Enabling Retargetable Optimizing Compilers for Quantum Accelerators via a Multi-Level Intermediate Representation

TL;DR

This paper introduces a multi-level IR framework that enables fast, retargetable quantum compilers supporting OpenQASM 3, with significant optimizations and compatibility with classical compiler techniques.

Contribution

It presents a novel multi-level IR built on MLIR for quantum compilers, supporting OpenQASM 3 and enabling rapid, optimized quantum-classical compilation.

Findings

Compiler is 1000x faster than Python approaches

Achieves 5-10x faster compilation than existing quantum compilers

Reduces entangling operations by 10x, lowering noise

Abstract

We present a multi-level quantum-classical intermediate representation (IR) that enables an optimizing, retargetable, ahead-of-time compiler for available quantum programming languages. To demonstrate our architecture, we leverage our proposed IR to enable a compiler for version 3 of the OpenQASM quantum language specification. We support the entire gate-based OpenQASM 3 language and provide custom extensions for common quantum programming patterns and improved syntax. Our work builds upon the Multi-level Intermediate Representation (MLIR) framework and leverages its unique progressive lowering capabilities to map quantum language expressions to the LLVM machine-level IR. We provide both quantum and classical optimizations via the MLIR pattern rewriting sub-system and standard LLVM optimization passes, and demonstrate the programmability, compilation, and execution of our approach via standard benchmarks and test cases. In comparison to other standalone language and compiler efforts available today, our work results in compile times that are 1000x faster than standard Pythonic approaches, and 5-10x faster than comparative standalone quantum language compilers. Our compiler provides quantum resource optimizations via standard programming patterns that result in a 10x reduction in entangling operations, a common source of program noise. Ultimately, we see this work as a vehicle for rapid quantum compiler prototyping enabling language integration, optimizations, and interoperability with classical compilation approaches.