Figure 13

Schematics of the proposed detection schemes: (a) General scheme for the generation of the photonic mode a, phononic mode b, and hybrid modes c, d, and their detection in the measurement unit M, which is shown in specific implementations using: (b) detection method 1 and (c) detection method 2. Key: \(U_\mathrm{LC}(\theta )\) stands for the linear-coupler transformation, which in special cases corresponds to multi-level SWAP (for \(\theta =\pi /2\)) and Hadamard-like (for \(\theta =\pm \pi /4\)) gates; BS is the balanced beam splitter, which corresponds to \(U_\mathrm{LC}(\pi /4)\), \(M'_a\) (\(M'_b\)) is a measurement unit for detecting photons (phonons), CCL is a coincidence and count logic unit, HBT stands for the standard Hanbury–Brown and Twiss optical interferometer. Mode \(e'\) (\(e''\)) is in the photonic (phononic) vacuum state.