Coupling single molecule magnets to quantum circuits

TL;DR

This paper theoretically explores the potential of single molecule magnets (SMMs) to achieve strong quantum coupling with circuits, enabling their use in quantum information storage and processing.

Contribution

It demonstrates the feasibility of strong and ultrastrong coupling regimes between SMMs and quantum circuits, and discusses optimal molecular candidates and practical integration methods.

Findings

Strong and ultrastrong coupling regimes are achievable with SMMs and superconducting circuits.

SMMs have coherence times of microseconds suitable for quantum information tasks.

Practical methods for integrating SMMs on chips are discussed.

Abstract

In this work we study theoretically the coupling of single molecule magnets (SMMs) to a variety of quantum circuits, including microwave resonators with and without constrictions and flux qubits. The main results of this study is that it is possible to achieve strong and ultrastrong coupling regimes between SMM crystals and the superconducting circuit, with strong hints that such a coupling could also be reached for individual molecules close to constrictions. Building on the resulting coupling strengths and the typical coherence times of these molecules (of the order of microseconds), we conclude that SMMs can be used for coherent storage and manipulation of quantum information, either in the context of quantum computing or in quantum simulations. Throughout the work we also discuss in detail the family of molecules that are most suitable for such operations, based not only on the coupling strength, but also on the typical energy gaps and the simplicity with which they can be tuned and oriented. Finally, we also discuss practical advantages of SMMs, such as the possibility to fabricate the SMMs ensembles on the chip through the deposition of small droplets.