Letter abstract
Nature Physics 5, 27 - 30 (2009)
Published online: 16 November 2008 | doi:10.1038/nphys1133
Subject Categories: Quantum physics | Techniques and instrumentation
Tomography of quantum detectors
J. S. Lundeen1, A. Feito2,3, H. Coldenstrodt-Ronge1, K. L. Pregnell2,3, Ch. Silberhorn4, T. C. Ralph5, J. Eisert2,3, M. B. Plenio2,3 & I. A. Walmsley1
Measurement connects the world of quantum phenomena to the world of classical events. It has both a passive role—in observing quantum systems—and an active one, in preparing quantum states and controlling them. In view of the central status of measurement in quantum mechanics, it is surprising that there is no general recipe for designing a detector that measures a given observable1. Compounding this, the characterization of existing detectors is typically based on partial calibrations or elaborate models. Thus, experimental specification (that is, tomography) of a detector is of fundamental and practical importance. Here, we present the realization of quantum detector tomography2, 3, 4. We identify the positive-operator-valued measure describing the detector, with no ancillary assumptions. This result completes the triad, state5, 6, 7, 8, 9, 10, 11, process12, 13, 14, 15, 16, 17 and detector tomography, required to fully specify an experiment. We characterize an avalanche photodiode and a photon-number-resolving detector capable of detecting up to eight photons18. This creates a new set of tools for accurately detecting and preparing non-classical light.
- Clarendon Laboratory, Oxford University, Parks Road, Oxford, OX1 3PU, UK
- Institute for Mathematical Sciences, Imperial College London, SW7 2PG, UK
- QOLS, The Blackett Laboratory, Imperial College London, Prince Consort Road, SW7 2BW, UK
- Max-Planck Research Group for Optics, Information and Photonics, 91058 Erlangen, Germany
- Department of Physics, University of Queensland, Brisbane, QLD 4072, Australia
Correspondence to: J. S. Lundeen1 e-mail: j.lundeen1@physics.ox.ac.uk
Correspondence to: I. A. Walmsley1 e-mail: walmsley@physics.ox.ac.uk
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