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Picosecond coherent electron motion in a silicon single-electron source


An advanced understanding of ultrafast coherent electron dynamics is necessary for the application of submicrometre devices under a non-equilibrium drive to quantum technology, including on-demand single-electron sources1, electron quantum optics2,3,4, qubit control5,6,7, quantum sensing8,9 and quantum metrology10. Although electron dynamics along an extended channel has been studied extensively2,3,4,11, it is hard to capture the electron motion inside submicrometre devices. The frequency of the internal, coherent dynamics is typically higher than 100 GHz, beyond the state-of-the-art experimental bandwidth of less than 10 GHz (refs. 6,12,13). Although the dynamics can be detected by means of a surface-acoustic-wave quantum dot14, this method does not allow for a time-resolved detection. Here we theoretically and experimentally demonstrate how we can observe the internal dynamics in a silicon single-electron source that comprises a dynamic quantum dot in an effective time-resolved fashion with picosecond resolution using a resonant level as a detector. The experimental observations and the simulations with realistic parameters show that a non-adiabatically excited electron wave packet15 spatially oscillates quantum coherently at ~250 GHz inside the source at 4.2 K. The developed technique may, in future, enable the detection of fast dynamics in cavities, the control of non-adiabatic excitations15 or a single-electron source that emits engineered wave packets16. With such achievements, high-fidelity initialization of flying qubits5, high-resolution and high-speed electromagnetic-field sensing8 and high-accuracy current sources17 may become possible.

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Fig. 1: Internal coherent dynamics in the single-electron source.
Fig. 2: Schematic three-dimensional (left) and top (right) images of the device structure.
Fig. 3: Experimental observation of current oscillations related to the coherent dynamics.
Fig. 4: Frequency dependence of the current oscillations.
Fig. 5: Calculated frequency dependence of the current oscillations.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Code availability

The computer codes that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.


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We thank K. Chida, H. Tanaka, T. Karasawa, S. P. Giblin, J. D. Fletcher and T. J. B. M. Janssen for useful discussions. This work was partly supported by JSPS KAKENHI Grant no. JP18H05258, by the UK Department for Business, Innovation, and Skills and by the EMPIR 15SIB08 e-SI-Amp Project. The latter project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. This work was also supported by the National Research Foundation (Korea NRF) funded by the Korea Government via the SRC Center for Quantum Coherence in Condensed Matter (Grant no.2016R1A5A1008184).

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Authors and Affiliations



G.Y. measured the device, analysed the data, and performed the calculation of the pump map. S.R. performed the numerical calculation of the Schrödinger equation. G.Y. and M.K. conceived the idea of the experiment. S.R. and H.-S.S. developed the theory of the coherent dynamics and the scheme for the effective time-resolved detection with picosecond resolution. N.J. took supporting data of the current oscillations. A.F. fabricated the device. All the authors discussed the results. G.Y., S.R. and H.-S.S. wrote the manuscript with feedback from all authors. M.K., A.F. and H.-S.S. supervised the project.

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Correspondence to Gento Yamahata, H.-S. Sim or Masaya Kataoka.

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Supplementary Information

Supplementary Sections I–XV, Figs. 1–13, Table 1 and refs. 1–26.

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Yamahata, G., Ryu, S., Johnson, N. et al. Picosecond coherent electron motion in a silicon single-electron source. Nat. Nanotechnol. 14, 1019–1023 (2019).

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