Unimon qubit

Abstract

Superconducting qubits seem promising for useful quantum computers, but the currently wide-spread qubit designs and techniques do not yet provide high enough performance. Here, we introduce a superconducting-qubit type, the unimon, which combines the desired properties of increased anharmonicity, full insensitivity to dc charge noise, reduced sensitivity to flux noise, and a simple structure consisting only of a single Josephson junction in a resonator. In agreement with our quantum models, we measure the qubit frequency, ω01/(2π), and increased anharmonicity α/(2π) at the optimal operation point, yielding, for example, 99.9% and 99.8% fidelity for 13 ns single-qubit gates on two qubits with (ω01, α) = (4.49 GHz, 434 MHz) × 2π and (3.55 GHz, 744 MHz) × 2π, respectively. The energy relaxation seems to be dominated by dielectric losses. Thus, improvements of the design, materials, and gate time may promote the unimon to break the 99.99% fidelity target for efficient quantum error correction and possible useful quantum advantage with noisy systems.

Research Trends in Quantum Computers by Focusing on Qubits as Their Building Blocks

“…It consists of a single Josephson junction, a linear inductor, and a capacitor. The qubit operates in a new parameter regime, has high anharmonicity, is resilient against low-frequency charge noise, and is partially protected from flux noise [29]. The competition to modify the materials used in superconducting qubits or find a new and improved mainstream superconducting qubit is still ongoing.…”

Meet the Unimon, the New Qubit on the Block

“…By Mark Buchanan P hysicists developing quantum computers have increasingly turned to a superconducting element called the transmon to store quantum information and protect it from noise. Now researchers have demonstrated a related circuit element, the unimon, which they say is less prone to disruption by noise [1]. With further development, the team behind the unimon thinks that it could be used to build quantum computing systems with higher computing accuracy than those that use transmons.…”

Characterization of a Transmon Qubit in a 3D Cavity for Quantum Machine Learning and Photon Counting

“…The best transmon performances in terms of coherence time now approach 500 µs [19]. Different designs have been proposed to exceed transmon performances, including the 0-π qubit, the fluxonium, or the unimon [20][21][22]. However, they usually have much more complex circuits or control schemes with respect to the transmon and a net superiority has not been established yet.…”