Large scale quantum computers are believed to outperform the power of classical computers in solving numerous practical problems ranging from combinatorial optimisation and simulation of quantum many-body systems to machine learning and cryptography. However, despite the tremendous experimental progress, near term quantum computers will operate with noisy, intermediate-scale quantum processors with hundreds of qubits.

An ongoing challenge for researchers is to develop algorithms that can operate on these intermediate quantum computers and demonstrate computational advantage over their classical counterparts; known as “quantum advantage” schemes.

A well-known quantum sampling algorithm using fermionic gates can be easily implemented on such devices, however quantum advantage was not thought to be possible because such fermionic systems can be easily simulated by classical computers.

In research published in PRX Quantum, a team of international researchers, including PhD student Mr Mauro Morales from the University of Technology Sydney, were able to show that with suitable input states, a novel quantum advantage scheme based on fermionic gates can be realised.

The results were inspired by one of the paradigmatic and leading quantum advantage schemes – Boson Sampling, which can be demonstrated with photonic interferometer networks.

“Boson Sampling, is one of the leading quantum advantage schemes, however, there is no natural way of simulating Boson Sampling on the large-scale superconducting quantum devices that are being built in the coming years.” Says CQC²T PhD Student Mr Mauro Morales.

“In contrast, fermionic gates can be easily implemented on semiconductor and similar devices. Thus, the natural question arose: Could there be a quantum advantage scheme similar to Boson Sampling using fermionic gates?”

The team were able to demonstrate quantum advantage was feasible using Fermionic Linear Optics, by proving strict hardness guarantees and showing efficient certification methods for Fermionic sampling, and that sampling procedures can be implemented naturally with Fermionic systems.

“Fermionic linear optical circuits have already been implemented in proof-of-principle demonstrations with superconducting qubit architectures and are used readily in Quantum chemistry.” Says Prof Michael Bremner, CQC²T Chief Investigator and supervisor for Mr Morales.

“Now with the proven quantum advantage results, this scheme is a very natural candidate for future experiments.”