Pulse-induced acoustoelectric vibrations in surface-gated GaAs-based quantum devices

We present the results of a numerical investigation which show the excitation of acoustoelectric modes of vibration in GaAs-based heterostructures due to sharp nanosecond electric-field pulses applied across surface gates. In particular, we show that the pulses applied in quantum information processing applications are capable of exciting acoustoelectric modes of vibration including surface acoustic modes which propagate for distances greater than conventional device dimensions. We show that the pulse-induced acoustoelectric vibrations are capable of inducing significant undesired perturbations to the evolution of quantum systems.

Figure 1

(a) A schematic representation of the device used in our simulations. The orientation of the crystal axes in relation to the coordinate axes is shown. The parameters $a$ and $d$ represent the width of the gates and distance between the gates, respectively. (b) The shape of the pulse used in the electrical pulse experiments. The parameters $A$, $t_r$, and $t_d$ are the amplitude, rise time, and pulse duration, respectively.

Figure 2

(a) Time series plot of the electric potential as a function of the $x$ coordinate from time $t=0.4\mathrm{ns}\text{to}t=2.0\mathrm{ns}$, with $\Delta t=0.1\mathrm{ns}$. The induced waves propagate outward from the center at $x=8\mu \mathrm{m}$ with increasing time. For clarity, the inset shows the curve at $t=2.0\mathrm{ns}$ with a maximum amplitude of $\sim 2.0\mathrm{mV}$. The data were taken at a depth of $100\mathrm{nm}$ from the surface. (b) Grayscale plot of the pulse-induced electric potential at time $t=2.0\mathrm{ns}$. The regions of higher electric field at $x\sim 3\mu \mathrm{m}$ and $x\sim 13\mu \mathrm{m}$ (outlined) correspond to single minima (or maxima) of a surface acoustic wave.

Figure 3

The effect of a pulse-induced surface acoustic wave on a double-quantum-dot device.

Figure 4

(a) The dependence of the amplitude of the pulse-induced acoustoelectric vibrations $\varphi$ on the pulse duration $t_d$. (b) Time series plot of the $z$ component $u_z$ of displacement across the device for a sequence of times $t=0$ to $t=0.5\mathrm{ns}$ with $\Delta t=0.025\mathrm{ns}$. A small offset is applied between curves. (c) For clarity, the value of $u_z$ at $x=8\mu \mathrm{m}$ for the sequence of times $t=0$ to $t=0.5\mathrm{ns}$.