Quantum computing for beginners: a guide


Quantum computing is equal parts fascinating, vital and confusing. Along with AI, it’s arguably positioned to be the defining technology of the 21st century, but general understanding of the principles is still pretty limited. Ask the average person what ‘quantum’ means, and they’ll say, “A really big jump?” or possibly, “A James Bond movie.”

There’s no way we can cover the ins and outs of quantum computing in a single article, but this blog isn’t meant to be exhaustive. It’s a beginner’s guide to quantum computing – a quick run through the basics.

What is quantum computing?

Imagine for a second that regular silicon-based computers are really fast runners, going around a track. They’re quick, but they can only run along one distinct path. Quantum computers are runners that can take multiple paths at the same time. It’s a paradox, but it works.

In a classical computer, a bit (the smallest unit of information) can either be 0 or 1. That’s more or less the building block for our entire digital world. In a quantum computer, there are quantum bits, or ‘qubits’, which can represent both 1 and 0 at the same time. It means quantum computers are (in theory) orders of magnitude more powerful than traditional computers.

Understanding Qubits

Qubits are the building blocks of quantum computers. They’re the basic unit of information. Think of them like magical switches – thanks to a special state called ‘superposition’, they can represent 1 and 0 simultaneously. Kind of like a light switch that’s permanently hovering in the middle: it’s not on, and it’s not off, it’s both at the same time.

This property of qubits is what lets quantum computers solve incredibly big, complex problems. Problems that would take traditional computers years – literally thousands of years – of number-crunching.

How is quantum computing hardware different from a regular computer?

Classical computers use silicon chips for all their computational functions. Quantum computers do not. Instead, they use quantum processors to manipulate qubits. These processors might take the form of superconducting circuits, made of materials like niobium. Other machines use photons or manipulate trapped ions using lasers and magnetic fields.

Have we achieved Quantum Supremacy?

Think of quantum supremacy as the tipping point. It’s the line where quantum computers officially become faster and more powerful than regular computers. In October 2019, Google announced that it had achieved quantum supremacy with its 53-qubit quantum processor, Sycamore. So yes, we’ve more or less achieved quantum supremacy. Still, the term is controversial. Some experts are skeptical that Google really smashed this milestone, and we’re still a fair way off a quantum computer with practical, real-world applications.

Quantum computing and cryptography

With their ability to quickly crunch and brute-force truly huge numbers, quantum computing has the potential to make many traditional encryption schemes obsolete. It hasn’t done so yet, but even quantum algorithms like Shor’s Algorithm (which has technically been around since 1994) could theoretically threaten the security of widely used public-key encryption systems like RSA.

To counter this threat, researchers are currently breaking ground on ‘post-quantum cryptography’. The goal is to quickly transition digital systems to quantum-resistant cryptographic methods, like lattice-based cryptography, before quantum computing goes mainstream.

Getting started with quantum computing

You don’t necessarily need an advanced knowledge of quantum mechanics and entanglement theory to get started in quantum computing (although it couldn’t hurt). Anyone can learn the basics, and many tertiary institutions are starting to offer courses and degrees in quantum computing. If you want a sound knowledge base, learn up on concepts like qubits, superposition, quantum gates and quantum algorithms. Developing your programming skills, particularly in languages like Qiskit (for IBM) and CIrq (for Google), is also a good idea.

Will quantum computing change the world? It’s still too early to say. It certainly has the potential to revolutionize society, but despite some high-profile claims of quantum supremacy, quantum computers are in an awkward teenage phase right now. They’re notoriously finicky, prone to bugs and errors that can jam their calculations.

Still, when a breakthrough in this field arrives, hold on to your horses. Because the human race is about to get much, much faster.