Researchers at MIT have developed a groundbreaking superconducting qubit architecture that significantly improves the accuracy of quantum operations between qubits, marking a significant step toward practical quantum error correction and large-scale quantum computing. This new architecture uses a relatively recent superconducting qubit called “fluxonium,” known for its extended lifespan compared to traditional qubits.

The key innovation in this architecture involves a specialized coupling element connecting two fluxonium qubits, allowing for precise, logical operations or gates while suppressing background interactions that can introduce errors into quantum operations. As a result, the researchers achieved two-qubit gates with over 99.9% accuracy and single-qubit gates with 99.99% accuracy. This remarkable level of accuracy is crucial in quantum computing because quantum errors accumulate rapidly, making it essential to minimize them.

The longer coherence times of fluxonium qubits, a measure of how long they can perform operations before the information is lost, allowed the researchers to achieve these high-fidelity gates. Fluxonium qubits demonstrated coherence times more than ten times longer than traditional Transmon qubits.

The novel architecture, called the “Fluxonium-Transmon-Fluxonium” (FTF) architecture, utilizes a circuit with two fluxonium qubits at each end and a tunable Transmon coupler in the middle, offering stronger coupling between qubits while minimizing unwanted background interactions.

These impressive results surpass the fidelity threshold required for certain error-correcting codes, making detecting and correcting errors in larger-scale quantum systems feasible. The researchers emphasize that building a practical quantum computer starts with high-quality quantum operations that meet or exceed this fidelity threshold.

Inspired by their findings, some researchers have founded a quantum computing startup called Atlantic Quantum, aiming to use fluxonium qubits to develop commercially viable quantum computers for various applications.

Although a fully functional quantum computer is still likely a decade away, this research represents a significant advancement in the field. It offers a promising path toward the realization of fault-tolerant quantum computing. Future work will demonstrate the FTF architecture’s advantages in systems with more than two connected qubits. The research was supported by various funding sources, including the U.S. Army Research Office and IBM PhD fellowships.

Reference:

Ding, L. et al. (2023). High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler. Phys. Rev. X, 13, 031035. https://doi.org/10.1103/PhysRevX.13.031035