Universal quantum control over bosonic network

Abstract: Perfect transfer of unknown states across distinct nodes is fundamental in the construction of bosonic quantum networks. We here develop a general theory to control an $N$-node bosonic network governed by the time-dependent Hamiltonian, as the universal quantum control theory for continuous-variable systems. In particular, we can activate nonadiabatic passages superposed of initial and target modes by the commutation condition for the Hamiltonian's coefficient matrix in the representation of time-independent ancillary modes, which serves as the necessary and sufficient condition to solve the time-dependent Schr\"odinger equation of the entire network. To exemplify the versatility of our theory on the Heisenberg-picture passages, we perform arbitrary state exchange between two nodes, chiral NOON-state transfer among three bosonic nodes, and chiral Fock-state transfer among three of four bosonic nodes. Our work provides a promising avenue toward universal control of any pair of nodes or modes in bosonic networks as well as the whole network.