Spatially resolved excitation of Rydberg atoms and surface effects on an atom chip

We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold-coated chip surface. We measure distance-dependent shifts ($~$$10$ MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow ($<4$ MHz) and the observed widths are independent of atom-surface distance down to $~$$20$ $\mu$m, indicating relatively long lifetime of the Rydberg states. Our results open the way to studies of dipolar physics, collective excitations, quantum metrology, and quantum information processing involving interacting Rydberg excited atoms on atom chips.

Figure 1

(a) Level scheme of our system; shifts in the Rydberg state are denoted by ${\Delta }_c$, additional decay channels lead to a broadening of the Rydberg transition (i.e., an increase in ${\Gamma }_c$). (b) Schematic picture of the experimental setup. Probe beam, coupling beam, and the imaging system are depicted. (c) Typical absorption image taken on the $5s-5p$ transition. The chip is located at the top of the figure. The induced transparency due to the coupling laser is visible around $x=$ 100 $\mu$m.

Figure 2

Optical spectra extracted from a series of absorption images for 80 probe detunings, with coupling to the 38$d_{5/2}$ Rydberg state. Square points indicate the measured optical density spectrum taken in the absence of the coupling laser, with a fit to Eq. (1) with ${\Omega }_c=0$ (dashed line). Circles correspond to the EIT spectrum with the solid line a fit to the data using Eq. (1). Both spectra are obtained at a distance of $~$200 $\mu$m from the surface of the chip.

Figure 3

Panels (a)–(c) show absorption spectra for three different points marked in the main figure (d). Markers and colors correspond to those used in Fig. 2. The vertical lines in these figures denote the resonance position at large distances. The main figure (d) shows measured shifts of the EIT resonance for various excited states as a function of distance from the surface. The measurement of 27$d$${}_{5/2}$ indicates typical error bars (standard deviation) calculated from repeated measurements of the same state over a time span of 3 weeks. The lower panel (e) shows fitted values for ${\Gamma }_c$ for all states presented.

Figure 4

Local electric field strength inferred from the measured Rydberg energy-level shifts and averaged over the probe direction. The solid line shows the results of a fit to the data assuming the field originates from a Gaussian patch of surface dipoles (see inset) with $d_0=7\times {10}^5$Debye/$\mu$m${}^2$, and radius $w=$ 100 $\mu$m, averaged over the $e^{-1/2}$ cloud radius of ${\sigma }_y=$ 130 $\mu$m. The dotted line indicates the peak field strength at the center of the atom cloud ($y=0$).