Although Carter has not pursued physics as a career, he has emerged in his various roles in and out of the Defense Department as a forceful advocate on the importance of scientific research in national defense. He may well act as a counterweight to budget-cutting lawmakers if President Barack Obama moves ahead to nominate him.
The White House plans to make the official announcement on Friday.
Carter earned his Ph.D. in theoretical physics from Oxford University in 1979, but has spent much of his career in various defense-related roles, most recently as the department's deputy secretary, the No. 2 spot at the Pentagon.
Perhaps because of his academic background, Carter believes in the importance of basic research in protecting the U.S. "Investing in science and technology early on," wrote Carter in a Foreign Affairs essay earlier this year, "ensures that the Pentagon will have something on the shelf when it needs it, so that it does not have to start from scratch when it is too late."
The White House has not officially acknowledged that Carter will replace Defense Secretary Chuck Hagel, who recently announced plans to quit as soon Obama announces a successor.
Carter is a Rhodes Scholar who earned undergraduate degrees, summa cum laude, at Yale in Medieval history and physics.
Science, technology, engineering and math (STEM) graduates with a Ph.D. who become CEOs aren't unusual, "and the higher degrees bring with them mental discipline and good cognition for dealing with challenges on the job," provided they have the prior management training, said Dr. Billie Blair, an organizational psychologist who heads Change Strategists.
The DOD funds what it describes as "high-risk, high-payoff" science in pursuit of technological superiority. It is heavily invested in the basic science underlying such areas as quantum computing, robotics, life sciences, high-energy lasers, materials and other areas that may ultimately find their way into commercial applications. It spends about $50 billion annually in R&D out of a budget of about $600 billion.
There's hope that Carter will serve as an advocate in Congress for science.
"It's clear he understands the critical role the investment in fundamental research plays" in defense, said Peter Harsha, director of government affairs at the Computing Research Association. "And I think there's optimism in the research community that he'll carry that forward into the secretary role."
Defense spending helps to fund basic research in the private sector, but U.S. R&D capability has been increasingly moving overseas. A defense department task force formed by Carter that looked specifically at basic research concluded, in a 2012 report, that "in order to avoid technological surprise, it is important for DOD to be involved in the cutting edge of basic research on topics of specific interest to the Department -- whether the cutting edge is in the U.S. or overseas."
Carter is also a believer in the power of start-up culture to deliver new technologies.
"Smaller firms, start-ups and new entrants provide needed new technology, new faces, and new ideas to the defense the defense industry," said Carter, in a speech at a technology conference in 2011.