Maxwell's demon based on a single-electron pump

We propose and analyze a possible implementation of Maxwell's demon (MD) based on a single-electron pump. It presents a practical realization of MD in a solid-state environment. We show that measurements of the charge states of the pump and feedback control of the gate voltages lead to a net flow of electrons against the bias voltage ideally with no work done on the system by the gate control. The information obtained in the measurements converts thermal fluctuations into energy stored in a capacitor. We derive the conditions on the detector back action and measurement time necessary for implementing this conversion.

Figure 1

Three-junction electron pump biased by the voltage $V$ that is created by charge $eN$, $N\gg 1$, on a large capacitor $C_0$. The time-dependent gate voltages $V_{g1},V_{g2}$ can move electrons even against the bias from right to left. The number $n$ counts the electrons transferred through the pump. Electron numbers $n_1,n_2$ on the internal islands of the pump can be monitored by a charge detector (not shown) with subelectron resolution, e.g., by a single-electron transistor.

Figure 2

Stability diagram of the pump, and the demon operation cycle. The black solid lines crossing at $n_{g1}=n_{g2}=1/3$ separate the stable charge configurations $(0,0),(1,0)$, and $(0,1)$ of the pump at $V=0$. The dashed lines that form a triangle encircling $n_{g1}=n_{g2}=1/3$ are the corresponding borders for $V=0.3E_C$. Inside this triangle there are no stable charge states, and current runs along the bias. The arrows indicate a possible trajectory of the demon operation which converts information into free energy.