Flip a coin. Heads or tails, right? Sure, once we see how the coin lands. But while the coin is still spinning in the air, it’s neither heads nor tails. It’s some probability of both.

This gray area is the simplified foundation of quantum computing.

Digital computers have been making it easier for us to process information for decades. But quantum computers are poised to take computing to a whole new level. Quantum computers represent a completely new approach to computing. They have the potential to solve very complex statistical problems that are beyond the limits of today’s computers. Quantum computing has so much promise and momentum that McKinsey has identified it as one of the next big trends in tech. Quantum computing alone—just one of three main areas of emerging quantum technology—could account for nearly $1.3 trillion in value by 2035. Investors of all kinds are perking up their ears—and opening up their wallets: government investors alone have pledged $34 billion in investments. In 2022, the US government announced $1.8 billion in funding, bringing its total investment to $3.7 billion.

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How does a quantum computer work?

Here’s how quantum computing works: classical computing, the technology that powers your laptop and smartphone, is built on bits. A bit is a unit of information that can store either a zero or a one. By contrast, quantum computing is built on quantum bits, or qubits, which can store zeros and ones. Qubits can represent any combination of both zero and one simultaneously—this is called superposition, and it is a basic feature of any quantum state. Chips are the physical hardware that store qubits, just like in classical computing.

When a classical computer solves a problem with multiple variables, it must conduct a new calculation every time a variable changes. Each calculation is a single path to a single result. Quantum computers, however, can explore many paths in parallel through superposition.

Additionally, qubits can interact with one another. This is known as entanglement. Entanglement allows qubits to scale exponentially; two qubits, for example, can store and process four bits of information, three can process eight, and so on. This exponential scaling gives the quantum computer much more power than classical computers.

Heavyweight tech organizations are already placing bets on quantum technology. In 2019, Google claimed that its quantum computer had solved in just 200 seconds a problem that would have taken a classical computer 10,000 years (although other tech organizations and academics have surfaced doubts about the validity of Google’s claim).

Even if Google’s claim was accurate, the achievement was more of a theoretical leap forward than a practical one since the problem its quantum computer solved had no real-world use. But we’re rapidly approaching a time when quantum computers will have a real impact on our lives.

What are quantum computers used for?

Today’s classical computers are relatively straightforward. They work with a limited set of inputs and use an algorithm and spit out an answer—and the bits that encode the inputs do not share information about one another. Quantum computers are different. For one thing, when data are input into the qubits, the qubits interact with other qubits, allowing for many different calculations to be done simultaneously. This is why quantum computers are able to work so much faster than classical computers. But that’s not the end of the story: quantum computers don’t deliver just one clear answer like classical computers do; rather, they deliver a range of possible answers.

For calculations that are limited in scope, classical computers are still the preferred tools. But for very complex problems, quantum computers can save time by narrowing down the range of possible answers.

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