UCSB Makes Photon Find

Quantum research physicists at UCSB have made a scientific breakthrough by controlling particles of light.

Physicists Max Hofheinz, Haohua Wang, John Martinis and Andrew Cleland trapped photons in a qubit, sometimes called an “artificial atom,” and were able to control it in order to create a superposition of states - where multiple states of photons exist simultaneously. The researchers were then able to force the photons into any state when measured. According to Cleland, the study was the first to create the superposition in a controlled manner.

“These superposition states are a fundamental concept in quantum mechanics, but this is the first time they have been controllably created with light,” Cleland said in a press release.

The qubit contains a two-level system for measuring the photons, which provides a binary output for the researchers to measure. Martinis said in a press release that the experiment was comparable to a digital-to-analog converter in classical electronics.

According to Hofheinz, the study, which was funded by the Intelligence Advanced Research Projects Activity and the National Science Foundation, provides fundamental research that can be applied toward the fields of quantum communications and computing.

Quantum computing research has attracted interest from government agencies for future applications in quantum cryptography and ultra-safe communications. Banks and other sensitive institutions could then use such communication technologies.

Researchers hope advancements in the field will lead to the eventual development of a quantum computer capable of processing information far beyond the ability of traditional computers. However, Hofheinz said, there is still a significant amount of research needed to produce a quantum computer.

“I’m a bit nervous about talking about quantum computing,” Hofheinz said. “Many in the field of quantum computing believe [that a quantum computer] is still a long-term goal.”

There are still many obstacles on the road to quantum computing. For instance, controlling qubits requires temperatures near absolute zero. UCSB’s Awschalom group is researching a method of containing electrons in diamonds, which will allow scientists to work with quantum-level particles at room temperature.

The paper was published in the May 28 edition of the journal Nature. Wang, a post-doctoral researcher and second author of the paper, built the devices necessary for the experiments.

Hofheinz said the best part of the study was seeing fundamental quantum theories come to fruition in an experimental setting.

“[The study] has a lot of interesting physics in it,” he said. “It’s nice to see what you learn [doing] purely theoretical work.”