Abstract
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.
Highlights
Detecting a very weak signal which is almost inaccessible within the classical regime is one of the most important subjects in quantum information science
5 Approximate back-action evasion We have demonstrated in Sections . and that the BAE condition can be achieved by engineering an appropriate auxiliary system and connecting it to the plant
6 Conclusion The main contribution of this paper lies in that it first provides the general theory for constructing a back-action evading sensor for linear quantum systems, based on the welldeveloped classical geometric control theory
Summary
Detecting a very weak signal which is almost inaccessible within the classical (i.e., nonquantum) regime is one of the most important subjects in quantum information science. A strong motivation to devise such an ultra-precise sensor stems from the field of gravitational wave detection [ – ]. The measurement noise is lower bounded by the standard quantum limit (SQL) [ , ], which is mainly due to the presence of back-action noise. High-precision detection of a weak signal requires us to devise a sensor that evades the back-action noise and eventually beats the SQL; i.e., we need to have a sensor achieving back-action evasion (BAE). Many BAE methods have been developed especially in the field of gravitational wave detection, e.g., the variational measurement technique [ – ] or the quantum locking scheme [ – ].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
