Quantum science and technology: tutorial

The United Nations Year of Quantum Science and Technology 2025 featured a wide range of events aimed at conveying to a broad audience the fascination brought to us by the second quantum revolution and its anticipated societal impact. This paper is based on GL’s plenary lecture at the Photonics North Conference, held in Ottawa in May 2025, and is largely intended for readers without specialized training in quantum physics. The presentation focuses on three central themes. First, it highlights the distinctive role of measurement in quantum mechanics, emphasizing how quantum measurements fundamentally differ from their classical counterparts. Second, it illustrates the importance of noncommutativity of objects A and B residing in a higher-dimensional space, exemplified by the fact that, in general, A B ≠ B A . While noncommutativity is not exclusive to quantum theory, it does play a central role in quantum dynamics and information processing. Third, the paper discusses how these foundational concepts underpin emerging applications, with particular attention to quantum sensing and quantum computing.