Trusting Quantum Links Without Trusting Quantum Devices
In quantum communication, the principles of quantum physics are used to send information securely. A key challenge is ensuring that these transmissions are accurate in scenarios where the setup cannot be fully trusted to operate correctly—either because of inevitable imperfections or because of potential attacks from an adversary. Now Eleni Diamanti and her colleagues at Sorbonne University, France, report a protocol that allows communicators to quantify the accuracy of their transmissions [1]. Their work could improve the reliability of a wide range of quantum networks.
The new protocol uses a previously demonstrated method in which measuring certain quantum correlations implies that the quantum operations are functioning correctly. Crucially, that method does not require the inner workings of the quantum hardware to be understood or trusted. It was previously applied to quantum key distribution, random-number generation, and other operations. But attempts to extend it to quantum-information transmission could not quantify the transmission’s accuracy because they did not completely account for various complications, such as unavoidable information loss. Those previous attempts also destroyed the quantum information that was sent.
Diamanti and her colleagues performed an experiment in which a sender possessed trusted quantum hardware, but a receiver did not. The sender transmitted information to the receiver in the form of entangled pairs of photons. This transmission was subjected to various levels of information loss and, in some cases, to emulated adversarial attempts to disrupt the information. The researchers showed that they could use their protocol to estimate the transmission’s accuracy under these different conditions, while also preserving the information. They say that their demonstration highlights the protocol’s practical relevance and widespread applicability.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- S. Neves et al., “Experimentally certified transmission of a quantum message through an untrusted and lossy quantum channel via Bell’s theorem,” PRX Quantum 6, 030312 (2025).