Does Quantum Entanglement Hold the Key to Unhackable Communications?

Scientists have uncovered a new type of quantum cryptography that utilizes one of the same laws of physics used in building quantum computers: quantum entanglement.

Quantum entanglement, or what Einstein called “spooky action at a distance,” refers to the phenomenon of two subatomic particles being linked to one another in an exclusive relationship despite distance. If a change occurs in one particle, the other will be affected as well, no matter how far apart they are.

This week, an international research team, consisting of theoretical and applied physicists and computer scientists, has experimentally implemented a “bug-proof” type of quantum cryptography using quantum entanglement that could pave the way for secure communication between real-world devices.

The researchers “demonstrated a complete quantum key distribution (QKD) protocol immune to the vulnerabilities and defects of physical devices that plague current quantum protocols.” This QKD protocol uses entangled particles as “secret keys” that will allow for the detection of third-party security breaches and render unhackable devices.

Hardware makers recently warned of the potential security crisis that could arise with the eventual development of fault-tolerant quantum computers. Public key cryptology is a method of encryption that is the current foundation for online encryption, and it works because classical computers are incapable of calculating the prime factors of large numbers. Quantum computers will one day be capable of launching sophisticated security attacks through advanced calculations and will quickly break through current encryption technology.

Once two parties have obtained a secret key using device-independent quantum key distribution, they can use it for provably secure communication. Illustrating this in the experiment, the sender transmits to receiver an encrypted picture of John Stewart Bell, whose theoretical arguments about the limits to correlations in nature lie at the heart of device-independent security. Credit: David Nadlinger/University of Oxford. Original photo of Bell: CERN

This new system of quantum cryptography uses quantum entanglement to generate a secret key to encrypt a message in two separate places. For this study, ions of the element Strontium were entangled, and a sender transmitted an encrypted picture over an optical fiber while measuring the properties of one ion to create the key. The recipient then measured the properties of the second ion, which were exactly the same thanks to quantum entanglement. This means that both the sender and recipient have the same security key, ensuring the information is encrypted. The Strontium ions were only separated by two meters in this case, but the researchers say the distance could be greatly increased in the future.

Although advancements have been made in quantum key distribution for security against communication channel attacks, devices themselves are still vulnerable. The researchers say their system allows for “device-independent” QKD encryption, meaning that hackers will not be able to exploit flaws in devices to break in.

Professor David Lucas from the University of Oxford explains, “The real breakthrough here is that we were not able to show that our quantum network had theoretically good enough performance to do this new kind of QKD, but that we were actually able to do it in practice and get all the way to distributing a shared secret key. Although originally designed for experiments in quantum computing, this shows the versatility of quantum networking for other applications.”

This research was carried out at the University of Oxford with contributions from the University of Geneva, the French Alternative Energies and Atomic Energy Commission (CEA), EPFL, and ETH Zurich. View the scientific paper published in Nature at this link.

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