Quantum Data Centres in the Presence of Noise

Distributed quantum computing is a promising way of overcoming the scalability challenges of quantum computers, but establishing quantum links over large distances remains difficult. Therefore, in this thesis, we explore quantum data centres (QDCs), in which multiple quantum processing units (QPUs) are housed together within the same warehouse and linked together over short links. By considering such a setting, we avoid the challenges of long-distance quantum communications while retaining the scalability of distributed architectures.

We focus primarily on understanding and quantifying the role of noise in QDCs. We compare the impact of different types of noise in the QDC setting and explore various types of inter-QPU gate. Both individual inter-QPU gates and an assortment of larger distributed quantum circuits are investigated. Based on our findings, we evaluate strategies for the handling of noise, considering both quantum error detection and entanglement distillation based solutions. We also provide a preliminary investigation into the use of QDCs for generating entangled resource states suitable for quantum communications or measurement based quantum computing applications.

A major contribution of this thesis is the development of a novel simulation framework for distributed quantum computing, which formed the basis of many of the results obtained. The framework enables users to easily specify distributed quantum circuits or import circuits designed for a single-QPU and convert them to a distributed circuit. Many of the complications of interpreting a distributed quantum circuit, such as the management of communication qubits are also handled automatically. Moreover, the framework's built-in interpreter can interpret common building blocks of distributed quantum computing, such as inter-QPU gates.