Jahn-Teller instability in dissipative quantum systems

Abstract

We consider the steady states of a harmonic oscillator coupled so strongly to a two-level system (a qubit) that the rotating wave approximation cannot be made. The Hamiltonian version of this model is known as the E ⊗ β Jahn-Teller model. The semiclassical version of this system exhibits a fixed-point bifurcation, which in the quantum model leads to a ground state with substantial entanglement between the oscillator and the qubit. We show that the dynamical bifurcation survives in a dissipative quantum description of the system, amidst an even richer bifurcation structure. We propose an experimental implementation of this model based on a superconducting cavity: a superconducting junction in the central conductor of a coplanar waveguide.

Two-frequency Jahn-Teller systems in circuit QED

“…This implies, according to the relations in Eq. (23), that λ 1 > λ 2 ,J . Therefore, in the experiment the flux qubit has to be ultrastrongly coupled to one resonator and strongly coupled to the other resonator, while the resonator-resonator coupling must be close to the qubitresonator strong coupling.…”

“…The coupling strength between the * omustecap@ku.edu.tr cavities can be utilized to alter the frequency ratio of the modes to simulate different frequency ratios encountered in different JT impurities in solids [26]. In addition to more realistic simulations of JT systems, establishing a link between multimode JT models and coupled circuit QED systems could enable the exploration of many-body physics, such as quantum chaos [13,14], quantum phase transitions [15], and quantum entanglement in JT systems [23,27], by using coupled cavity arrays.…”

“…The system consists of two coupled lumped-element LC resonators interacting with a two-level artificial atom, a superconducting flux qubit. In the ultrastrong coupling regime the rotating-wave approximation is not valid, so that the qubit-resonator coupling is of JT type rather than Jaynes-Cummings type [21,23], allowing strongly coupled multifrequency JT systems to be simulated. The switchable ultrastrong coupling architecture can also be applied if a tunable coupling strength between the resonators and the flux qubit is desired [33].…”

“…Circuit QED [17] offers the possibility of operating in the ultrastrong coupling regime [18][19][20][21][22][23] for efficient JT and related spin-boson or Dicke model simulations. Photonic waveguide arrays are alternatively proposed [24] for reaching the deep ultrastrong coupling regime (DSC) [25] of JT-type light-matter interaction.…”

Quantum entanglement between a nonlinear nanomechanical resonator and a microwave field

“…We do this by numerically computing the quantum steady correspondence principle has proven to be the case for other dissipative nonlinear quantum systems [31][32][33][34][35][36].…”