Experimental Realization of Two Qutrits Gate with Tunable Coupling in Superconducting Circuits

TL;DR

This paper demonstrates a high-fidelity, scalable two-qutrit gate in superconducting circuits using tunable coupling, advancing the development of qutrit-based quantum computing.

Contribution

It introduces a novel, efficient method for implementing a two-qutrit gate with high fidelity and tunable coupling, crucial for scalable qutrit quantum computation.

Findings

Achieved a two-qutrit gate fidelity of 89.3%.

Prepared a two-qutrit EPR state with 95.5% fidelity.

Utilized tunable coupler for high on/off ratio and low cross talk.

Abstract

Gate-based quantum computation has been extensively investigated using quantum circuits based on qubits. In many cases, such qubits are actually made out of multilevel systems but with only two states being used for computational purpose. While such a strategy has the advantage of being in line with the common binary logic, it in some sense wastes the ready-for-use resources in the large Hilbert space of these intrinsic multi-dimensional systems. Quantum computation beyond qubits (e.g., using qutrits or qudits) has thus been discussed and argued to be more efficient than its qubit counterpart in certain scenarios. However, one of the essential elements for qutrit-based quantum computation, two-qutrit quantum gate, remains a major challenge. In this work, we propose and demonstrate a highly efficient and scalable two-qutrit quantum gate in superconducting quantum circuits. Using a tunable coupler to control the cross-Kerr coupling between two qutrits, our scheme realizes a two-qutrit conditional phase gate with fidelity 89.3% by combining simple pulses applied to the coupler with single-qutrit operations. We further use such a two-qutrit gate to prepare an EPR state of two qutrits with a fidelity of 95.5%. Our scheme takes advantage of a tunable qutrit-qutrit coupling with a large on:off ratio. It therefore offers both high efficiency and low cross talk between qutrits, thus being friendly for scaling up. Our work constitutes an important step towards scalable qutrit-based quantum computation.