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

Abstract

We present a model to describe a generic circuit QED system which consists of multiple artificial three-level atoms, namely qutrits, strongly coupled to a cavity mode. When the state transition of the atoms disobey the selection rules the process that does not conserve the number of excitations can happen determinatively. Therefore, we can realize coherent exchange interaction among three or more atoms mediated by the exchange of virtual photons. In addition, we generalize the one cavity mode mediated interactions to the multi-cavity situation, providing a method to entangle atoms located in different cavities. Using experimental feasible parameters, we investigate the dynamics of the model including three cyclic-transition three-level atoms, for which the two lowest-energy levels can be treated as qubits. Hence, we have found that two qubits can jointly exchange excitation with one qubit in a coherent and reversible way. In the whole process, the population in the third level of atoms is negligible and the cavity photon number is far smaller than 1. Our model provides a feasible scheme to couple multiple distant atoms together, which may find applications in quantum information processing.

One- and three-photon dynamical Casimir effects using a nonstationary cyclic qutrit

“…We consider a single cavity mode of constant frequency ω that interacts with a qutrit in the cyclic configuration [28,[53][54][55][56], so that all the atomic transitions are allowed via one-photon transitions. The Hamiltonian readŝ…”

“…Here we explore theoretically the prospects of implementing nontraditional versions of cavity DCE using 3level atoms (qutrits) in the cyclic (also known as ∆-) configuration subject to parametric modulation. In this case all the transitions between the atomic levels can occur simultaneously via the cavity field [53][54][55][56], so the total number of excitations is not conserved even upon neglecting the counter-rotating terms (rotating wave approximation). Although prohibited by the electric-dipole selection rules for usual atoms, the ∆-configuration can be implemented for certain artificial atoms in circuit QED [28] by breaking the inversion symmetry of the potential energy.…”

Dynamical Casimir effect via four- and five-photon transitions using a strongly detuned atom

“…Moreover, when the cavity field is coherently coupled to other quantum subsystems (e. g., multilevels atom or harmonic oscillators [15][16][17]) photons can be generated (or annihilated [18,19]) for several other modulation frequencies at the cost of entangling the subsystems. In particular, a dispersive cyclic qutrit [20][21][22][23][24] * Electronic address: adodonov@fis.unb.br with time-dependent energy splittings permits the generation of photons from vacuum for η ≈ ν and η ≈ 3ν via effective one-and three-photons transitions, respectively [25].…”

Single-photon-induced two qubits excitation without breaking parity symmetry

“…Such a regime has been experimentally reached in a variety of solid systems by replacing natural atoms with artificial atoms [5][6][7][8][9][10][11][12][13], giving rise to the rapidly growing of the circuit QED. In this system, superconducting qubits even can strongly interact with a single-mode resonator with a coupling rate reaching the order of 0.1 of the field frequency, i.e., the ultrastrong coupling regime [14][15][16][17][18][19]. Moreover, much higher values of coupling rate have been reached in the experiments in recent years [20,21].…”