Thousands of years ago the Archimedes screw emerged as a superb design to pump water into irrigation ditches. It is believed to be of critical historical importance to the ancient world. On the physics side, in 1983 D.J. Thouless (Physics Nobel Laureate 2016) proposed an elegant quantum pump , which directly connects topological invariants with quantized matter transport. Thouless pump has opened up new applications of quantum physics and continues to influence fundamental research.
Prof. Gong’s group [2,3] discovered a coherence-induced correction to Thouless pump. Based on an experimental proposal designed by Prof. Gong’s research fellow Dr. Zhou Longwen, a collaborative study between NUS and a group from University of Science and Technology, China finally confirmed the NUS theory. In particular, the experiment implemented the Thouless pump that exploits quantum coherence as a useful resource. Such a generalized Thouless pump is somewhat more reminiscent of the Archimedes screw, because now the amount of pumped matter per cycle is no longer restricted by the underlying topological properties of the quantum system, but becomes continuously tuneable and highly sensitive to quantum coherence features. As experimentally demonstrated, even the rate at which the pump is switched on can be used to extensively control the amount of transported matter. The experimental results have thus verified one new face of Thouless pump and may find innovative applications in coherence-based quantum control and in the detection of topological phase transitions.
Figure caption: Schematic of Thouless pumping in the absence or presence of interband coherence. Qa and Qb represent pumping contributed by individual bands, and QIBC represents the interband coherence induced correction to the conventional Thouless pumping.
 D. J. Thouless, Quantization of particle transport, Phys. Rev. B 27, 6083 (1983).
 H.L. Wang, L. W. Zhou, and J. B. Gong, Interband coherence induced correction to adiabatic pumping in periodically driven systems, Phys. Rev. B 91, 085420 (2015).
 L.W. Zhou, D.Y. Tan, and J.B. Gong, Effects of dephasing on quantum adiabatic pumping with nonequilibrium initial states, Phys. Rev. B 92, 245409 (2015).
 M. W. Ma, L.W. Zhou, Q. Zhang, M. Li, C.Y. Cheng, J.P. Geng, X. Rong, F.Z. Shi, J.B. Gong, and J.F. Du, Experimental observation of a generalized Thouless pump with a single spin, Phys. Rev. Lett. 120, 120501 (2018).