Quantum frequency processor for provable cybersecurity

1. A method of quantum key distribution, comprising:

receiving a frequency bin photon at a location;

selecting a frequency bin photon quantum key distribution measurement basis;

with a quantum frequency processor, performing a measurement basis transformation on the received frequency bin photon so that the frequency bin photon is measurable in the selected frequency bin photon quantum key distribution measurement basis; and

detecting the frequency bin photon in the selected quantum key distribution measurement basis and assigning a quantum key distribution key value based on the detection to a portion of a quantum key distribution key.

2. The method of claim 1 , further comprising repeating the steps of claim 1 and forming the quantum key distribution key from the assigned quantum key distribution key values.

3. The method of claim 2 , further comprising:

receiving a transmission encoded with the quantum key distribution key; and

decoding the transmission with the quantum key distribution key.

4. The method of claim 2 , wherein the forming comprises forming the quantum key distribution key as a one-time pad.

5. The method of claim 2 , wherein the forming comprises:

publishing the selected frequency bin photon quantum key distribution measurement bases;

discarding assigned quantum key distribution key values that do not have a matching measurement basis between a sender and receiver and retaining assigned quantum key distribution key values that do have a matching measurement basis to form the quantum key distribution key;

comparing a subset of the retained assigned quantum key distribution values to determine a quantum bit error rate for the quantum key distribution key; and

determining whether to keep the quantum key distribution key based on the quantum bit error rate.

6. The method of claim 5 , further comprising amplifying the privacy of the quantum key distribution key.

7. The method of claim 1 , wherein the performing the measurement basis transformation comprises defining a Hadamard gate with the quantum frequency processor and performing the measurement basis transformation with the Hadamard gate.

8. The method of claim 1 , wherein the performing the measurement basis transformation with the quantum frequency processor comprises:

directing the received frequency bin photon through a first electro-optic modulator configured to mix frequency modes of the received frequency bin photon and form a mode-mixed frequency bin photon,

directing the mode-mixed frequency bin photon through a pulse shaper configured to selectively adjust a phase of different frequency modes of the mode-mixed frequency bin photon, and

directing the pulse-shaped mode-mixed frequency bin photon through a second electro-optic modulator configured to return frequency modes scattered outside of an encoding space of the pulse-shaped mode-mixed frequency bin photon.

9. The method of claim 8 , wherein the performing the measurement basis transformation with the quantum frequency processor comprises directing the received frequency bin photon through N+1 electro-optic modulators and N pulse shapers alternately arranged in series.

10. The method of claim 1 , further comprising:

receiving additional frequency bin photons across a range of frequency bin channels of a frequency comb spectrum simultaneous with the received frequency bin photon.

11. The method of claim 10 , further comprising parallel processing the additional frequency bin photons with the quantum frequency processor.

12. The method of claim 11 , wherein the parallel processing comprises, simultaneous or nearly simultaneous with receiving the frequency bin photon:

selecting frequency bin photon quantum key distribution measurement bases for the additional frequency bin photons;

with the quantum frequency processor, performing measurement basis transformations on the additional frequency bin photons so that the additional frequency bin photons are measurable in the selected frequency bin photon quantum key distribution measurement bases; and

detecting the additional frequency bin photons in the selected quantum key distribution measurement bases and assigning quantum key distribution key values to the quantum key distribution key based on the detection to (i) another portion of the quantum key distribution key or (ii) one or more other quantum key distribution keys different from the quantum key distribution key.

13. The method of claim 1 , wherein the receiving the frequency bin photon comprises receiving one or more photons along a common optical path of a single-mode optical fiber.

14. The method of claim 1 , wherein the receiving the frequency bin photon comprises receiving the frequency bin photon as a single photon generated, encoded, and sent from a distant location.

15. The method of claim 1 , wherein the receiving the frequency bin photon comprises receiving the frequency bin photon as an entangled state photon generated at a distant location without being encoded with any information at the distant location such that a distant photon forms an entangled state partner of the entangled state photon.

16. The method of claim 1 , wherein the performing the measurement basis transformation with the quantum frequency processor comprises directing the received frequency bin photon through an integrated photonic chip.

17. The method of claim 1 , wherein the receiving the frequency bin photon comprises receiving the frequency bin photon as a photon in superposition with a plurality of frequency bins.

18. The method of claim 1 , further comprising receiving an other frequency bin photon at the location, wherein the other frequency bin photon is entangled with the frequency bin photon and separated by a plurality of frequency bins from the frequency bin photon, wherein the frequency bin photon and the other frequency bin photon form an entangled photon pair.