# Voltage-Current curves for small Josephson junction arrays

## TL;DR

This paper analyzes the voltage-current characteristics of small Josephson junction arrays with potential applications in topologically protected qubits, revealing non-monotonous behavior that can be used to probe quantum transitions.

## Contribution

It provides a theoretical computation of the voltage-current curves for Josephson junction chains, highlighting their non-monotonous behavior and proposing experimental measurement as a tool for quantum characterization.

## Key findings

- Voltage-current curves show a maximum voltage and a region where V ∝ 1/I.
- Behavior is sensitive to quantum transition amplitudes.
- Measurement can directly probe quantum properties of Josephson circuits.

## Abstract

We compute the current voltage characteristic of a chain of identical Josephson circuits characterized by a large ratio of Josephson to charging energy that are envisioned as the implementation of topologically protected qubits. We show that in the limit of small coupling to the environment it exhibits a non-monotonous behavior with a maximum voltage followed by a parametrically large region where $V\propto 1/I$. We argue that its experimental measurement provides a direct probe of the amplitude of the quantum transitions in constituting Josephson circuits and thus allows their full characterization.