“Rydberg Atoms in Semiconductors” as part of “Quantum Frontiers with Rydberg atoms”

Rydberg states have become essential in neutral-atom quantum computing as a way of coupling otherwise weakly interacting qubits. Storing information in relatively stable, compact ground states while using large excited states as temporary interaction resources is one of the key lessons that atomic Rydberg physics offers to other quantum platforms. Semiconductor spin qubits provide a very different route to quantum information processing. Their appeal lies in their small footprint, long spin coherence, compatibility with mature fabrication techniques, and potential integration with classical electronics. However, semiconductor architectures also face challenges: interactions are often short-ranged, individual addressing and wiring become increasingly complex at scale, and devices are sensitive to disorder, interfaces, strain, and charge noise. These difficulties motivate the search for other mechanisms that can enhance coupling or provide new readout and control channels without sacrificing advantages. Dopant-bound Rydberg states offer one such possibility. Shallow donors and acceptors in semiconductors possess hydrogenic excited states whose spatial extent and electric-dipole moments are much larger than those of their ground states. These states can be accessed by THz radiation and have already been studied extensively through impurity spectroscopy and, more recently, coherent-control experiments. In analogy with neutral-atom platforms, they need not serve as long-lived qubits themselves. Rather, they may act as auxiliary states that temporarily enhance interactions or provide new qubit control and readout pathways. In this chapter, we review dopant-bound Rydberg states from this perspective.