Moving beyond the transmon: Noise-protected superconducting quantum circuits

TL;DR

This paper reviews the development of noise-protected superconducting qubits, emphasizing their theoretical foundations, recent experimental advances, and potential for robust quantum information processing beyond traditional transmon devices.

Contribution

It provides a comprehensive overview of the principles, recent experimental progress, and future prospects of noise-protected superconducting quantum circuits, highlighting their advantages over conventional transmons.

Findings

Noise-protected circuits decouple computational states from noise channels

Multimode or hybrid circuits enable complete noise protection

Recent experiments demonstrate improved qubit robustness

Abstract

Artificial atoms realized by superconducting circuits offer unique opportunities to store and process quantum information with high fidelity. Among them, implementations of circuits that harness intrinsic noise protection have been rapidly developed in recent years. These noise-protected devices constitute a new class of qubits in which the computational states are largely decoupled from local noise channels. The main challenges in engineering such systems are simultaneously guarding against both bit- and phase-flip errors, and also ensuring high-fidelity qubit control. Although partial noise protection is possible in superconducting circuits relying on a single quantum degree of freedom, the promise of complete protection can only be fulfilled by implementing multimode or hybrid circuits. This Perspective reviews the theoretical principles at the heart of these new qubits, describes recent experiments, and highlights the potential of robust encoding of quantum information in superconducting qubits.