# Mitigating state transition errors during readout with a synchronized flux pulse

**Authors:** Yulong Li, Wuerkaixi Nuerbolati, Chunqing Deng, Xizheng Ma, Haonan Xiong, Haifeng Yu  
**arXiv:** [2507.14436](https://arxiv.org/abs/2507.14436)  
**Date:** 2025-07-19  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2507.14436v1/

## Key points

- Study focused on detrimental effects of state transitions during qubit measurements on quantum tasks
- Transitions can occur due to excessive measurement power or inadvertent coupling to lossy modes like TLSs
- Experimental verification of TLS impact in qubit readout through measuring transition errors at different qubit flux biases
- State transitions are often localized in frequency space
- Researchers demonstrated ability to avoid state transitions during fluxonium readout by leveraging qubit's flux-tunability
- Achieved optimal readout fidelity of 99% (98.4%) in integration times of 1 us (0.5 us)
- Work advances understanding of state transitions in superconducting circuit measurements and highlights potential of fluxonium qubits for fast and high-fidelity readout
- Findings offer insights for improving quantum tasks requiring repeated measurements and enhancing quantum error correction protocols

## Summary

A recent study investigated the detrimental effects of state transitions during qubit measurements on quantum tasks that rely on repeated measurements, such as quantum error correction. These transitions can occur due to excessive measurement power leading to qubit excitations outside its computational space or inadvertent coupling to lossy modes like two-level systems (TLSs). Experimental verification of TLS impact in qubit readout was done by measuring transition errors at different qubit flux biases. The study highlighted that these state transitions are often localized in frequency space. To address this issue, researchers demonstrated the ability to avoid them during a fluxonium readout by leveraging the qubit's flux-tunability. By synchronizing the flux bias with the readout photon dynamics, they achieved an optimal readout fidelity of 99% (98.4%) in integration times of 1 us (0.5 us). This work not only advances our understanding of state transitions in superconducting circuit measurements but also showcases the potential of fluxonium qubits for achieving fast and high-fidelity readout. The findings provide valuable insights for improving quantum tasks that require repeated measurements and offer a promising avenue for enhancing quantum error correction protocols.