Microwave readout of Majorana qubits

TL;DR

This paper proposes a microwave-based measurement scheme for Majorana qubits using a voltage-biased Josephson junction, enabling nondestructive, quantum-limited readout with controllable interaction.

Contribution

It introduces a novel microwave measurement setup for Majorana qubits that allows quantum nondemolition detection and tunable interaction via Josephson junction biasing.

Findings

Enables nondemolition measurement of Majorana qubits.

Achieves quantum-limited measurement sensitivity.

Interaction can be switched on and off by bias control.

Abstract

Majorana qubits offer a promising way to store and manipulate quantum information by encoding it into the state of Majorana zero modes. As the information is stored in a topological property of the system, local noise cannot lead to decoherence. Manipulation of the information is achieved by braiding the zero modes. The measurement, however, is challenging as the information is well hidden and thus inherently hard to access. Here, we discuss a setup for measuring the state of a Majorana qubit by employing standard tools of microwave engineering. The basic physical effect that we employ is the fact that a voltage-biased Josephson junction hosting Majorana fermions allows photons to be emitted and absorbed at half the Josephson frequency. We show that in the dispersive regime, our setup allows us to perform a quantum nondemolition measurement and to reach the quantum limit. An appealing feature of our setup is that the interaction of the Majorana qubit with the measurement device can be turned on and off at will by changing the dc bias of the junction.