Quantum Computing: A Reality Check

Quantum computing generates headlines every few months, and most of them are accurate about a narrow thing and misleading about the broad one. The narrow thing is real: researchers keep demonstrating better qubits, better error correction and larger systems. The broad claim, that useful quantum computers are imminent, is not supported by what has been shown.

What has been demonstrated

• Physical qubit counts in the hundreds to low thousands across several hardware approaches.
• Error-correction experiments in which logical qubits outperform their physical components.
• Specific computational tasks where quantum devices outpace classical simulation, with limited practical use.

What has not

• Fault-tolerant machines with enough logical qubits for commercially valuable chemistry or optimisation.
• A clear, reproducible quantum advantage on a problem a business would pay to solve.
• Stable cost and timeline estimates that survive contact with engineering reality.

The cryptography clock

Data encrypted today can be stored and decrypted later if a sufficiently powerful quantum computer arrives. For data with long confidentiality lifetimes, such as government, health and financial records, the migration to post-quantum algorithms is a present-tense obligation. Standards bodies have published post-quantum algorithms, and migration programmes in critical sectors are under way. This is the quantum story with a deadline.

Why now

• Error-corrected logical qubit demonstrations are accelerating.
• Governments treat quantum as strategic infrastructure with dedicated funding.
• Post-quantum standards are published and migration timelines are being set.