Realization of a Rydberg-Dressed Ramsey Interferometer and Electrometer

Abstract

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, static electric fields with high sensitivity. This provides the means to combine the outstanding coherence properties of Ramsey interferometers based on atomic ground states with a controllable coupling to strongly interacting states, thus expanding the number of systems suitable for metrological applications and many-body physics studies.Ramsey interferometers involving trapped ensembles of neutral atoms or single ions have enabled the most precise measurements ever made. Besides their importance for defining time and frequency standards [1,2], they also hold great promise for searches for physics beyond the standard model [3][4][5][6][7], exploring the physics of complex quantum systems [8], and for realizing sensors capable of operating close to the Heisenberg limit [9][10][11]. By design however, the most precise Ramsey interferometers typically involve the coherent evolution of atoms that interact very weakly, either with one another or with external fields, seemingly precluding many possible applications.Here we demonstrate a Ramsey interferometer involving two magnetically insensitive hyperfine clock states, where one state is continuously coupled to a Rydberg state by an off-resonant laser field. This Rydberg-dressing approach provides the means to combine the outstanding coherence properties of atomic ground states with greatly enhanced sensitivity to external fields or controllable interparticle interactions mediated by the Rydberg state admixture. We show that strong Rydberg atom-light coupling can be reached with Ramsey coherence times that are orders of magnitude longer than the bare Rydberg state lifetime. We precisely measure the Rydberg-atom light coupling strength and independently determine the effective population decay and dephasing rates for the dressed-states, thereby identifying the dominant decoherence effects. Finally we demonstrate the suitability of the Rydberg-dressed Ramsey interferometer for metrological applications by precisely measuring a small applied electric field.The starting point for our experiments is an ultracold gas of 39 K atoms prepared in a crossed-beam optical dipole trap (shown in Fig. 1a) following Refs. [12,13]. To realize the Ramsey interferometer we use the magnetically insensitive hyperfine ground states |0 = |4S 1/2 , F = 1, m F = 0 and |1 = |4S 1/2 , F = 2, m F = 0 . The sample is spinpolarized in the initial |0 state using a sequence of optical pumping pulses and radio-fre...

Precision measurement of the ionization energy and quantum defects ofK39i

“…The discrepancy between our value and the value reported by Arias et al [44] is almost 50 Hz or 10 σ and can be mostly explained by the quadratic Zeeman shift resulting from the presence of a magnetic background field of about 60 mG in the latter experiment, as explained in Ref. [44]. Reference [45] reports an all-optical measurement of the hyperfine splitting with low statistical uncertainty, but uncontrolled systematical errors.…”

Single-photon stored-light Ramsey interferometry using Rydberg polaritons

“…We employ highly excited Rydberg states, which allows the splitting and recombining of the optical paths to be performed using a microwave field. Similar to other Rydberg experiments [9][10][11], the output is sensitive to DC and AC electric fields. As the interferometer is localized over a length scale of only a few micrometers, the Rydberg blockade mechanism [12] forces the interferometer to operate with only one photon at a time.…”

“…A hybrid atom-light interferometer using internal atomic states to form a beam splitter has also been demonstrated [7,8]. Interferometry using atomic Rydberg states is useful in the detection of electric fields, as demonstrated using individual atoms [9], atomic beams [10], and Rydberg-dressed cold-atom ensembles [11]. For all types of interferometry, the measurement sensitivity is limited by the time between the splitting and recombination processes, which is typically proportional to the length of the interferometer arms.…”

“…Applications of the single-photon interferometer will be explored in further work. For sensing applications, the current experiment is limited by shot noise (in contrast to classical measurements [11], quantum measurement is limited to only one photon per shot) and photon storage time. The latter could be greatly increased by eliminating motional dephasing of the spin wave, by using either a Doppler-free configuration [26] or an optical lattice to localize the atoms [27].…”

Ultralong-range molecule engineering via Rydberg dressing

“…While Rydberg dressing faces several technical difficulties such as dissipation and spontaneous scattering, it has been recently observed in optical tweezers [29] and optical lattices [30] after some earlier efforts to overcome these difficulties [31]. Applications of Rydberg dressing have been proposed to achieve three-dimensional self-trapping of matter waves [32], to tune chemical reactions [33], and to model frustrated quantum magnets [34], and more recently Rydberg dressing was achieved in a Ramsey interferometer and electrometer experiment [35]. Other approaches to achieve Rydberg dressing such as using Förster resonances have also been proposed [36].…”