# Detector Tomography on IBM 5-qubit Quantum Computers and Mitigation of Imperfect Measurement

## TL;DR

This paper applies quantum detector tomography to IBM's 5-qubit quantum computers to characterize measurement imperfections, revealing deviations from ideal detectors and suggesting improvements for more accurate quantum measurements.

## Contribution

It provides the first detailed detector characterization on IBM 5-qubit devices and explores mitigation strategies for measurement imperfections.

## Key findings

- Detector models deviate by a few percent from ideal projectors
- Unexpected behavior observed in qubit 3 of IBM Q 5 Tenerife
- Characterized POVMs can estimate ideal detection distributions

## Abstract

We use quantum detector tomography to characterize the qubit readout in terms of measurement POVMs on IBM Quantum Computers IBM Q 5 Tenerife and IBM Q 5 Yorktown. Our results suggest that the characterized detector model deviates from the ideal projectors by a few percent. Further improvement on this characterization can be made by adopting two- or more-qubit detector models instead of independent single-qubit detectors for all the qubits in one device. An unexpected behavior was seen in the physical qubit labelled as qubit 3 of IBM Q 5 Tenerife, which can be a consequence of detector crosstalk or qubit operations influencing each other and requires further investigation. This peculiar behavior is consistent with characterization from the more sophisticated approach of the gate set tomography. We also discuss how the characterized detectors' POVM, despite deviation from the ideal projectors, can be used to estimate the ideal detection distribution.