Dispersive readout of molecular spin qudits

TL;DR

This paper explores how magnetic molecules with multiple spin states can be read out using cavity quantum electrodynamics, enabling non-demolition measurements of molecular spin qudits with potential applications in quantum information processing.

Contribution

It provides a theoretical framework for dispersive readout of molecular spin qudits, incorporating magnetic anisotropy and proposing experimental protocols for non-demolition measurement.

Findings

Cavity transmission uniquely determines the spin state of the qudits.

Magnetic anisotropy enables addressable spin transitions.

Simulations demonstrate feasibility with realistic molecular models.

Abstract

We study the physics of a magnetic molecule described by a "giant" spin with multiple ($d > 2$) spin states interacting with the quantized cavity field produced by a superconducting resonator. By means of the input-output formalism, we derive an expression for the output modes in the dispersive regime of operation. It includes the effect of magnetic anisotropy, which makes different spin transitions addressable. We find that the measurement of the cavity transmission allows to uniquely determine the spin state of the qudits. We discuss, from an effective Hamiltonian perspective, the conditions under which the qudit read-out is a non-demolition measurement and consider possible experimental protocols to perform it. Finally, we illustrate our results with simulations performed for realistic models of existing magnetic molecules.