Demonstration of dual Shapiro steps in small Josephson junctions

Abstract

Bloch oscillations in small Josephson junctions were predicted theoretically as the quantum dual to Josephson oscillations. A significant consequence of this prediction is the emergence of quantized current steps, so-called dual Shapiro steps, when synchronizing Bloch oscillations to an external microwave signal. These steps potentially enable a fundamental standard of current $I$, defined via the frequency $f$ of the external signal and the elementary charge $e$, $I=\pm n\times 2ef$, where $n$ is a natural number. Here, we realize this fundamental relation by synchronizing the Bloch oscillations in small Al/AlO${}_{\mathrm{x}}$/Al Josephson junctions to sinusoidal drives with frequencies varying from $1$ to $6\mathrm{GHz}$ and observe dual Shapiro steps up to $I\approx 3\mathrm{nA}$. Inspired by today's voltage standards and to further confirm the duality relation, we investigate a pulsed drive regime, which is dual to the single flux quantum mode of Josephson oscillations, and observe a similar asymmetric pattern of dual Shapiro steps. This work confirms quantum duality effects in Josephson junctions and paves the way towards a range of applications in quantum metrology based on well-established fabrication techniques and straightforward circuit design.

References in corpus (4)

• Quantized current steps due to the a.c. coherent quantum phase-slip effect
• Granular superconductors for high kinetic inductance and low loss quantum devices
• On chip synchronization of Bloch oscillations in a strongly coupled pair of small Josephson junctions
• Superconducting nitridized-aluminum thin films

Cited by in corpus (8)

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• Tunable diode effect in a superconducting tunnel junction with biharmonic drive
• High Impedance Granular Aluminum Ring Resonators
• The superconducting clock-circuit: Improving the coherence of Josephson radiation beyond the thermodynamic uncertainty relation
• Scalable Parallel Single-Electron Pumps in Silicon with Split-Source Control in the Nanoampere Regime