Title: “Exploring Propagating Quantum Microwave Fields: Parity Detection, Wigner Tomography and Heralded Cat States” Speaker: Andreas Wallraff, ETH Zurich, Switzerland
Abstract: Single-photon detection, challenging to realize in the microwave domain, is an essential component in many quantum optics experiments. In this talk I describe a quantum non-demolition (QND), single-shot parity detector for propagating microwave fields and characterize its performance using a true single-photon source. The parity detection is based on performing a cavity-assisted conditional phase gate between an incident photon and a superconducting three-level system. By reading out the state of the qutrit with single-shot resolution, we reach an external (internal) detection fidelity of 50% (71%) for individual photons . We illustrate the single-shot and QND character of our parity detector for multi-photon propagating microwave fields by heralding propagating cat states with average fidelity of 90 % from an incident coherent radiation field . In the same setup, we combine parity measurements with real-time displacement operations to perform complete Wigner tomography of propagating fields. We also demonstrate a mode reduction technique which enables joint parity measurements of photons encoded in multiple time bins. We expect multi-photon QND measurements of itinerant fields to develop into an important tool for the creation of future quantum communication networks in the microwave domain.
 J.-C. Besse et al., Phys. Rev. X 8, 021003 (2018)  J.-C. Besse et al., Quantum Devvice Lab (2019)
This research was performed in a collaboration between Jean-Claude Besse, Simone Gasparinetti, Michele C. Collodo, Theo Walter, Philipp Kurpiers, Marek Pechal, Ants Remm, Jonas Krause, Christopher Eichler, and Andreas Wallraff
Host: Vladimir Manucharyan Refreshments 1:30pm John S Toll Physics Bldg Room 1117