MilestoneHardwareConfirmed

Knill, Laflamme and Milburn show how to compute with photons and linear optics

Jun 20, 2000

Emanuel Knill and Raymond Laflamme of Los Alamos and Gerard Milburn of the University of Queensland show that efficient quantum computing is possible with single photons using only beam splitters, phase shifters, photon sources and detectors, avoiding hard-to-build interactions between photons.

Why it matters

Their protocol made light a serious candidate for building quantum computers and became the starting point for later photonic designs.

Emanuel Knill · Raymond Laflamme · Gerard J. Milburn · Los Alamos

See it on the timeline

Sources (3)

Nature A scheme for efficient quantum computation with linear optics
Primary sourceJan 4, 2001

“Until now, it suffered from the requirement for non-linear couplings between optical modes containing few photons. Here we show that efficient quantum computation is possible using only beam splitters, phase shifters, single photon sources and photo-detectors.”
arXiv (Knill, Laflamme and Milburn) Efficient Linear Optics Quantum Computation
Primary sourceJun 20, 2000

“We show that single photon sources, passive linear optics and photo-detectors are sufficient for implementing reliable quantum algorithms.”
arXiv (Kok et al.) Review article: Linear optical quantum computing
Independent coverageDec 9, 2005

“Linear optics with photon counting is a prominent candidate for practical quantum computing. The protocol by Knill, Laflamme, and Milburn [Nature 409, 46 (2001)] explicitly demonstrates that efficient scalable quantum computing with single photons, linear optical elements, and projective measurements is possible.”

Added Oct 15, 2026 · Updated Oct 27, 2026. Spotted an error? Tell us and we will review it.