Speaker: Adam Miranowicz, Adam Mickiewicz University (Poznań) and RIKEN (Wako)
Experimental demonstrations and control of strong coupling of light and matter has lead to various applications for lasers, quantum sensing, and quantum information processing since 1980s. In my talk, I will review  recent theoretical and experimental progress in the ultrastrong coupling (USC) and deep-strong coupling (DSC) regimes of light and matter, which are characterized by the coupling strengths comparable to their transition frequencies. In the last few years, the USC regime has been experimentally achieved in a wide range of different systems with very different spectral ranges. These systems include: superconducting quantum circuits, intersubband polaritons, Landau polaritons, organic molecules, magnetic systems, nano-plasmonics, and optomechanical systems. Emerging applications of the USC and DSC regimes are focused on quantum technologies and quantum information processing.
The ground state of light-matter systems in the DSC regime is a Schroedinger-cat state, where virtual photons are entangled with virtual excitations of the matter. A recent experimental demonstration of the cat state can be considered as the discovery of a new stable molecular state in which light and matter are hybridized . The USC and DSC regimes can be effectively reached by squeezing a cavity field as proposed in  and experimentally demonstrated in . This type of light squeezing can also be used to increase spin squeezing , which is of paramount importance for quantum metrology. The USC and DSC regimes enable also generating giant Schrodinger cat states of real photons and atomic real excitations by applying squeezing [6,7]. The USC methods have inspired developing a promising technique to beat the 3 dB limit for intracavity squeezing and, thus, to effectively apply it for nondemolition qubit experiments .
Co-authors: Franco Nori, Wei Qin, Ye-Hong Chen, Anton Kockum, Simone De Liberato, Salvatore Savasta
 A. F. Kockum, A. Miranowicz, S. De Liberato, S. Savasta, and F. Nori: Ultrastrong coupling between light and matter, Nat. Rev. Phys. 1, 19 (2019).
 F. Yoshihara, T. Fuse, S. Ashhab, K. Kakuyanagi, S. Saito, and K. Semba, Superconducting qubit-oscillator circuit beyond the ultrastrong-coupling regime, Nat. Phys. 13, 44 (2017).
 W. Qin, A. Miranowicz, P.-B. Li, X.-Y. Lu, J.-Q. You, and F. Nori: Exponentially Enhanced Light-Matter Interaction, Cooperativities, and Steady-State Entanglement Using Parametric Amplification, Phys. Rev. Lett. 120, 093601 (2018).
 S. C. Burd, R. Srinivas, H. M. Knaack, W. Ge, A. C. Wilson, D. J. Wineland, D. Leibfried, J. J. Bollinger, D. T. C. Allcock, and D. H. Slichter, Quantum amplification of boson-mediated interactions, Nat. Phys. 17, 898 (2021).
 W. Qin, Y.-H. Chen, X. Wang, A. Miranowicz, and F. Nori: Strong Spin Squeezing Induced by Weak Squeezing of Light inside a Cavity, Nanophotonics 9, 4853 (2020).
 W. Qin, A. Miranowicz, H. Jing, and F. Nori: Generating long-lived macroscopically distinct superposition states in atomic ensembles, Phys. Rev. Lett. 127, 093602 (2021).
 Y.-H. Chen, W. Qin, X. Wang, A. Miranowicz, F. Nori: Shortcuts to Adiabaticity for the Quantum Rabi Model: Efficient Generation of Giant Entangled Cat States via Parametric Amplification, Phys. Rev. Lett. 126, 023602 (2021).
 W. Qin, A. Miranowicz, and F. Nori: Beating the 3 dB Limit for Intracavity Squeezing and Its Application to Nondemolition Qubit Readout, Phys. Rev. Lett. 129, 123602 (2022).
Deadline February 26 2023 for Bronze and Silver KCIK Awards approaching!