The first quantum phase battery

A phase battery in a hybrid superconducting circuit.

In a new study, scientists presented the results from a theoretical and experimental collaboration that has led to the fabrication of the first quantum phase battery. A phase battery is a quantum device that provides a persistent phase bias to the wave function of a quantum circuit. It represents an essential element for quantum technologies based on phase coherence.

The idea was first conceived in 2015, by Sebastian Bergeret from the Mesoscopic physics group at the Materials Physics Center (CFM, CSIC-UPV/EHU), a joint initiative of Consejo Superior de Investigaciones científicas (CSIC) and the University of the Basque Country (UPV/EHU), and Ilya Tokatly, Ikerbasque Professor in the Nano-Biospectroscopy group of the UPV/EHU, both Donostia International Physics Center (DIPC) associate researchers.

They proposed a theoretical system with the properties needed to build the phase battery. It consists of a combination of superconducting and magnetic materials with an intrinsic relativistic effect called spin-orbit coupling.

A few years later, Francesco Giazotto and Elia Strambini from the NEST-CNR Institute, Pisa, identified a suitable material combination and fabricated the first quantum phase battery in a hybrid superconducting circuit.

It consists of an n-doped InAs nanowire with unpaired-spin surface states, which is proximities by Al superconducting leads.

Scientists noted“We apply an external in-plane magnetic field and, thereby, achieve continuous tuning of φ0. Hence, we can charge and discharge the quantum phase battery.”

“Our results demonstrate how the combined action of spin-orbit coupling and exchange interaction induces a strong coupling between charge, spin, and superconducting phase, able to break the phase rigidity of the system.”

Journal Reference:
  1. Elia Strambini et al. A Josephson phase battery, Nature Nanotechnology. DOI: 10.1038/s41565-020-0712-7

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