CNAM COLLOQUIUM: Andreas Wallraff, ETH Zurich, Switzerland

Thu, Sep 5, 2019 2:00 pm - 3:30 pm
Room 1201; John S Toll Physics Bldg.


Title: “Exploring Propagating Quantum Microwave Fields: Parity Detection, Wigner Tomography and Heralded Cat States”
Speaker: Andreas Wallraff, ETH Zurich, Switzerland

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 [1]. 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 [2]. 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.

[1] J.-C. Besse et al., Phys. Rev. X 8, 021003 (2018)
[2] 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

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