Quantum computers solve certain problems in a completely different way than regular computers

A regular computer — the one on your desk or in your phone — stores information as bits. Each bit is either a 0 or a 1. Everything your computer does, from displaying this page to running video calls, comes down to millions of these 0s and 1s flipping on and off very quickly.

A quantum computer uses quantum bits, called qubits. A qubit can be a 0, a 1, or both at the same time. This property is called superposition. Because a qubit can exist in multiple states simultaneously, a quantum computer can explore many possible solutions to a problem at once, rather than checking them one at a time the way a regular computer does.

This difference matters only for specific kinds of problems — the ones where you need to search through an enormous number of possibilities or simulate how molecules behave. For everyday tasks like email, video, or spreadsheets, a regular computer is faster and more practical.

Key Takeaways

  • Quantum computers use qubits instead of regular bits, and qubits can represent 0, 1, or both simultaneously, allowing them to explore many solutions at once.
  • Quantum computers excel at specific problems like breaking certain types of encryption, discovering new medicines, and optimizing complex logistics — not at everyday computing tasks.
  • Quantum computers are extremely fragile and must be kept at temperatures colder than outer space to function, which is why they are not in homes or offices.
  • Current quantum computers are still experimental and make errors frequently, so they are not yet practical for most real-world applications.

How superposition and entanglement give quantum computers their power

Superposition is the first key property. When a qubit is in superposition, it holds multiple values at once. If you have three regular bits, you can represent one combination at a time: 001, or 110, or 111. With three qubits in superposition, you can represent all eight combinations simultaneously. Add more qubits and the advantage grows exponentially — 20 qubits can represent over one million combinations at the same time.

The second property is entanglement. When qubits become entangled, they are linked in a way that has no equivalent in regular computing. The state of one entangled qubit when ready influences the state of another, even if they are not physically connected. This allows a quantum computer to process information in ways that exploit these correlations, making certain calculations far faster than any regular computer could manage.

Together, superposition and entanglement let a quantum computer solve problems that would take a regular computer thousands of years to solve — but only if the problem has the right structure. A quantum computer cannot straightforward make every task faster.

What quantum computers are actually used for right now

Quantum computers today are research tools, not consumer devices. Companies like IBM, Google, and others operate quantum computers in laboratories and offer access through cloud services for researchers and companies testing specific problems.

The most realistic near-term uses include drug discovery (simulating how molecules interact), optimization (finding the best route for thousands of delivery trucks), and materials science (designing new compounds with specific properties). Financial firms are exploring quantum computers for portfolio optimization and risk analysis. Cryptography is another area — quantum computers could eventually break certain encryption methods that protect banking and government communications, which is why organizations are already working on quantum-resistant encryption.

For most of these applications, quantum computers are still not faster or more reliable than regular computers. The technology is in the experimental phase, similar to where regular computers were in the 1950s.

Why quantum computers are so difficult to build and maintain

Qubits are extremely fragile. They lose their quantum properties when exposed to heat, vibration, electromagnetic radiation, or even stray air molecules. This state of fragility is called decoherence. To prevent it, most quantum computers must be kept at temperatures near absolute zero — around 0.015 Kelvin, which is colder than outer space.

Maintaining these conditions requires specialized equipment like dilution refrigerators that cost millions of dollars. Even with perfect cooling, qubits typically remain stable for only microseconds before decoherence destroys the quantum state. This means calculations must happen extremely quickly, and any errors that occur during the computation are hard to correct without losing the quantum advantage.

Error rates are another major challenge. Current quantum computers make mistakes frequently — sometimes in 1 out of every 100 to 1,000 operations. Regular computers make errors far less often. Researchers are working on error correction, but adding the extra qubits needed to detect and fix errors reduces the number of qubits available for actual computation.

The difference between quantum computers and regular computers

A regular computer is deterministic — given the same input, it always produces the same output following a fixed set of steps. A quantum computer is probabilistic — you run it multiple times and get a distribution of answers, with the correct answer appearing more frequently than wrong ones. You then need to run the calculation many times to be confident in the result.

Regular computers are also general-purpose. The same laptop can run email, video games, spreadsheets, and web browsers. Quantum computers are specialized. Each one is designed for a narrow set of problems, and reprogramming it for a different problem is not straightforward.

Speed is another difference, but not in the way many people think. A quantum computer is not straightforward "faster" at everything. It is faster at specific problem types where you can structure the calculation to take advantage of superposition and entanglement. For most everyday computing, a regular computer is faster and more practical.

Where quantum computing stands in 2024 and beyond

As of now, no quantum computer has demonstrated a practical advantage over regular computers for any real-world problem that matters to most people. Google announced in 2023 that it had achieved "quantum advantage" on a specific mathematical problem, but that problem was designed to showcase quantum computing — it has no practical process.

The field is advancing. IBM, Google, IonQ, and others are building machines with more qubits and lower error rates each year. However, experts disagree on how long it will take before quantum computers solve practical problems faster than regular computers. Some estimate 5 to 10 years; others say 20 or more.

In the meantime, quantum computers will remain in research labs and universities. They will not replace regular computers. Instead, they may eventually become specialized tools that work alongside regular computers — handling the specific problems where quantum approaches excel while regular computers handle everything else.

Frequently Asked Questions

Will quantum computers replace my laptop or phone?

No. Quantum computers are specialized tools for specific problems like drug discovery and optimization. Regular computers are far better at everyday tasks like browsing, email, and video. A quantum computer would be impractical and unnecessary for these uses.

Can quantum computers break all encryption?

Quantum computers could theoretically break certain types of encryption used today, particularly RSA encryption that protects banking and government communications. However, they cannot break all encryption methods. Researchers are already developing quantum-resistant encryption to prepare for this possibility.

How many qubits does a quantum computer need to be useful?

That depends on the problem. Current machines have 50 to 400 qubits, but most experts believe practical quantum computers will need thousands or millions of stable, low-error qubits. We are not there yet.

Why do quantum computers need to be so cold?

Qubits lose their quantum properties when exposed to heat or vibration. Cooling to near absolute zero slows down atomic motion and reduces interference, keeping qubits stable long enough to perform calculations. Without extreme cooling, decoherence happens in microseconds.

Can I use a quantum computer through the cloud?

Yes. IBM, Google, and other companies offer cloud access to quantum computers for researchers and companies. You submit a problem, and the quantum computer runs it remotely. However, access is limited and typically reserved for research and development rather than commercial use.