Abstract
We propose a finite-time quantum Szilard engine (QSE) with a quantum particle with spin as the working substance (WS) to accelerate the operation of information engines. We introduce a Maxwell's demon (MD) to probe the spin state within a finite measurement time t_ M to capture the which-way information of the particle, quantified by the mutual information I(t_M) between WS and MD. We establish that the efficiency η of QSE is bounded by η≤1-(1-η_C) ln2/I(t_ M), where I(t_ M)/ln2 characterizes the ideality of quantum measurement, and approaches 1 for the Carnot efficiency reached under ideal measurement in quasi-static regime. We find that the power of QSE scales as P∝ t_ M³ in the short-time regime and as P∝ t_ M⁻¹ in the long-time regime. Additionally, considering the energy cost for erasing the MD's memory required by Landauer's principle, there exists a threshold time that guarantees QSE to output positive work.