Electrical post-fabrication tuning of aluminum Josephson junctions at room temperature

TL;DR

This study demonstrates room-temperature electrical tuning of aluminum Josephson junctions, allowing controllable resistance adjustments that help mitigate frequency crowding in quantum processors without degrading qubit quality.

Contribution

We experimentally show that voltage pulses can tune aluminum Josephson junctions at room temperature, providing a practical method for post-fabrication adjustments in quantum devices.

Findings

Resistance can be increased by up to 270% using voltage pulses.

The resistance increase rate scales exponentially with pulse amplitude.

Spontaneous resistance increase halts at cryogenic temperatures.

Abstract

Josephson junctions are a key element of superconducting quantum technology, serving as the core building blocks of superconducting qubits. We present an experimental study on room-temperature electrical tuning of aluminum junctions, showing that voltage pulses can controllably increase their resistance and adjust the Josephson energy while maintaining qubit quality factors above 1 million. We find that the rate of resistance increase scales exponentially with pulse amplitude during manipulation, after which the spontaneous resistance increase scales proportionally to the amount of manipulation. We show that this spontaneous increase halts at cryogenic temperatures, and resumes again at room temperature. Using our stepwise protocol, we achieve up to a 270% increase in junction resistance, corresponding to a reduction of nearly 2 GHz of the qubit transition frequency. These results establish the achievable range, relaxation behavior, and practical limits of electrical tuning, enabling post-fabrication mitigation of frequency crowding in quantum processors.