Hearing about quantum computers everywhere can be confusing. If you are asking what is quantum computing, here is the short answer: it is a way of computing that uses qubits and quantum physics to tackle a few hard problems, not a faster laptop.
This explainer is part of our technology news coverage, written for readers who want the substance without the hype.
| Item | Value |
|---|---|
| Basic unit | Qubit: 0, 1 or a blend of both |
| Key ideas | Superposition, entanglement and interference |
| Best at | Simulating molecules, factoring, some optimisation |
| Not better at | Everyday computing tasks |
| Main obstacle | Errors and decoherence in fragile qubits |
| Google’s 2019 benchmark | Millions of times faster than a classical supercomputer (benchmark only) |
These figures come from Quantum Zeitgeist’s beginner guide and Educative’s introduction. They can change as the field moves, so check the sources before you rely on them.
What a quantum computer actually is
A quantum computer stores and processes information using the rules of quantum physics, the laws that govern atoms, electrons and particles of light. According to Quantum Zeitgeist, it is not simply a faster version of the laptop on your desk.
The idea came before the hardware. Physicists including Richard Feynman and David Deutsch sketched it in the early 1980s, and the machines are still catching up.
Educative describes a quantum computer as having three main parts:
- A part that holds the qubits.
- A part that sends signals to the qubits, which can use microwaves, lasers and voltage.
- A classical computer that runs programs and gives instructions.
That last part matters. A quantum computer works alongside a classical one rather than instead of it.
Bits versus qubits
Classical computers store everything as bits, tiny switches that are either off or on, written as zero or one. Every photo, message and program is in the end a long string of those two values.
A qubit can be zero, one, or any blend of the two at the same time. Physically it can be the state of a superconducting circuit chilled to near absolute zero, among other things, and the hardware matters less than the fact that it obeys quantum rules.
Quantinuum, a quantum hardware company, says on its own explainer that the highest quality qubits are atoms, but that there are multiple types of qubits. Quantum Zeitgeist adds that which design will win is still an open question.
Superposition, entanglement and interference
Three ideas do most of the work in quantum computing:
- Superposition: a qubit holds a blend of states. Quantum Zeitgeist says just sixty qubits in superposition can represent more combinations than there are grains of sand on Earth, because each extra qubit doubles the number of states the machine can hold.
- Entanglement: when two qubits are entangled they cannot be described independently of each other, even when they are separated by a large distance, according to Quantinuum.
- Interference: a well-designed quantum algorithm makes the wrong answers cancel out while the right ones add up.
It is tempting to say a quantum computer tries every answer at once, but Quantum Zeitgeist calls that not quite right. Reading the result collapses everything to a single outcome, so the skill lies in arranging things so the answer you want is the likeliest one.
Just as classical machines use logic gates on bits, Quantinuum notes that quantum computers use quantum gates to manipulate qubits.
What quantum computers are good for
The advantage is narrow. The most natural fit is simulating nature, which Quantum Zeitgeist says could transform chemistry, drug discovery and battery design.
Sources name a short list of promising areas:
- Simulating molecules and materials.
- Factoring, the task behind Shor’s algorithm.
- Some optimisation problems.
- Educative also lists cryptography and drug discovery among the areas of promise.
Quantinuum says certain tasks that would have taken 10,000 years on a classical computer might now take days. Read that as a vendor claim about specific cases, not a general speedup.
You would normally reach such machines remotely: the same company describes hardware-as-a-service access on-premise, in the cloud, or both. If that model is unfamiliar, our guide to what is cloud computing explains how remote access works.
What quantum computers are not
Most of the confusion comes from treating a specialist tool as a universal one. Quantum Zeitgeist says machines like these are best understood as specialised co-processors rather than universal replacements.
- Not a faster laptop: for browsing the web, writing documents or playing video, a classical machine is the right tool.
- Not a try-everything machine: the result collapses to one outcome when you read it.
- Not a proven practical winner yet: see the next section for what the evidence shows.
Security is a common worry, and cryptography is on the list of areas where researchers see promise. Today’s data exposures are a separate matter, and our explainer on what is a data breach shows how they happen.
Where quantum computing stands today
The main obstacle is fragility. Quantinuum notes that even a single stray photon can change the state of a qubit, and Educative says measuring qubits can collapse their superposition, causing errors that need quantum error correction.
Quantinuum also claims that trapped ions have some of the longest coherence times in the industry. That is a company’s description of its own approach, so weigh it accordingly.
As of Educative’s guide dated May 12, 2026, Google had demonstrated a benchmark calculation millions of times faster than a classical supercomputer in 2019. The same guide says no quantum device had yet solved a useful real-world problem beyond classical reach.
When you read the next headline, run through these checks:
- Is the result a benchmark, or a useful real-world problem?
- Who is making the claim, and do they sell the hardware?
- Does the claim address errors and error correction?
Frequently asked questions
What is quantum computing in simple terms?
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It is computing that uses the rules of quantum physics, through qubits, superposition, entanglement and interference, to attack a narrow set of hard problems such as simulating molecules.
Will quantum computers replace classical computers?
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Not on the evidence in these sources. Educative says classical computers are better for everyday processing needs, and Quantum Zeitgeist describes quantum machines as specialised co-processors.
What is a qubit?
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A qubit is the basic unit of quantum information. Unlike a bit, it can be zero, one or a blend of both, and quantum gates manipulate it.
Why are quantum computers hard to build?
Show answer
Qubits are delicate. Stray disturbances can change their state, and the resulting errors need quantum error correction to keep computations useful.
