Our objective is to develop high-efficiency semiconductor-quantum-dot-based quantum light sources for applications in optical quantum computing and quantum communication. 
We aim at establishing the physical understanding necessary to engineer sources of single indistinguishable photons as well as entangled photon pairs with near-unity efficiency approaching 100 %.


Niels Gregersen

Niels Gregersen Group Leader, Professor Department of Electrical and Photonics Engineering Phone: +45 45253789



We design, simulate and fabricate quantum devices such as single-photon sources and entangled photon pair generators for application in photonic quantum technology
Quantum Light Group Research

What does "photonic quantum technology" mean?

The term "photonic quantum technology" refers to the use of photons as carriers of information for information and communication technology (ICT) applications. Examples include, among others:

  • protocols for secure long-distance communication making use of quantum cryptography,
  • quantum computing platforms that outperforms any classical computer, 
  • the realization of a quantum internet where each node operates according to the laws of quantum mechanics, 
  • in all these cases, a single photon is used as the fundamental unit of information, that is as a quantum bit (or qubit). Thus, quantum information platforms based on optical protocols rely crucially on the availability of a deterministic source of single-photons.

What is a single-photon source?

A single-photon source (SPS) is a quantum device that is able to deterministically provide a single-photon on-demand, with an efficiency as close as possible to 100%. On top of that, an ideal single-photon source has to deliver photons that are quantum-mechanically indistinguishable (i.e. identical to each other) and pure (i.e. each wave-packet contains one and only one photon per time). Typically, an SPS consists of two ingredients:

  • a quantum emitter, such as a quantum dot or a point defect in a crystalline lattice, 
  • an electromagnetic microcavity embedding the quantum emitter. This is often realized by sandwiching the emitter between two highly reflective mirrors, which results in the enhancement of its spontaneous decay rate (a phenomenon known as Purcell enhancement)

What do we do in our group?

Our main goal is to design, simulate and fabricate an SPS with an excellent performance with respect to all the above-mentioned figures of merit (efficiency, indistinguishability, and purity). We focus on three main areas of activity:

Our Group 2022/2023


You are welcome to contact us by email. You find our contact details in the section "People". You can also see the open vacancies in the section "Job and career" below.

For more information about our projects, please take a look at DTU project bank or visit our section “For students”.

Job and career

No open positions at this time.



Niels Gregersen

Niels Gregersen Group Leader, Professor



Luca Vannucci

Luca Vannucci Assistant Professor





External collaborations

We collaborate with national and international research partners.

  • Julien Claudon
    Experimental fabrication of nanowire SPS devices at CEA Grenoble.
  • Jean-Michel Gérard
    Head of Nanophysics and Semiconductors CEA-CNRS Laboratory in Grenoble.
  • Sven Höfling
    Fabrication of microcavity pillars at the University of Würzburg.
  • Stephan Reitzenstein
    Cavity QED in microcavity systems at the Technical University of Berlin.

For students


PhD Course

We teach the Ph.D. course 34092 Nano-Optics during the fall semester. The student taking this course will be familiarized with the theoretical foundation of nano-optics, understand the physics of light emission and optical interactions in nanoscale environments and master various methods for computing the optical field, including the Green’s function formalism.


We are involved in the MSc course 10380 Quantum Optics, which is taught during the fall semester. The course deals with the quantum mechanical description of light and the interaction between light and matter. Here the students are introduced to the physics of quantum states of light, cavity quantum electrodynamics, light absorption and emission in micro- and nano-structures, quantum entanglement and quantum decoherence.

PhD Course

We also run the PhD course 34094 Quantum Information Journal Club, both in the fall and spring semesters. Each session of the course is organized as an informal study group where a relevant paper in the field of quantum information technology is presented and discussed in detail, with a particular focus on semiconductor-based photonic structures.

Students projects

We offer "Fagprojekt", BSc., MSc. and special course projects related to quantum light sources, nano-optics and optical simulation methods. Examples are:

Additional material

Every year DTU celebrates the new PhD graduates. One of them is: PhD, Andreas Dyhl Østerkryger, DTU Fotonik. The title of his thesis is: “Single-photon sources for quantum information applications”.
Niels Gregersen, DTU, winner of the Electro Award 2020, giving a talk on quantum light sources. The holy grail within quantum physics is the quantum computer, and here quantum light sources play an important role.

Past news:

  • Funding for the ERC-CoG UNITY project was granted.
  • Funding for the Marie Curie ITN QUDOT-TECH project was granted.
  • On the cover of Nature Photonics.
  • Funding for the QuantERA HYPER-U-P-S project was granted.
  • Our recent PRL paper on an efficient source of indistinguishable photons was highlighted among the most exciting Optics in 2016 in OPN.
  • Our recent JOSA-A paper on new open boundary condition formalism was highlighted with a Spotlight on Optics by OSA.
  • Funding for the LOQIT project secured from the Danish Research Council for Technology and Production.
  • On the cover of ChemPhysChem.
  • EMRP Research Excellence Grant awarded as part of the EURAMET project SIQUTE.
  • NG start 34092 Nano-Optics fall semester course.
  • Proof of concept funding received.
  • Postdoc funding received.
  • Nanowire SPSs in the media: videnskab.dk (Danish)
  • On the cover of Nature Photonics.