Native Approach to Controlled-Z Gates in Inductively Coupled Fluxonium Qubits.

Area of Science:

• Quantum Information Science
• Superconducting Quantum Computing
• Quantum Error Correction

Background:

• Fluxonium qubits are a promising platform for quantum computation due to their robustness against charge noise.
• Capacitive coupling of fluxonium qubits primarily enables XX interactions, limiting the implementation of other essential gate types.
• Previous methods for achieving ZZ or XZ interactions in fluxonium qubits were complex, involving higher energy states or microwave driving.

Purpose of the Study:

• To propose and demonstrate a novel inductive coupling scheme for fluxonium qubits.
• To enable a wider range of native qubit-qubit interactions beyond XX, specifically ZZ interactions.
• To achieve high-fidelity quantum gates and entanglement for fluxonium-based quantum processors.

Main Methods:

• Implemented an inductive coupling scheme to facilitate direct qubit-qubit interactions.
• Utilized a built-in, flux-controlled tunable ZZ interaction for entanglement operations.
• Employed a continuous dynamical decoupling technique for noise filtering against flux noise.

Main Results:

• Demonstrated a 20 nanosecond controlled-Z gate with a high mean fidelity of 99.53%.
• Successfully performed qubit entanglement using the proposed inductive coupling and flux-controlled ZZ interaction.
• Identified a unique parameter space within the fluxonium system suitable for efficient gate operations.

Conclusions:

• The inductive coupling scheme significantly expands the native interaction capabilities of fluxonium qubits.
• The demonstrated high-fidelity controlled-Z gate validates the efficacy of the proposed inductive coupling and noise filtering techniques.
• This work highlights a promising avenue for advancing fluxonium-based quantum computing through optimized qubit coupling and gate design.