In this interview, we talked to Dr. Imad Limame, postdoctoral researcher at the Institute of Physics and Astronomy at TU Berlin, about his work on scalable quantum photonic circuits using on-demand quantum emitters. He shares insights into his research journey, the advantages of Berlin’s interdisciplinary quantum ecosystem, and how the city’s openness and cultural diversity have shaped both his scientific and personal growth.
What inspired you to pursue a career in quantum physics?
My fascination with the quantum world began when I joined Professor Reitzenstein's research group as a PhD student. Immersed, alongside my colleague Dr. Ching-Wen Shih, in cutting-edge work on quantum light sources based on InGaAs quantum dots, I quickly became captivated by the fundamental principles of quantum physics and their potential to revolutionize today’s technologies.
Why did you choose to conduct your research in Berlin?
Initially, I didn’t choose Berlin specifically for its research opportunities—and I believe few people actually do—but rather for the unique cultural landscape and the vibrant atmosphere the city offers, especially at night. However, over the course of my PhD, my perspective evolved significantly. I decided to remain in Berlin and pursue a BERLIN QUANTUM Postdoctoral Fellowship largely because of the exceptional research environment I experienced in Professor Reitzenstein’s group.
What advantages does Berlin offer for quantum physics research compared to other cities or countries?
Berlin offers a unique combination of academic excellence, infrastructure, and interdisciplinary collaboration that makes it an outstanding location for quantum physics research. One of the key advantages is the dense network of world-class institutions, such as TU Berlin, Humboldt University, Freie Universität, and research centers like the Ferdinand-Braun-Institut and the Helmholtz Association. These institutions foster a collaborative ecosystem where physicists, engineers, and materials scientists work closely together on cutting-edge quantum technologies. Moreover, BERLIN QUANTUM now connects all these world-class institutions, making collaborations even easier.
Can you tell us about a current project or experiment you are working on?
The project I’m currently working on is about building integrated quantum photonic circuits—essentially tiny chips that can control and process single particles of light, or photons, for quantum technologies. We use special semiconductor structures called quantum dots that act as single-photon sources. The goal is to create a system that can perform basic quantum operations like CNOT gates and entanglement purification, and eventually scale up to generate complex photonic states that are useful for fault-tolerant quantum computing. What makes our approach unique is a special technique we use called in-situ electron beam lithography, which allows us to place these quantum dots precisely where we need them in the circuit. We then integrate these circuits with optical fibers and test them in advanced quantum optics labs. In the long term, this technology could become a key part of future quantum communication networks.
How does BERLIN QUANTUM and the Berlin research landscape support your work, and which resources are particularly helpful?
I have to admit that I have not yet fully benefited from the support offered by BERLIN QUANTUM and the broader Berlin research landscape, as my project is somewhat unique. It is currently the only one that combines epitaxial (MOCVD) growth of semiconductor single-photon sources, fabrication of complete photonic circuits, and basic spectroscopic characterization. In contrast, many other projects focus on more advanced applications, such as quantum key distribution (QKD), using different platforms like trapped atoms or nitrogen-vacancy (NV) centers in diamond.
However, events like the BERLIN QUANTUM BBQ and other regular workshops and networking formats offer valuable opportunities to meet fellow researchers, exchange ideas, and build long-term collaborations. This unique combination of technical infrastructure and a vibrant scientific community makes Berlin an exceptional place for quantum research.
What role does collaboration with other scientists and institutions in Berlin play in your research?
At the current stage of my project, where the focus is on developing the foundational techniques and defining the platform architecture, collaboration with other scientists and institutions in Berlin is still somewhat limited. However, the strong interdisciplinary environment already allows me to benefit from a broad range of expertise—whether in materials science, quantum optics, or nanofabrication. Although my project is highly specialized, I still value and rely on the insights and informal exchanges with colleagues working on related topics within the BERLIN QUANTUM community. As the project progresses and becomes more application-oriented, collaboration will play an increasingly important role, particularly in integrating components and exploring system-level functionalities.
How does living in Berlin influence your personal and professional development?
Living in Berlin has had a profound impact on both my personal and professional development. Professionally, being part of such a vibrant and international scientific community constantly motivates me. The city's excellent research infrastructure, global networks, and frequent academic events create a dynamic environment that fosters collaboration, learning, and innovation.
On a personal level, Berlin offers a unique blend of rich cultural life and a relaxed, open-minded atmosphere. What surprised me most is how green the city is—full of lakes, parks, and nature, which provide a great balance to the intensity of research life. The diversity and openness of the people—many of whom come to Berlin for the freedom it represents—make the city feel truly inclusive and inspiring.
And then there are the people I’ve met here. From chance encounters on the subway, in university hallways, or even in late-night bars, to colleagues in the lab—many of them have become close friends. These connections have shaped my experience just as much as any academic achievement.
In your opinion, what are the most exciting developments or trends in quantum physics that we can expect in the coming years?
In my humble opinion, scientists are the worst people to ask about the future of their own work or field. We’ve spent so much time crafting the motivation sections of our papers that we’ve not only convinced editors and reviewers of the impact of our research—but sometimes blinded ourselves to the broader reality.
That being said, I would personally say that some of the most exciting developments in quantum physics in the coming years will revolve around the transition from fundamental research to scalable technologies. One key trend is the rapid progress in quantum hardware integration—especially in photonic platforms—where we’re seeing increasing control over single photons, better integration of quantum light sources, and the development of compact, chip-based quantum circuits.
Another major area is quantum networks, where efforts are underway to build the first functional quantum communication links between cities, and eventually, quantum internets. This will require not only advances in entanglement distribution and quantum repeaters, but also new methods for integrating different quantum systems such as atoms, ions, and solid-state emitters.
Overall, the field is moving steadily toward real-world applications, and the next few years will be critical in demonstrating which technologies can truly scale—and which can deliver meaningful advantages over classical systems.
Do you have a special experience or anecdote from your time in Berlin that you would like to share with us?
What I love about Berlin is that it gives space for anything to happen. The city has this quiet but powerful philosophy of “Leben und leben lassen”—live and let live. People here don’t care where you come from or what your status is; what matters is who you are and what you bring into the moment. That openness has shaped my personal journey as much as any academic achievement. It taught me to let go, be more present, and appreciate the diversity of paths that all somehow lead through this city.
What advice would you give to young scientists who aspire to a career in quantum physics and might consider coming to Berlin?
My advice to young scientists interested in quantum physics—and considering Berlin—is simple: be curious, be open, and don’t be afraid to ask. Quantum physics can be intimidating at first, but it’s one of the most exciting and fast-growing fields out there. Berlin, in particular, offers a unique environment where top-level research meets a vibrant, creative, and international community.
If you're coming to Berlin, take full advantage of the opportunities here—from world-class institutions and collaborative research groups to shared facilities and open scientific events. Don’t isolate yourself—talk to people across disciplines. Some of the most valuable insights come from informal discussions over a beer, not from boring lectures.
And beyond the lab: embrace the spirit of the city. Berlin is not only a great place to work, but also to grow personally. It has this rare quality of letting people be who they are, which is incredibly important when you're navigating the challenges of a research career.
So come with an open mind, stay curious, and don’t rush—science, like Berlin, takes time to reveal its beauty.