The use of computational technologies by States for both offensive and defensive purposes has become a central feature of contemporary international relations. Quantum information technologies (QIT) are expected to influence these dynamics by transforming State capabilities in cybersecurity, encryption, and information analysis. This chapter examines how the strategic use of QIT by States intersects with the principles and rules of public international law. The analysis situates QIT within the jurisprudence of sovereignty, jurisdiction, and the use of force, drawing on the Tallinn Manual and related sources of international law. It also explores how game theory may illuminate patterns of quantum cooperation and competition among States in both peacetime and conflict.