Novel and universal Gaussian control of hybrid bosonic quantum systems

The ability to control interactions between bosonic modes is crucial for bosonic quantum information processing and plays an important role in the design of hybrid quantum computers and networks. In theory, general interfaces can be constructed through complicated combinations of quantum transducers. However, the key building block of quantum transducers as well as the other more general Gaussian operations —namely, clean two-mode beam-splitters— are largely unavailable in hybrid quantum systems, due to practical experimental imperfections such as undesired coupling to auxiliary modes. Moreover, constructing interfaces using quantum transducers often sacrifices hardware efficiency. To tackle these challenges, we utilize the mathematical structure of multi-mode bosonic interactions induced by the fundamental canonical quantization relations. Starting from a generic coupler characterized by a Gaussian unitary operation, we develop a universal scheme that can construct general target Gaussian operations on desired subset of bosonic modes, while decoupling them from the undesired modes. Our scheme is hardware-aware: just a given bosonic interaction implemented multiple times and the ability to perform single-mode Gaussian unitary operations, both of which are readily available in experimental settings. This scheme can also be implemented using a constant overhead in the generic case, thus enabling efficient Gaussian operation construction.