Quantum characterization of superconducting photon counters

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

doi:10.1088/1367-2630/14/8/085001

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.

Highlights

The possibility of discriminating the number of impinging photons on a detector is a fundamental tool in many different fields of optical science and technology [1], including nanopositioning and the redefinition of candela unit in quantum metrology [2, 3], foundations of quantum mechanics [4], quantum imaging [5] and quantum information [6, 7, 8, 9], e.g for communication and cryptography
The most promising genuine Photon Number Resolving (PNR) detectors are the visible light photon counters [15] and Transition Edge Sensors (TESs) [16, 17, 18, 19, 20, 21], i.e. microcalorimeters based on a superconducting thin film working as a very sensitive thermometer [22]
It is generally assumed that TESs are linear photon counters, with a detection process corresponding to a binomial convolution

Summary

Introduction

The possibility of discriminating the number of impinging photons on a detector is a fundamental tool in many different fields of optical science and technology [1], including nanopositioning and the redefinition of candela unit in quantum metrology [2, 3], foundations of quantum mechanics [4], quantum imaging [5] and quantum information [6, 7, 8, 9], e.g for communication and cryptography. It is generally assumed that TESs are linear photon counters, with a detection process corresponding to a binomial convolution. It is expected that dark counts are not present in TESs. It is expected that dark counts are not present in TESs Taken together, these assumptions allow one to characterize a TES by a single number assessing the quantum efficiency of the detector, i.e. the probability 0 ≤ η ≤ 1 that a photon impinging onto the detector is revealed. We present the first experimental reconstruction of the POVM describing the operation of a TES and, in turn, the first demonstration of the linearity.

POVM reconstruction technique

Experiment

Results