An Eberly College researcher is working to create a collaborative program to investigate the fundamental physics of quantum photonic devices that may help advance the field of quantum computing.
Quantum computers are used for specific, extremely difficult problems like breaking encryption systems, very fast database search algorithms and simulating other difficult-to-calculate quantum systems. To further the search for this technology, Edward Flagg, an associate professor leading the Semiconductor Quantum Optics Laboratory in the Department of Physics and Astronomy, will partner with the National Institute of Standards and Technology (NIST) in Gaithersburg, MD to create a specialized device called an "all-on-chip nanophotonicentangled photon source." [EF1] [EF2] This small chip uses microscopic crystals called quantum dots to create entangled photons, which are light particles [EF3] linked in a unique way that can facilitate quantum computing.
“Quantum dots are of interest to scientists and engineers because they interact very strongly with light, much more strongly than a single atom does, because they're bigger,” Flagg said. Quantum dots are useful for doing things that involve absorbing or emitting light, like quantum dot-based LEDs, computer monitors, lasers and fluorescent labels for biomarkers.
Quantum dots emit one or two photons at a time, depending on how they are excited, which helps in transferring quantum information in a secure way or to perform a quantum computation.
“You don't want the information spread over multiple particles,” Flagg said. “We would like to encode that quantum information onto just one photon. A quantum dot is [EF4] what we call a quantum emitter. It emits light, one photon at a time. That is one of the reasons why people are interested in quantum dots. Because if you have a series of identical quantum emitters that all emit identical photons, you can arrange those photons in a photonic circuit, which is kind of like an electrical circuit, to accomplish a quantum computation task.”
One potential advantage for photonic quantum computation is that, because of the vast industry of micro-electronics developed over the last 80 years to make computers, the same kind of technologies that can put a billion transistors on a chip can also make a billion photonic devices, in principle.
“So, it's very scalable,” Flagg said, but he adds that the difficulty lies in making a source of identical single photons scalable to a size that would facilitate quantum computing.
“The problem is we don’t yet know quite how to make those devices well enough to do all the things we need them to do. So, going from where we are now to that potential future requires us to figure out how to make photonic devices that produce quantum light.”
Flagg won’t be working alone, however. The project will solidify a partnership between WVU and NIST and involve students — especially those from regions with fewer educational opportunities — in high-level research, as well as offer internships and research programs at advanced labs. Moreover, it will pave the way for productive collaboration on future research initiatives.
“I'm an expert at making measurements on quantum dots,” he said. “But I'm not an expert at making these photonic nanostructures. However, my collaborator at the National Institute of Standards and Technology, Marcelo Davanco, is an expert. For two summers, I’ll go to NIST with a graduate student and learn how to use their nanofabrication facilities to make these kinds of devices.”
The expertise gained by Flagg and his students will jumpstart a program at WVU to investigate the fundamental physical behavior of photonic devices. The devices to be made in this project have the potential to transform the prospects of photon-based quantum computation on a microchip.
