A newly proposed protocol to boost privacy in quantum sensor networks

Devices that leverage quantum mechanics effects, broadly referred to as quantum technologies, could help to tackle some real-world problems faster and more efficiently. In recent years, physicists and engineers have introduced various promising quantum technologies, including so-called quantum sensors.

Networks of quantum sensors could theoretically be used to measure specific parameters with remarkable precision. These networks leverage a quantum phenomenon known as entanglement, which entails a sustained connection between particles, which allows them to instantly share information with each other, even at a distance.

While quantum sensor networks (QSNs) could have various advantageous real-world applications, their effective deployment also relies on the ability to ensure that the information shared between sensors remains private and is not accessible to malicious third parties.

In a paper published in Physical Review Letters, researchers at Sorbonne University introduce a new protocol that could help to enhance the privacy of information shared between networked quantum sensors.

“Networked sensing represents a promising avenue of research within the broader field of quantum sensing,” Majid Hasani, first author of the paper, told Phys.org. “Given the inevitable presence of malicious adversaries who intercept quantum channels to gain some information, we set out to devise a private protocol in which one can estimate unknown parameters without any leakage of information.”

The new protocol devised by Hasani and his colleagues relies on an established mathematical tool known as the quantum Fisher information matrix (QFIM). This matrix essentially quantifies the precision of parameter estimates associated with quantum measurement devices or processes.

“The QFIM is a well-known quantity in the field of quantum metrology and sensing, which quantifies the maximum amount of extractable information about known parameters over all possible measurements and sets a lower bound on the precision of estimation,” explained Hasani.

“The mathematical properties of this matrix, such as the continuity relation between its entries, enabled us to construct a private protocol.”

Essentially, Hasani and his colleagues’ proposed protocol entails manipulating the QFIM to identify the quantum state in a quantum sensor network that maximizes privacy. Their paper also introduced the idea of quasiprivacy (𝜀-privacy), which is a measurement of how close a quantum state is to ensuring “perfect privacy.”

To illustrate the potential of their protocol, the researchers provided an example of how it could be applied to a network of quantum sensors. In the example they outlined, the quantum sensor network specifically estimated the average of unknown parameters and the team showed how their protocol could boost privacy.

“The presented method provides a systematic way to construct a protocol with tunable extractable information from the network,” said Hasani. “This tunabiliity enables us to control the information leakage and thereby protect our information from malicious adversaries.”

So far, the newly proposed privacy protocol was only theoretically demonstrated, yet Hasani and his colleagues soon hope to implement it and test it in an experimental setting. In the future, their efforts could contribute to the realization of secure quantum sensing and communications.

“Our next step will be to implement the protocol experimentally,” added Hasani. “This ongoing project with our collaborators will be crucial for the development of real-life quantum sensors.”

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