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arXiv:1103.2991 · New Journal of Physics

Quantum characterization of superconducting photon counters

Giorgio Brida, Luigi Ciavarella, Ivo Pietro Degiovanni, Marco Genovese, Lapo Lolli, Maria Griselda Mingolla, Fabrizio Piacentini, Mauro Rajteri, Emanuele Taralli, Matteo G A Paris

Published Aug 1, 2012• 82 citations
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Abstract

We address the quantum characterization of photon counters based on transition-edge sensors (TESs) and present the first experimental tomography of the positive operator-valued measure (POVM) of a TES. We provide the reliable tomographic reconstruction of the POVM elements up to 11 detected photons and M = 100 incoming photons, demonstrating that it is a linear detector.

DOI
10.1088/1367-2630/14/8/085001

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We address the quantum characterization of photon counters based on transition-edge sensors (TESs) and present the first experimental tomography of the positive operator-valued measure (POVM) of a TES. We provide the reliable tomographic reconstruction of the POVM elements up to 11 detected photons and M = 100 incoming photons, demonstrating that it is a linear detector.
Transition-Edge Sensors (TESs) are microcalorimeters that measure the energy of incident single photons by the resistance increase of a superconducting film biased within the superconducting-to-normal transition. TES are able to detect single photons from IR to X-ray with an intrinsic energy resolution and photon-number discrimination capability. Metrology, astronomy and quantum \ncommunication are the fields where these properties can be particularly useful. In this work, we report about characterization of different TESs based on Ti films. Single photons have been detected from 200nm to 800 nm working at transition temperature Tc ∼ 100 mK. Using a pulsed laser at 690nm we have demonstrated the capability to resolve up to five photons.
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Superconducting transition-edge sensors (TESs), working as single-photon detectors with high quantum efficiency, low dark count rate, and photon number resolving capability, have been successfully used in quantum information experiments as well as astronomical transient object observations. Aiming to achieve high count rate, we are developing titanium-based superconducting TES single-photon detectors with a critical temperature of ~300 mK. Ti-based TESs with active area from 10 × 10 μm to 40 × 40 μm are first fabricated on silicon substrate coated with SiOx. The fabricated TES devices show a thermal conductance scaling with the active area and an effective time constant of ~4 μs from pulsed laser diode illumination. In order to get high quantum efficiency, we further design and fabricate a 1550-nm optical cavity based on dielectric mirror and antireflection layer, and study its absorption with an IR spectrometer. Ti TES devices on the dielectric mirror are then fabricated and the superconducting transition is measured.
Photon counting is a cornerstone of quantum optics. Here, we demonstrate precisely counting from 0 to over 9000 photons, beating the Poisson noise limit by at least 4.1 dB4.1~\mathrm{dB}4.1 dB across this range. We achieve sub-single-photon precision up to 276 photons per pulse. To do so, we multiplex eight intrinsically photon-number-resolving superconducting nanowire single-photon detectors across 128 temporal modes. We use a model-informed characterization of each of the 1024 detection bins, for optimal precision. We perform quantum detector tomography to reconstruct the positive operator valued measures (POVMs) of the complete device, which consists of 1.38⋅1081.38\cdot10^81.38⋅108 matrix elements. At the repetition rate of our experiment of 80 kHz80~\mathrm{kHz}80 kHz, we can precisely count photons corresponding to an optical power of approximately 71 pW71~\mathrm{pW}71 pW, bridging the gap from single-photon measurements to high-sensitivity optical power meters. A photon-number-resolving detector of this size, and the tools used to analyze it, will become increasingly important to characterize large quantum states, as well as tasks in precision metrology and optical power standards.