Thouless pumping and topology

Physicists and engineers from all around the world are constantly thinking of ways to improve the performance of conventional electronic devices by reducing the dissipated energy and to this aim recently is working its way employing quantum technologies. In a conductor a direct current is usually associated with a dissipative flow of electrons in response to an applied bias voltage. In quantum systems, however, a dissipationless transport can be induced via adiabatic cyclic variation of the system parameters in the absence of any external bias. An example is the quantum pump, or Thouless pump, the quantum version of the famous Archimede’s screw in which water from a low-level is pushed up the tube by the slow and periodic rotation of the helicoid. The quantum device is obtained slowly time periodic potential. Interestingly, the charge pumped after a period is quantized and is connected to a bulk property of the system, the so called topological invariant, i.e. a property of a geometric shape that does not change when the shape is stretched or distorted and thus is robust to external perturbations. The exciting developments in the exploitation of quantum pumps have been reported in an article of the prestigious journal Nature Reviews Physics involving the Department of Physics at University of Salerno, where a research on quantum devices is coordinated by Prof. Roberta Citro, and the Quantum Optics group at Ludwig Maximilian University of Munich, led by Prof. Monika Aidelsburger. The article describes in details various quantum pumps, arguing how they produce a lot less heat than conventional electric currents generators, making them promising candidates for future electronic devices with significantly reduced power consumption. Quantum pumping has received much attention in mesoscopic electronic systems, mainly owing to its potential of reducing the dissipation of energy as wasteful heat, for defining a better current standard for metrological purpose or even being used for quantum computing. Recent experimental realizations of Thouless pumps have been observed in photonics, magneto-mechanical and electro-mechanical systems and other examples cover the fields of spintronics with implications in the efficiency of data storage and transfer