Samenvatting

Multiple scientific and industrial applications such as telecommunication and quantum cryptography causing a rise in the development of the superconducting nanowire single photons detectors (SNSPD). In the last decade, the characteristics of the detectors improved but run against the problem that the technology demands larger detectors with the same characteristics. However, the larger the detector the bigger the trade off with other properties of the detector. Therefore, multiple single detectors are fabricated and operate as one multi-pixel detector. This multi-pixel SNSPD has the advantage that the size of every single pixel can stay the same. Therefore, keep the optimized characteristics of the single pixel detector but the opening the possibilities for photon number resolving.

The downside of a multi-pixel SNSPD is that it is more sensitive to electrical crosstalk. when the nanowires of the detector are placed in close proximity to each other, electromagnetic wave propagation at high frequencies and the _m scale can become a problem. Four potential sources of crosstalk will be examined further, starting with the transmission line effects, following the capacitive and magnetic field coupling between nanowires of adjacent pixels. At last, the electric schema of the detectors is examined.

The measurements are performed by biasing one of the four detectors close to the critical current. The other three detectors are not biased and therefore, nonsensitive to photon absorption. The only electrical signal the three pixels will transport is noise and potential crosstalk. The noise is averaged out by measuring over 10,000 sweeps, therefore, only the crosstalk signal remains. To identify a potential source of crosstalk, an estimation of the amount of coupled signal is made using a simple model and simple electric scheme’s of the detector setup.

Measurements of crosstalk resulted in measuring an inverted voltage pulse compared to the signal measured due to photon absorption. In addition, the inverted signal is attenuated with 40-50 dB in voltage.The potential source of crosstalk is not due to the capacitive coupling, as the amount of coupled signal should be a positive pulse and is too weak to measure. The amount of magnetic field coupling is too small to be the source of crosstalk as the meander structure of the nanowire has a negative effect on the coupled signal. The source of crosstalk is due to the connection from the detector to the ground as the bonding wires have a resistance which causes a negative pulse to be measured in the other pixels.

The crosstalk source is identified and is caused by the connection from the detector to the ground. This is a positive result for Single Quantum as the signal is too small to trigger a false detection event. In addition, the signal will not become larger when more multi-pixels are used or when the detectors become larger.