Motional Kerr-Cat States of an Atom in an Optical Tweezer

Research Approach

This study explores the use of neutral atoms in optical tweezers as a platform for quantum state engineering. While optical tweezers are typically used for trapping and moving atoms, the researchers utilize the inherent geometric anharmonicity—or self-Kerr nonlinearity—of the Gaussian trapping potential to create non-Gaussian quantum states. By applying time-dependent modulations to the trap depth (quadratic drive) and position (linear drive), they manipulate the atom's motional states within the trap. They further introduce a technique called "painting," where the trap position is modulated at high frequencies to tune the effective anharmonicity of the potential, allowing for precise control over the motional Hilbert space.

The researchers successfully generated even- and odd-parity Kerr-cat states, achieving fidelities for even-parity states as high as 94.4%. By employing a linear drive, they demonstrated coherent parity rotations between these states. A key finding is the intrinsic robustness of the cat-state encoding: unlike Fock-state transitions, which are highly sensitive to trap-frequency fluctuations, the cat-state parity rotations remain largely unaffected by these fluctuations because the resonance condition is defined by the drive parameters rather than the trap frequency itself. This makes the cat-state approach a more stable paradigm for quantum information processing in dynamic tweezer arrays.

This work establishes a new framework for bosonic-state engineering in optical tweezers, a platform that is highly reconfigurable and scalable. By demonstrating that Kerr-based control is possible without requiring auxiliary degrees of freedom like spin or Josephson junctions, the study provides a path toward implementing quantum error-correcting codes, such as grid states, and developing quantum-enhanced sensors. The ability to tune the nonlinearity of the trap via "painting" offers a versatile tool for tailoring quantum states to specific metrological or computational requirements.