Quantum binary field multiplication with subquadratic Toffoli gate count and low space-time cost

Abstract

Multiplication over binary fields is a crucial operation in quantum algorithms designed to solve the discrete logarithm problem for elliptic curve defined over $GF(2^n)$. In this paper, we present an algorithm for constructing quantum circuits that perform multiplication over $GF(2^n)$ with $\mathcal{O}(n^{\log_2(3)})$ Toffoli gates. We propose a variant of our construction that achieves linear depth by using $\mathcal{O}(n\log_2(n))$ ancillary qubits. This approach provides the best known space-time trade-off for binary field multiplication with a subquadratic number of Toffoli gates. Additionally, we demonstrate that for some particular families of primitive polynomials, such as trinomials, the multiplication can be done in logarithmic depth and with $\mathcal{O}(n^{\log_2(3)})$ gates.