Subwavelength-width optical tunnel junctions for ultracold atoms

Abstract

We propose a new method for creating far-field optical barrier potentials for ultracold atoms with widths that are narrower than the diffraction limit and can approach tens of nanometers. The reduced widths stem from the nonlinear atomic response to control fields that create spatially varying dark resonances. The subwavelenth barrier is the result of the geometric scalar potential experienced by an atom prepared in such a spatially varying dark state. The performance of this technique, as well as its applications to the study of many-body physics and to the implementation of quantum information protocols with ultracold atoms, are discussed, with a focus on the implementation of tunnel junctions.Comment: 7 pages, 2 figures; V2: slightly changed experimental parameter

Sharpening the Features of Optical Lattices

“…An alternative approach uses the spatial dependence of the nonlinear atomic response associated with the dark state of a three-level system [11][12][13][14][15][16] as a means to realize subwavelength atomic addressing and excitation. The subwavelength resolution arises when optical fields are arranged so that the internal dark state composition varies rapidly ("twists") over a short length scale.As proposed in [3,4], such a subwavelength twist can also be used to create a conservative potential with narrow spatial extent, due to the energy cost of the kinetic energy term of the Hamiltonian [2,17,18]. Unlike ac-Stark shift potentials, this twist-induced potential is a quantum effect, with magnitude proportional to ℏ.…”

“…As proposed in [3,4], such a subwavelength twist can also be used to create a conservative potential with narrow spatial extent, due to the energy cost of the kinetic energy term of the Hamiltonian [2,17,18]. Unlike ac-Stark shift potentials, this twist-induced potential is a quantum effect, with magnitude proportional to ℏ.…”

“…Developing tools to overcome the diffraction limit, allowing coherent optical manipulation of atoms on the subwavelength scale, is thus an outstanding challenge. Following recent proposals [2][3][4], we report below first experiments demonstrating coherent optical potentials with subwavelength spatial structure, by realizing a KronigPenney-type optical lattice with barrier widths below λ=50.…”

“…The potential VðxÞ can be viewed as arising from nonadiabatic corrections to the BO potential [3,4] or artificial scalar gauge potential [18,20,21]. When ϵ ≪ 1, this creates a lattice of narrow barriers spaced by λ=2, with the barrier height scaling as 1=ϵ 2 and the full width at half maximum scaling as 0.2λϵ…”

“…1(b), the fields are arranged in such a way that the dark state changes composition over a narrow region, depending on the ratio ϵ ¼ Ω p =Ω c . The kinetic energy associated with this large gradient in the spin wave function gives rise to a conservative optical potential VðxÞ [3,4] for atoms in jE 0 ðxÞi,…”