Any manufacturing process invariably results in a few defects, and the more precise and sensitive the device, the more these defects impact its function. Nowhere is this more apparent than the quantum world, where the tiniest defects can have a massive impact.
Improving resiliency against defects has been a central theme in the research and production of quantum devices. Researchers at the University of Calgary recently achieved a breakthrough with a new method to enhance the generation of quantum light from integrated photonic circuits. This approach is not only highly efficient but also resilient to the imperfections and defects that often arise during fabrication. Led by Dr. Shabir Barzanjeh, postdoctoral researcher Dr. Shirin Afzal, and their team, this method is a step forward in developing practical quantum devices for applications in quantum computing and communications.
Dr. Shirin Afzal in the Barzanjeh lab, using equipment that helped achieve the new breakthrough in quantum light generation. Photo Credit: Colette Derworiz, Faculty of Science
Why do defects matter in quantum devices?
Defects and imperfections create significant challenges in the fabrication of electronic and photonic devices, particularly in quantum technologies. Even minor fabrication errors, such as slight size variations or unintended breaks, can drastically reduce a device's performance. For quantum devices, which rely on delicate quantum states like entangled photon pairs, these imperfections can be especially detrimental.
Diagram shows the topological structure developed by Dr. Barzanjeh's team, with light flowing from left to right along the edge to create entangled photon pairs.
Entangled photon pairs are key elements for many quantum technologies, including ultra-secure communication, advanced computing, and precise sensing. Their fragile nature, however, makes them highly susceptible to disruptions caused by material defects or environmental factors. Overcoming these challenges is essential for advancing quantum technologies toward practical, real-world applications.
A new approach to quantum resilience
The UCalgary team, in collaboration with researchers from the University of Alberta led by Dr. Vien Van, has developed a solution. Their recent work, published in PRX Quantum, introduces a new method that is both highly efficient and robust against defects.
How does it work?
Quantum devices depend on generating and transporting quantum particles like photons. These processes must be both efficient - i.e. low-loss - and resilient, capable of resisting imperfections in the system.
To address these challenges, the team utilized topological photonic insulators, a special structure that can guide light along its edges without being affected by defects or irregularities.
"Topological insulators are special because they allow light to flow along their edges while avoiding any imperfections in the material," explains Dr. Shirin Afzal. "This unidirectional flow bypasses obstacles without sacrificing efficiency."
Building on this concept, the team designed topologically protected resonance modes in a compact silicon chip. These modes enhance the generation of quantum light, making the process highly efficient while consuming less power. The result is a quantum source that produces pure and robust entangled photon pairs, even in the presence of imperfections.
What's next?
The team developed and built a micrometer-sized chip with a topological insulator. Their next goal is to make this system programmable, enabling it to support a wide range of applications, such as quantum communication networks and sensing systems.
"We're excited to take this robust and efficient system to the next level," says Dr. Afzal. "This opens up the possibility of developing versatile quantum circuits on a single compact chip."
A quantum future in Alberta
This breakthrough reflects the strength of UCalgary's quantum research ecosystem, which includes the Institute for Quantum Science and Technology, Quantum City, and Quantum Horizons. Together, these initiatives are driving Alberta's vision of becoming a global leader in quantum science and technology. Dr. Barzanjeh and his team's achievement is an impressive step forward, demonstrating how innovation at UCalgary is shaping the future of quantum technology.
