Dr. Jelmer Renema, Leiden University

Jeudi 1 Octobre 2015 14h
Amphi Holweck, Esc C, 1ème etage

The physics of nanowire superconducting single photon detectors

Superconducting single photon detectors (SSPDs) are single-photon detectors consisting of a thin superconducting wire biased close to the critical current. With 93% efficiency, negligible dark counts, and multi-pixel detectors at telecommunication wavelengths, these detectors will find substantial use in quantum optics and quantum communications applications. However, the working mechanism of SSPDs is not fully understood.

In this talk, I will present our results on this problem. I will show experimentally that a combination of a broad band of weakened superconductivity and the crossing of a vortex are responsible for the detection event. Furthermore, I will discuss the temperature dependence of the detection mechanism which is of great importance for applications.

Our results were achieved by means of quantum detector tomography (QDT). QDT is a technique for complete characterization of a detector at the quantum level. The great advantage of QDT is that it is model-agnostic, in the sense that no previous assumptions about the working mechanism have to be made. It is therefore particularly suited to this problem.

Furthermore, I will present our results on the magnetic field response of the detection mechanism. We will demonstrate that for the usual meander-shaped wires, no enhancement of the detection response in an external magnetic field is possible. I will discuss the implications of our results for our understanding of the detection mechanism.

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