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Stanford engineers and physicists study quantum characteristics of ‘combs’ of light

Silicon carbide microrings under a microscope
(Image credit: Vučković Lab)
Dec 16 2021
Faculty, Fellow, Research, Stanford

Unlike the jumble of frequencies produced by the light that surrounds us in daily life, each frequency of light in a specialized light source known as a “soliton” frequency comb oscillates in unison, generating solitary pulses with consistent timing.

Each “tooth” of the comb is a different color of light, spaced so precisely that this system is used to measure all manner of phenomena and characteristics. Miniaturized versions of these combs – called microcombs – that are currently in development have the potential to enhance countless technologies, including GPS systems, telecommunications, autonomous vehicles, greenhouse gas tracking, spacecraft autonomy and ultra-precise timekeeping.

The lab of Stanford University electrical engineer Jelena Vučković only recently joined the microcomb community. “Many groups have demonstrated on-chip frequency combs in a variety of materials, including recently in silicon carbide by our team. However, until now, the quantum optical properties of frequency combs have been elusive,” said Vučković, the Jensen Huang Professor of Global Leadership in the School of Engineering and professor of electrical engineering at Stanford. “We wanted to leverage the quantum optics background of our group to study the quantum properties of the soliton microcomb.”

While soliton microcombs have been made in other labs, the Stanford researchers are among the first to investigate the system’s quantum optical properties, using a process that they outline in a paper published Dec. 16 in Nature Photonics. When created in pairs, microcomb solitons are thought to exhibit entanglement – a relationship between particles that allows them to influence each other even at incredible distances, which underpins our understanding of quantum physics and is the basis of all proposed quantum technologies. Most of the “classical” light we encounter on a daily basis does not exhibit entanglement.

Study co-authors include, Melissa Guidry, a 2018 EDGE Fellow and 2018 SGF Fellow, Daniil Lukin, a 2017 SGF Fellow, and Rahul Trivedi, a 2016 SGF Fellow.

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