A Nature Physics experiment, published September 3 and highlighted here, combined quantum optics with relativity to verify a participant’s position. Two verifiers about 1.24 miles apart achieved accuracy better than 246 feet. Weak laser pulses and tightly timed responses make this a different problem from accepting a device’s reported GPS coordinates. The security result depends on the paper’s adversary assumptions, including restrictions on pre-shared entanglement; it is not a universal guarantee against arbitrary collusion. Read the experiment.