Konrad W. Lehnert

Konrad W. Lehnert is an American experimental physicist and the Eugene Higgins Professor of Physics at Yale University. He has worked in quantum electromechanics, including cooling the motion of macroscopic mechanical oscillators to their quantum ground state, entangling mechanical oscillators with electrical circuits, and applying quantum-enhanced measurement techniques to searches for axion dark matter.

Education and early career

Lehnert received his B.S. from Harvey Mudd College in 1993 and his Ph.D. in physics from the University of California, Santa Barbara in 1999, under the supervision of S. James Allen. His dissertation, titled "Nonequilibrium Dynamics in Mesoscopic Superconductor-Semiconductor-Superconductor Junctions," investigated AC Josephson effects in mesoscopic Nb-InAs-Nb junctions. He was a postdoctoral researcher at Yale University from 1999 to 2003, where he worked with Robert Schoelkopf on qubit structures built from superconducting circuits.

Career

In 2003, Lehnert joined JILA, a joint institute of the University of Colorado Boulder and the National Institute of Standards and Technology (NIST), as an Associate Fellow. He was promoted to JILA Fellow in 2007 and served as JILA Chair from 2022 to 2024. At JILA, Lehnert established a research group studying microwave quantum circuits, mesoscopic electronics, and quantum nanomechanics. His group performs measurements of electrical circuits and mechanical oscillators that reach quantum-limited sensitivity.

Research

Quantum electromechanics

Lehnert's research centers on building electrical and electromechanical devices that exhibit quantum behavior. A central question motivating his work is: "What is the largest and most tangible object that can be in two places at once?"

His group has also developed quantum-limited microwave amplifiers based on Josephson junctions, electro-optic transduction systems for connecting microwave and optical quantum information, and techniques for resolving individual phonon Fock states in mechanical oscillators.

Electro-optic transduction

Lehnert's group has developed methods for converting quantum information between microwave and optical frequencies using electro-optic transduction, a key technology for linking superconducting quantum computers into quantum networks. In 2022, his group demonstrated superconducting-qubit readout via low-backaction electro-optic transduction.

Awards and honors

Vannevar Bush Faculty Fellowship, United States Department of Defense (2020) Fellow, American Association for the Advancement of Science (2020) Kavli Fellow (2010, 2011) Department of Commerce Silver Medal Fellow, American Physical Society (2013)

Selected publications