Parallel quantized charge pumping

Two quantized charge pumps are operated in parallel. The total current generated is shown to be far more accurate than the current produced with just one pump operating at a higher frequency. With the application of a perpendicular magnetic field the accuracy of quantization is shown to be $<20\text{ppm}$ for a current of 108.9 pA. The scheme for parallel pumping presented in this work has applications in quantum information processing, the generation of single photons in pairs and bunches, neural networking, and the development of a quantum standard for electrical current. All these applications will benefit greatly from the increase in output current without the characteristic decrease in accuracy as a result of high-frequency operation.

Figure 1

(Color online) Scanning electron microscopy image of the device and schematic of electrical connections. The source and drain reservoirs are linked outside the dilution refrigerator. The same sinusoidal rf voltage signal is used to drive both pumps. Static offset voltages $V_1^{\text{entrance}}$ and $V_2^{\text{entrance}}$ are added to this rf signal.

Figure 2

(Color online) Pumped current for the range of gate voltages at which a quantized number $n$ of electrons were transported per cycle of the rf signal. (a) and (b) show the numerical derivative of the pumped current for pump 1 and pump 2, respectively, in an applied field of $B=5\text{T}$. Annotations are explained in the text. (c) and (d) show line scans across the first plateau. The insets are magnifications of the plateau regions.

Figure 3

(Color online) Pumped current for the first plateau at 340 and 587.5 MHz. The inset shows the plateaus magnified and normalized in gate voltage. The plateau at 587.5 MHz has been scaled to $ef$ at 340 MHz for comparison.

Figure 4

(Color online) Pumped current when both pumps are operating in parallel. The total current produced is $2ef$. The inset is a magnified plot of the plateau region.