What quantum computer to buy?

TL;DR

This paper proposes a practical framework for quantum computer procurement, emphasizing capability layers, institutional fit, and strategic flexibility over hardware selection.

Contribution

It introduces a procurement framework that distinguishes capability layers, compares main commercial platforms, and guides institutions on quantum acquisition strategies.

Findings

Most institutions should start with small, near-term capable systems.

Large on-premises quantum systems are justified only with clear mission and upgrade plans.

The framework helps compare platforms based on institutional needs and access models.

Abstract

The phrase ``buy a quantum computer'' hides several different procurement problems. An institution may be seeking cloud access for teaching, reserved capacity for research, a local instrument for hardware training, an optimization appliance, or a strategic installation that reshapes facilities, staffing, and budgets. Because these choices differ in purpose, operating burden, and useful lifetime, the decision should be framed as acquisition of \emph{quantum capability} rather than selection of a presumed hardware winner. This manuscript develops a practical procurement framework that distinguishes five capability layers, separates peer-reviewed results from commercial offerings, pricing anchors, and public roadmaps, and compares the main commercial platform families -- superconducting circuits, trapped ions, neutral atoms, quantum annealing, and photonics -- through the lens of institutional fit, access model, and refresh pressure. The main conclusion is that most institutions should begin with the smallest layer of capability that produces repeatable near-term value, builds internal expertise, and preserves strategic flexibility. Large on-premises systems are justified only when mission requirements, site readiness, staffing, governance, and upgrade paths are already clear.