Optical codeword demodulation with error rates below the standard quantum limit using a conditional nulling receiver

Jian Chen, Jonathan L. Habif, Zachary Dutton, Richard Lazarus, Saikat Guha

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

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. Here, we report the first experimental demonstration of a joint-detection receiver, demodulating quaternary pulse-position-modulation 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 pulse-position-modulation systems, such as in deep-space communication. We anticipate our experiment to motivate future work towards building Holevo-capacity-achieving joint-detection receivers.

Original languageEnglish (US)
Pages (from-to)374-379
Number of pages6
JournalNature Photonics
Volume6
Issue number6
DOIs
StatePublished - Jun 2012
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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