Speaker
Description
We investigate the interplay between on-demand single-electron emission and superconducting correlations within the framework of electron quantum optics. Specifically, we study a semiconductor quantum dot proximitized by a superconductor and driven by a time-dependent electrostatic potential.
In the absence of superconductivity, a driven quantum dot may operate as a single-electron emitter, generating clean, quantized electron wave packets on demand, as demonstrated in Ref. [1]. In this regime, raising the dot energy level above the Fermi energy results in a deterministic emission of an electron into the lead.
Here, we explore how this emission mechanism is fundamentally modified when superconducting proximity effects are present. Due to induced pairing, the quantum dot no longer hosts states with a well-defined particle number, but instead supports coherent superpositions of empty and doubly occupied states. As a consequence, driving the dot does not simply lead to electron emission. Instead, two competing processes emerge: (i) emission of an electron to the lead and (ii) hole emission to the lead due to Andreev reflection.
We show that this mechanism enables the controlled generation of coherent electron–hole superpositions. Importantly, these are superpositions of an electron and a hole, not electron-hole pairs. We analyze the emission process and the properties of the resulting superposition.
Bibliography:
[1] J. Keeling, A. V. Shytov, and L. S. Levitov, “Coherent Particle Transfer in an On-Demand Single-Electron Source,” Phys. Rev. Lett., vol. 101, no. 19, p. 196404, Nov. 2008, doi: 10.1103/PhysRevLett.101.196404.