SPICE Workshop on Quantum Functionalities of Nanomagnets, June 17th - 19th 2025
Gabriel Aeppli
Quantum nanomagnets rarely exist in isolation, and it is therefore important to ask how they interact with each other as well an overall “bath”. They can be thought of as quantum sensors and qubits, which are - in the simplest case - two-level systems, quantum analogs of classical bits assuming binary values ‘0' or ‘1'. For dense networks, they undergo quantum phase transitions, while when dilute, they are useful to the extent to which superpositions of ‘0’ and ‘1’ persist despite a noisy environment. We show that rare earth insulators can act as excellent model systems for examining networks of quantum nanomagnets in both dense and dilute limits. After reviewing the basic and long-standing concepts for non-interacting and interacting ions, we describe recent work which challenges the standard prescription to avoid decoherence of solid-state qubits via extreme dilution in ultrapure materials. In particular, we show that qubits with ultralong decoherence times in much denser systems can emerge because of rather than in spite of the interactions. The results are placed in the context of an architecture for solid state rare-earth based quantum processors, for which preliminary experiments are also presented.
References:
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Grimm, A. et al. PRX Quantum 2, 010312 (2021)
Dutta et al., Quantum Phase Transitions in Transverse Field Spin Models, Cambridge
University Press (2015)