Quantum amplitude damping for solving homogeneous linear differential equations: A noninterferometric algorithm

Abstract: In contexts where relevant problems can easily attain configuration spaces of enormous sizes, solving Linear Differential Equations (LDEs) can become a hard achievement for classical computers; on the other hand, the rise of quantum hardware can conceptually enable such high-dimensional problems to be solved with a foreseeable number of qubits, whilst also yielding quantum advantage in terms of time complexity. Nevertheless, in order to bridge towards experimental realizations with several qubits and harvest such potential in a short-term basis, one must dispose of efficient quantum algorithms that are compatible with near-term projections of state-of-the-art hardware, in terms of both techniques and limitations. As the conception of such algorithms is no trivial task, insights on new heuristics are welcomed. This work proposes a novel approach by using the Quantum Amplitude Damping operation as a resource, in order to construct an efficient quantum algorithm for solving homogeneous LDEs. As the intended implementation involves performing Amplitude Damping exclusively via a simple equivalent quantum circuit, our algorithm shall be given by a gate-level quantum circuit (predominantly composed of elementary 2-qubit gates) and is particularly nonrestrictive in terms of connectivity within and between some of its main quantum registers. We show that such an open quantum system-inspired circuitry allows for constructing the real exponential terms in the solution in a non-interferometric way; we also provide a guideline for guaranteeing a lower bound on the probability of success for each realization, by exploring the decay properties of the underlying quantum operation.