Forbidden atomic transitions driven by an intensity-modulated laser trap

Abstract

Spectroscopy is an essential tool in understanding and manipulating quantum systems, such as atoms and molecules. The model describing spectroscopy includes the multipole-field interaction, which leads to established spectroscopic selection rules, and an interaction that is quadratic in the field, which is not often employed. However, spectroscopy using the quadratic (ponderomotive) interaction promises two significant advantages over spectroscopy using the multipole-field interaction: flexible transition rules and vastly improved spatial addressability of the quantum system. Here we demonstrate ponderomotive spectroscopy by using optical-lattice-trapped Rydberg atoms, pulsating the lattice light and driving a microwave atomic transition that would otherwise be forbidden by established spectroscopic selection rules. This ability to measure frequencies of previously inaccessible transitions makes possible improved determinations of atomic characteristics and constants underlying physics. The spatial resolution of ponderomotive spectroscopy is orders of magnitude better than the transition frequency would suggest, promising single-site addressability in dense particle arrays for quantum computing applications.

Probe of Rydberg-Atom Transitions via an Amplitude-Modulated Optical Standing Wave with a Ponderomotive Interaction

“…In order to obtain the best ∆ν/ν, it is desirable to increase ν while decreasing ∆ν. In recently-developed ponderomotive spectroscopy [4], Rydberg atoms are trapped in a standingwave laser field (optical lattice). Electronic transitions are driven by modulating the lattice-light intensity at the transition frequencies of interest.…”

Measuring the Rydberg constant using circular Rydberg atoms in an intensity-modulated optical lattice

“…The same ponderomotive term that traps atoms is also used to drive transitions between circular and nearcircular states [10]. In ponderomotive spectroscopy, the optical-field intensity varies substantially within the volume of the atom, and the lattice amplitude modulation frequency is resonant with an atomic transition or a subharmonic of it [23].…”

“…5). In order to model the spectra, we employ a simulation program that treats the center-of-mass dynamics of the atoms (due to lattice-induced forces) classically and the internal, modulation-driven dynamics quantummechanically [10,23,39]. The effects of temperature on the population fraction that becomes excited into the upper state are shown in Fig.…”

“…Transitions are driven using a recently-developed spectroscopic method, which is based on lattice modulation at microwave frequencies [10]. The critical advantages of circular states, in comparison with low-lying states of hydrogen, are their long radiative lifetimes (on the order of ms) [11], their small QED corrections [12], and the absence of any overlap with the nucleus, hence eliminating nuclear charge dis-tribution effects (see Fig.…”

“…A key method is ponderomotive spectroscopy [10], which allows for circular-to-near-circular transitions to be driven by amplitude-modulating the ponderomotive optical lattice. The method permits us to drive the quadrupolar transition needed in our work as a first-order process and to eliminate Doppler broadening.…”