1998/06/23 by L. Knoell, L. Knöll, S. Scheel +6 · 1 citation
Computer Science · Physics and Astronomy · #Neural Networks and Reservoir Computing #Quantum Information and Cryptography #Quantum and electron transport phenomena #quant-ph
paper · pdf · doi:10.1103/physreva.59.4716
published as Phys. Rev. A 59, 4716 (1999) · 24 pages, RevTeX
arxiv created 1998/06/23 · openalex publication_date 1999/06/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The recently derived input-output relations for radiation at a dispersive and absorbing four-port device [T. Gruner and D.-G. Welsch, Phys. Rev. A 54, 1661 (1996)] are used to derive the unitary transformation that relates the output quantum state to the input quantum state, including radiation and matter and without placing frequency restrictions. It is shown that for each frequency component the transformation can be regarded as a U(4) group transformation, which can directly be calculated from the underlying complex refractive-index profile of the device without additional postulates. If for narrow-bandwidth radiation far from the medium resonances the absorption matrix of the four-port device can be disregarded, the well-known U(2) group transformation for a lossless device is recognized. Explicit formulas for the transformation of Fock states, coherent states, and phase-space functions are given.