2025 Physics Nobel Cites Research by Northwestern Faculty Member
How Jens Koch’s “transmon” qubit design underpins prize-winning breakthroughs. Pictured above: A device consisting of four transmon qubits, fabricated by IBM.
The 2025 Nobel Prize in Physics went to John Clarke, Michel Devoret, and John Martinis for demonstrating that quantum effects—tunneling and discrete energy levels—can exist in chip-scale superconducting circuits. They showed that carefully designed electrical circuits can act like “artificial atoms” and let current cross barriers that it couldn’t pass classically.
Their research proves that the weird rules of quantum mechanics aren’t limited to tiny particles; they reliably show up in human-made circuits you can pattern on a chip. That shift from “observing” to “engineering” quantum behavior is huge: once quantum effects live in circuits, we can wire them up, control them with microwaves, copy and scale designs, and build instruments around them. The same physics enables:
- more stable qubits for quantum computing,
- ultrasensitive detectors and amplifiers (useful in astronomy and materials research), and
- precise, chip-based experiments that test quantum theory and push new technologies.
These advances have a Northwestern connection, one cited by the Nobel laureates.
Why the transmon mattered
Turning delicate quantum effects into reliable technology required qubits that can withstand real-world noise. (A qubit, or quantum bit, is the fundamental unit of a quantum computer. Unlike a classical bit, which is either 0 or 1, a qubit can exist in a combination of both states simultaneously—superposition—and can also be entangled with others. Superconducting qubits are created from tiny circuits that exhibit quantum behavior at very low temperatures.)
Enter the transmon qubit, introduced in 2007 by a team including Northwestern physicist Jens Koch. By 
operating where the Josephson energy dominates the charging energy (think of Josephson energy like a “push” that keeps electrons moving across a tiny “bridge”), the transmon makes its energy levels exponentially less sensitive to stray electric charges to function as a clean, controllable two-level system. That stability turned transmons into the workhorse of today’s superconducting quantum processors and enabled more precise studies of tunneling and quantized levels, the physics celebrated by this year’s Nobel.
“The transmon’s big idea was simple: push into a regime where the qubit hardly notices random charges, but still behaves like a true quantum two-level system,” says Koch. “That balance made superconducting circuits far more reliable and opened the door to the larger, cleaner experiments we see today.”
Northwestern connection
Koch is a Northwestern physics professor and a co-architect of the transmon qubit, a design that helped make superconducting quantum circuits far more stable and practical. He is a national leader in efforts to advance superconducting-qubit performance. Previously, he served as deputy director for the DOE’s Superconducting Quantum Materials and Systems (SQMS) Center and is an active member of INQUIRE (the Institute for Quantum Information Research and Engineering), one of Northwestern’s 22 University-wide Research Institutes and Centers that draw talent from across the University’s schools. Through INQUIRE, Koch collaborates with researchers in arts and sciences, engineering, and other disciplines to advance quantum information science—linking foundational theory with devices, experiments, and training that prepare the next generation of quantum scientists. —Matt Golosinski