Spectroscopy on multiple nearly symmetric SQUID devices found transition features that a standard 2π-periodic cosine Josephson potential could not explain, but a model with a second-harmonic term reproduced accurately.
The researchers used the SQUID design to separate two suspected sources of higher-order harmonics—the junctions’ intrinsic current-phase relation and the inductance of metallic traces linking the junction to the rest of the circuit.
Scaling with Josephson junction size showed the second harmonic came almost entirely from metallic trace inductance rather than the tunnel junctions themselves.
The result identifies a concrete design constraint for superconducting quantum circuits and could guide next-generation qubit hardware and studies of the supercurrent diode effect.
Is it better to design circuits around quantum flaws or to engineer new materials that eliminate them entirely?
This breakthrough fixes one quantum flaw, but how many more 'unknowns' stand between us and a truly reliable quantum computer?
If simple connecting wires can derail quantum computers, what does this reveal about the true challenge of scaling them?
Diagnosing and Mitigating Second-Order Harmonic Errors: A Breakthrough for Scalable, Fault-Tolerant Quantum Computing
Overview
Quantum computing holds the promise of solving problems that are too complex for classical computers, such as modeling intricate molecular interactions for drug discovery and materials science. However, to unlock this potential, scientists must overcome major engineering challenges, especially in building large, resilient superconducting quantum computers with thousands of precisely engineered circuits. A key barrier is reducing computational errors, which requires ensuring each quantum circuit operates with the lowest possible error rate. Recent breakthroughs in diagnosing and mitigating fundamental error sources mark a critical step forward, paving the way for more reliable and scalable quantum technologies.