IQIM Postdoctoral and Graduate Student Seminar

Friday May 3, 2019 3:00 PM

Single Photon Detectors, Parity Measurements and Heralded Cat States in the Microwave Domain

Speaker: Andreas Wallraff, Department of Physics, ETH Zurich, Switzerland
Location: East Bridge 114

Note: this is a special IQIM seminar beginning at 3 pm on May 3.

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) detector for propagating microwave photons and characterize its performance using a single-photon source. To this aim, we implemented 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) photon-detection fidelity of 50% (71%) [1]. By characterizing the coherence and average number of photons in the field reflected off the detector, we demonstrate the QND character of the detector. Similarly, we realize a single-shot QND parity detector for multi-photon propagating microwave fields. By exploiting the measurement back-action on an incident coherent field we herald propagating cat states of the radiation field with average fidelity of 90 % [2]. In the same setup, we combine parity measurements with a real-time displacement operations to perform complete Wigner tomography of propagating fields. We also demonstrate a mode reduction technique which enables parity measurements of the number 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 Device 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

Series IQIM Postdoctoral and Graduate Student Seminar Series

Contact: Marcia Brown at 626-395-4013