Solid-State Single Photon Emitters

We are investigating the fundamental light-matter interaction of solid-state quantum emitters and in particular the dynamics of the excitation and emission processes. In recent experiments, we probe semiconductor quantum dots with light pulses of varying photon statistics and investigate the nonlinear response. Furthermore, we study how the quantum coherence of the excitation field can be transferred to the few-level system and is preserved in the photonic output state upon recombination.Results of our research impacts both the field of photonic quantum computing and quantum cryptography. Already today, quantum dots serve as source of highly pure and indistinguishable single photons, entangled photon pairs or photonic cluster states generated by spin-photon coupling. This makes them a crucial resource for our linear-optical quantum computing schemes based on time-loops, as well as for the fusion-based quantum computing scheme. Notably, we have demonstrated a key building block of this approach: the generation of a three-photon heralded GHZ state. Moreover, quantum dots can act as a highly nonlinear medium (and thus an effective mediator of photon-photon interaction), a key functionality to implement deterministic gates in photonic quantum computing. Besides, quantum dots are excellent sources for communication tasks. For instance, our recent work included both experimental and theoretical investigations into optimizing pumping parameters to achieve optimal performance in various cryptographic applications, ranging from quantum key distribution to quantum bit commitment and quantum strong coin flipping. Above all, we enjoy exploring the rich physics and deepen our understanding of this unique platform sitting at the interface of quantum information and cavity quantum electrodynamics.

Publications (Selected)

Photonic Source of Heralded Greenberger-Horne-Zeilinger States
H. Cao, L. M. Hansen, F. Giorgino, L. Carosini, P. Zahalka, F. Zilk, J. C. Loredo, P. Walther,
Physical Review Letter 132, 130604 (2024).

Programmable multiphoton quantum interference in a single spatial mode
L. Carosini, V. Oddi, F. Giorgino, L. M. Hansen, S. Piacentini, T. Guggemos, I. Agresti, J. C. Loredo, P. Walther,
Science Advances 10, eadj0993 (2024).

Robust excitation of C-band quantum dots for quantum communication
M. Vyvlecka, L. Jehle, C. Nawrath, F. Giorgino, M. Bozzio, R. Sittig, M. Jetter, S. L. Portalupi, P. Michler, P. Walther,
Applied Physics Letters 123, 174011 (2023).

Enhancing quantum cryptography with quantum dot single-photon sources
M. Bozzio, M. Vyvlecka, M. Cosacchi, C. Nawrath, T. Seidelmann, J. C. Loredo, S. L. Portalupi, V. M. Axt, P. Michler, P. Walther,
npj Quantum Information 8, 104 (2022).

Quantum cryptography with highly entangled photons from semiconductor quantum dots
C. Schimpf, M. Reindl, D. Huber, B. Lehner, S.F. Covre Da Silva, S. Manna, M. Vyvlecka, P. Walther, A. Rastelli,
Science Advances 7, 16 (2021).