Figure 5 | Scientific Reports

Figure 5

From: The Goldilocks principle of learning unitaries by interlacing fixed operators with programmable phase shifters on a photonic chip

Figure 5

Geometric array for the passive matrix F using power dividers (3-dB directional coupler). (a) Power divider array composed of p layers as defined in (5). Light-shaded and dark-shaded layers denote \(\mathscr {L}_{1}=\mathbb {I}_{5}\otimes \mathscr {T}_{0}\) and \(\mathscr {L}_{2}=\mathbb {I}_{1}\oplus (\mathbb {I}_{4}\otimes \mathscr {T}_{0})\oplus \mathbb {I}_{1}\), respectively. Density criterion (b) and error norm (log\(_{10} L\)) (c) of the mesh architecture in (a) as a function of the number of layers p.

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