Multiphoton quantum Rabi oscillations in ultrastrong cavity QED

Abstract

When an atom is strongly coupled to a cavity, the two systems can exchange a single photon through a coherent Rabi oscillation. This process enables precise quantum-state engineering and manipulation of atoms and photons in a cavity, which play a central role in quantum information and measurement. Recently, a new regime of cavity QED has been reached experimentally where the strength of the interaction between light and artificial atoms (qubits) becomes comparable to the atomic transition frequency or the resonance frequency of the cavity mode. Here we show that this regime can strongly modify the concept of vacuum Rabi oscillations, enabling multiphoton exchanges between the qubit and the resonator. We find that experimental state-of-the-art circuit-QED systems can undergo two-and three-photon vacuum Rabi oscillations. These anomalous Rabi oscillations can be exploited for the realization of efficient Fock-state sources of light and complex entangled states of qubits.

Circuit QED with qutrits: Coupling three or more atoms via virtual-photon exchange

“…This behavior indicates that the excitation of the 1st atom does not convert to a single atom (the 2nd atom or the 3rd atom) but the two atom jointly [47]. In the Appendix A, we also consider the four-atom case, and obtain similar results.…”

“…The coherent exchange interaction between multiple distant atoms via intermediate virtual states connected by the counterrotating interaction terms, can happen deterministically. Furthermore, the excitation number nonconserving process in the USC regime, including multi-photon Rabi oscillation [29,30], a single photon exciting multi-atom simultaneously [31], quantum nonlinear optics with atoms and virtual photons [32,33] have also been theoretically predicted. However, although a few experiments have recently achieved the USC regime in solidstate quantum system [34][35][36], quantum state manipulating and high-fidelity readout are still a tough challenge with existing technique, hindering the practical implementation of these coherent exchange interactions at present.…”

Holonomic quantum computation in the ultrastrong-coupling regime of circuit QED

“…In this case, the light-matter coupling strength is comparable to the cavity and the qubit frequencies [25], and in the dipolar approximation, it is described by the quantum Rabi model (QRM) [26,27]. Apart from the fundamental interest of the USC regime, it has been intensively studied for demonstrating novel quantum optics phenomena [28][29][30][31][32], implementing quantum information tasks [33,34], as well as fast quantum computation [35][36][37][38][39] within circuit quantum electrodynamics (QED) [40,41]. The latter provides a promising solid-state architecture for performing quantum computation due to the desirable properties of superconducting qubits, such as long coherence times, and most importantly, its controllability and scalability [42].…”

On-chip photonic transistor based on the spike synchronization in circuit QED

“…Input-output relations in the ultrastrong coupling regime makes the multiphoton transitions possible in three-level cascaded atomic system. Conversion of the virtual photons into real photons is succeeded by suitable designs of the Hamiltonians of the cascaded three-level atoms supporting the dark states [40][41][42][43]. In the presence of atomic transitions, Waveguide-QED systems reveal the importance of the correlation functions in describing the output cavity fields by relating the scattering theory and input output formalism of single and few photon transportation [44][45][46].…”

“…Interactions between the cavities is described by the hoping term corresponding to the atomic transitions in the lowest lying states of the artificial atom [39]. Input/output formalism is employed to describe the extracavity emission in terms of the quadrature operators in the absence of the input field [40][41][42][43]. Two frequency JT hamiltonian is described as the interaction of the bright and dark polaritons and diagonalized in terms of the upper and lower polariton components.…”