Optimizing state transfer in a three-qubit array via quantum brachistochrone method [Invited]

The quantum brachistochrone method has recently emerged as a technique that allows one to implement the desired unitary evolution operator in a physical system within a minimal time. Here, we apply this approach to the problem of time-optimal quantum state transfer in an array of three qubits with time-varying nearest-neighbor couplings and analytically derive the fastest protocol.