Measurement of the faintest signals has become a vital part of disciplines as diverse as medicine, astronomy, interplanetary communications and intelligence gathering. While our curiosity has drive us to probe ever-weaker signals in Nature, the framework and philosophy for our measurement tools has remained largely unchanged for centuries, entrenched in a classical interpretation of our world – which we know to be incomplete. in this talk I will present a holistic approach to sensing which combines quantum mechanics, information theory and measurement. We will explore the fundamental differences between a classical and quantum understanding of weak signals. With a quantum representation of Nature, applying a quantum information theoretic analysis can inspire paradigmatic shifts in the design of measurement tools. We will explore several examples where a quantum theoretic approach to sensing has resulted in radical improvements