Contact
Are you interested in joining our group?
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.
QUANTUM LIGHT SOURCES GROUP
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 %.
Welcome to the Quantum Light Sources group (QLIGHT)
In our website you can read about:
Contact
Niels Gregersen Professor, Group Leader Department of Electrical and Photonics Engineering Phone: +45 45253789 ngre@dtu.dk
News
- (10/2023) Luca receives the Best Young Research Talk Award for his talk at Quantum 2023 in Turin
- (09/2023) Martin and Yujing have successfully defended their PhD thesis. Congratulations!
- (01/2023) Battulga receives 3M DKK from The Villum Foundation for project that will make significant advancements in developing a novel and efficient single-photon source that can be integrated with other on-chip photonic circuits.
- (12/2022) Battulga receives 1.5M EUR from The European Research Council for his project "Tunable Nanoengineered Transition Metal Dichalcogenides for Quantum Nanophotonics".
- (03/2021) Our APL paper about suppressing the background emission in micropillar single-photon sources was selected as "Editor's Pick".
- (02/2021) Our recent APL paper on single-photon emission from elliptical micropillars received an "Editor's Pick".
- (09/2020) Niels receives "Elektroprisen" from the Danish Society of Engineers (IDA).
Research
We design, simulate and fabricate quantum devices such as single-photon sources and entangled photon pair generators for application in photonic quantum technology
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.
Single-photon source (SPS)
Scheme of a micropillar cavity SPF
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:
Optical simulation of the electromagnetic field in photonic structures
We use advanced numerical tools such as Modal Methods and Finite Element Methods to design electromagnetic cavities around an individual quantum emitter. The main goal is to maximize the fraction of emitted light that couples to the fundamental cavity mode, which is usually referred to as efficiency β factor.
We have developed an-open geometry formalism allowing for optical simulations of advanced asymmetric structures using open boundary conditions. We have recently demonstrated a vertical cavity design allowing for a beta factor up to 96%, and we are working towards on-chip designs with 90% emission efficiency directly into a waveguide mode.
Quantum-mechanical microscopic modeling
A key feature of any SPS design is that the quantum emitter can never be separated from its environment, which leads to the deterioration of the SPS figures of merit.
We use the theory of cavity quantum electrodynamics (cavity QED) and optical master equation techniques to analyze how the solid-state environment affects the performance of the source, with a particular emphasis on the coupling with quantized lattice vibrations – i.e. phonons. To this end, we develop analytical and numerical methods including Python, Matlab, and Wolfram Mathematica programming.
Nanofabrication and optical characterization
We use state-of-the-art nano-fabrication techniques and clean-room equipment to image quantum emitters and fabricate micro- and nano-cavities which are deterministically centered around the emitter. Here we rely on the DTU Nanolab clean-room facilities, which provide advanced equipment for reactive ion etching, e-beam lithography, thermal processing, and thin film deposition among others.
We subsequently test the device performance in our optical lab, where we design, build and operate optical setups to excite the SPS with laser light and collect the emitted photons with high efficiency.
Job and career
No open positions at this time.
People
Contact
Niels Gregersen Professor, Group Leader ngre@dtu.dk
Contact
Battulga Munkhbat Senior Researcher bamunk@dtu.dk
Contact
Luca Vannucci Assistant Professor lucav@dtu.dk
Contact
Abdulmalik Abdulkadir Madigawa PhD student abmad@dtu.dk
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Athanasios Paralikis PhD Student athpa@dtu.dk
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Christine Pepke Gunnarsson PhD student cpepe@dtu.dk
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Claudia Piccinini PhD student clapi@dtu.dk
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José Ferreira Neto PhD student jofer@dtu.dk
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Martin Arentoft Jacobsen Postdoc maaja@dtu.dk
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Pietro Metuh PhD Student piemet@dtu.dk
Contact
Pawel Wyborski Postdoc pawyb@dtu.dk
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
Courses
PhD Course
Nano-Optics
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.
Course
Quantum Optics
PhD Course
Quantum Information Journal Club
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:
- B.Sc./M.S.c. Project - Two photon interference from semiconductor quantum dots (QD).
- Numerical modeling of quantum confinement effects in semiconductor quantum dot.
- Special course - Optical Simulations of structured Materials.
- Fag/B.Sc./M.S.c. Project - Theory of single-photon sources.
Find more of our projects at DTU Career Hub
Additional material
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.