What is… quantum computing?

A monthly tech explainer series about the technology shaping our world today, from the Garage.

By Jeff Wise — June 7, 2022

Computer science is about to make a quantum leap. Thanks to a radically different kind of architecture, computers of the future will be able to carry out feats that are impossible on today’s machines. The technology is called quantum computing, and while it’s a little hard to wrap your head around how it works, experts say it could transform information technology in a profound way by enabling new forms of computation, such as rapidly cracking unbreakable codes, modeling drug interactions at the molecular level, and modeling complex investments. In the decades ahead it could become a $1 trillion industry, and some heavyweights are already planning to take their share, including Microsoft, Google, IBM, and Honeywell. China, too, wants a place at the table, and has reportedly committed billions to developing its own applications.

Illustration by Eric Chow

How it works

Today’s digital processors make calculations and store data using electronic bits that are either 1 or 0. But with quantum computing, there’s another possibility. Back in the 1920s, physicists realized that particles like electrons or protons can exist in a condition called “superposition,” where they can exist in multiple states. Whereas a toy top, for example, can spin in one direction or the other, an electron can potentially do both at the same time. A quantum bit (or “qubit”) takes advantage of that principle so can be both a 1 and a 0 simultaneously. What’s more, two or more particles could be “entangled” so that their states were related to one another, so that observing one would instantly identify the state of the other, no matter how far away. (Einstein was famously flummoxed by this idea, calling it “spooky action at a distance.”) Together superposition and entanglement allow qubits to carry out an entirely new type of computation. Because they operate on very different principles than conventional computers, you compare their performance by the speed with which they solve problems. In certain repetitive tasks, today’s quantum computers are already more than a 100 million times faster than the world’s most powerful supercomputer.


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The a-ha moment

The challenge has been to make a machine that can take advantage of quantum mechanics. Because these properties are very small scales, and superposition is extremely fragile, it wasn’t until 1998 that scientists were able to make a functioning quantum computer (with just two qubits). Today, researchers are racing to build machines that incorporate ever greater numbers of qubits. The largest currently in existence has 127, but plans are already afoot for room-sized quantum computers made of up one million qubits.

What it means for everyday life

Theorists believe that quantum computers will be able to swiftly carry out certain kinds of calculations that would take billions of years on a conventional computer. Demonstrating practical applications for that will take a little time, though. For now, quantum computers are bulky, expensive, and very limited in the number of qubits that can be coherently operated together. But research dollars continue to flow, quantum computing will inevitably become commonplace.

How it might change the world

One of the tasks that’s impossible for today’s computers, but easy for quantum computers, is figuring out what numbers you need to multiply together in order to make any given really big number, a process called prime factorization. This matters because factorization is what underlies digital cryptography. Once quantum computing arrives in force, today’s secure encryption techniques for communications are toast. So is bitcoin. (The National Institute for Standards and Technology (NIST) is working on post-quantum encryption algorithms.)

On the other hand, quantum mechanics will make it much easier for scientists to model the way that large molecules assemble themselves in three dimensions. Since this is crucial to the functioning of molecules like proteins, quantum computing could usher in a golden age of rapid medical innovation and testing.

Another exciting frontier will be quantum artificial intelligence. As a machine learning algorithm is trained, it sifts through vast amounts of data, so a quantum computer’s ability to process multiple possibilities at once might allow it to reach unprecedented levels of performance.

And that’s just for starters. Quantum information science could well be one of those technologies that’s so radically different that we might not be able to appreciate its impact until it’s ubiquitous enough for anyone to innovate with its powers. After all, if even Einstein called it weird science, it’s bound to have a few surprises in store.