Quantum communication through devices with indefinite input-output direction

Certain quantum devices, such as half-wave plates and quarter-wave in optics, are bidirectional, meaning that the roles of their input output ports can be exchanged. Bidirectional devices used a forward mode backward mode, corresponding to two opposite choices input-output direction. They also coherent superposition modes, giving rise new operations with indefinite In this work we explore potential indefiniteness for transfer classical information through noisy channels. We first formulate model communication from sender receiver via channel Then, show direction yields advantages over standard protocols which given is fixed These range general reduction noise bidirectional processes, heralded noiseless transmission states, and, some special cases, complete removal. The due experimentally demonstrated current photonic technologies, providing way investigate operational consequences exotic scenarios characterised by superpositions forward-time backward-time processes.