About this episode
Dr. Eli Levenson-Falk joins Sebastian Hassinger, host of The New Quantum Era to discuss his group’s recent advances in quantum measurement and control, focusing on a new protocol that enables measurements more sensitive than the Ramsey limit. Published in Nature Communications in April 2025, this work demonstrates a coherence stabilized technique that not only enhances sensitivity for quantum sensing but also promises improvements in calibration speed and robustness for superconducting quantum devices and other platforms. The conversation travels from Eli’s origins in physics, through the conceptual challenges of decoherence, to experimental storytelling, and highlights the collaborative foundation underpinning this breakthrough.Guest BioEli Levenson-Falk is an Associate Professor at USC. He earned his PhD at UC Berkeley with Professor Irfan Siddiqui, and now leads an experimental physics research group working with superconducting devices for quantum information science. Key TopicsThe new protocol described in the paper: “Beating the Ramsey Limit on Sensing with Deterministic Qubit Control." Beyond the Ramsey measurement: How the team’s technique stabilizes part of the quantum state for enhanced sensitivity—especially for energy level splittings—using continuous, slowly varying microwave control, applicable beyond just superconducting platforms. From playground swings to qubits: Eli explains how the physics of a playground swing inspired his passion for the field and lead to his understanding of the transmon qubit, and why analogies matter for intuition. Quantum decoherence and stabilization: How the method controls the “vector” of a quantum state on the Bloch sphere, dumping decoherence into directions that can be tracked or stabilized, markedly increasing measurement fidelity. Calibration and practical speedup: The protocol achieves greater measurement accuracy in less time or greater accuracy for a given time investment. This has implications for both calibration routines in quantum computers and for direct quantum measurements of fields (e.g., magnetic) or material properties. Applicability: While demonstrated on superconducting transmons, the protocol’s generality means it may bring improved sensitivity to a variety of platforms—though the greatest benefits will be seen where relaxation processes dominate decoherence over dephasing. Collaboration and credit: The protocol was the product of a collaborative effort with theorist Daniel Lidar and his group, also at USC. In Eli's group, Malida Hecht conducted the experiment.Why It MattersBy breaking through the Ramsey sensitivity limit, this work provides a new tool for both quantum device calibration and quantum sensing. It allows for more accurate and faster frequency calibrati
