Quantum computing uses qubits instead of ordinary bits to tackle a narrow set of problems, such as simulating molecules, that are very hard for classical computers. It is real research, but it is not a faster everyday computer: IBM says quantum advantage, a clear practical win over all known classical methods, had not yet been established when its overview was published. The main practical effect for most people is indirect, through the shift to new encryption standards that protect data against future quantum machines.
Bits and qubits
According to IBM, classical computers store information in bits that are either 0 or 1. Qubits can hold 0, 1 or a weighted combination of both, a property called superposition. Two qubits span four possible two-bit strings, three span eight, and the range grows exponentially from there. Measuring a qubit collapses it to a definite 0 or 1, so results are probabilistic. Qubits can also be entangled, meaning their states are correlated, and quantum algorithms use interference to reinforce correct answers and cancel wrong ones.
That is why the common line that a quantum computer “tries every answer at once” is misleading. The machine does not read out every possibility; algorithms are designed so that the right answer becomes the most likely result.
Why quantum computers are hard to build
- Decoherence. IBM explains that a quantum state collapses into an ordinary one through measurement or interference from the environment, so engineers work to minimise it.
- Errors. Because qubits are error-prone, error correction spreads one unit of quantum information across more physical qubits than would otherwise be needed. IBM reported a 2024 error-correcting code about ten times more efficient than earlier methods.
- Hardware. IBM lists several qubit types. Superconducting qubits are fast and finely controlled but need very low temperatures, trapped ions have long coherence times and high-fidelity measurement but are slower, quantum dots are semiconductor-based and may suit existing chip technology, and photons are used for quantum communication.
Utility, advantage and IBM’s targets
IBM separates two milestones. Quantum utility means reliable results on problems beyond brute-force classical simulation, which IBM says it first showed in 2023. Quantum advantage means beating every known classical method, and IBM says it expects the first quantum advantages by late 2026, if the quantum and high-performance computing communities collaborate. That is a company projection, not an accomplished result. IBM’s stated roadmap targets a system with 200 logical qubits running 100 million gates by 2029, and 2,000 logical qubits running 1 billion gates by 2033.
What quantum computers may be useful for
IBM points to simulating molecular behaviour, which could speed up work on drugs, chemicals and catalysts, and to semiconductor design, energy infrastructure and financial modelling. It adds that quantum algorithms may offer speed-ups for some machine learning problems. These are areas of research, not products you can buy, and IBM does not expect quantum computers to outperform classical machines on most tasks.
Why encryption is the part that affects everyone
NIST explains that many current encryption methods depend on the difficulty of factoring large numbers, and that a sufficiently capable quantum computer could make that factoring far faster. IBM notes that Shor’s algorithm (1994) showed quantum computers could potentially break widely used cryptography. A machine that can do it does not exist today. NIST says expert estimates for when one might appear range from a few years to a few decades, and some think it could come in under ten years.
The concern is “harvest now, decrypt later”: adversaries can capture encrypted data today and store it until a quantum computer can read it. That matters most for information that must stay secret for many years.
Post-quantum standards and timelines
NIST began its post-quantum cryptography effort in 2015, assessed 82 algorithms from 25 countries, and released its first three finalized post-quantum standards in August 2024. Of the four algorithms first selected, three are based on structured lattices and one on hash functions. NIST notes that full adoption of a new standard has historically taken 10 to 20 years, which is why it urges moving as soon as possible.
The UK’s National Cyber Security Centre (NCSC) has set milestones for organisations: by 2028, define migration goals, complete a discovery exercise to find what depends on cryptography and build a plan; by 2031, finish the highest-priority migration for the most critical assets; by 2035, complete migration of all systems, services and products. The NCSC says small organisations using commodity IT should largely get this through supplier updates, while custom software follows the same timetable as larger organisations.
What ordinary users should do
- Keep operating systems, browsers and apps updated, since most migration will arrive through vendor updates.
- Ignore claims that a quantum computer is about to replace a laptop or a gaming PC.
- Focus first on basics that stop real attacks today: unique passwords and two-factor authentication. See how to protect yourself online and how to check whether a password was leaked.
- Businesses holding long-lived secrets should ask suppliers about post-quantum plans.
For how cloud providers fit into this picture, see AWS vs Azure vs Google Cloud.
Bottom line
Quantum computing is a serious research field with narrow expected uses. The practical action is on the security side, where standards already exist and migration is under way. Treat any claim of an imminent breakthrough with caution and look for the source, the date and whether it is a result or a target.
Sources
- IBM, What is quantum computing?
- NIST, What is post-quantum cryptography?
- NCSC, Timelines for migration to post-quantum cryptography
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