Photon detection system including an avalanche photodiode and a biasing circuit to supply a gating signal
A photon detection system comprising an avalanche photodiode configured to generate a photodiode signal in response to an incident photon. The photon detection system also comprises a biasing circuit configured to supply a gating signal to the avalanche photodiode. The gating signal is a periodic signal configured to reverse bias the avalanche photodiode above and below its breakdown voltage for photon detection during each period. The photon detection system further comprises a non-reflective filter circuit configured to receive, at an input port, the photodiode signal, and provide, at a first output port, a first filtered output signal by applying a low-pass filter with a first cut-off frequency to the received photodiode signal.
1. A photon detection system, comprising:
an avalanche photodiode configured to generate a photodiode signal in response to an incident photon;
a biasing circuit configured to supply a gating signal to the avalanche photodiode, wherein the gating signal is a periodic signal configured to reverse bias the avalanche photodiode above and below a breakdown voltage for photon detection of the avalanche photodiode during each period;
a transmission line configured to receive the photodiode signal and to provide the photodiode signal to a non-reflective filter circuit, and
the non-reflective filter circuit configured to:
receive, at an input port, the photodiode signal from the transmission line, and
provide, at a first output port, a first filtered output signal by applying a low-pass filter with a first cut-off frequency to the received photodiode signal,
wherein the input port of the non-reflective filter circuit is configured to be impedance matched to the transmission line up to a frequency higher than a gate frequency of the gating signal.
2. The photon detection system of claim 1 , wherein the gate frequency is higher than the first cut-off frequency.
3. The photon detection system of claim 1 , wherein the non-reflective filter circuit is further configured to provide, at a second output port, a second filtered output signal by applying a high-pass filter with a second cut-off frequency to the received photodiode signal.
4. The photon detection system of claim 3 , wherein the first cut-off frequency and second cut-off frequency are substantially the same.
5. The photon detection system of claim 3 , further comprising a power measuring circuit configured to determine a signal power based on the second filtered output signal.
6. The photon detection system of claim 5 , wherein the biasing circuit is further configured to receive a feedback signal generated based on the determined signal power, and to adjust, based on the feedback signal, the gating signal to match a target gating signal.
7. The photon detection system of claim 1 , wherein the non-reflective filter circuit is a diplexer.
8. The photon detection system of claim 1 , further comprising a discriminator circuit configured to output an electrical pulse based on the first filtered output signal.
9. The photon detection system of claim 1 , wherein the gating signal is in the form of square wave or a sinusoid.
10. The photon detection system of claim 1 , wherein the frequency is greater than 1 GHz.
11. The photon detection system of claim 1 , wherein the avalanche photodiode is an InGaAs/InP single-photon avalanche photodiode.
12. A quantum communication system, comprising:
a sender configured to send light pulses encoded using a basis selected from at least two bases, and
a receiver comprising the photon detection system according to claim 1 .
13. A method of detecting a photon using an avalanche photodiode, the method comprising:
supplying a gating signal to the avalanche photodiode, wherein the gating signal is a periodic signal configured to reverse bias the avalanche photodiode above and below its breakdown voltage for photon detection during each period;
providing, to a transmission line, a photodiode signal generated by the avalanche photodiode in response to an incident photon;
providing the photodiode signal from the transmission line to an input port of a non-reflective filter circuit; and
providing, at a first output port of the non-reflective filter circuit, a first filtered output signal by applying a low-pass filter with a first cut-off frequency to the provided photodiode signal,
wherein the input port of the non-reflective filter circuit is configured to be impedance matched to the transmission line up to a frequency higher than a gate frequency of the gating signal.
14. The method of claim 13 , wherein the gating signal has a gate frequency which is higher than the first cut-off frequency.
15. The method of claim 13 , further comprising:
providing, at a second output port of the non-reflective filter circuit, a second filtered output signal by applying a high-pass filter with a second cut-off frequency to the received photodiode signal.
16. The method of claim 15 , wherein the first cut-off frequency and second cut-off frequency are substantially the same.
17. The method of claim 15 , further comprising:
determining, by a power measuring circuit, a signal power based on the second filtered output signal.
18. The method of claim 17 , further comprising:
receiving a feedback signal generated based on the determined signal power, and
adjusting, based on the feedback signal, the gating signal to match a target gating signal.
19. The method of claim 13 , wherein the non-reflective filter circuit is a diplexer.
20. The method of claim 13 , further comprising:
determining the presence or absence of photon induced spikes in the first filtered output signal, and
in response to determining the presence of photon induced spikes in the first filtered output signal, generating as an output an electrical signal.