RQC Seminar

257th RQC Seminar

• Speaker

  Prof. Adrian Lupascu
  ( University of Waterloo, Canada )

• Date

  13:30-14:30, (1:30 p.m.-5:30 p.m.) Thursday, February 19, 2026

• Venue

  Hybrid( Zoom,
  Large Meeting Room, 2F, Welfare and Conference Building, Wako Campus / 和光地区 統合支援施設2階 大会議室 (C61))

• Title

  Quantum Simulation Using a Waveguide Quantum Electrodynamics Platform Based on Superconducting Flux Qubits

• Inquiries

  yasunobu.nakamura[at]riken.jp

Abstract
We present our recent work on the demonstration of switchable coupling between a two-level system and a quantum field. The two-level system is implemented as a superconducting flux quantum bit, with a transition frequency in the GHz range, and the field is the electromagnetic field in a superconducting waveguide. The coupling is realized based on a magnetic field controlled superconducting device. The normalized coupling strength, defined as the ratio of the qubit emission rate to the qubit frequency, ranges from effectively zero (with an experimental bound of 6 x 10^-5) to the ultrastrong coupling regime (2 x 10^-2). We performed a detailed characterization of the system using microwave scattering experiments, which allows for the extraction of the two-level system transition frequency, coupling to the field, and decoherence, relative to the system control parameters.
Our waveguide quantum electrodynamics platform provides a building block for quantum simulation. We discuss primarily two directions. The first direction is the simulation of the spin boson model, where our platform has the advantage of large achievable coupling strength and the ability to switch the coupling very fast. The second direction is the implementation of entanglement harvesting, an experiment where entanglement in a quantum field can be measured using two qubits coupled to the field.