ORNL Researchers Summarize Results from Quantum Experiments

Oak Ridge National Laboratory (ORNL) researchers Joseph Lukens, Pavel Lougovski, Brian Williams, and Nicholas Peters, with collaborators from Purdue University and the Technological University of Pereira in Colombia, summarized results from several of their recent academic papers in Optics & Photonics News, a publication of The Optical Society (OSA).

The researchers optimized telecomm equipment used in traditional optics research to experiment with quantum states. Specifically, they designed a quantum frequency beamsplitter using standard lightwave communications technology. The ORNL device allows in photons in red and blue wavelengths simultaneously, then produces energy in either the red or blue frequency.

Researchers in ORNL’s Quantum Information Science group summarized their contributions to quantum networking and quantum computing in a special issue of Optics & Photonics News. Courtesy of Christopher Tison and Michael Fanto/Air Force Research Laboratory.

Interactions between photons are difficult to induce and control, but control is necessary for developing quantum computers and quantum gates. By adjusting the beamsplitter for quantum frequencies, the ORNL team was able to change the frequencies of photons in a controlled way. This led to useful photon interactions based on quantum interference (the phenomenon of photons interfering with their own trajectories).

“It turned out that off-the-shelf devices can deliver impressive control at the single-photon level, which people didn’t know was possible,” researcher Pavel Lougovski said.

The researchers also demonstrated a frequency tritter, which splits a beam into three different frequencies instead of two. Their experimental results indicate that multiple quantum information processing operations can run at the same time without introducing errors or damaging data.

The team also designed and demonstrated a coincidence-basis controlled-NOT gate, which enables one photon to control a frequency shift in another photon. The development of this device completed a universal quantum gate set. Any quantum algorithm can now be expressed as a sequence within those gates.

The team also encoded quantum information in multiple independent values, known as degrees of freedom, within a single photon. This allowed the researchers to observe quantum entanglement-like effects without the need for two separate photons.

The researchers also completed quantum simulations of real-world physics problems. In collaboration with scientists at the Air Force Research Laboratory, they are now developing specialized silicon chips to further improve photonic performance. “In theory, we can get all these operations onto a single photonic chip, and we see a lot of potential for doing similar quantum experiments on this new platform,” researcher Joseph Lukens said. “That’s the next step to really move this technology forward.”