Fig. 5
From: A CNOT gate between multiphoton qubits encoded in two cavities
Undesired entanglement induced by the coupling ancilla. Concurrence vs. wait time for an initially separable state (red) using single-photon encoding, and for an initial Bell state (blue) obtained by applying the CNOT gate to the separable state. The presence of the cross-Kerr interaction between the two cavities is responsible for the observed oscillatory behavior, whereas dephasing due to thermal excitations in the ancilla results in a gradual decay of the entanglement. By fitting simulations (solid curves) to the measured data, we determine a cross-Kerr interaction rate of χCT/2π = 2 kHz. Error bars indicate the standard error derived from bootstrapping
