Fig. 9

Autocompensating devices for codirectional modes and phase modulators. Light enters local loops through OCs. In the local loops, a DC with κL=π/2 plus a phase shifter introducing a phase π, for instance, in path 2. A HWP rotated π/4 is placed for polarization autocompensation. Afterwards, a phase modulator is placed, so as to introduce the phase θ and generate quantum states in order for Alice and Bob to encode their bits