The out of equilibrium nature of active systems can be exploited for the design of information-based engines. We design two types of an active Szilard engine that use a Maxwell demon to extract work from an active bath composed of noninteracting active Brownian particles. The two engines exploit either the quasistatic active pressure of active Brownian particles or the long correlation time of their velocities. For both engines the active bath allows us to overcome the Landauer principle and to extract larger work compared to conventional Szilard engines operating in quasithermal equilibrium. For both of our engines, we identify the optimal regimes at which the work extracted and the efficiency are maximized. Finally, we discuss them in the context of synthetic and biological active systems.

• Received 24 March 2022
• Revised 6 July 2022
• Accepted 1 November 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.228005