Novel Detection System for the Characterization of Single Photon Sources Based on a SPAD Array Detector

Future quantum technologies promise to deliver unprecedented computing power, guarantee secure communications, and yield ultra-high precision measurements. In quantum optics, the capability to analyze quantum signatures of the emitted light from single photon sources is essential and current experimental configurations offer limited capabilities for the metrology of quantum-light sources. So far, the primary method to probe non-classical properties of light is measuring the second order correlation function (g⁽²⁾(τ)) with a Hanbury-Brown and Twiss (HBT) intensity interferometer. Most of these experiments use single-photon counting detectors based on avalanche photodiodes or superconducting nanowires. These are so-called “click detectors”, since the arrival of a single photon causes the detector output state to move from 0 to 1 followed by a dead-time, where photon detection is not possible. Therefore, click detectors cannot discriminate the number of photons present in a light field at a given time offering limited capabilities for the metrology of quantum-light sources. Hence, the development of detectors capable to resolve the number of photons hitting them (so-called photon-number-resolving (PNR) detectors) is crucial for many applications in quantum-information science. Single photon avalanche diode (SPAD) array detectors provide PNR functionality by having the incoming photons hitting an array of parallel SPADs. Here, we take advantage of the exceptional properties of SPAD array detectors for the implementation of a new detection method for the measurement and analysis of single photons emitted by colloidal quantum dots (QDs). The data collected with this system provide a complete characterization of the analyzed single photon emitter giving information on the lifetime, antibunching effect and enable also quantum-imaging microscopy. In order to evaluate the performance of this new detection system, we performed spectroscopic measurements of photons correlation using commercial single photon detectors in Hanbury-Brown and Twiss (HBT) configuration on a sample composed by an array of 50x50 holes filled with single QDs. This type of sample enable us to compare directly the measurements performed with both experimental configurations on the exact same colloidal QDs. The work proposed here could lead to a new technological platform for the characterization of single photon sources that overcomes the limitation of conventional standard click detectors in HBT configuration.