2011/11/25 by Jian Chen, Jonathan L. Habif, Zachary Dutton +3 · 113 citations
Computer Science · Engineering · Mathematics · Physics and Astronomy · #Algorithm #Channel (broadcasting) #Code word #Computer science #Decoding methods #Demodulation #Electronic engineering #Engineering #Limit (mathematics) #Mathematical analysis #Mathematics #Neural Networks and Reservoir Computing #Optical Network Technologies #Physics #Quantum #Quantum Information and Cryptography #Quantum capacity #Quantum information #Quantum limit #Quantum mechanics #Quantum network #Telecommunications #quant-ph
paper · pdf · doi:10.1038/nphoton.2012.113
published in Nature Photonics 6(6), 374-379 (Nature Portfolio) · 6 pages, 4 figures
arxiv created 2011/11/25 · openalex publication_date 2012/05/18 · arxiv updated 2015/03/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The quantum states of two laser pulses---coherent states---are never mutually orthogonal, making perfect discrimination impossible. Even so, coherent states can achieve the ultimate quantum limit for capacity of a classical channel, the Holevo capacity. Attaining this requires the receiver to make joint-detection measurements on long codeword blocks, optical implementations of which remain unknown. We report the first experimental demonstration of a joint-detection receiver, demodulating quaternary pulse-position-modulation (PPM) codewords at a word error rate of up to 40% (2.2 dB) below that attained with direct-detection, the largest error-rate improvement over the standard quantum limit reported to date. This is accomplished with a conditional nulling receiver, which uses optimized-amplitude coherent pulse nulling, single photon detection and quantum feedforward. We further show how this translates into coding complexity improvements for practical PPM systems, such as in deep-space communication. We anticipate our experiment to motivate future work towards building Holevo-capacity-achieving joint-detection receivers.