Feedback traps are tools for trapping single charged objects in solution. They periodically measure an object’s position and apply a feedback force to counteract Brownian motion. The feedback force can be calculated as a gradient of a potential function, effectively creating a “virtual potential.” Its flexibility regarding the choice of form of the potential gives an opportunity to explore various fundamental questions in stochastic thermodynamics. Here, we review the theory behind feedback traps and apply it to measuring the average work required to erase a fraction of a bit of information. The results agree with predictions based on the nonequilibrium system entropy. With this example, we also show how a feedback trap can easily implement the complex erasure protocols required to reach ultimate thermodynamic limits.
Momčilo Gavrilov and John Bechhoefer, "Direct measurement of a nonequilibrium system entropy using a feedback trap," Proc. SPIE 10347, Optical Trapping and Optical Micromanipulation XIV, 103470U (Presented at SPIE Nanoscience + Engineering: August 07, 2017; Published: 25 August 2017); https://doi.org/10.1117/12.2277602.
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