What’s a
quantum computer?

A quantum computer isn’t really a computer—at least, not in the way we use the word “computer” today. Usually when we speak about “computers” we’re referring to something with a screen. A keyboard. Some kind of pointing device like a mouse, trackpad, or even a touch screen. Your desktop or laptop computer might even have a camera, microphone, or speakers. A quantum computer doesn’t have any of those things.

Like a graphics card

Quantum computers are more like graphics cards. If you’re not familiar, a graphics card is a piece of hardware that slots into your computer’s innards and boosts its ability to render complex, high resolution graphics. The crown jewel of a graphics card is its GPU, or Graphics Processing Unit. The GPU is a special computer chip built for rendering graphics quickly. Graphics cards aren’t “computers” in the way we commonly use that word, but they are absolutely computers in the sense that their job is to compute. In fact, that is all that they do.

Different tools for different problems

So why bother with a graphics card? Your computer already contains a CPU, or Central Processing Unit. Isn’t that good enough? Yes and no. CPUs are designed to execute a very long series of instructions incredibly quickly, one instruction at a time. But a GPU is engineered to execute millions of copies of one tiny program at once. Most software, like applications for composing and editing text documents, are perfectly suited for CPUs. But some problems, like computing the color values for millions of pixels in order to paint one frame of a large 3D scene, are more efficiently solved by GPUs. Certain procedures lend themselves to one kind of tool, while other procedures are more efficiently solved by another.

A new kind of tool

That’s where quantum computers come in. A quantum computer has its own crown jewel: the QPU, or Quantum Processing Unit. QPUs are a third style of hardware architecture, engineered to more efficiently answer a special set of logic questions that are not as easily answered by either CPUs or GPUs. Just like a graphics card, a quantum computer must be attached to a “regular computer”— that is, a computer that has a screen, keyboard, and pointing device—in order for us humans to tell the quantum computer what to do. (And for receiving / rendering the results of a quantum computation.) Quantum computers are a different kind of tool for a different kind of problem.

A quantum tool

Quantum computers are different because unlike other computing architectures, they harness properties of quantum mechanics in order to solve logic problems. These properties include interesting and often counterintuitive behaviors like superposition, entanglement, interference, and teleportation. (No, quantum teleportation is not like Star Trek, sadly.) There are different types of quantum computer hardware architectures, but all of them leverage these same quantum principles.

Math, not physics

Thankfully, you don’t need to be an expert in quantum physics to begin coding quantum programs (known in the industry as “quantum circuits”) for a quantum computer. In fact, you don’t need to understand the physics at all. Quantum software is just software. And software is just math expressed as a story. In order to write your quantum stories you’ll need to brush up on a tiny bit of math. To assist you with this, we’ve written a few quantum concept primers. These cover complex numbers, matrices, qubits, and quantum logic gates. With just these intellectual tools under your belt, you’ll understand the building blocks of quantum algorithms—and you’ll be able to write your own.

Why do quantum computers matter?

Quantum computers allow us compute using the physics of the universe itself, opening up problems that are inaccessible to classical computation. They allow us to solve certain logic puzzles that would otherwise take a lot longer—sometimes longer than a human lifespan. Let’s look at some examples.

1. They access exponentially large state spaces

A classical computer stores one configuration of bits at a time. A quantum computer stores a [complex-valued](/learn/basics/complex-numbers) amplitude over 2ⁿ possible bitstrings simultaneously.

• 10 qubits → amplitudes over 1,024 states.
• 50 qubits → amplitudes over 1 quadrillion states.
• 1,000 logical qubits → amplitudes over 10³⁰⁰ states (more than atoms in the universe).

This doesn’t mean “magical parallel computing.” It means quantum computers can represent (and operate on) huge structured spaces compactly. They matter for tasks where that structure can be used instead of collapsing into noise.

2. They use interference as a computational primitive

Classical bits don’t “cancel each other out.” Quantum amplitudes do. Quantum algorithms work by: Spreading amplitude over many candidate solutions Computing a phase pattern that encodes a problem Using interference to amplify the correct solutions and suppress incorrect ones This interference is the heart of algorithms like: Grover (search) Shor (period finding → factoring) HHL (linear systems) VQE & QAOA (optimization via physics dynamics) Interference is why the right answer “pops out” without needing to know it ahead of time.

3. They implement linear algebra natively

Quantum operations are matrices. Quantum states are vectors. Quantum evolution is matrix multiplication. Anything that requires huge vectors, huge matrices, transformations (like Fourier transforms, eigenvalue estimation, or simulation of unitary dynamics), all get a natural hardware-level boost. This is why quantum computers matter for:

• Chemistry. Simulating molecules is exponentially hard classically because electron wavefunctions live in huge Hilbert spaces. Quantum hardware matches that structure.
• Materials. Superconductors, catalysts, batteries, photovoltaics—these are quantum many-body systems.
• Optimization & machine learning. Quantum systems naturally explore complex energy landscapes and encode correlations compactly.

4. They can simulate physics in ways classical computers fundamentally cannot

Our universe is quantum mechanical. If you’re aiming to simulate the nitty-gritty aspects of it, you just can’t rely on classical computation. You need quantum computation in order to match the behavior of our reality. Quantum simulation is likely the first mega-use-case that reaches real-world impact:

• Drug discovery.
• Materials design.
• Climate and energy applications.
• Quantum chemistry (enzymes, catalysts).
• Superconductivity and quantum phases of matter.

How can I play with quantum computing?

Use the Resources sitemap below as your personal roadmap to quantum computing. First, we’ll brush up on just a tiny bit of math. Then, we’ll get some quantum programming software setup on your own personal computer. From there we can run quantum simulations either on your own machine or in the cloud. And that’s when we reach the summit: We’ll run your quantum circuits on actual quantum computing hardware connected to the cloud.

Resources sitemap

You don’t need to be a physicist to write quantum software. Let’s get you up and running.

Quantum concept primers

These math references are your foundation for understanding the building blocks of quantum algorithms. (No physics degree required.) They progress in order, so start from the top.

1. Complex numbers
2. Matrices
3. Qubits (quantum bits)
4. Quantum logic gates

Quantum software tools

You know what a Hadamard gate is and you feel you’re ready to cook. Let’s look at some common software tools—programming languages and software development kits (SDKs)—that will allow you to replicate tutorial examples, simulate quantum outcomes, potentially execute your code on actual quantum hardware, and begin dreaming up your very own quantum algorithms. These tutorials are in progress, so if you don’t find what you’re looking for check back soon.

• Python (programming language)
• IBM Qiskit SDK

Upskill to quantum

Looking to make the leap from your current day job to a quantum computing role? Stay tuned! We’re drafting a roster of “upskill” tutorials to take you from roles like Web developer, AI engineer, or even musician, to a future entry-level role in quantum computing.