Native approach to controlled-Z gates in inductively coupled fluxonium qubits

Abstract

The fluxonium qubits have emerged as a promising platform for gate-based quantum information processing. However, their extraordinary protection against charge fluctuations comes at a cost: when coupled capacitively, the qubit-qubit interactions are restricted to XX-interactions. Consequently, effective XX- or XZ-interactions are only constructed either by temporarily populating higher-energy states, or by exploiting perturbative effects under microwave driving. Instead, we propose and demonstrate an inductive coupling scheme, which offers a wide selection of native qubit-qubit interactions for fluxonium. In particular, we leverage a built-in, flux-controlled ZZ-interaction to perform qubit entanglement. To combat the increased flux-noise-induced dephasing away from the flux-insensitive position, we use a continuous version of the dynamical decoupling scheme to perform noise filtering. Combining these, we demonstrate a 20 ns controlled-Z (CZ) gate with a mean fidelity of 99.53%. More than confirming the efficacy of our gate scheme, this high-fidelity result also reveals a promising but rarely explored parameter space uniquely suitable for gate operations between fluxonium qubits.

References in corpus (20)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Charge insensitive qubit design derived from the Cooper pair box
• Dynamical decoupling and noise spectroscopy with a superconducting flux qubit
• Optimized Dynamical Decoupling in a Model Quantum Memory
• Controllable coupling of superconducting flux qubits
• Fluxonium: an alternative qubit platform for high-fidelity operations
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• High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler
• Parametric coupling for superconducting qubits
• Universal fast flux control of a coherent, low-frequency qubit
• High fidelity two-qubit gates on fluxoniums using a tunable coupler
• High-fidelity controlled-Z gate with maximal intermediate leakage operating at the speed limit in a superconducting quantum processor
• Tunable coupling scheme for flux qubits at the optimal point
• Scalable High-Performance Fluxonium Quantum Processor
• Fast logic with slow qubits: microwave-activated controlled-Z gate on low-frequency fluxoniums
• Engineering Dynamical Sweet Spots to Protect Qubits from 1/$f$ Noise
• Overlap junctions for high coherence superconducting qubits
• Fast high-fidelity gates for galvanically-coupled fluxonium qubits using strong flux modulation
• Coupler microwave-activated controlled phase gate on fluxonium qubits
• Free Mode Removal and Mode Decoupling for Simulating General Superconducting Quantum Circuits

Cited by in corpus (11)

• Blueprint for all-to-all connected superconducting spin qubits
• Efficient initialization of fluxonium qubits based on auxiliary energy levels
• High coherence fluxonium manufactured with a wafer-scale uniformity process
• Balanced cross-Kerr coupling for superconducting qubit readout
• Verifying the analogy between transversely coupled spin-1/2 systems and inductively-coupled fluxoniums
• Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler
• Parametric phase modulation in superconducting circuits
• Transmon-assisted high-fidelity controlled-Z gates for integer fluxonium qubits
• Enhanced Quantum Signal Control and Sensing Under Multicolored Noise via Generalized Filter Function Framework
• Spin amplification in realistic systems
• Mitigating state transition errors during readout with a synchronized flux pulse