How to read a "quantum breakthrough" headline
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Quantum computing produces a steady stream of exciting headlines: "breakthrough", "supremacy", "years ahead of schedule", "solves in minutes what would take a supercomputer millennia". Some of them describe real progress. Many describe real progress wrapped in a lot of marketing. Here are five questions that separate the two, with real examples of each.
1. Was the problem useful?
The most common trick isn't dishonesty; it's choosing the right test. Many "quantum advantage" results use problems designed to be easy for quantum hardware and hard for ordinary computers, whether or not anyone needs them solved.
The best-known example is from 2019, when Google announced that its 53-qubit Sycamore processor had performed a task in about 200 seconds that would take the world's best supercomputer around 10,000 years. The task was sampling the output of random quantum circuits. It was a genuine scientific milestone, the first time a quantum machine had clearly done something very hard to simulate classically. But the task itself had no practical use. It was chosen because it's hard to fake.
Ask: would anyone pay to have this problem solved, if quantum computers didn't exist?
2. Was the comparison fair?
A quantum speed-up is only as impressive as the classical method it's compared against. If the comparison uses an old or naive approach, the gap can look enormous and then vanish.
The Sycamore result is a good example here too. Within days, IBM argued that a better classical method could do the same task in about two and a half days rather than 10,000 years. Over the following years, researchers found classical methods that narrowed the gap much further.
Something similar happened in 2018, when an 18-year-old student named Ewin Tang showed that a celebrated quantum algorithm for recommendation systems, the kind of maths behind "you might also like", could be matched by a cleverly designed classical algorithm. The quantum advantage everyone had assumed simply wasn't there.
Ordinary computing isn't standing still. Every claimed quantum advantage invites classical experts to try to beat it, and sometimes they do.
3. Physical qubits or logical qubits?
Qubit counts make great headlines, so they're usually the biggest number in the press release. But as Why qubits are so fragile explains, a raw physical qubit and an error-corrected logical qubit are very different things. Useful algorithms need logical qubits, and each one can take hundreds or more physical qubits to build.
Qubit count also isn't the only measure of quality. Two machines with the same number of qubits can differ hugely in error rates, in how long their qubits last and in which qubits can talk to each other. A smaller, cleaner machine can outperform a bigger, noisier one.
Ask: how many of these qubits are error-corrected, and what are the error rates?
4. Has anyone independent checked it?
Big claims deserve independent confirmation. In quantum computing, checking is genuinely hard: if a quantum computer does something no classical computer can, how do you verify the answer? Researchers have developed clever statistical tests for this, but they rely on assumptions that other experts need to scrutinise.
Look for whether other research groups have reproduced the result or at least reviewed it, and whether critics have responded. A result that has survived a year of expert pushback is worth much more than one announced last Tuesday.
5. Paper or press release?
Companies in this field compete for investment and talent, so they have every reason to present their results generously. That doesn't make their claims false, but it does mean the press release and the underlying research paper can tell slightly different stories.
If there's a paper, check whether it's published in a peer-reviewed journal or posted as a preprint, which is normal and useful but hasn't been reviewed yet. Read the abstract and the conclusion: researchers are usually more careful with their own words than marketing teams are.
Words to watch
- "Could", "may", "up to", "potential": a statement about the future, not something that has happened.
- "Quantum-inspired": runs on ordinary computers. It may be useful, but it isn't quantum computing.
- "Quantum-safe" or "quantum-resistant": about new encryption that resists quantum attack. A different field from building quantum computers.
- "Supremacy" or "advantage": usually means beating classical computers on a specific, often artificial, task.
- "Millions of years": often based on a particular classical method that may later be improved.
Let's read one together
Here's an invented headline, typical of the genre: "Startup unveils 1,000-qubit processor that could crack today's encryption within years."
Useful problem? The headline doesn't mention solving anything; it announces hardware. That's fine, but it's not evidence of capability yet.
Fair comparison? There's no comparison at all. The encryption claim is a prediction, flagged by the word "could".
Physical or logical? Almost certainly 1,000 physical qubits. Breaking encryption is estimated to need over a thousand logical qubits, so this is likely hundreds of times short.
Independent check? A brand-new announcement hasn't had time for one. Look for error rates and benchmarks published by others over the coming months.
Paper or press release? A product launch is almost always a press release first. See if a technical paper follows.
Verdict: possibly real engineering progress, worth noting, but the encryption angle is speculation attached to a hardware announcement.
Hype cuts both ways
None of this means quantum computing is all hype. The field has made steady, real progress: error rates have fallen, error correction has started to work as theory predicts, and estimates for useful machines keep coming down. Being sceptical of individual headlines is compatible with taking the overall direction seriously. That's also why security teams prepare now rather than waiting for a headline they can trust.
- Check whether the problem is useful and whether the classical comparison is the best available.
- Ask about logical qubits and error rates, not just qubit counts.
- Give more weight to results that independent experts have reviewed and reproduced.
Sources and further reading
Tags show what kind of source each one is. A standard or government guidance is an official document; a peer-reviewed paper has been checked by other experts; a preprint has not been peer-reviewed yet; an experiment reports a real-world demonstration; a company announcement is the company's own account. Dates and figures were checked against these sources on 11 October 2026. Spotted an error? Email hello@plainquantum.com and it will be corrected, with a note.
- ExperimentQuantum supremacy using a programmable superconducting processorArute et al. (Google), Nature, 2019
- Company announcementOn "quantum supremacy"IBM Quantum blog, 2019
- Peer-reviewed paperA quantum-inspired classical algorithm for recommendation systemsEwin Tang, STOC, 2019
- Peer-reviewed paperRead the fine printScott Aaronson, Nature Physics, 2015
- Peer-reviewed paperQuantum Computing in the NISQ era and beyondJohn Preskill, Quantum, 2018