CQE PI Feature – Dr. Robert McConnell

Featured in QSEC June newsletter 2024

Dr. Robert McConnell, a Member of the Technical Staff at MIT Lincoln Laboratory, is developing technology to enable the next generation of compact optical clocks and scalable quantum information processors based on trapped ions.

The best optical clocks in the world are now so exquisitely precise that they would lose less than one second over the entire age of the universe. These clocks achieve such precision by locking a vary narrow-linewidth laser, which serves as the clock local oscillator, to a long-lived transition in a reference atom or ion. By stabilizing the laser frequency to the atomic transition, the optical clock removes drifts in the laser frequency and provides an absolute reference. But today’s precision optical clocks are bulky devices—even the most “transportable” of these systems requires several racks of equipment or a small trailer to contain the clock. McConnell’s work focuses on using microfabrication to develop much smaller pieces of the clockwork, including ion traps with integrated light delivery and collection, and integrated narrow-linewidth lasers, such that bulky optical tables of equipment can be replaced with a few chip-scale devices. “We hope to take one of these ultra-precise clocks and make it smaller than a toaster oven,” explained McConnell.

What is time? This and similar questions often kept McConnell awake as a young child. With a desire to understand the nature of the strange reality that surrounds us, McConnell was led to science at a young age. As he grew older, McConnell began to combine his curiosity about the mysteries of nature with his enjoyment of mathematics. “It was fascinating to see the way that these abstract mathematical equations could be used to represent real phenomena in the world—and then, later on, to be able to build experiments to shed further light on quantum phenomena,” he says.

When McConnell started graduate school, he became excited by the prospect of utilizing antimatter to enable precision tests of the Standard Model of physics. Working in the research group of Prof. Gerald Gabrielse, McConnell pursued efforts to produce and trap atoms of antihydrogen—the simplest antimatter atom—for spectroscopic comparison with hydrogen. This work took him to CERN, the only source of trappable antiprotons in the world, and resulted in an early signal of a few trapped antihydrogen atoms near the end of his doctorate. His graduate work taught McConnell many of the experimental techniques he still uses, from vacuum technology to RF electronics to stable laser locks. After earning his Ph.D., McConnell pursued postdoctoral work at MIT in the group of Prof. Vladan Vuletic. There, he worked on efforts to engineer many-atom entangled states that can allow metrology beyond the standard quantum limit that is typically imposed by atomic projection noise. Similar methods may one day enable even higher precision out of both lab-sized optical clocks and the more compact versions that McConnell is working on.

McConnell joined MIT Lincoln Laboratory’s ion trapping group in 2014. He initially worked on efforts to improve the scalability of trapped-ion based quantum computers. In 2017, he and some other researchers at Lincoln began discussing the possibility of utilizing microfabrication to greatly miniaturize optical clocks. A collaboration spanning several groups at the Laboratory was born. “The resources and the broad expertise available at the Laboratory really make this research possible,” McConnell explained.