Decoupling bosonic modes using sequential quantum transducers

Quantum transducers are devices that can faithfully convert quantum signals from one mode to another. Building robust quantum transducers will be crucial to the development of hybrid quantum networks and scalable quantum computers. Previous studies have explored techniques to achieve perfect transduction using even imperfect transducers -- however, these methods either require infinite squeezing or apply only to the case of two modes. Here, we develop a new protocol that works for an arbitrary number of modes and requires only finite squeezing. Specifically, we show that by operating transducers in sequence, interspersed with appropriate single-mode operations, it is possible to decouple unwanted degrees of freedom and so reduce a three-mode transduction problem to the solved two-mode case. Furthermore, we investigate the dependence of the squeezing needed on the mode-coupling strength for a given transducer and propose some potential experimental setups.