Improvement In Quantum Key Distribution

One of the most common uses of quantum computers will undoubtedly be quantum cryptography applications.

The basic logic of quantum cryptography is to transfer the desired information securely and quickly between the receiver and the transmitter. This process occurs when the receiver and transmitter create and share quantum key distributions with each other.

If an eavesdropper intervenes during this information exchange, one of the assumptions of quantum mechanics, the quantum state vector collapses, and the sent information is corrupted before it reaches the actual receiver. Therefore, the quantum key distribution is very important here.

With our current technology, superconducting nanowire single-photon detectors operating at cryogenic temperatures are used. When a small region of the nanowire absorbs a photon, it heats up and temporarily switches from a superconductor to a normal material. This causes an increase in the electrical resistance of the detected nanowire. Once the photon is absorbed, the nanowire must cool down before it can detect the next photon, and this recovery time limits how fast a superconducting nanowire single photon detector can operate.

Hugo Zbinden and his colleagues at the University of Geneva have come up with a new solution for the optimization of this problem.

According to this solution, the new design of superconducting nanowire single-photon detectors consists of 14 nanowires intertwined in such a way that all of them are evenly illuminated by the light emanating from the optical fiber. Also, the superconducting nanowire of each nanowire is shorter than the nanowires usually used in single-photon detectors. This means that individual nanowires can cool faster.

Thanks to this improvement, the latest generation superconducting nanowire single photon detector can detect photons quickly, making a QKD system all necessary error corrections and realizing privacy enhancement.

However, the researchers still envision a wide range of possibilities for ultrafast, highly efficient superconducting nanowire single-photon detectors. These range from secure communication between distant spacecraft to next-generation advanced optical sensors that could be particularly useful in medical imaging.

You can find the details of the study in the article in the references.

Reference

Grünenfelder, F., Boaron, A., Resta, G.V. et al. Fast single-photon detectors and real-time key distillation enable high secret-key-rate quantum key distribution systems. Nat. Photon. 17, 422–426 (2023). https://doi.org/10.1038/s41566-023-01168-2

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