Cavity polariton in a quasi-lattice of qubits and its selective radiation

TL;DR

This paper investigates how a chain of inhomogeneously coupled qubits in a circuit QED system forms a quasi-lattice with unique polariton modes, leading to selective radiation and uneven decay rates influenced by lattice deformation.

Contribution

It introduces the concept of a quasi-lattice formed by inhomogeneously coupled qubits and analyzes its polariton modes and radiation properties, highlighting effects of lattice deformation.

Findings

Polariton transition probability is affected by lattice deformation.

Uneven decay rates in the quasi-lattice are linked to superradiance effects.

Selective spontaneous radiation spectrum can be achieved through lattice deformation.

Abstract

In a circuit quantum eletrodynamic system, a chain of N qubits inhomogeneously coupled to a cavity field forms a mesoscopic quasi-lattice, which is characterized by its degree of deformation from a normal lattice. This deformation is a function of the relative spacing, that is the ratio of the qubit spacing to the cavity wavelength. A polariton mode arise in the quasi-lattice as the dressed mode of the lattice excitation by the cavity photon. We show that the transition probability of the polariton mode is either enhanced or decreased compared to that of a single qubit by the deformation, giving a selective spontaneous radiation spectrum. Further, unlike a microscopic lattice with large-N limit and nearly zero relative spacing, the polariton in the quasi-lattice has uneven decay rate over the relative spacing. We show that this unevenness coincides with the cooperative emission effect expected from the superradiance model, where alternative excitations in the qubits of the lattice result in maximum decay.