TECH FOCUS SINGLE PHOTON COUNTING
Single-photon detection advance to speed up quantum communications
A new single-photon avalanche diode system enables low-noise photon counting at superior speeds
1. A photon is absorbed, creating an electron–hole pair (carrier pair)
S
cientists at the National Institute of Standards and Technology (NIST)
in the US have devised a method they say can detect individual photons at a rate 10 times faster than existing technology – with lower error rates, higher detection efficiency and less noise. It is hoped that this advance
could improve internet data speeds, because the speed at which communications systems can operate depends on how fast – and how accurately – detectors on the receiving end can discriminate and process photons travelling through fibre optic cables. In fibre optic communications,
information travels in the form of a stream of light pulses typically travelling through fibre optic cables. Each pulse can be as faint as a single photon, the smallest possible unit (quantum) of light. ‘While classical communication and detection can operate at blazing speeds, quantum systems, which need that ultimate sensitivity for those faintest of pulses, are limited to much lower speeds,’
32 Electro Optics July 2021
2. The electron and hole are accelerated by the applied bias voltage
3. The accelerated electron knocks other electrons loose, creating an avalanche of carrier pairs
4. This avalanche produces a rapidly growing current across the junction, which can be detected
5. The bias voltage is then lowered, “quenching” the semiconductor to remove the existing carrier pairs
6. Finally, the bias voltage is raised back to its initial state, resetting the device
@electrooptics |
www.electrooptics.com
Sean Kelley/NIST
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