Fig. 6: Quantum state tomography in the frequency-bin subspace.

a Reconstructed density matrix for the input power corresponding to the 1 Gpair/s emission rate for qubit a. b Dependence of the Purity and Fidelity of the reconstructed density matrix on the pump power for the three measured qubits. The green dashed line marks the power for which the device generates 1 Gpair/s on-chip, while the red dashed line marks the power that corresponds to a net rate of 1 Gpair/s after fiber coupling.