Figure 5
The fourth gate (QD4) and the operations dependent on the measurements in Fig. 2. For the alignment of the path of photon C, the fourth gate utilizes the reflection operator \({\hat{\text{R}}}_{2}^{{{\text{Id}}}} \left( \omega \right)\) given by Eq. 6 with a frequency of \(\omega - \omega_{c} = 0\) for the interaction between a photon C and an electron spin 4, which is prepared to the state \(\left| { +_{{\text{e}}} } \right\rangle_{4}\), in QD4. Subsequently, due to the measurement outcomes of QD1, QD2, QD3, and QD4, the operations, depending on measurements, are performed on photons A, B, C, and D by Feed-Forward.
