Quantum Computing
Emanuel Knill, Raymond Laflamme and Gerard Milburn
Showed that ordinary optics and photon detectors suffice for quantum computing.
active from the 1990s · working in the United States, Canada and Australia
Who they were
Three theorists who worked on different aspects of quantum information. Knill and Laflamme had worked at Los Alamos National Laboratory on error correction; Milburn at the University of Queensland on quantum optics.
What they found or built
Photons barely interact, which makes them excellent carriers of quantum information and poor for logic. In 2001 their 'KLM' scheme showed that beam splitters, phase shifters, single-photon sources and detectors, together with measurement and feed-forward, could in principle perform universal quantum computation without any direct photon–photon interaction.
Why it mattered
KLM is the theoretical basis of photonic quantum computing, pursued today by companies including PsiQuantum and Xanadu. Photons work at room temperature and travel through ordinary optical fibre, but losses, and the need to generate and detect many single photons reliably, remain the central engineering problem.
Equations and key ideas
- Linear optical quantum computing
- Photonic qubits
- Measurement-based computing