Sandia Labs and Arizona State U collaborate on quantum photonics

29 Aug 2024

Aim is to transform large optical systems into compact integrated microsystems.

Sandia National Laboratories and Arizona State University are collaborating, as they say, “to push the boundaries of quantum technology and transform large-scale optical systems into compact integrated microsystems”.

Nils Otterstrom, a Sandia physicist specializing in integrated photonics, is working on scaling down optical systems to the size of a chip. This innovation promises performance advantages and scalability for an array of applications from advanced computing to secure communications.

“Integrated photonics takes optical systems that are macroscale and makes them microscale,” said Otterstrom, who earned his doctorate in applied physics from Yale and joined Sandia as a Harry S. Truman fellowship recipient.

“What we do in integrated photonics is develop novel devices and explore device physics to provide all the functionalities that we need to do fundamental research and create next-generation quantum microsystems.”

Quantum collaboration

Otterstrom has been collaborating with Senior Director of Quantum Networking at Arizona State University Joe Lukens, who is an expert on using the frequency of light to carry quantum information for quantum computing and networking.

This effort was recently formalized through a new Cooperative Research and Development Agreement funded by the Quantum Collaborative. The Quantum Collaborative (QC) brings together academic and research institutions — including national labs. The state of Arizona funds the QC and Arizona State University manages the initiative.

“The inspiration for the QC is the recognition that the future is quantum. If we’re going to be successful, it cannot be done by single investigators or even single institutions,” Lukens said. “The collaborative is an intentional network of like-minded individuals who are interested in building up quantum information technology, and it’s a way for us to connect and work together.”

Before the agreement with Sandia, Lukens focused on fiber-optic systems for his work in frequency-bin quantum information processing. He explained that qubits exist in all sorts of platforms, including photonics.

“In the frequency approach, your qubit is a photon that can possess two different wavelengths simultaneously,” he said. “A zero corresponds to one color, and one corresponds to the other. That encoding is advantageous for quantum communications. It’s transmitted well in optical fiber.”

This is the point at which Sandia’s resources for integrated photonics come into play. “Sandia has one of the most flexible foundries in the world, not only in microelectronics but also in photonics,” Lukens said, referring to the MESA complex. “Sandia can fabricate small photonic integrated circuits that can realize the same capabilities as a big square meter-size optical table.”

Quantum photonics components

“In this frequency encoding paradigm, we need to create special types of beam splitters that instead take one color of light and split it into two,” Otterstrom said. “What we have developed here at Sandia, in collaboration with professor Peter Rakich’s team at Yale University, are these very efficient novel phase modulator devices.”

The devices are based on suspended silicon waveguides that convey light and gigahertz soundwaves, which are generated by co-integrated aluminum nitride electro-mechanical transducers.

“The result is highly flexible optomechanical structures that acousto-optically split a photon into multiple frequencies. This allows you to do quantum information processing on a much higher dimensional space,” Otterstrom said. “You can think about it as the light’s color can actually carry the quantum information.”

Next steps

Lukens’ goal is to move work from proof-of-principle experiments to deployment in quantum networks. “In order to do that, we need systems with lower loss than what we can achieve today with commercial devices, and we need systems that are a bit cheaper,” he said.

The collaboration is paying off. Sandia’s Laboratory Directed Research program has awarded $17 million to advance the team’s work in frequency-based quantum photonics. The funding comes in the form of a Grand Challenge program called Error-Corrected Photonic Integrated Qubits, or EPIQ.

Otterstrom said the funding will enable large-scale implementation and integration of the device physics explored in the early collaboration with Arizona State University to create a useful photonic qubit that can be error-corrected.