Transmon qutrit-based simulation of spin-1 AKLT systems

Abstract: Qutrit-based quantum circuits could help reduce the overall circuit depths, and hence the noise, when the system of interest has local dimension of three. Accessing second excited states in superconducting transmons provides a straightforward hardware realization of three-level systems, or qutrits, useful for such ternary encoding. In this work, we successfully calibrate pulse gates to a low error rate to obtain transmon qutrits. We use these qutrits to simulate one-dimensional spin-1 AKLT states (Affleck, Lieb, Kennedy, and Tasaki) which exhibit a multitude of interesting phenomena such as topologically protected ground states, string order and the existence of a robust Berry phase. We demonstrate the efficacy of qutrit-based simulation by preparing high-fidelity ground states of the AKLT Hamiltonian with open boundaries for various chain lengths. We then use ground state preparations of the perturbed AKLT Hamiltonian with periodic boundaries to calculate the Berry phase and illustrate non-trivial ground state topology. We further present scalable methods for preparing the AKLT state and computing its Berry phase, and use tensor network simulations to establish the advantage of qutrit-based implementation over qubit-based ones in the presence of noise. Our work provides a pathway toward more general spin-1 physics simulations using transmon qutrits, with applications in chemistry, magnetism, and topological phases of matter.