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Generalized parity measurements and efficient large multicomponent cat state preparation with quantum signal processing

Sina Zeytinoğlu*

  • Physics and Informatics Laboratory, NTT Research, Inc., 940 Stewart Drive, Sunnyvale, California 94085, USA and Institute of Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10/136, A-1040 Vienna, Austria

  • *Contact author: sinazeytinoglu@hotmail.com, sina.zeytinoglu@tuwien.ac.at
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Phys. Rev. Research 8, 023208 – Published 26 May, 2026

DOI: https://doi.org/10.1103/xsgf-txnq

Abstract

Generalized parity measurements are instrumental for the preparation of nontrivial quantum states and the detection of errors in error-correction codes. However, realizing such measurements in current experimental platforms becomes prohibitively difficult with growing system size. Here, using algorithmic methods of quantum signal processing, we detail a simple and efficient control protocol for implementing generalized parity measurements. Crucially, our measurement protocol does not depend on the size of the system and implements the desired measurement in constant time. We benchmark the performance of the proposed measurement protocol in preparing large multicomponent cat states on superconducting circuit quantum electrodynamics platforms. We show that a 20-component cat state with 400 photons can be prepared with success probability >2% and fidelity ≈90% limited by the cavity decay rate and higher-order qubit-cavity coupling. Our results demonstrate the feasibility of generalized parity measurements in current bosonic and spin systems, paving the way to improvements in state-preparation and error-correction capabilities.

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Phys. Rev. Research 8, 023208– Published 26 May, 2026
  • Received 28 July 2024
  • Revised 24 July 2025
  • Accepted 13 March 2026
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