Fig. 1: Schematic of the experiment.
From: A subwavelength atomic array switched by a single Rydberg atom
a, The atomic array and laser beam orientations. The transmission (reflection) probe beam is overlapped and co- (counter-)propagating with the control beam along −z (+z). We monitor the transmissive (reflective) response of the atomic array by imaging the probe beam onto an EMCCD, while filtering out the control beam. The atomic array is aligned in the x–y plane, containing up to 1,500 atoms in an atomic Mott insulator of a single atom per lattice site in state \(\left\vert g\right\rangle\), while a single ancilla atom is prepared in a different hyperfine state \(\left\vert {g}^{{\prime} }\right\rangle\) at a target lattice site at the centre of the array. We control the Rydberg excitation of the ancilla using an ultraviolet (UV) beam propagating in the atomic plane. The inset shows an exemplary site-resolved fluorescence image of a Mott insulator with 1,500 atoms. b, Electronic level scheme and relevant light fields. The control and probe fields with Rabi frequencies Ωc and Ωp, respectively, couple the ground state \(\left\vert g\right\rangle\) to a Rydberg S-state \(\left\vert S\right\rangle\) via an intermediate state \(\left\vert e\right\rangle\). The UV field excites the ancilla \(\left\vert {g}^{{\prime} }\right\rangle\) with Rabi frequency ΩUV to a Rydberg P-state of the same principal quantum number \(\left\vert P\right\rangle\). The \(\left\vert S\right\rangle -\left\vert P\right\rangle\) Rydberg states experience a strong dipolar interaction, creating a distance-dependent shift in energy, Uint(r). c, Spatially resolved optical response in transmission, the atomic array with the relevant light fields and the corresponding experimental pulse sequences. Left: With the probe field alone, the atomic array acts as a cooperative mirror. Middle: Applying an additional resonant control field, we render the atomic array transparent by exploiting the EIT condition. Right: Preparing the ancilla in the \(\left\vert P\right\rangle\) state, the dipolar Rydberg interaction shifts the control field out of resonance, restoring the reflectivity within a finite radius around the ancilla. The dashed line indicates the estimated blockade radius of rb = 4.6 μm (Supplementary Information).
