Single-shot parity readout of a minimal Kitaev chain

TL;DR

This paper demonstrates a novel quantum capacitance-based method for single-shot, real-time readout of fermionic parity in a minimal Kitaev chain, advancing topological qubit measurement techniques.

Contribution

It introduces a global quantum capacitance measurement technique for parity readout in a minimal Kitaev chain, enabling single-shot detection and real-time monitoring.

Findings

Parity lifetimes exceeding one millisecond

Global quantum capacitance effectively distinguishes parity states

Local charge sensing cannot resolve the parity

Abstract

Protecting qubits from noise is essential for building reliable quantum computers. Topological qubits offer a route to this goal by encoding quantum information non-locally, using pairs of Majorana zero modes. These modes form a shared fermionic state whose occupation -- either even or odd -- defines the fermionic parity that encodes the qubit. Crucially, this parity cannot be accessed by any measurement that probes only one Majorana mode. This reflects the non-local nature of the encoding and its inherent protection against noise. A promising platform for realizing such qubits is the Kitaev chain, implemented in quantum dots coupled via superconductors. Even a minimal chain of two dots can host a pair of Majorana modes and store quantum information in their joint parity. Here we introduce a new technique for reading out this parity, based on quantum capacitance. This global probe senses the joint state of the chain and enables real-time, single-shot discrimination of the parity state. By comparing with simultaneous local charge sensing, we confirm that only the global signal resolves the parity. We observe random telegraph switching and extract parity lifetimes exceeding one millisecond. These results establish the essential readout step for time-domain control of Majorana qubits, resolving a long-standing experimental challenge.