeter sensitivity, for the TAI scenarios studied. We show that spinor-TAI supports matter-wave beam splitters that are more robust against non-adiabatic effects than their scalar-TAI counterparts. We confirm the validity of semiclassical path-integral phases taken along the programmed paths of the TAI. Aspects for future experimental realizations of TAI are discussed.

physics.atom-ph↗

arXiv2021

Long-range Rydberg-atom-ion molecules of Rb and Cs

We propose a novel type of Rydberg dimer, consisting of a Rydberg-state atom bound to a distant positive ion. The molecule is formed through long-range electric-multipole interaction between the Rydberg atom and the point-like ion. We present potential energy curves (PECs) that are asymptotically connected with Rydberg $nP$- or $nD$-states of rubidium or cesium. The PECs exhibit deep, long-range wells which support many vibrational states of Rydberg-atom-ion molecules (RAIMs). We consider photo-association of RAIMs in both the weak and the strong optical-coupling regimes between initial and Rydberg states of the neutral atom. Experimental considerations for the realization of RAIMs are discussed.

physics.atom-ph↗

arXiv2020

Measurement of Rb g-series quantum defect using two-photon microwave spectroscopy

We utilize two-photon high-precision microwave spectroscopy of $ng\rightarrow(n+2)g$ transitions to precisely measure the high-angular-momentum $g$-series quantum defect of $^{85}$Rb. Samples of cold Rydberg atoms in the $ng$ state are prepared via a three-photon optical excitation combined with controlled electric-field mixing and probed with 40-$μ$s-long microwave interaction pulses. The leading systematic uncertainty arises from DC Stark shifts, which is addressed by a cancellation of background electric fields in all three dimensions. From our measurements and an analysis of systematic uncertainties from DC and AC Stark shifts, van der Waals interactions, and microwave frequency calibration, we obtain $δ_0=0.0039990(21)$ and $δ_2=-0.0202(21)$. We discuss our results in context with recent work elsewhere, as well as applications towards precision measurement.

physics.atm-clus↗

arXiv2020

Doppler narrowing, Zeeman and laser beam-shape effects in $Λ$-type Electromagnetically Induced Transparency on the $^{85}$Rb D2 line in a vapor cell

We study $Λ$-type Electromagnetically Induced Transparency (EIT) on the Rb D2 transition in a buffer-gas-free thermal vapor cell without anti-relaxation coating. Experimental data show distinguished features of velocity-selective optical pumping and one EIT resonance. The Zeeman splitting of the EIT line in magnetic fields up to 12 Gauss is investigated. One Zeeman component is free of the first-order shift and its second-order shift agrees well with theory. The full width at half maximum (FWHM) of this magnetic-field-insensitive EIT resonance is reduced due to Doppler narrowing, scales linearly in Rabi frequency over the range studied, and reaches about 100~kHz at the lowest powers. These observations agree with an analytic model for a Doppler-broadened medium developed in Ref. \cite{PhysRevA.66.013805,7653385}. Numerical simulation using the Lindblad equation reveals that the transverse laser intensity distribution and two $Λ$-EIT systems must be included to fully account for the measured line width and line shape of the signals. Ground-state decoherence, caused by effects that include residual optical frequency fluctuations, atom-wall and trace-gas collisions, is discussed.

physics.atom-ph↗

arXiv2019

Modulation spectroscopy of Rydberg atoms in an optical lattice

We develop and study quantum and semi-classical models of Rydberg-atom spectroscopy in amplitude-modulated optical lattices. Both initial- and target-state Rydberg atoms are trapped in the lattice. Unlike in any other spectroscopic scheme, the modulation-induced ponderomotive coupling between the Rydberg states is spatially periodic and perfectly phase-locked to the lattice trapping potentials. This leads to a novel type of sub-Doppler mechanism, which we explain in detail. In our exact quantum model, we solve the time-dependent Schrödinger equation in the product space of center-of-mass (COM) momentum states and the internal-state space. We also develop a perturbative model based on the band structure in the lattice and Fermi's golden rule, as well as a semi-classical trajectory model in which the COM is treated classically and the internal-state dynamics quantum-mechanically. In all models we obtain the spectrum of the target Rydberg-state population versus the lattice modulation frequency, averaged over the initial thermal COM momentum distribution of the atoms. We investigate the quantum-classical correspondence of the problem in several parameter regimes and exhibit spectral features that arise from vibrational COM coherences and rotary-echo effects. Applications in Rydberg-atom spectroscopy are discussed.

quant-ph↗

arXiv2019

DC Electric Fields in Electrode-Free Glass Vapor Cell by Photoillumination

Rydberg-atom-enabled atomic vapor cell technologies show great potentials in developing devices for quantum enhanced sensors. In this paper, we demonstrate laser induced DC electric fields in an all-glass vapor cell without bulk or thin film electrodes. The spatial field distribution is mapped by Rydberg electromagnetically induced transparency spectroscopy. We explain the measured with a boundary-value electrostatic model. This work may inspire new ideas for DC electric field control in designing miniaturized atomic vapor cell devices. Limitations and other charge effects are also discussed.

