Paradigm shift in the field of optically active quantum dots: improved qubit and the nuclear interface*

Epitaxial Quantum Dots (QDs) are world-leading single-photon sources owing to their efficient light-matter coupling [1]. Despite that, they have underperformed as spin-photon interfaces due to a short spin coherence time of a few microseconds. This cap, inherent to self-assembled QDs, originates from substantial strain inhomogeneity affecting the mesoscopic nuclear environment of the qubit. This talk will focus on the solution to this long-standing problem offered by lattice-matched QDs, in which significantly reduced strain inhomogeneity leads to a hundred-fold extension of coherence time [2]. Together with progress in photon collection, these experimental advances promote QDs to robust quantum nodes and allow for generating multi-photon entangled states. Beyond, the improved homogeneity of the collective qubit-nuclear coupling enables the exploration of many-body phenomena relying on feedback [3] and coherent exchange [4,5]. In the second part of the talk, I will review the recent experimental achievements and emerging proposals in this field.

[1] N. Tomm, …, R. J. Warburton, Nature Nanotechnology 16, pages 399–403 (2021)

[2] L. Zaporski, …, C. Le Gall, Nature Nanotechnology 18, 257–263 (2023)

[3] D. M. Jackson, ..., D. A. Gangloff, PRX 12, 031014 (2022)

[4] D. A. Gangloff, ..., M. Atature, Science 364, 62-66 (2019)

[5] L. Zaporski, …, D. A. Gangloff, arXiv:2301.10258 (2023)