Unique identifiers based on quantum effects

1. A method for determining a unique identifier of a device, the device including a quantum tunnelling barrier unique to the device, the method comprising:

applying a potential difference across the quantum tunnelling barrier, the potential difference sufficient to enable tunnelling of charge carriers through the quantum tunnelling barrier;

measuring an electrical signal, the electrical signal representative of a tunnelling current through the quantum tunnelling barrier, the tunnelling current characteristic of the quantum tunnelling barrier; and

determining, from the measured electrical signal, a unique identifier for the device.

2. The method according to claim 1 , wherein the device includes a single quantum tunnelling barrier.

3. The method according to claim 1 , wherein the quantum tunnelling barrier has an average thickness of less than or equal to five nanometres.

4. The method according to claim 1 , further comprising providing the unique identifier for use in a communication protocol or a data transaction, optionally in encrypting or authenticating an aspect thereof, and/or providing the unique identifier as a digital identifier of a physical object or a digital object.

5. The method according to claim 1 , further comprising using the unique identifier in a communication protocol or a data transaction and/or using the unique identifier as a digital identifier of a physical object or a digital object.

6. The method according to claim 1 , wherein the characteristics of the quantum tunnelling barrier revealed by the measured electrical signal result from one or more distinctive nanoscale properties of the device that arise from device-to-device variability between ostensibly identical devices produced by the same semiconductor manufacturing process.

7. The method according to claim 6 , wherein the distinctive nanoscale properties that are variable from device-to-device are beyond the control of a semiconductor manufacturing process used to produce the device.

8. The method according to claim 1 , further comprising:

applying a same potential difference across the quantum tunnelling barrier of an ostensibly identical second device,

measuring an electrical signal representative of a second tunnelling current through the second quantum tunnelling barrier, and

determining a second unique identifier for the ostensibly identical second device,

wherein the electrical signals are representative of tunnelling currents through the quantum tunnelling barrier of the ostensibly identical first and second devices are different.

9. The method according to claim 1 , further comprising comparing the unique identifier of the device with a database containing the unique identifier for the device and unique identifiers for other devices, wherein each of the other devices includes a quantum tunnelling barrier unique to that other device.

10. The method according to claim 1 , further comprising, prior to applying the potential difference, receiving a challenge from a third party.

11. The method according to claim 10 , further comprising communicating the unique identifier to the third party in response to the challenge.

12. The method according to claim 1 , wherein the device comprises a physically unclonable function, and wherein the unique identifier is a unique identifier of the physically unclonable function.

13. The method according to claim 1 , wherein determining a unique identifier for the device comprises determining a mean value of the tunnelling current.

14. The method according to claim 1 , wherein measuring an electrical signal comprises measuring an electrical signal multiple times, and wherein determining a unique identifier for the device comprises interpolating a current spectrum from the multiple measurements of the electrical signal.

15. A non-transitory computer readable medium having instructions stored thereon which, when executed by a processor, cause the processor to determine a unique identifier of a device by performing the method according to claim 1 .

16. A device comprising:

a first terminal and a second terminal;

a quantum tunnelling barrier unique to the device, the quantum tunnelling barrier located between the first terminal and the second terminal; and

a processor configured to:

apply a potential difference between the first terminal and the second terminal and across the quantum tunnelling barrier, the potential difference sufficient to enable tunnelling of charge carriers through the quantum tunnelling barrier;

measure an electrical signal, the electrical signal representative of a tunnelling current through the quantum tunnelling barrier, the tunnelling current characteristic of the quantum tunnelling barrier; and

determine, from the measured electrical signal, a unique identifier for the device.

17. The device according to claim 16 , wherein the device comprises a complementary metal-oxide-semiconductor, CMOS, chip.

18. The device according to claim 16 , wherein the device comprises a single unique quantum tunnelling barrier.

19. The device according to claim 16 , wherein the quantum tunnelling barrier has an average thickness of less than or equal to five nanometres.

20. The device according to claim 16 , wherein the device further comprises a power supply for applying the potential difference.