Fusion-based quantum computation

TL;DR

Fusion-based quantum computing (FBQC) introduces a model where entangling measurements on small resource states enable universal quantum computation, offering architectural simplifications and improved fault-tolerance tailored to physical systems like photonics.

Contribution

The paper develops a stabilizer formalism for FBQC, demonstrating fault-tolerant schemes with higher thresholds and analyzing their performance under realistic error models.

Findings

FBQC can tolerate a 10.4% photon loss rate in each fusion.

The fault-tolerance framework achieves higher thresholds than previous schemes.

FBQC simplifies hardware architecture with many identical modules.

Abstract

We introduce fusion-based quantum computing (FBQC) - a model of universal quantum computation in which entangling measurements, called fusions, are performed on the qubits of small constant-sized entangled resource states. We introduce a stabilizer formalism for analyzing fault tolerance and computation in these schemes. This framework naturally captures the error structure that arises in certain physical systems for quantum computing, such as photonics. FBQC can offer significant architectural simplifications, enabling hardware made up of many identical modules, requiring an extremely low depth of operations on each physical qubit and reducing classical processing requirements. We present two pedagogical examples of fault-tolerant schemes constructed in this framework and numerically evaluate their threshold under a hardware agnostic fusion error model including both erasure and Pauli error. We also study an error model of linear optical quantum computing with probabilistic fusion and photon loss. In FBQC the non-determinism of fusion is directly dealt with by the quantum error correction protocol, along with other errors. We find that tailoring the fault-tolerance framework to the physical system allows the scheme to have a higher threshold than schemes reported in literature. We present a ballistic scheme which can tolerate a 10.4% probability of suffering photon loss in each fusion.