UCSB final report for the CSQ program: Review of decoherence and materials physics for superconducting qubits

TL;DR

This paper reviews UCSB's recent progress in understanding and mitigating decoherence mechanisms in superconducting qubits, highlighting advances in design that improve coherence and scalability of quantum circuits.

Contribution

The paper provides a comprehensive review of decoherence sources and demonstrates improved qubit performance through design optimizations at UCSB.

Findings

Identification of key decoherence mechanisms in superconducting qubits

Enhanced qubit coherence with improved design strategies

Scalability of high-coherence qubits to 9-qubit systems

Abstract

We review progress at UCSB on understanding the physics of decoherence in superconducting qubits. Although many decoherence mechanisms were studied and fixed in the last 5 years, the most important ones are two-level state defects in amorphous dielectrics, non-equilibrium quasiparticles generated from stray infrared light, and radiation to slotline modes. With improved design, the performance of integrated circuit transmons using the Xmon design are now close to world record performance: these devices have the advantage of retaining coherence when scaled up to 9 qubits.