What Is a Quantum Computer?
A quantum computer uses quantum physics to calculate differently. Learn why it helps with particular problems, not every task.
Free video lesson · 1:18
What Is a Quantum Computer?
Quantum Computing & Encryption for Beginners
Music: “Thinking Music” by Kevin MacLeod. Creative Commons Attribution 4.0.
A quantum computer uses quantum physics to compute in a different way and is useful for particular problems.
Read the video transcript
A quantum computer uses the rules of quantum physics to do calculations. Those are the rules followed by very small things, such as atoms. It is a different kind of computer, with different strengths.
One useful way to picture the difference is with waves. When two waves meet, they can make a bigger wave or cancel each other. This is called interference.
Quantum calculations use a related effect. Carefully chosen steps change how possible results combine. For some problems, that can make a useful result more likely when the computer is measured.
This does not mean it gives you every answer at once. You still have to design the right calculation and read its result. Many everyday jobs are better suited to ordinary computers.
Quantum computers are real, but building large, reliable ones is difficult. Their promise comes from particular tasks, such as studying molecules. A quantum computer is not simply a laptop that makes every program run faster.
What does a quantum computer work with? Watch What Is a Qubit? For one security question, watch Can Quantum Computers Break Encryption?
The short answer
A quantum computer uses the rules of quantum physics to do calculations. Those are the rules followed by very small things, such as atoms. It is a different kind of computer, with different strengths.
A simple example
One useful way to picture the difference is with waves. When two waves meet, they can make a bigger wave or cancel each other. This is called interference.
Quantum calculations use a related effect. Carefully chosen steps change how possible results combine. For some problems, that can make a useful result more likely when the computer is measured.
This does not mean it gives you every answer at once. You still have to design the right calculation and read its result. Many everyday jobs are better suited to ordinary computers.
Quantum computers are real, but building large, reliable ones is difficult. Their promise comes from particular tasks, such as studying molecules. A quantum computer is not simply a laptop that makes every program run faster.
Different tools for different jobs
A bicycle and a boat both move people, but they solve different travel problems. In the same way, a quantum computer is not simply a faster version of every ordinary computer. The task and the available algorithm matter.
Check your understanding
Does buying a quantum computer make every game run faster?
Answer
No. Quantum computers are intended for particular kinds of calculations, not an automatic speed-up for every program.
Keep learning
Follow the free video course one question at a time. For help applying these ideas at work, explore team training or a cryptography audit.