Does quantum entanglement hold the key to unhackable communications?

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Scientists have discovered a new kind of quantum cryptography that uses one of the same laws of physics used to build quantum computers: quantum entanglement.

Quantum entanglement, or what Einstein called “spooky action at a distance,” refers to the phenomenon of two subatomic particles bound together in an exclusive relationship despite distance. If a change occurs in one particle, the other will also be affected, regardless of the distance between them.

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

The researchers “demonstrated a comprehensive quantum key distribution (QKD) protocol immune to the vulnerabilities and flaws in physical devices that plague current quantum protocols.” This QKD protocol uses entangled particles as “secret keys” that will detect third-party security flaws and make devices tamper-proof.

Hardware manufacturers have recently warned of the potential security crisis that could arise with the eventual development of fault-tolerant quantum computers. Public key cryptology is an encryption method that is the current basis of online encryption, and it works because conventional computers are unable to calculate the prime factors of large numbers. Quantum computers will one day be able to launch sophisticated security attacks using advanced calculations and will quickly break 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. To illustrate this in the experiment, the sender transmits to the receiver an encrypted image of John Stewart Bell, whose theoretical arguments about the limits of correlations in nature are central to device-independent security. Credit: David Nadlinger/University of Oxford. Original photo by Bell: CERN

This new quantum cryptography system 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 image over an optical fiber while measuring the properties of an ion to create the key. The receiver then measured the properties of the second ion, which were exactly the same thanks to quantum entanglement. This means that the sender and receiver have the same security key, ensuring that the information is encrypted. The Strontium ions were only two meters apart in this case, but the researchers say the distance could be significantly increased in the future.

While progress has been made in quantum key distribution for security against communication channel attacks, the devices themselves are still vulnerable. The researchers say their system allows for “device-independent” QKD encryption, which means hackers won’t be able to exploit loopholes in devices to break in.

Professor David Lucas from the University of Oxford explains: “The real breakthrough here is that we were not only able to show that our quantum network theoretically had sufficient performance to do this new type of QKD, but that we were actually able to do it. in practice and go as far as distributing a shared secret key. Although originally designed for quantum computing experiments, this shows the versatility of the quantum network for other applications.

This research was conducted 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. See the scientific article published in Nature at this link.

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