Measuring the absolute photo detection efficiency using photon number correlations.pdfVIP

a r X i v : q u a n t - p h / 0 6 0 6 0 4 1 v 2 6 A u g 2 0 0 6 Measuring the Absolute Photo Detection Efficiency Using Photon Number Correlations Michael Lindenthal and Johannes Kofler Institut fu?r Experimentalphysik, Universita?t Wien, 1090 Wien, Austria Institut fu?r Quantenoptik und Quanteninformation, O?sterreichische Akademie der Wissenschaften, 1090 Wien, Austria (Dated: February 1, 2008) We present two methods for determining the absolute detection efficiency of photon-counting de- tectors directly from their singles rates under illumination from a nonclassical light source. One method is based on a continuous variable analogue to coincidence counting in discrete photon ex- periments, but does not actually rely on high detector time resolutions. The second method is based on difference detection which is a typical detection scheme in continuous variable quantum optics experiments. Since no coincidence detection is required with either method, they are useful for detection efficiency measurements of photo detectors with detector time resolutions far too low to resolve coincidence events. I. INTRODUCTION High detection efficiency is crucial in many contexts within quantum optics. In particular, recent linear optics quantum computation methods have been shown to require detection efficiencies higher than 90% to be scalable [1, 2, 3, 4]. Another well known example comes from Bell inequality experiments where a detection efficiency of at least 2/3 is required to close the detection loophole [5]. Thus higher detector efficiencies do not only have the obvious advantage of providing more signal, but are also of great relevance for both current quantum information science and fundamental quantum physics. Therefore building new high efficiency detectors is a crucial area of research. In this article we present methods to evaluate their absolute detection efficiency. The typical way to measure detection efficiency is to use a calibrated reference detector, and to