Superconducting fluxonium qubits are among the leading qubit candidates for building useful quantum computers. Since their first realization in 2009, research on fluxonium qubits has demonstrated great progress in improving qubit coherence times, control efficiency, and coupling architectures. Following the growing number of academic research groups, the industrial startup Atlantic Quantum is the first to focus on this technology, owing to the fluxonium's exceptional potential for enabling high-fidelity qubit operations.

Like the more widely used transmon design, fluxoniums rely on the anharmonicity of a Josephson junction to engineer individually addressable quantum states of a superconducting circuit, and on a shunting element to suppress sensitivity to environmental charge noise.

The key advantage that fluxoniums have over transmons is that it is possible to optimize two important quantities independently of each other: a large anharmonicity for fast state control and a large noise insensitivity for long coherence times. This is achieved by using a superinductor instead of a capacitor as the shunting element. The superinductor is typically realized as a chain of large Josephson junctions.

Current research focuses on these topics:

• Optimizing fabrication and design for higher yield and lower intrinsic losses
• Two-qubit gate technologies
• Scalable architectures