Quantum Data Centers in the Presence of Noise

TL;DR

This paper explores the impact of noise on quantum data centers with multiple interconnected quantum processing units, comparing different remote gate implementations and highlighting the importance of understanding error propagation for optimization.

Contribution

It introduces a simulation-based analysis of noise effects in quantum data centers and compares cat-comm and TP-comm methods for remote gates, emphasizing error propagation insights.

Findings

Inter-QPU entanglement links influence fidelity more than gate count alone.

Error propagation understanding can optimize distributed quantum circuit compilation.

Remote gate implementation impacts robustness to noise.

Abstract

Quantum data centres (QDCs) could overcome the scalability challenges of modern quantum computers. Single-processor monolithic quantum computers are affected by increased cross talk and difficulty of implementing gates when the number of qubits is increased. In a QDC, multiple quantum processing units (QPUs) are linked together over short distances, allowing the total number of computational qubits to be increased without increasing the number of qubits on any one processor. In doing so, the error incurred by operations at each QPU can be kept small, however additional noise will be added to the system due to the latency cost and errors incurred during inter-QPU entanglement distribution. We investigate the relative impact of these different types of noise using a classically simulated QDC with two QPUs and compare the robustness to noise of the two main ways of implementing remote gates, cat-comm and TP-comm. We find that considering the quantity of gates or inter-QPU entangled links is often inadequate to predict the output fidelity from a quantum circuit and infer that an improved understanding of error propagation during distributed quantum circuits may represent a significant optimisation opportunity for compilation.