physics.atom-ph↗

arXiv2019

Electromagnetically-induced transparency, absorption, and microwave field sensing in a Rb vapor cell with a three-color all-infrared laser system

A comprehensive study of three-photon electromagnetically-induced transparency (EIT) and absorption (EIA) on the rubidium cascade $5S_{1/2} \rightarrow 5P_{3/2}$ (laser wavelength 780~nm), $5P_{3/2} \rightarrow 5D_{5/2}$ (776~nm), and $5D_{5/2}\rightarrow 28F_{7/2}$ (1260~nm) is performed. The 780-nm probe and 776-nm dressing beams are counter-aligned through a Rb room-temperature vapor cell, and the 1260-nm coupler beam is co- or counter-aligned with the probe beam. Several cases of EIT and EIA, measured over a range of detunings of the 776-nm beam, are studied. The observed phenomena are modeled by numerically solving the Lindblad equation, and the results are interpreted in terms of the probe-beam absorption behavior of velocity- and detuning-dependent dressed states. To explore the utility of three-photon Rydberg EIA/EIT for microwave electric-field diagnostics, a sub-THz field generated by a signal source and a frequency quadrupler is applied to the Rb cell. The 100.633-GHz field resonantly drives the $28F_{7/2}\leftrightarrow29D_{5/2}$ transition and causes Autler-Townes splittings in the Rydberg EIA/EIT spectra, which are measured and employed to characterize the performance of the microwave quadrupler.

physics.atom-ph↗

arXiv2017

Paschen-Back effect and Rydberg-state diamagnetism in vapor-cell electromagnetically induced transparency

We report on rubidium vapor-cell Rydberg electromagnetically induced transparency (EIT) in a 0.7~T magnetic field where all involved levels are in the hyperfine Paschen-Back regime, and the Rydberg state exhibits a strong diamagnetic interaction with the magnetic field. Signals from both $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ are present in the EIT spectra. This feature of isotope-mixed Rb cells allows us to measure the field strength to within a $\pm 0.12$\% relative uncertainty. The measured spectra are in excellent agreement with the results of a Monte Carlo calculation and indicate unexpectedly large Rydberg-level dephasing rates. Line shifts and broadenings due to small inhomogeneities of the magnetic field are included in the model.

physics.atom-ph↗

arXiv2016

Control of spatial correlations between Rydberg excitations using rotary echo

We manipulate correlations between Rydberg excitations in cold atom samples using a rotary-echo technique. The correlations are due to interactions between the Rydberg atoms. In the rotary-echo excitation sequence, the phase of the excitation pulse is flipped at a selected time during the pulse. We measure the resultant change in the spatial pair correlation function of the excitations via direct position-sensitive atom imaging. For zero detuning of the lasers from the interaction-free Rydberg-excitation resonance, the pair-correlation value at the most likely nearest-neighbor Rydberg-atom distance is substantially enhanced when the phase is flipped at the middle of the excitation pulse. In this case, the rotary echo eliminates most uncorrelated (un-paired) atoms, leaving an abundance of correlated atom pairs at the end of the sequence. In off-resonant cases, a complementary behavior is observed. We further characterize the effect of the rotary-echo excitation sequence on the excitation-number statistics of the atom sample.

physics.atom-ph↗

arXiv2016

Atom-pair kinetics with strong electric-dipole interactions

Rydberg-atom ensembles are switched from a weakly- into a strongly-interacting regime via adiabatic transformation of the atoms from an approximately non-polar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar $C_3$ coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.

physics.atom-ph↗

arXiv2015

Measurement of van-der-Waals interaction by atom trajectory imaging

We study the repulsive van der Waals interaction of cold rubidium $70S_{1/2}$ Rydberg atoms by analysis of time-delayed pair correlation functions. After excitation, Rydberg atoms are allowed to accelerate under the influence of the van der Waals force. Their positions are then measured using a single-atom imaging technique. From the average pair correlation function of the atom positions we obtain the initial atom-pair separation and the terminal velocity, which yield the van der Waals interaction coefficient $C_{6}$. The measured $C_{6}$ value agrees well with calculations. The experimental method has been validated by simulations. The data hint at anisotropy in the overall expansion, caused by the shape of the excitation volume. Our measurement implies that the interacting entities are individual Rydberg atoms, not groups of atoms that coherently share a Rydberg excitation.

physics.atom-ph↗

arXiv2012

Guiding of Rydberg atoms in a high-gradient magnetic guide

We study the guiding of $^{87}$Rb 59D$_{5/2}$ Rydberg atoms in a linear, high-gradient, two-wire magnetic guide. Time delayed microwave ionization and ion detection are used to probe the Rydberg atom motion. We observe guiding of Rydberg atoms over a period of 5 ms following excitation. The decay time of the guided atom signal is about five times that of the initial state. We attribute the lifetime increase to an initial phase of $l$-changing collisions and thermally induced Rydberg-Rydberg transitions. Detailed simulations of Rydberg atom guiding reproduce most experimental observations and offer insight into the internal-state evolution.

