By harnessing quantum entanglement, the researchers said they could develop secure communications “fundamentally beyond” an adversary’s control.

An international team of researchers has tested a new form of quantum cryptography that could lead to the ultimate standard for secure communications with real-world devices.

It is based on Quantum Key Distribution (QKD), which is a method of sharing encryption keys between two parties that can be used to encrypt and decrypt messages. This promises communication security unattainable in conventional cryptography.

Encryption involves complex mathematical problems that modern computers cannot solve to ensure data security. But as technology advances, quantum computers will likely be able to solve these problems and circumvent current cryptographic protocols.

The researchers said existing forms of QKD rely on communication between two “trusted” quantum devices. This requires detailed knowledge of the devices, which can open up potential for quantum hacking.

However, their new approach enables secure communication between devices without needing to know much about them, paving the way for secure cryptography for real-world devices.

A representation of the device-independent quantum key distribution. Image: Scixel/Enrique Sahagu

“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 kind of QKD, but we were actually able to do it in practice and go all the way to distribution of a shared secret key,” said Professor David Lucas from the University of Oxford.

Device independence

The research was a collaborative effort between the University of Oxford, the French Alternative Energies and Atomic Energy Commission and Swiss universities ETH Zurich, EPFL and the University of Geneva.

In their study published in Nature, the researchers said they successfully demonstrated an approach to QKD between two devices based on high-quality quantum entanglement. It is the relationship between two particles that can span great distances, but remain connected and work in tandem.

The experiment involved two single ions (one for the transmitter and one for the receiver) confined in separate traps connected by a fiber optic link. While these devices were in the same room, the researchers said there is a “clear path” to extend the distance to miles and beyond.

Sender and receiver can produce shared results through the entangled quantum system, without any third party being able to interfere.

The researchers said this method could lead to forms of communication between two parties that are “fundamentally beyond” any adversary’s control, and that an equivalent guarantee of security is impossible with conventional cryptography methods.

The team also said that this method can ensure the privacy of communications with only a few general assumptions about the physical devices used. This helps lay the foundation for a “device-independent QKD”.

Professor Renato Renner of ETH Zurich said that the history of cryptography has been a competition between cryptographers and cryptoanalysts tackling new methods of encryption.

“But device-independent quantum cryptography can finally end this competition – there’s simply no room left for an attack,” Renner said.

Earlier this month, the U.S. National Institute of Standards and Technology selected four encryption algorithms it says can withstand the onslaught of a quantum computer, which will be part of a new quantum-resistant cryptographic standard.

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