Curator's Take
This research brilliantly demonstrates how superconducting quantum processors can serve as precision laboratories for exploring fundamental quantum mechanics, implementing classic wave-particle duality experiments with unprecedented control over measurement strength. The team's ability to continuously tune between wave-like and particle-like behavior while simultaneously tracking entanglement breakdown and information leakage provides new quantitative insights into complementarity that weren't possible with traditional optical setups. Particularly intriguing is their observation of the quantum Zeno effect during continuous monitoring, where the act of measurement itself alters the system's evolution in measurable ways. This work showcases how today's quantum hardware has evolved beyond just computation to become powerful tools for probing the deepest mysteries of quantum mechanics with remarkable precision.
— Mark Eatherly
Summary
Wave--particle duality demonstrates the peculiar nature of quantum mechanics. In which-way experiments, depending on the measurement scheme, a particle exhibits either wave-like or particle-like properties, as summarized by Bohr's principle of complementarity. In this work, we implement Mach-Zehnder (MZ) interferometry on a two-dimensional (2D) superconducting quantum processor. With precise control of the which-way measurement strength, we demonstrate the transition of a photon from wave-like to particle-like behavior. Furthermore, by performing quantum state tomography on two qubits located in the two paths, we demonstrate that which-way measurements break the entanglement and coherence between the two paths and cause information leakage from the quantum system to the environment. To capture this behavior quantitatively, we derive complementarity relations between the entropy and the fringe visibility. By applying a continuous which-way measurement during the evolution, we also observe the quantum Zeno effect that partially obstructs the interferometer path, giving rise to nonmonotonic behavior of purity and von Neumann entropy. Our experiments provide a detailed characterization of the full interferometer dynamics, reveal the relation between wave--particle duality and quantum information, and demonstrate the potential of superconducting quantum processors for testing quantum foundations under high precision and controllability.