At the QIA PI+ Meeting 2024, the Best Paper Award was presented to a remarkable team of researchers for their groundbreaking work, “A quantum-network register assembled with optical tweezers in an optical cavity.” In this study Lukas Hartung, Gerhard Rempe, Matthias Seubert, Stephan Welte, and Emanuele Distante introduced an innovative approach to advancing quantum networking through multiplexed atom-photon entanglement. We sat down with Lukas Hartung and Gerhard Rempe to find out more.

Mr. Hartung, your paper explores fascinating concepts. Could you explain the core idea of this research and its significance for quantum networking?

Our paper is about the implementation of a scalable quantum network register. This register uses optical tweezers and optical lattices to assemble a 2D array of atoms in an optical cavity. By individually addressing each atom with a laser beam, we can stimulate the emission of a photon from each atom and generate multiplexed atom-photon entanglement. This is a key step towards the deterministic entanglement distribution between network nodes, which is essential for building quantum networks.

What motivated you and your team to pursue this specific line of research, and how does it address current challenges in building scalable quantum networks?

Scalable quantum network nodes are necessary in future quantum networks for different applications, e.g. quantum communication or distributed quantum computing. A major challenge is overcoming the intrinsic losses in the generation and transmission of entangled optical photons, which severely limits the rate at which entanglement can be distributed in quantum networks. This is exactly the challenge that we are tackling in this work by using an array of atoms to implement a multiplexed atom-photon entanglement generation protocol.

Collaboration plays a crucial role in quantum research. Could you share how your collaboration with the other researchers came about and how it contributed to the success of this paper?

This project has been a real team effort. Emanuele Distante and Stephan Welte, as PostDocs, shared their experimental experience and were always ready to help with the daily challenges in the lab. Matthias Seubert and I, as PhD students, worked together on the hands-on tasks like aligning optics, programming, measuring, calibrating and getting the setup to run smoothly. Gerhard Rempe, our PI, was always there to help when we got stuck and provided lots of helpful advice, especially with writing the paper. Everyone contributed in their own way and made this project enjoyable, even when sometimes the days in the lab were long and tiring.

In what ways do you see the results of your paper impacting future developments in quantum communication or quantum computing? Could this potentially revolutionize any areas of the field?

The results in this paper have the potential to advance the areas of quantum communication or computing by providing a route towards networks nodes with large qubit registers. Such nodes can increase the entanglement distribution rates in networks, which is necessary to establish entanglement over large distances. Of course, this work is not a complete solution, but it represents a first step into this direction.

Looking ahead, what are the next steps for your research? Are there any open questions or new directions you’re particularly excited to explore after this breakthrough?

Based on this work, two main directions are possible: one possibility is to implement quantum networking protocols with multiple nodes. Since we have similar setups to the one described in the publication in our group, we can connect different setups and implement networking protocols, such as the multiplexed, heralded generation of atom-atom entanglement. Another possibility is to continue to increase the number of qubits in the register in the optical resonator by changing the trap structure, which would allow us to host larger arrays of atoms.

Prof. Rempe, winning the Best Paper Award at the QIA PI+ Meeting was quite a surprise for you. How did your co–authors feel when you told them about the award?

It was a delightful surprise for all of us. When I shared the news with my co-authors, they responded with enthusiasm and pride. Lukas Hartung expressed his happiness about the recognition of our work, while Emanuele Distante emphasized how well-deserved the award was. I also received very positive feedback from Matthias Seubert and Stephan Welte, reflecting the team’s shared sense of accomplishment in this recognition of our collaborative effort.