From left: Prof Mehul Malik, Suraj Goel, Dr Saroch Leedumrongwatthanakun, Sophie Elisabeth-Lerchbaumer, Dr Sabine Wollmann, lead author of the paper Vatshal Srivastav, Sophie Engineer, Natalia Herrera Valencia and Dr Will McCutcheon. Image: Heriot-Watt University
Researchers found a way for quantum entanglement to handle noise and loss over long distances, opening the door to ‘practical quantum networks with the ultimate form of security’.
New research into quantum entanglement could help deliver unhackable communication networks in the future.
Quantum entanglement is when two particles – such as photons – remain connected and operate in tandem, even when they’re separated over a vast distance.
This could provide the potential for truly secure communications in the future, even if a communication device is unsafe or in criminal hands. A sender and receiver would be able to produce shared outcomes through an entangled quantum system, without a third party being able to interfere.
However, researchers at Scotland’s Heriot-Watt University noted that entangled photons can be disrupted by noise from real-world environments over long distances. Stormy weather, background noise and signal losses can jeopardise the security of a quantum network.
“Even the best optical fibres in the world will have a certain amount of loss per kilometre, so this is a big hurdle in making this form of quantum communication possible,” said Prof Mehul Malik, who led the research team.
Working with colleagues at the University of Geneva in Switzerland, the Heriot-Watt team said they have developed a way for quantum entanglement to survive under extreme conditions of noise and loss.
Quantum steering
Malik said his team was able to show that quantum entanglement can tolerate both noise and loss through a form of “quantum steering”.
This process aims to make the quantum entanglement more robust by using photons entangled in multiple dimensions – called qudits – compared to the standard two-dimensional quantum units known as qubits.
Researchers said this method of entanglement uses the spatial structure of light to entangle photons in a 53-dimensional space made up of pixels of light.
In their study, published in Physical Review X, the team steered entangled photons through loss and noise conditions equivalent to 79km of telecoms fibre optic cable.
Illustration of high-dimensional entanglement being robust against noise. Image: Vatshal Srivastav
The researchers said the results demonstrated the advantages of this form of quantum entanglement, which “opens the door towards practical quantum networks with the ultimate form of security”.
The research also indicates that increasing the number of dimensions in quantum entanglement dramatically reduces the time it takes to measure the results.
Malik said that quantum technology is an “emerging area” in both academia and industry and that this research is “incredibly relevant to both”.
“In academia, it can help advance fundamental research, and in industry, it could help future quantum networks operate over global distances,” he explained.
Earlier this year, an international team of researchers tested a form of quantum cryptography based on high-quality quantum entanglement.
In October, three scientists were jointly awarded the 2022 Nobel Prize in Physics for “groundbreaking experiments” in quantum mechanics. This research was focused on entangled quantum states, paving the way for new tech based on quantum information.
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