On-Demand Single-Electron Source via Single-Cycle Acoustic Pulses

TL;DR

This work addresses the need for scalable, on-demand single-electron control for electron-quantum optics by eliminating the need for a loaded quantum dot. It introduces a single-cycle SAW pump driven by a chirp-IDT that transports a single electron across a depleted quantum rail, achieving quantized acousto-electric current with tunable delays. The key results include a measurable single-electron transport with $I = n f e$ and a quantified accuracy of $I_{\rm N} = 0.037 \pm 0.013$, along with demonstrated delays above $9\ \mathrm{ns}$ and crosstalk mitigation via timing control. The approach promises scalable, parallel single-electron sources for flying qubits and quantum-optical interfaces, with further improvements enabled by broader bandwidths and alternative piezoelectric materials.

Abstract

Surface acoustic waves (SAWs) are a reliable solution to transport single electrons with precision in piezoelectric semiconductor devices. Recently, highly efficient single-electron transport with a strongly compressed single-cycle acoustic pulse has been demonstrated. This approach, however, requires surface gates constituting the quantum dots, their wiring, and multiple gate movements to load and unload the electrons, which is very time-consuming. Here, on the contrary, we employ such a single-cycle acoustic pulse in a much simpler way - without any quantum dot at the entrance or exit of a transport channel - to perform single-electron transport between distant electron reservoirs. We observe the transport of a solitary electron in a single-cycle acoustic pulse via the appearance of the quantized acousto-electric current. The simplicity of our approach allows for on-demand electron emission with arbitrary delays on a ns time scale. We anticipate that enhanced synthesis of the SAWs will facilitate electron-quantum-optics experiments with multiple electron flying qubits.

Figures (5)

• Figure 1: (a) Experimental setup. Schematic of a chirp IDT emitting a compressed SAW towards a quantum rail and a broadband SAW detector, showing a perspective view of the sample that is realized via a metal surface gate in a GaAs/AlGaAs heterostructure. (b) Conductance across the quantum rail as a function of the voltages $V_{\rm t}$ and $V_{\rm b}$. The current is measured from the ohmic contact $O_{\rm l}$ while applying a DC bias voltage (336µ V) to the ohmic contact $O_{\rm r}$. $G_0 = 2e^{2}/h$, where $e$ is the electron charge and $h$ is the Planck constant. (c) Trace of the broadband detector's response to the compressed SAW generated by the chirp IDT (gray solid line) with impulse-response simulation (light gray dotted line) and the corresponding SAW shape (red dashed line) which is derived by deconvolving the detector response to remove the contribution of the detector IDT in the simulation. The measurement is performed at 4K.
• Figure 2: Acousto-electric current, $I_{\rm SAW}$, induced by the compressed SAW pulse as a function of the voltage $V_{\rm b}$ with $V_{\rm u}=-2.2V$. The SAW amplitude varies from 30meV to 36meV (from right to left) (refer to Appendix B). The range indicated in red is a flat region where the gradient is less than a certain value of the most left curve (refer to Appendix A).
• Figure 3: Acousto-electric current, $I_{\rm SAW}$, as a function of the voltage $V_{\rm b}$ with offset for clearly OffsetFig3. Two SAW pulses within $T_{\rm cycle}$ with changing delay between the pulses from 2ns to 30ns (from left to right).
• Figure 4: (a)Schematic of the arrival time of electromagnetic waves and SAW pulses at the quantum rail. The SAW arrives at the quantum rail approximately 505ns after generation at the IDT. (b)Acousto-electric current, $I_{\rm SAW}$, as a function of the voltage $V_{\rm b}$ with $V_{\rm u}=-2.06V$ with and without crosstalk.
• Figure 5: Acousto-electric current, $I_{\rm SAW}$, of maximum SAW amplitudes in Fig. \ref{['fig:Figure2']} and its gradient. The left y-axis represents $I_{\rm SAW}$ (gray and red), and the right y-axis represents the gradient of $I_{\rm SAW}$ (black). The gradient is smoothed by averaging the values of the five neighboring points.