[phys4phys] IPB Colloquium: Žarko Gačević, Thursday, 25 December, 14:00

[Marija Mitrovic Dankulov]

Dear colleagues,

You are cordially invited to the IPB COLLOQUIUM which will be held on 
Thursday, 25 December 2025 at 14:00 in the “Zvonko Marić” lecture hall 
of the Institute of Physics Belgrade. The talk entitled

GaN-Based Single-Photon Sources and Their Potential for Quantum Key 
Distribution

will be given by Žarko Gačević (Technical University of Madrid, Madrid, 
Spain). The abstract of the talk:

For more than two decades, the quest for practical, stable, and scalable 
single-photon sources has been at the forefront of quantum photonics 
research. While numerous material platforms, such as quantum dots, color 
centers, and two-dimensional materials, have demonstrated promising 
performance, many still face limitations including cryogenic operation, 
spectral instability, or technological incompatibility with established 
semiconductor processes. In this context, the III-nitride material 
system, and GaN in particular, has recently emerged as a highly 
compelling candidate for SPS technologies thanks to its robustness, wide 
bandgap, mature industrial ecosystem, and compatibility with visible and 
telecom-wavelength emission.

This colloquium reviews the current state of semiconductor single-photon 
sources, highlighting recent advances achieved in the development of 
InGaN/GaN nanowire–based emitters grown by molecular beam epitaxy at 
ISOM-UPM [1–3]. These nanostructures naturally host localized quantum 
emitters capable of producing antibunched light with good stability. The 
talk will highlight the underlying physical mechanisms leading to 
single-photon generation, the role of nanoscale composition and strain 
fluctuations, and the fabrication strategies to improve control of 
emitter formation. Building on this quantum-light platform, the seminar 
will then introduce the principles of quantum key distribution, focusing 
on hybrid time-bin/phase encoding architecture for fiber-based 
communication. Together, these developments illustrate a coherent path 
toward single photon driven photonic quantum technologies.

[1] Ž. Gačević, N. Vukmirović, N. García-Lepetit, A. Torres-Pardo, M. 
Müller, S. Metzner, S. Albert, A. Bengoechea-Encabo, F. Bertram, P. 
Veit, J. Christen, J. M. González-Calbet, and E. Calleja, “Influence of 
composition, strain, and electric field anisotropy on different emission 
colors and recombination dynamics from InGaN nanodisks in pencil-like 
GaN nanowires”, Phys. Rev. B 93, 125436 (2016).
[2]Ž. Gačević, M. Holmes, E. Chernysheva, M. Müller, A. Torres-Pardo, P. 
Veit, F. Bertram, J. Christen, J. M. González-Calbet, Y. Arakawa, E. 
Calleja, and S. Lazić, “Emission of linearly polarized single photons 
from quantum dots contained in nonpolar, semipolar, and polar sections 
of pencil-like InGaN/GaN nanowires”, ACS Photonics 4, 657–664 (2017).
[3] J. Obradović, M. Tinoco, L. Monge Bartolomé, V. J. Gómez Hernández, 
A. Torres-Pardo, S. Fernández-Garrido, Á. de Guzmán, and Ž. Gačević, 
“Formation mechanisms of (In,Ga)N nanoshells conformally grown around 
pencil-like GaN nanowires”, Cryst. Growth Des. (2026, accepted for 
publication).

The visit of Prof. Žarko Gačević is supported by the Science Fund of the 
Republic of Serbia, Grant No. 226, Development of GaN Nanowire Based 
Quantum Light Emitters – PhotonGaN.

Best regards,
Marija Mitrović Dankulov

-- 
Marija Mitrovic Dankulov
E-mail: mitrovic at ipb.ac.rs

Phone: +381 11 3713068
Fax: +381 11 3162190

Scientific Computing Laboratory
Institute of Physics Belgrade
Pregrevica 118, 11080 Belgrade, Serbia