# The microwave phase locking in Bloch transistor

## TL;DR

A new quantum device called the Bloch transistor is introduced, which uses phase locking to deliver quantized current in superconducting circuits.

## Contribution

The novel mechanism of charge-induced phase locking in Josephson junctions enables quantized current control via gate voltage.

## Key findings

- The Bloch transistor uses coherent phase slips to deliver quantized non-dissipative current.
- Phase locking is achieved via the Aharonov-Casher effect, allowing gate voltage control of current quantization.
- The device is scalable and compatible with other superconducting quantum technologies.

## Abstract

Recent experimental demonstration of the quantum coherent phase slip and current quantization in the superconductors, the fundamental phenomena dual to the coherent Cooper pair tunneling and voltage quantization (Shapiro steps), enables the development of a new quantum device, the Bloch transistor (BT). BT has a unique functionality: it can deliver quantized non-dissipative current to the quantum circuit. BT consists of two coupled Josephson Junctions (JJ) in the regime of coherent quantum phase slip. At the heart of the BT operation is a new mechanism for phase-locking the Bloch oscillations in JJs to microwaves via induced charge. The charge phase locking allows not only quantization of current but also gate voltage control of this quantization through the Aharonov-Casher effect. We study the operation of the BT and analyze its parameters. BT technology is scalable and compatible with other superconducting quantum devices, making it part of an emerging cryogenic quantum technology platform.

Recent work has revealed quantum coherent phase slips and current quantization in superconductors, phenomena dual to Cooper pair tunneling and voltage quantization. By combining the two effects, the authors demonstrate a Bloch transistor, a device that delivers quantized current and features a unique phase-locking mechanism.