Entanglement Swapping Enables the Practical Security of Quantum Cryptography
Yang-Fan Jiang, L L Huang, Yuzhe Zhang +9 more
Entanglement is one of the most striking phenomena in quantum physics, playing important roles in fundamental physics and quantum information science. It enables a secure means of communication—quantum cryptography—and builds up the foundation of its unconditional security. Entanglement-based quantum cryptography has received great attention from the early demonstrations to the recent remarkable achievements. In a practical scenario, although entanglement-based quantum cryptography can provide inherent source-independent security, its detection side has been shown to be vulnerable to external probing attacks. Here we show that entanglement swapping can effectively solve this critical issue, enabling a side-channel-free quantum cryptography.Entanglement swapping allows each user’s quantum state preparation and detection in a completely private station, which is immune to any external probing side channels. We demonstrate the entanglement-swapping quantum cryptography scheme in the field based on two independent entanglement photon sources. Based on the remote entangled photon pairs, we implement the Ekert-1991 protocol under a channel attenuation equivalent to 100 km of standard optical fiber, achieving a Bell violation value of S=2.659±0.092 and a secret key rate of 0.0163 bit/s. While recent device-independent QKD demonstrations have reached 100 km using atoms or ions, our photonic ES-QKD offers a complementary, all-optical pathway that is directly compatible with existing fiber networks and quantum repeaters.
Entropy•May 4, 2026•0 citations