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Line search by quantum logic spectroscopy enhanced with squeezing and statistical tests

Ivan Vybornyi1,*, Shuying Chen2, Lukas J. Spieß2, Piet O. Schmidt2,3, and Klemens Hammerer1,4,5

  • 1Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstrasse 2, 30167 Hannover, Germany
  • 2QUEST Institute for Experimental Quantum Metrology, Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116  Braunschweig, Germany
  • 3Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany
  • 4Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria
  • 5Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, 6020 Innsbruck, Austria

  • *Contact author: ivan.vybornyi@gmail.com
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Phys. Rev. A 113, 042613 – Published 13 April, 2026

DOI: https://doi.org/10.1103/gths-s15w

Abstract

In quantum logic spectroscopy, internal transitions of trapped ions and molecules can be probed by measuring the motional displacement caused by an applied light field of variable frequency. This provides a solution to “needle-in-a-haystack” problems, such as the search for narrow clock transitions in highly charged ions, recently discussed by Chen et al. [Phys. Rev. Appl. 22, 054059 (2024)]. The main bottleneck is the search speed over a frequency bandwidth, which can be increased by enhancing the sensitivity of displacement detection. In this work, we explore two complementary improvements: the use of squeezed motional states, explained using an analytical phase-space model, and optimal statistical postprocessing of data using a hypothesis-testing framework. We demonstrate that each method independently provides a substantial boost to search speed. Their combination effectively mitigates state preparation and measurement errors, improving the search speed by an order of magnitude and fully leveraging the quantum enhancement offered by squeezing.

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Phys. Rev. A 113, 042613– Published 13 April, 2026
  • Received 27 May 2025
  • Revised 11 February 2026
  • Accepted 16 March 2026
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