Kondo resonance of a microwave photon

Abstract

We emulate renormalization group models, such as the Spin-Boson Hamiltonian or the anisotropic Kondo model, from a quantum optics perspective by considering a superconducting device. The infra-red confinement involves photon excitations of two tunable transmission lines entangled to an artificial spin-1/2 particle or double-island charge qubit. Focusing on the propagation of microwave light, in the underdamped regime of the Spin-Boson model, we identify a many-body resonance where a photon is absorbed at the renormalized qubit frequency and reemitted forward in an elastic manner. We also show that asymptotic freedom of microwave light is reached by increasing the input signal amplitude at low temperatures which allows the disappearance of the transmission peak.

Anatomy of quantum critical wave functions in dissipative impurity problems

“…The Ohmic case (s = 1) can be realized in the context of waveguide QED [25][26][27][28] by coupling a superconducting qubit to a high-impedance transmission line consisting of a uniform Josephson junction array. In principle, a precise tailoring of the capacitance network could allow the sub-Ohmic regime to be realized as well.…”

Spontaneous emission of Schrödinger cats in a waveguide at ultrastrong coupling

“…The interaction fingerprints visible in the conductance of an infinite wire are indeed suppressed once the wire is smoothly connected to non-interacting leads [43,44]. The question of impedance matching in ultra-strongly coupled waveguides has not been addressed to our knowledge in the recent circuit-QED literature [14][15][16][17][18].…”

“…Long chains of Josephson junctions [10][11][12][13] constitute low-loss metamaterials for the propagation of microwave photons with characteristic impedance Z up to the order of R K , allowing to obtain values of the coupling constant a = Z R K of order one. This physical regime reveals anomalous scattering properties of photons [14][15][16][17][18] impinging on a non-trivial dressed vacuum [19]. This Letter aims at answering a seemingly simple question: is the radiation from a single emitter still described by a discrete photon in the ultrastrong coupling regime?…”

Microwave Characterization of Josephson Junction Arrays: Implementing a Low Loss Superinductance

“…Applications would include further suppression of offset charges in superconducting qubits [16], high Q and tunable lumped-element resonators, on-chip bias tees, and kinetic inductance particle detectors [28]. In addition, these arrays exhibit rich dynamics owing to many internal degrees of freedom, thus making them perfect candidates for the study of quantum many-body phenomena such as quantum impurity models [29,30], microwave photonics [31], and measurements of Bloch oscillations [32].…”