Quantum projection filter for a highly nonlinear model in cavity QED

Ramon Van Handel, Hideo Mabuchi

Research output: Contribution to journalReview articlepeer-review

37 Scopus citations


Both in classical and quantum stochastic control theory a major role is played by the filtering equation, which recursively updates the information state of the system under observation. Unfortunately, the theory is plagued by infinite dimensionality of the information state which severely limits its practical applicability, except in a few select cases (e.g. the linear Gaussian case). One solution proposed in classical filtering theory is that of the projection filter. In this scheme, the filter is constrained to evolve in a finite-dimensional family of densities through orthogonal projection on the tangent space with respect to the Fisher metric. Here we apply this approach to the simple but highly nonlinear quantum model of optical phase bistability of a strongly coupled two-level atom in an optical cavity. We observe near-optimal performance of the quantum projection filter, demonstrating the utility of such an approach.

Original languageEnglish (US)
Pages (from-to)S226-S236
JournalJournal of Optics B: Quantum and Semiclassical Optics
Issue number10
StatePublished - Oct 1 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Physics and Astronomy (miscellaneous)


  • Fisher metric
  • Model reduction
  • Quantum filtering
  • Wonham filter


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