Dan Browne (University College London)
Title: Universal Fault Tolerant Quantum Computing with 3D Surface Codes
Abstract: Quantum computing hardware is making impressive advances but the construction of a large scale fault tolerant quantum computer remains a significant challenge. Part of this difficulty is the very large ‘overhead’ incurred with leading approaches in fault tolerant quantum computation, in particular the topological surface code, defined on a 2D lattice. For every quantum bit (qubit) used for quantum computation many qubits are required to implement error correction to protect the data from decoherence, and implementing key logic operations (quantum gates) can require a large number of operations via a protocol called ‘magic state distillation’. I will present an approach to reducing the latter overhead by developing a quantum error correction approach where all necessary quantum gates can be achieved natively, removing the need for magic state distillation. We achieve this by increasing the dimension of our surface codes from 2D to 3D. I will talk about the intuition behind this approach , some of the practical hurdles to implement this and how they are starting to be overcome .
The talk is aimed at a general theoretical physics audience and will contain a self-contained overview of the key ideas of quantum error correction and surface codes. Michael Vasmer & Dan E. Browne, Three-Dimensional Surface Codes: Transversal Gates & Fault Tolerant Architectures. Phys. Rev A 012312 (2019).
 Ben Brown, A Tolerant Non-Clifford Gate for the Surface Code in Two Dimensions. Sci. Adv. 6 eaay4929 (2020).