Charge-Based Single-Shot Readout Systems in Quantum Computing

Measurement of a qubit (quantum bit) is a key element of quantum computation and is necessary for extracting information from a quantum processor. The physical implementation of a measurement protocol involves monitoring a physical quantity of a sensor, such as a current or a voltage, that is correlated with the state of the qubit to be measured. The monitoring of these sensors used to measure qubits in modern quantum computer architectures is typically divided between RF reflectometry and current/voltage monitoring. There are tradeoffs involved with both approaches for the reliable and accurate readout of qubits when it comes to scalable quantum computing architectures. In this article, we will review the working principles of a selection of sensors that are used to measure the state of qubits in semiconductors. The goal is to introduce electronic engineers with little or no background in quantum computing to the working principles of charge sensors in semiconductor quantum computers, their identification in various physical systems, and an overview of their design tradeoffs when measuring a qubit. This will allow electronic engineers to begin working with physics literature in the field of charge sensing.