Simulation of vibrational dynamics using qubits and qudits

We investigate the quantum computing of the vibrational dynamics of CO${}_2$ and H${}_2$O by constructing the vibrational Hamiltonian in qubit and qudit form by two types of qubit encodings (binary and direct) and a qudit encoding. We simulate the time-dependent vibrational population transfer using the three different encodings, including the effect of noise and find that the qudit encoding leads to the most accurate results both for CO${}_2$ and H${}_2$O because of the small number of terms in the qudit Hamiltonian as long as the same values of the entangling gate error rates are adopted.