Robust control of two-qubit Hamiltonian dynamics


Mio Murao, The University of Tokyo

We showed that it is possible to achieve robust control of Hamiltonian dynamics to implement an arbitrary target quantum gate for two-qubit Hamiltonian systems including an unknown parameter by adding a single-qubit control Hamiltonian. To perform the same task with conventional feedback control, we first need to perform quantum measurements and estimate the value of the unknown parameter, then derive and design the control Hamiltonian based on the estimated value.  In robust control, a control Hamiltonian is used to implement the target quantum gate for all values in the range of the parameters, therefore estimation of the value is not necessary.  Such robust controllability of quantum dynamics had been shown only for single-qubit systems before.  We analytically proved robust controllability of a class of two-qubit Hamiltonian dynamics based on group theory and also numerically presented robust controllability of wider classes of two-qubit Hamiltonian dynamics.

Ref: R. Sakai, A. Soeda, M. Murao and D. Burgarth, Phys. Rev. A 100, 042305 (2019)