QLunch: Nika Akopian

Speaker: Nika Akopian from DTU

Title: Quantum Nanophotonics with Quantum Dots, Nanowires and Atomic Systems

Abstract:
Quantum information systems will likely be hybrid — they will combine the key advantages of various quantum systems. Here we demonstrate a powerful example of such a hybrid system — a semiconductor-atomic interface 1 — where we couple a single semiconductor quantum dot in a nanowire to a vapor of rubidium atoms 2 . We grow GaAs quantum dots in AlGaAs nanowires with a nearly pure crystal structure and excellent optical properties. We then fine-tune the frequency of our nanowire quantum dots to the D 2 transition of 87 Rb. Our work brings highly desirable functionalities to quantum technologies, enabling, for instance, a realization of a quantum network, based on an arbitrary number of nanowire single-photon sources, all operating at the same frequency of an atomic transition.

Crystal-phase quantum dots are another original system that we discovered 3 . Here we develop multi-qubit photonic devices with the ultimate design control — at the single atomic layer during the fabrication. We also propose and numerically demonstrate, for the first time, a method for controlled charging of multiple quantum dots and charge transport between the dots 4 . We show that our method can be implemented in crystal-phase structures with fidelities greater than 99.9%.

Our work opens new practical avenues for realizations of advanced quantum photonic devices, for instance, solid-state quantum registers with a photonic interface.

1. Akopian, N., Wang, L., Rastelli, A., Schmidt, O. G. & Zwiller, V. Hybrid semiconductor-atomic

interface: slowing down single photons from a quantum dot. Nat. Photonics 5, 230–233 (2011).

2. Leandro, L., Gunnarsson, C. P., Reznik, R., Jöns, K. D., Shtrom, I., Khrebtov, A., Kasama, T.,

Zwiller, V., Cirlin, G. & Akopian, N. Nanowire Quantum Dots Tuned to Atomic Resonances. Nano

Lett. 18, 7217–7221 (2018).

3. Akopian, N., Patriarche, G., Liu, L., Harmand, J.-C. & Zwiller, V. Crystal phase quantum dots.

Nano Lett. 10, 1198–1201 (2010).

4. Hastrup, J., Leandro, L. & Akopian, N. All-optical Charging and Charge Transport in Quantum

Dots. Submitted for publication (2019).