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Measuring Entanglement Without Local Addressing in Quantum Many-Body Simulators via Spiral Quantum State Tomography

Giacomo Marmorini1,2,*, Takeshi Fukuhara3,4,†, and Daisuke Yamamoto1,3,‡

  • *Contact author: marmorini.giacomo@nihon-u.ac.jp
  • †Contact author: takeshi.fukuhara@riken.jp
  • ‡Contact author: yamamoto.daisuke21@nihon-u.ac.jp
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PRX Quantum 7, 010355 – Published 18 March, 2026

DOI: https://doi.org/10.1103/1xzz-njyy

Abstract

Quantum state tomography serves as a key tool for identifying quantum states generated in quantum computers and simulators, typically involving local operations on individual particles or qubits to enable independent measurements. However, this approach requires an exponentially larger number of measurement setups as quantum platforms grow in size, highlighting the necessity of more scalable methods to efficiently perform quantum state estimation. Here, we present a tomography scheme that scales far more efficiently and, remarkably, eliminates the need for local addressing of single constituents before measurements. Inspired by the “spin-spiral” structure in magnetic materials, our scheme combines a series of measurement setups, each with different spiraling patterns, with compressed-sensing techniques. The results of the numerical simulations demonstrate a high degree of tomographic efficiency and accuracy. Additionally, we show how this method is suitable for the measurement of specific entanglement properties of interesting quantum many-body states, such as entanglement entropy, under various realistic experimental conditions. This method offers a positive outlook across a wide range of quantum platforms, including those in which precise individual operations are challenging, such as optical lattice systems.

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Popular Summary

Understanding quantum many-body systems often requires measuring the full quantum state of the system—a task known as quantum state tomography (QST). However, conventional QST demands individually addressing and manipulating each particle, which becomes extremely challenging and resource-intensive as the number of particles grows. This has limited our ability to directly probe fundamental properties such as quantum entanglement in large-scale systems.

Inspired by the spin spirals found in magnetic materials, we introduce a set of global operations—“spiral measurements”—that can be implemented without needing to control individual qubits. By combining these spiral measurements with a powerful technique called compressed sensing, we show that one can efficiently and accurately reconstruct quantum states in a way that scales much better with system size.

Through detailed simulations, we demonstrate that this “spiral QST” method remains effective even under realistic experimental conditions, including imperfections in control fields and statistical measurement noise. Notably, our method is also capable of extracting important quantities like entanglement entropy, which is crucial for understanding quantum criticality, thermalization, and information spreading in many-body systems.

This technique is particularly suited for experimental platforms such as optical lattices, where precise local control is difficult or costly. Spiral QST opens a path toward scalable, robust, and information-rich characterization of quantum systems, facilitating a deeper understanding of entanglement and many-body quantum phenomena across a range of physical contexts.

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PRX Quantum 7, 010355– Published 18 March, 2026
  • Received 17 April 2025
  • Revised 25 December 2025
  • Accepted 3 February 2026
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