Simulating neutrino oscillations with a transmon qutrit.

Current cloud quantum processors based on superconducting qubits are primarily set up for employing the two lowest levels of transmon circuits as qubits. Here, we show that functionality made accessible to the user also enables the use of higher levels, turning the transmon into a qudit. As an illustration, we present a qutrit-based quantum simulation of three-flavor neutrino oscillations on a Rigetti cloud-access processor. Single-qutrit unitaries in this simulation are realized by two methods: quantum optimal control and gate decomposition. We discuss advantages and limitations of these schemes.