Quantum Position Verification with Remote Untrusted Devices

Many applications require or benefit from being able to securely localize remote parties. In classical physics, adversaries can in principle have complete knowledge of such a party's devices, and secure localization is fundamentally impossible. This limitation can be overcome with quantum technologies, but proposals to date require trusting vulnerable hardware. Here we develop and experimentally demonstrate a protocol for device-independent quantum position verification that guarantees security with only observed correlations from a loophole-free Bell test across a quantum network. The protocol certifies the position of a remote party against adversaries who, before each instance of the test, are weakly entangled, but otherwise have unlimited quantum computation and communication capabilities. Our demonstration achieves a one-dimensional localization that is 2.47(2) times smaller than the best, necessarily non-remote, classical localization protocol. Compared to such a classical protocol having identical latencies, the localization is 4.53(5) times smaller. This work anchors digital security in the physical world.