Quantum Wavelength-Division Multiplexer

Each input channel carries its own independent single-photon qubit, prepared in its own Bloch-sphere state, at its own tunable wavelength. A multiplexer combines every active channel onto one shared output fiber; a matching demultiplexer separates them again by wavelength at the far end. As long as the channels' wavelengths stay well apart, every channel's state comes through with high fidelity and zero cross-talk. Drag two wavelength sliders close together and watch their output fidelity fall as the demultiplexer starts mixing the two channels' quantum states.