Creating Motional-State Qubits with Anharmonic Optical Tweezer Potentials

Anharmonic oscillators provide a simple way to access a two-level system within a larger Hilbert space, enabling quantum information platforms such as the superconducting circuit. Here we demonstrate an atomic analogue using motional states of a single atom confined in an optical tweezer. Exploiting the intrinsic anharmonicity of the Gaussian potential, we isolate a qubit subspace and perform coherent rotations by modulating the position of the trap at its resonance frequency. Because the drive acts solely through the confining potential, motion is decoupled from internal spin, making the technique applicable in shallow traps with any species of neutral atom, molecule, or nanoparticle. Furthermore, we explore how the drive mechanism enables dynamic tuning of the tweezer potential between harmonic and anharmonic regimes, as well as the generation of complex non-Gaussian states. These results establish anharmonic optical potentials as a versatile tool for confinement-based control of atomic motion, opening new avenues for its use in quantum science applications.