Photon counter may enable QKD
A transistor that can count individual photons, has been designed and demonstrated at the US National Institute of Standards and Technology (NIST). The semiconductor device, containing around 1000 quantum dots, could be integrated easily into electronics, says NIST, and may be able to operate at higher temperatures than other single photon detectors. This latter feature may bring practical advantages in applications such as quantum key distribution (QKD) for ‘unbreakable’ encryption using single photons.
The NIST device, dubbed QDOGFET, is said to count 1, 2 or 3 photons accurately at least 83% of the time. As such, it’s the first transistor based detector to count numbers of photons; most similar detectors simply ‘click’ in response to any small number of photons.
Counting requires a linear, stepwise response and low noise operation. This capability is essential for advanced forms of precision optical metrology and could be used both to detect photons and to evaluate single photon sources for QKD.
