In-flight distribution of an electron within a surface acoustic wave

Abstract

Surface acoustic waves (SAWs) have large potential to realize quantum-optics-like experiments with single flying electrons employing their spin or charge degree of freedom. For such quantum applications, highly efficient trapping of the electron in a specific moving quantum dot (QD) of a SAW train plays a key role. Probabilistic transport over multiple moving minima would cause uncertainty in synchronization that is detrimental for coherence of entangled flying electrons and in-flight quantum operations. It is thus of central importance to identify the device parameters enabling electron transport within a single SAW minimum. A detailed experimental investigation of this aspect is so far missing. Here, we fill this gap by demonstrating time-of-flight measurements for a single electron that is transported via a SAW train between distant stationary QDs. Our measurements reveal the in-flight distribution of the electron within the moving acousto-electric quantum dots of the SAW train. Increasing the acousto-electric amplitude, we observe the threshold necessary to confine the flying electron at a specific, deliberately chosen SAW minimum. Investigating the effect of a barrier along the transport channel, we also benchmark the robustness of SAW-driven electron transport against stationary potential variations. Our results pave the way for highly controlled transport of electron qubits in a SAW-driven platform for quantum experiments.

Semiconductor-based electron flying qubits: Review on recent progress accelerated by numerical modelling

“…For a flying qubit employing the electron's charge, first observations of tunnel-related probability oscillations have been already reported from experimental studies on SAW-driven transport of a continuous stream of single electrons 66,67 . In congruency with the prediction of the aforementioned time-dependent simulations, the threshold of the SAW amplitude to significantly confine an electron in a single acousto-electric minimum was recently determined as A = (24 ± 3) meV in flight-time measurements 68 . For electron flying qubits defined by spin, increased SAW amplitude have already helped to demonstrate coherent transport of an entangled electron pair over 6 µm distance 69 .…”

Semiconductor-based electron flying qubits: review on recent progress accelerated by numerical modelling

“…For a flying qubit employing the electron's charge, first observations of tunnel-related probability oscillations have been already reported from experimental studies on SAW-driven transport of a continuous stream of single electrons [66,67]. In congruency with the prediction of the aforementioned time-dependent simulations, the threshold of the SAW amplitude to significantly confine an electron in a single acousto-electric minimum was recently determined as A = (24 ± 3) meV in flight-time measurements [68]. For electron flying qubits defined by spin, increased SAW amplitude have already helped to demonstrate coherent transport of an entangled electron pair over 6 μm distance [69].…”

Generation of a Single-Cycle Acoustic Pulse: A Scalable Solution for Transport in Single-Electron Circuits

“…Confirming the confinement location during flight, this acoustic chirped wavefront thus represents the scalable alternative for synchronized and unambiguous SAW-driven single-electron transport from multiple sources. This technique is compatible with all the essential building blocks developed for SAW-driven flying electron qubits such as on-demand single-electron partitioning [22], time-of-flight measurements [38] and electron-spin transfer [21,23]. The nonuniform IDT design enables the possibility to engineer arbitrary combinations of superposed pulses having high relevance for experiments where multiple charges are transferred successively [23].…”

“…The strongly increased error at the third peak of more than 40% indicates that it plays a rather negligible role since, without a sending trigger, this error is only 0.4%. Estimating an amplitude of (19 ± 3) meV of the first acoustic minimum-see Appendix H-the currently employed SAW confinement is slightly below the 95%-confinement threshold of approximately 24 meV [38]. Therefore, we cannot exclude transitions into the second minimum (τ ≈ 0.4 ns) during transport.…”

“…The SAW shapes shown in Figs. Let us estimate the amplitude of the chirped pulse employed in this work with the SAW from the regular IDT employed in the time-of-flight measurements reported in a previous work [38]. Such a comparison is valid since the chirped pulse experiment was conducted under the same experimental conditions of the flight-time measurement-same fabrication and measurement setup.…”