Fault-Tolerant High Level Quantum Circuits: Form, Compilation and Description

TL;DR

This paper introduces a new compiler package that converts high-level quantum circuits into a fault-tolerant form suitable for large-scale quantum computing, addressing a key gap in current hardware implementations.

Contribution

The authors present the ICM form and a compiler that transforms high-level circuits into fault-tolerant, hardware-compatible descriptions with ancillary protocols and decompositions.

Findings

Enables conversion of high-level circuits into fault-tolerant ICM form

Supports output of standard circuits or geometric descriptions for hardware

Facilitates circuit optimization for topological quantum codes

Abstract

Fault-tolerant quantum error correction is a necessity for any quantum architecture destined to tackle interesting, large-scale problems. Its theoretical formalism has been well founded for nearly two decades. However, we still do not have an appropriate compiler to produce a fault-tolerant, error corrected description from a higher level quantum circuit for state of the art hardware models. There are many technical hurdles, including dynamic circuit constructions that occur when constructing fault-tolerant circuits with commonly used error correcting codes. We introduce a package that converts high level quantum circuits consisting of commonly used gates into a form employing all decompositions and ancillary protocols needed for fault-tolerant error correction. We call this form the (I)initialisation, (C)NOT, (M)measurement form (ICM) and consists of an initialisation layer of qubits into one of four distinct states, a massive, deterministic array of CNOT operations and a series of time ordered $X$- or $Z$-basis measurements. The form allows a more flexbile approach towards circuit optimisation. At the same time, the package outputs a standard circuit or a canonical geometric description which is a necessity for operating current state-of-the-art hardware architectures using topological quantum codes.