FIG. 2.

Locations of Alice (A), Bob (B), and the source (S). Alice and Bob are separated by 194.8 ± 1.0 m (this is slightly further than in Refs. [7,35]). Faint gray lines indicate the paths that the entangled photons take from the source to Alice and Bob through fiber optic cables. The light-green quarter circles are the 2D projections of the expanding light spheres containing the earliest available information about the random bits used for Alice’s and Bob’s setting choices at the trial. When Bob finishes his measurement, the radius of the light sphere corresponding to the start of Alice’s QRNG has expanded to 127.3 0.5 m, after which it takes an additional 222.3 3.8 ns before the light sphere will intersect Bob’s location. Similarly, when Alice completes her measurement, the light sphere corresponding to the start of Bob’s QRNG has only reached a radius of 98.3 0.5 m, and it will take 315.5 3.8 ns more to arrive at Alice’s station. In this way, the actions of Alice and Bob are spacelike separated. Inset: Alice’s and Bob’s measurement apparatuses both consist of a Pockels cell (PC), operating at approximately 100 KHz, and a polarizer, constructed using two half-wavelength plates (HWPs), a quarterwavelength plate (QWP) and a polarizing beam displacer, in order to make fast polarization measurements on their respective photons. The measurement setting is controlled by a QRNG, the photon is detected by a high-efficiency superconducting nanowire single-photon detector, and the resulting signal is recorded on a time tagger, where a 10 MHz oscillator is used to keep Alice’s and Bob’s time taggers synchronized.