  The purpose of this paper is to evaluate the possibility of constructing a
large-scale storage-ring-type ion-trap system capable of storing, cooling, and
controlling a large number of ions as a platform for scalable quantum computing
(QC) and quantum simulations (QS). In such a trap, the ions form a crystalline
beam moving along a circular path with a constant velocity determined by the
frequency and intensity of the cooling lasers. In this paper we consider a
large leap forward in terms of the number of qubits, from fewer than 100
available in state-of-the-art linear ion-trap devices today to an order of 105
crystallized ions in the storage-ring setup. This new trap design unifies two
different concepts: the storage rings of charged particles and the linear ion
traps used for QC and mass spectrometry. In this paper we use the language of
particle accelerators to discuss the ion state and dynamics. We outline the
differences between the above concepts, analyze challenges of the large ring
with a revolving beam of ions, and propose goals for the research and
development required to enable future quantum computers with 1000 times more
qubits than available today. The challenge of creating such a large-scale
quantum system while maintaining the necessary coherence of the qubits and the
high fidelity of quantum logic operations is significant. Performing analog
quantum simulations may be an achievable initial goal for such a device.
Quantum simulations of complex quantum systems will move forward both the
fundamental science and the applied research. Nuclear and particle physics,
many-body quantum systems, lattice gauge theories, and nuclear structure
calculations are just a few examples in which a large-scale quantum simulation
system would be a very powerful tool to move forward our understanding of
nature.
