High-Fidelity Qutrit Entanglement in Superconducting Circuits

The workhorse qubit of modern superconducting systems – the transmon – has readily addressable higher states making it also a natural platform for qutrit operation. Provided high-fidelity multi-qutrit control, the larger, more connected computational space leveraged in a ternary approach to quantum computation can enable improvements to quantum simulation and error correction. Nonetheless, a significant impediment to realizing effective qutrit processing in a superconducting platform has been the ability to generate high-fidelity qutrit entangling gates. Recently, utilizing the Differential AC-Stark effect, we have demonstrated a dynamic cross-Kerr interaction between two fixed-frequency transmon qutrits and leveraged it to generate high-fidelity, maximally-entangling qutrit controlled-phase gates. Additionally, enabling coherent control over the full multi-qutrit Hilbert space allows one to compactly generate multi-controlled qubit entangling gates and achieve greater flexibility in generating two-qubit gates. In this talk, we present advanced control and characterization techniques in transmon qutrits that we leverage for high-fidelity qutrit entangling operations to improve both binary and ternary approaches to quantum computation.