What does "Afterpulsing" mean?
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Afterpulsing is a type of noise that can occur in certain types of photon detectors, especially in single-photon avalanche photodiodes (APDs). This noise happens when the detector mistakenly registers additional signals after it has already detected a photon.
How Afterpulsing Works
When a photon hits the detector, it can trigger an event known as an avalanche, which is a rapid increase in current. However, this process can also lead to some leftover charges within the detector. These leftover charges can cause the detector to react again, even when no new photon has come in. This leads to unwanted signals, known as afterpulses.
Impact on Performance
Afterpulsing can be a problem for systems that need to send secure information using quantum key distribution. It can increase errors in the data, making it less reliable. As the rate of detecting photons goes up, the chance of afterpulsing also increases, which can shorten the distance over which secure communication can happen.
Solutions to Reduce Afterpulsing
To combat afterpulsing, researchers have developed methods to limit how much charge builds up in the detector. For instance, using special circuits with rapid gates can help reduce the noise caused by afterpulsing. This allows the detectors to work more effectively, maintain a high rate of detection, and extend the range for secure communications.