physics.atom-ph↗

arXiv2012

Design and Fabrication of a Chip-based Continuous-wave Atom Laser

We present a design for a continuous-wave (CW) atom laser on a chip and describe the process used to fabricate the device. Our design aims to integrate quadrupole magnetic guiding of ground state Rb atoms with continuous surface adsorption evaporative cooling to create a continuous Bose-Einstein condensate; out-coupled atoms from the condensate should realize a CW atom laser. We choose a geometry with three wires embedded in a spiral pattern in a silicon subtrate. The guide features an integrated solenoid to mitigate spin-flip losses and provide a tailored longitudinal magnetic field. Our design also includes multiple options for atom interferometry: accomodations are in place for laser-generated atom Fabry-Perot and Mach-Zehnder interferometers, and a pair of atomic beam X-splitters is incorporated for an all-magnetic atom Mach-Zehnder setup. We demonstrate the techniques necessary to fabricate our device using existing micro- and nano-scale fabrication equipment, and discuss future options for modified designs and fabrication processes.

physics.atom-ph↗

arXiv2008

Role of the Mean-field in Bloch Oscillations of a Bose-Einstein Condensate in an Optical Lattice and Harmonic Trap

Using the Crank-Nicholson method, we study the evolution of a Bose-Einstein condensate in an optical lattice and harmonic trap. The condensate is excited by displacing it from the center of the harmonic trap. The mean field plays an important role in the Bloch-like oscillations that occur after sufficiently large initial displacement. We find that a moderate mean field significantly suppresses the dispersion of the condensate in momentum space. When the mean field becomes large, soliton and vortex structures appear in the condensate wavefunction.

physics.atom-ph↗

arXiv2008

1-D Mott insulator transition of a Bose-Einstein condensate

The superfluid to one-dimensional Mott-insulator transition of a 87Rb Bose-Einstein condensate is demonstrated. In the experiment, we apply a one-dimensional optical lattice, formed by two laser beams with a wavelength of 852 nm, to a three dimensional BEC in a shallow trap. We use Kapitza-Dirac scattering to determine the depth of the optical lattice without knowledge of its exact geometry. We further study the dynamics of the transition as well as steady-state phase behavior specific to the one-dimensional case.

physics.atom-ph↗

arXiv2003

Autler-Townes spectroscopy of the $5S_{1/2}-5P_{3/2}-44D$ cascade of cold $^{85}$Rb atoms

We study nonlinear optical effects in the laser excitation of Rydberg states. $5S_{1/2}$ and $5P_{3/2}$ levels of $^{85}$Rb are strongly coupled by a strong laser field and probed by a weak laser tuned to the $5P_{3/2} - 44D$ Rydberg resonance. We observe high contrast Autler-Townes spectra which are dependent on the pump polarization, intensity and detuning. The observed behavior agrees with calculations, which include the effect of optical pumping.

quant-ph↗

arXiv2002

A slow and dark atomic beam

We demonstrate a method to produce a very slow atomic beam from a vapour cell magneto-optical trap. Atoms are extracted from the trap using the radiation pressure imbalance caused by a push beam. An additional transfer beam placed near the center of the trap transfers the atomic beam into an off-resonant state. The velocity of the atomic beam has been varied by changing the intensity of the push beam or the position of the transfer beam. The method can be used to generate a continuous, magnetically guided atomic beam in a dark state.

cond-mat↗

arXiv2002

Nanometer scale period sinusoidal atom gratings produced by a Stern-Gerlach beam splitter

An atom interferometer based on a Stern-Gerlach beam splitter is proposed. Atom scattering from a combination of magnetic quadrupole and homogeneous magnetic fields is considered. Using Raman transitions, atoms are coherently excited into and de-excited from sublevels having nonzero magnetic quantum numbers. The spatial regions in which the atoms are in such sublevels are small and have magnetic fields designed to have constant gradients. Therefore, the atoms experience position-independent accelerations, and the aberration of the coherently separated and recombined atomic beams remains small. We find that because of these properties it is possible to envision an apparatus producing atomic density gratings with nm-scale periods and large contrasts over 10-100 $μ$m. We use a new method of describing the atomic interaction with a pulsed spatially homogeneous field. In our detailed analysis, we calculate corrections caused by the non-linear part of the potential and the finite value of the de-Broglie wave length. The chromatic aberration and the effects of an angular beam divergence are analyzed, and optimal conditions for an experimental demonstration of the technique are identified.%The $lin\bot %lin$ combination of resonant co-propagating traveling waves splits %atoms between different Zeeman sublevels. %For a given desirable atom %grating period and length, characteristics of the atomic beam and %magnetic field are found from requirements that corrections remain %below $10%.$

physics.atom-ph↗