Quantum key distribution network with centralized optical pulse generation
A node for a quantum key distribution (QKD) network includes an optical input that receives an optical pulse from a hub of the QKD network and an optical splitter that splits the optical pulse into an optical timing pulse and a pre-qubit pulse. The node also includes a qubit encoder controllable to encode the pre-qubit pulse into a photonic qubit; a qubit trigger circuit that controls, based on the optical timing pulse, the qubit encoder while the pre-qubit pulse propagates through the qubit encoder; and an optical output that transmits the photonic qubit to the hub.
1. A node for a quantum key distribution network, comprising:
an optical input configured to receive an optical pulse from a hub of the quantum key distribution network;
an optical splitter configured to split the optical pulse into an optical timing pulse and a pre-qubit pulse;
a qubit encoder configured to encode the pre-qubit pulse into a photonic qubit;
a qubit trigger circuit configured to control, based on the optical timing pulse, the qubit encoder while the pre-qubit pulse propagates through the qubit encoder; and
an optical output configured to transmit the photonic qubit to the hub.
2. The node of claim 1 , the qubit trigger circuit comprising a photodetector configured to convert the optical timing pulse into an electronic trigger signal.
3. The node of claim 2 , the qubit trigger circuit further comprising a waveform generator that, in response to being triggered by the electronic trigger signal, outputs one or more control signals to the qubit encoder.
4. The node of claim 1 , the photonic qubit being a single-photon pulse.
5. The node of claim 1 , the photonic qubit being a weakly coherent pulse.
6. The node of claim 1 , the qubit encoder comprising one or both of an intensity modulator and a polarization modulator.
7. The node of claim 6 , the polarization modulator comprising a circulator, a phase modulator, and a Faraday mirror.
8. The node of claim 1 , further comprising an optical delay unit configured to delay the pre-qubit pulse.
9. A method for quantum key distribution network, comprising:
receiving an optical pulse from a hub of the quantum key distribution network;
splitting the optical pulse into an optical timing pulse and a pre-qubit pulse;
encoding, based on the optical timing pulse, the pre-qubit pulse into a photonic qubit; and
transmitting the photonic qubit to the hub.
10. The method of claim 9 , further comprising converting, with a photodetector, the optical timing pulse into an electronic trigger signal.
11. The method of claim 10 , wherein:
the method further comprises triggering a waveform generator with the electronic trigger signal; and
the waveform generator, in response to said triggering, outputs one or more control signals used for said encoding.
12. The method of claim 9 , the photonic qubit being a single-photon pulse.
13. The method of claim 9 , the photonic qubit being a weakly coherent pulse.
14. The method of claim 9 , wherein said encoding comprises encoding the pre-qubit pulse with one or both of an intensity modulator and a polarization modulator.
15. The method of claim 14 , wherein said encoding the pre-qubit pulse with a polarization modulator comprises encoding the pre-qubit pulse with a circulator, a phase modulator, and a Faraday mirror.
16. The method of claim 9 , further comprising delaying the pre-qubit pulse.