2005/07/20 by Timothy C. Ralph, T. C. Ralph, Austin P. Lund +3 · 2 citations
Computer Science · Physics and Astronomy · #Advanced Fiber Laser Technologies #Neural Networks and Reservoir Computing #Quantum Information and Cryptography #quant-ph
paper · pdf · doi:10.1088/1464-4266/7/10/007
published as J. Opt. B: Quantum Semiclass. Opt., 7, S245-S249, 2005
arxiv created 2005/07/20 · openalex publication_date 2005/09/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
Photon counting induces an effective non-linear optical phase shift in certain states derived by linear optics from single photons. Although this non-linearity is non-deterministic, it is sufficient in principle to allow scalable linear optics quantum computation (LOQC). The most obvious way to encode a qubit optically is as a superposition of the vacuum and a single photon in one mode—so-called 'single-rail' logic. Until now this approach was thought to be prohibitively expensive (in resources) compared to 'dual-rail' logic where a qubit is stored by a photon across two modes. Here we attack this problem with real-time feedback control, which can realize a quantum-limited phase measurement on a single mode, as has been recently demonstrated experimentally. We show that with this added measurement resource, the resource requirements for single-rail LOQC are not substantially different from those of dual-rail LOQC. In particular, with adaptive phase measurements an arbitrary qubit state can be prepared deterministically .