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Science & Nature • Quantum computing

Quantum computer

A quantum computer is a computing device that uses quantum-mechanical effects, such as superposition, entanglement, and interference, to process information.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

A quantum computer is a computing device that uses quantum-mechanical effects, such as superposition, entanglement, and interference, to process information. It uses qubits instead of classical bits and is expected to be useful for certain specialized problems, including some simulations and cryptographic tasks.

How quantum computers work

Quantum computers encode information in qubits and manipulate them with quantum operations. Unlike classical bits, qubits can exist in superposition and become entangled, which changes how information is processed.

Potential advantages

Quantum computers are expected to speed up some problems dramatically, especially those involving simulation, certain optimisation tasks, and algorithms that exploit quantum interference.

Current limitations

Most present-day quantum computers are still rudimentary, noisy, and suited only to specialised experiments or narrow tasks. Building scalable, reliable, universal machines remains an active research challenge.

Applications and research

Research in quantum computing spans hardware, algorithms, and error correction. Proposed uses include modelling chemical and physical systems and exploring problems that are difficult for conventional computers.

Key facts

  • Quantum computers represent and process information using quantum states.
  • Their basic unit of information is the qubit, the quantum analogue of a classical bit.
  • Quantum effects can allow some computations to be performed much faster than on classical computers.
  • Large-scale quantum computers could help simulate physical and molecular systems.
  • Current quantum hardware is still largely experimental and error-prone.
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Canadian context

Canadian researchers, universities, and companies are active in quantum computing research and development, and Canada has a visible role in the global quantum technology ecosystem. This topic is also relevant to Canadian readers because of its implications for cybersecurity, science, and advanced computing.

Frequently asked questions

What is a quantum computer?
A quantum computer is a computer that uses quantum-mechanical states to store and process information instead of ordinary binary bits.
What is a qubit?
A qubit, or quantum bit, is the basic unit of information in quantum computing and can exist in a superposition of states.
Why are quantum computers considered powerful?
They can exploit superposition, entanglement, and interference to approach some problems in ways classical computers cannot, sometimes with major speed advantages.
Are quantum computers widely used today?
No. Current quantum computers are still experimental and error-prone, so they are mainly used in research and specialised demonstrations.
What problems might quantum computers help solve?
They may be useful for simulating quantum systems, certain optimisation problems, and some cryptographic or number-theoretic tasks.

References

  1. Wikipedia — https://en.wikipedia.org/wiki/Quantum_computing
    Supports: Definition of quantum computer, use of quantum states, qubits, superposition, entanglement, and potential applications.
  2. Encyclopaedia Britannica — https://www.britannica.com/technology/quantum-computer
    Supports: General definition of a quantum computer as a device using quantum mechanics.
  3. NIST — https://www.nist.gov/quantum-information-science/quantum-computing-explained
    Supports: Qubits, superposition, entanglement, current limitations, and potential for faster problem solving.
  4. IBM — https://www.ibm.com/think/topics/quantum-computing
    Supports: Core distinctions from classical computers, qubits, and quantum phenomena used in computation.
  5. Microsoft — https://learn.microsoft.com/en-us/azure/quantum/overview-understanding-quantum-computing
    Supports: Features of a good quantum computer and the role of quantum phenomena in computation.
  6. Google Quantum AI — https://quantumai.google/whatisqc
    Supports: Exponential computational space from qubits and superposition; general explanation of quantum computing.