Quantum Risk Explained: What, When, How? Summary - Quantum computing is moving from theory toward early practical use, with direct implications for encryption, authentication, and long-term data confidentiality. - The primary risk is the eventual emergence of cryptographically relevant quantum computers (CRQCs), which would break today’s public-key cryptography and undermine encryption, digital identity, and software trust at scale. - Quantum risk is already present: “harvest now, decrypt later” activity exposes long-lived sensitive data today, regardless of when CRQCs ultimately arrive. - Regulatory mandates and procurement standards are accelerating post-quantum cryptography (PQC) adoption, making quantum readiness a multi-year compliance and resilience priority. - Organizations that delay preparation beyond 2026 are likely to face compressed migration timelines, higher transition costs, and increased operational disruption. Quantum Computing Explained Quantum computing applies principles of physics to solve certain complex problems far more efficiently than classical computers. Its security relevance lies primarily in cryptanalysis and optimization: A sufficiently powerful quantum computer will reduce the calculations required to protect today's public-key encryption from thousands of years to hours or less. Researchers have used the term “Q-Day” to refer to the hypothetical point at which quantum computers will be powerful enough to break encryption. Quantum computing is now moving from theory toward early practical use, bringing “Q-Day” closer to reality. Industry estimates suggest quantum computing alone could generate up to $1.3 trillion in value by 2035. Major cloud providers, including IBM, Google, and Microsoft, are expanding their quantum services, while specialised firms such as Quantinuum and PsiQuantum continue to improve system stability and error correction. While these advances are not yet transformative, they are consistent with the early stages of commercial adoption. Alongside its potential benefits across finance, pharmaceuticals, defense, and other sectors, quantum computing introduces four key security risks. Risk 1: Breaking Public-Key Encryption The most