MilestoneTheory & algorithmsConfirmed

Researchers run a hybrid quantum-classical algorithm for chemistry on a photonic chip

Apr 10, 2013

A team from Bristol and Harvard reports a small photonic processor working with a classical computer to estimate the lowest energy of HeH+. The variational quantum eigensolver appears as a preprint in April 2013 and in Nature Communications in July 2014.

Why it matters

Combining a short quantum calculation with classical optimization opened a route to chemistry experiments on small quantum processors.

Alberto Peruzzo · Jarrod McClean · Alán Aspuru-Guzik · Jeremy L. O'Brien · Bristol · Harvard

See it on the timeline

MIT physicists propose QAOA, a quantum algorithm for approximate optimization (Nov 14, 2014)
John Preskill names the "NISQ" era of noisy, intermediate-scale quantum computers (Jan 2, 2018)

Sources (3)

Nature Communications A variational eigenvalue solver on a photonic quantum processor
Primary sourceJul 23, 2014

“We implement the algorithm by combining a highly reconfigurable photonic quantum processor with a conventional computer. We experimentally demonstrate the feasibility of this approach with an example from quantum chemistry—calculating the ground-state molecular energy for He–H+.”
arXiv (Peruzzo et al.) A variational eigenvalue solver on a quantum processor
Primary sourceApr 10, 2013

“We have implemented the algorithm by combining a small-scale photonic quantum processor with a conventional computer.”
arXiv (Tilly et al.) The Variational Quantum Eigensolver: a review of methods and best practices
Independent coverageNov 9, 2021

“The VQE may be used to model complex wavefunctions in polynomial time, making it one of the most promising near-term applications for quantum computing.”

Added Oct 15, 2026 · Updated Oct 24, 2026. Spotted an error? Tell us and we will review it.

Researchers run a hybrid quantum-classical algorithm for chemistry on a photonic chip

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