Two distant quantum emitters, embedded in a nanophotonic structure, get mutually excited through a bound state in the continuum induced by an optical Fano resonance.

Novel physics promote long-range interaction of quantum emitters

Tuesday 14 Dec 21
by Tobias Sydradal Lund


Yi Yu
Senior Researcher
DTU Electro
+45 45 25 36 43

About Yi Yu

Yi Yu is doing research within the field of Nanophotonics, Lasers, and Quantum optics. He is part of the DNRF Center of Excellence NanoPhoton – Center for Nanophotonics, and the Quantum and Laser Photonics group at DTU Fotonik.

This work is funded by Yi Yu’s project Quantum Fano (Danmarks Frie Forskningsfond (7026-00059B)), a DFF-International Postdoc Grant supported by the Independent Research Fund Denmark.

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Senior Researcher at DTU Fotonik Yi Yu has published a paper in the high-impact journal Optica. 
The paper describes a theoretical proposal and experimental demonstration of a new approach to generating long-range interaction between quantum emitters. 
In this article, he answers four questions about the paper. 

What is the paper about?

Distant interaction between quantum emitters is essential for constructing quantum networks. A particular challenge is realizing such interaction in a compact solid platform, which is important for chip-scale applications. However, previous demonstrations in this respect are limited to only a few wavelengths for the interaction distance. In this work, we show, theoretically and experimentally, that by employing optical Fano resonance which introduces an optical bound-state-in-the-continuum, one can realize remote interaction between two quantum emitters separated by more than 17 wavelengths in space. In addition, unlike conventional schemes, our results hold promise for achieving arbitrary long-distance interaction without compromising the interaction efficiency.

Read more about Fano resonance and bound-state-in-the-continuum

What about this research makes you most excited?

This project was carried out during my external stay in Prof. Eli Kapon’s group at École Polytechnique Fédérale de Lausanne (EPFL). Two things make me most excited.

"In addition, unlike conventional schemes, our results hold promise for achieving arbitrary long-distance interaction without compromising the interaction efficiency"
Yi Yu, Senior Researcher at DTU Fotonik

The first thing is that it challenges a fundamental problem. There is a fundamental trade-off between interaction distance and efficiency when coupling quantum emitters via photon. In this work, I found that by exploiting a bound-state-in-the-continuum induced by optical Fano resonance, it is possible to elongate the interaction distance without compromising the interaction efficiency. 

The second thing is that it conquers a difficult technical issue. To demonstrate the proposal experimentally, a key importance is to remove the problem of random quantum emitter positioning, a well-known challenge for solid quantum emitters. This was achieved by an advanced site-controlled quantum dot technology, as implemented by my collaborators at EPFL. Therefore, it is the physics of Fano resonance combined with this technology that eventually enables the remote interaction of quantum emitters.


How can this research benefit society?

The current work is designed for chip-scale applications, but we expect the same scheme could also benefit off-chip applications with even longer interaction distances. Using photons to generate highly efficient remote interaction between quantum emitters, will have strong applications in quantum communication and scaling up quantum computers, which has profound impacts in cryptography, optimization problems, design of new materials, drug discovery, etc.

What is the next step you will take?

The general physical concept in this work gives rise to many intriguing questions and possibilities in both theory and applications. Currently, practical issues such as the inhomogeneous broadening of solid quantum emitters and the material loss limit the device’s functionalities and performance. But these problems are not fundamental. In the next step, by processing optimizations or using other platforms, I would like to investigate extending such a scheme for even longer interactions to explore the fundamental boundaries of the theories as well as performance limitations in various applications.

Read the paper in Optica

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