RQC Seminar

18th RQC Seminar

• Speaker

  Prof. Stephen Hughes
  (Department of Physics, Queen’s University, Ontario, Canada ）

• Date

  16:00-17:00 (JST), November 10, 2022 (Thursday)

• Venue

  Hybrid (Zoom / 2F Large Conference Room, Admin. Headquarters Bldg. RIKEN Wako branch)

• Title

  Understanding waveguide-QED systems with time-delayed coherent feedback

• Inquiries

  rqc_info[at]ml.riken.jp

Abstract
Waveguide-QED allows one to efficiently couple quantum emitters (e.g., quantum dots and flux qubits) via confined waveguide modes and provides a platform for harnessing the quantum coherence of light. Introducing time-delayed coherent feedback is a proposed method for improving the figures of merit for various quantum protocols. However, quantum feedback manifests in a non-Markovian dynamic that is notoriously difficult to model using traditional approaches in quantum optics (such as Markovian master equations, which fail). I will discuss and exemplify two methods to address this problem [1-4]: (i) a new quantum trajectory discretized-waveguide model, and (ii) matrix product states. These two techniques are quite different in origin, but can be complimentary, and I will highlight their main advantages and disadvantages. Several applications will be shown, including the quantum dynamics and output spectra from 1, 2 and 3 qubit systems, and the roles of off-chip photon decay and qubit pure dephasing on population trapping.

[1] Sofia Arranz Regidor, Gavin Crowder, Howard Carmichael, Stephen Hughes. Modelling quantum light-matter interactions in waveguide-QED with retardation, nonlinear interactions and a time-delayed feedback: matrix product states versus a space-discretized waveguide model, Phys. Rev. Research, 3, 023030 (2021)
[2] Gavin Crowder, Lora Ramunno, Stephen Hughes, Quantum Trajectory Theory and Simulations of Nonlinear Spectra and Multi-Photon Effects in Waveguide-QED Systems with a Time-Delayed Coherent Feedback, Phys. Rev. A 106, 013714 (2022)
[3] Sofia Arranz Regidor, Stephen Hughes, Cavity-like strong coupling in macroscopic waveguide QED using three coupled qubits in the deep non-Markovian regime, Phys. Rev. A 104, L031701 (2021)
[4] Sofia Arranz Regidor, Stephen Hughes, Probing dressed states and quantum nonlinearities in a strongly coupled three-qubit waveguide system under optical pumping, e-print: arXiv:2209.10403 (2022)