RQC Seminar

60th RQC Seminar

• Speaker

  Prof. Salvatore Savasta
  ( Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Universit`a di Messina, Italy )

• Date

  16:00-17:00, July 14th, 2023 (Friday)

• Venue

  Hybrid(ZOOM・ Wako Main Research 3F 345-347 Seminar Room)

• Title

  Probing the symmetry breaking of a light–matter system by an probe qubit

• Inquiries

  rqc_info[at]ml.riken.jp

Abstract
Hybrid quantum systems in the ultrastrong, and even more in the deep-strong coupling regimes can exhibit exotic physical phenomena [1]. In these nonperturbative regimes, a qubit–resonator system has an entangled quantum vacuum with a nonzero average photon number in the resonator, where the photons are virtual and cannot be directly detected. It has been shown theoretically that the vacuum field is able to induce the symmetry breaking of a dispersively coupled probe qubit [2]. We discuss a recent experimental observation of the parity symmetry breaking of an ancillary Xmon artificial atom induced by the field of a lumped element superconducting resonator deep-strongly coupled with a flux qubit [2]. This result opens a way to experimentally explore the novel quantum vacuum effects emerging in the deep-strong coupling regime.

[1] A. F. Kockum et al., Ultrastrong coupling between light and matter, Nat. Rev. Phys. 1, 19 (2019).
[2] L. Garziano et al., Vacuum-induced symmetry breaking in a superconducting quantum circuit, Phys. Rev. A 90,446
043817 (2014). [3] S.-P. Wang et al., Probing the symmetry breaking of a light–matter system by an ancillary qubit (arXiv preprint arXiv:2209.05747), under review.