Geometric control theory for quantum back-action evasion

Yu Yokotera, Naoki Yamamoto

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Engineering a sensor system for detecting an extremely tiny signal such as the gravitational-wave force is a very important subject in quantum physics. A major obstacle to this goal is that, in a simple detection setup, the measurement noise is lower bounded by the so-called standard quantum limit (SQL), which is originated from the intrinsic mechanical back-action noise. Hence, the sensor system has to be carefully engineered so that it evades the back-action noise and eventually beats the SQL. In this paper, based on the well-developed geometric control theory for classical disturbance decoupling problem, we provide a general method for designing an auxiliary (coherent feedback or direct interaction) controller for the sensor system to achieve the above-mentioned goal. This general theory is applied to a typical opto-mechanical sensor system. Also, we demonstrate a controller design for a practical situation where several experimental imperfections are present.

Original languageEnglish
Article number15
JournalEPJ Quantum Technology
Issue number1
Publication statusPublished - 2016 Dec 1


  • Back-action evasion
  • Coherent feedback
  • Geometric control theory
  • Opto-mechanical system

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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