Fig. 2: High-fidelity entangled network links.
From: Qubit teleportation between non-neighbouring nodes in a quantum network
a, Simplified schematic of the optical link used for generating entanglement between neighbouring nodes. Photons emitted by the communication qubits are filtered by a dichroic mirror (DM) to separate the resonant (zero-phonon line, ZPL) photons (3% of emission) from the off-resonant (phonon-side band, PSB) photons (97% of emission). The resonant photons are sent to the beam splitter (BS); detection of a single photon at one of the ZPL detectors heralds successful generation of an entangled state between the two nodes. b, Measured correlations of the communication qubits in the computational basis, conditioned on a heralding event on the ZPL detectors. c, Left, histograms of the PSB photon detection times on Alice (top) or Bob (bottom), conditioned on a simultaneous ZPL detection in the same entanglement generation attempt. Grey lines show expected correlations on the basis of a quantum-optical model (see Supplementary Information). The correlations measured in the other measurement bases can be found in Extended Data Fig. 1. d, Measured fidelity of the network links, without PSB rejection (left), with PSB rejection (middle) and with PSB rejection plus shortened detection window (right). The dark blue bars indicate the corresponding expected fidelity on Alice–Charlie after entanglement swapping for each case (see Methods). All error bars represent one standard deviation.
