  Detector blinding attacks have been proposed in the last few years, and they
could potentially threaten the security of QKD systems. Even though no complete
QKD system has been hacked yet, it is nevertheless important to consider
countermeasures to avoid information leakage. In this paper, we present a new
countermeasure against these kind of attacks based on the use of multi-pixel
detectors. We show that with this method, we are able to estimate an upper
bound on the information an eavesdropper could have on the key exchanged.
Finally, we test a multi-pixel detector based on SNSPDs to show it can fulfill
all the requirement for our countermeasure to be effective.

Quantum Physics