Borrowing Dirty Qubits in Quantum Programs

TL;DR

This paper introduces a formal framework and verification algorithm for safely borrowing and uncomputing dirty qubits in quantum programs, enabling more efficient qubit reuse in quantum computing.

Contribution

It formally defines dirty qubit borrowing semantics, introduces safe uncomputation, and provides an efficient verification algorithm with experimental validation.

Findings

Verified safe uncomputation in quantum circuits

Reduced demand for clean qubits in quantum programs

Provided a formal language semantics for dirty qubits

Abstract

Dirty qubits are ancillary qubits that can be borrowed from idle parts of a computation, enabling qubit reuse and reducing the demand for fresh, clean qubits-a resource that is typically scarce in practice. For such reuse to be valid, the initial states of the dirty qubits must not affect the functionality of the quantum circuits in which they are employed. Moreover, their original states, including any entanglement they possess, must be fully restored after use-a requirement commonly known as safe uncomputation. In this paper, we formally define the semantics of dirty-qubit borrowing as a feature in quantum programming languages, and introduce a notion of safe uncomputation for dirty qubits in quantum programs. We also present an efficient algorithm, along with experimental results, for verifying safe uncomputation of dirty qubits in certain quantum circuits.