Quantum Computing with Circular Rydberg Atoms

Abstract

Arrays of neutral atoms provide a promising platform for quantum computing and simulation by taking advantage of interactions between high energy Rydberg states. These systems offer advantages over other platforms due to their large sizes and flexible geometries, however their performance when implementing quantum gates is limited largely by the short lifetime of Rydberg state atoms. One potentially promising path to increasing the fidelities in these systems then is to employ circular state (CS) Rydberg atoms, which due to their single channel decay path have inherently much longer lifetimes. The challenge then becomes how to manipulate these CS atoms in a way that allows us to construct quantum systems and perform computations while leveraging these long lifetimes for fi- delity gains. In a recent collaboration with Jeff Thompson, we proposed a novel approach to quantum computing with CS Rydberg atoms that predicts two qubit gate error rates of $10^{−5}$ [1], 100 times lower than the current state of the art for gates with Rydberg atoms. In order to achieve such an improvement, several key innovations were required, including a novel microwave structure to store the atoms in, a method to state-insensitively trap CS atoms, a nondestructive way to measure which CS an atom is in, a technique for locally manipulating CS atoms, a gate protocol leveraging the CS manifold, and error-robust dynamical decoupling sequences to decouple from unwanted interactions and errors. In this thesis, we will first give a summary of all these innovations, as outlined in detail in [1], and how they allow for the performance of the new quantum computing scheme. Then we will discuss in full the details of those innovations which we made the largest independent contributions to. We will discuss the details of how the ponderomotive potential is used to manipulate the atoms with Laguerre-Gaussian (LG) modes, and how it is used to trap the atoms and the scattering errors that come with this. From there we will discuss the formalism of dynamical decoupling and extend it so we can decouple from motional errors. And finally, we will detail out the design considerations for the novel microwave structure that simultaneously enhances the CS lifetimes and allows for the implementation of the rest of the scheme, as well as test a scale model of a subcomponent of this structure.