Exploring Ququart Computation on a Transmon using Optimal Control

Abstract

Contemporary quantum computers encode and process quantum information in binary qubits (d = 2). However, many architectures include higher energy levels that are left as unused computational resources. We demonstrate a superconducting ququart (d = 4) processor and combine quantum optimal control with efficient gate decompositions to implement high-fidelity ququart gates. We distinguish between viewing the ququart as a generalized four-level qubit and an encoded pair of qubits, and characterize the resulting gates in each case. In randomized benchmarking experiments we observe gate fidelities greater 95% and identify coherence as the primary limiting factor. Our results validate ququarts as a viable tool for quantum information processing.

References in corpus (3)

• Charge insensitive qubit design derived from the Cooper pair box
• Robust randomized benchmarking of quantum processes
• Quantum Process Tomography: Resource Analysis of Different Strategies

Cited by in corpus (11)

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• Qutrit and Qubit Circuits for Three-Flavor Collective Neutrino Oscillations
• Taming quantum systems: A tutorial for using shortcuts-to-adiabaticity, quantum optimal control, and reinforcement learning
• Multi-frequency control and measurement of a spin-7/2 system encoded in a transmon qudit
• Randomised benchmarking for universal qudit gates
• Direct pulse-level compilation of arbitrary quantum logic gates on superconducting qutrits
• Local fermion-to-qudit mappings: a practical recipe for four-level systems
• Synthesis of Single Qutrit Circuits from Clifford+R