Mr. Yoni Shalibo

Superconducting Josephson circuits made their debut in quantum information research more than a decade ago. With these remarkable devices, a truly macroscopic quantum state can be easily generated, extending millimeters in space and already approaching a size of 10 independently controlled units having non-classical correlations. Yet, while most of the effort has so far been directed towards implementing multi-qubit devices, most of the constituting elements in these devices are inherently multi-level quantum systems.
In principle, a quantum computing scheme based on d-level elements (qudits) is equivalent to the qubit scheme but requires less physical resources to implement. In this talk I will present our recent experiments, showing the first steps in controlling and measuring multi-level states in superconducting Josephson circuits. We show that the system’s response to the control signal changes from quantum to classical upon varying the drive and system parameters. We also demonstrate a new method of fully characterizing the quantum state of a single system, composed of up to 5 levels. Our experiments make it feasible to optimize arbitrary single-qudit quantum gates within this subspace with high fidelities.