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Quantum computing explained simply

By Alma Fabiani

Jun 1, 2020


What is quantum computing?

Let’s start with the basics so we can move on to more tricky specifics. Take your everyday computer, its chip uses what is called ‘bits’—not to confuse with the saying ‘to do bits with someone’ commonly used in Love Island. The bits we’re talking about here can either be in the ‘off’ position, which is represented by a zero, or in the ‘on’ position, which is represented by a one.

Every website we visit, app we use, and even photograph we take is ultimately made up of a lot of these bits in some combination of ones and zeros. To put it simply, which is what we’re aiming to do, everything a computer does is based on ones and zeros—all code is binary.

And although so far it’s worked pretty well for us, this binary code represents a problem now. Our world, our universe, aren’t that simple. Things are uncertain (even though some people might argue that everything is predictable, this is another complicated topic) and uncertainty means that our computers—even our supercomputers—are struggling to deal with.

Why is that a problem, you might wonder. Well, because, in the last hundred years, as physicists discovered more and more about our world, they found out that if you wish to go down to a really small scale, we’re talking really small, things stop working correctly. That’s where the problem is.

In order to solve this problem, physicists have developed a whole new field of science to try and explain these malfunctions: quantum mechanics. Quantum mechanics is the foundation of physics which underlies chemistry, which is the foundation of biology—meaning quantum mechanics is a pretty big deal.

That’s exactly why scientists need help from a new technology that can handle making calculations while taking our world’s uncertainty into the equation. And that’s what quantum computers are here to—the dirty work! Just as when you typed in 12 + 8 into your calculator in math class because you couldn’t be bothered, scientists are using quantum computing to do some crazy calculations.

How does a quantum computer work?

Hopefully things are a bit clearer by now; either that or we’ve lost you already! On to the next one: quantum computers and the way they function. So, you’ve read about bits for ordinary computers. Quantum computers use something called qubits. As we explained before, the problem with bits was that they can be either on or off. 

Qubits can be on and off too, but can also be in ‘superposition’, which means they’re both on and off at the same time, or somewhere in between. This in-between option that a qubit offers means that it allows for uncertainty, and that’s exactly what scientists are looking for.

The best way to explain the difference between an ordinary computer and a quantum computer is by using the metaphor of the maze. If you asked an ordinary computer to figure out which path will take it out of the maze, it would have to try every path individually, one after the other, in order to finally find the right one. A quantum computer, on the other hand, would be able to simultaneously go down every path of the maze, making the whole process way quicker.

But qubits can do even more than taking uncertainty into consideration; they can do what is called ‘entanglement’. Physicists still don’t fully understand how or why entanglement works, but it means that you can move information around, even if it contains uncertainty.

For example, a quantum computer can take two separate spinning coins and perform complex calculations by linking two particles together, even if they’re physically separate. This means that, by stringing together multiple qubits, the quantum computer can solve problems that would take our best computers millions of years to crack.

But quantum computers are not only here to do quick maths. They’ve allowed us to achieve things that even supercomputers would have not been able to do.

Supercomputers VS quantum computers

At the moment, supercomputers, which are the fastest and most powerful type of ordinary computer you can find, can only analyse the most simple molecules. On the other hand, quantum computers actually use the same quantum properties as the molecules they’re trying to simulate. This means they have no problem handling even the most complicated reactions.

From helping in the search for a cure for Alzheimer’s and improving solar panels to rapidly accelerating the development of artificial intelligence (AI), quantum computers are, without a doubt, going to be a vital element in furthering our advancement.

What is cryptography?

Quantum computing comes with another key application: cryptography. At the moment, many encryption systems rely on the difficulty of breaking down large numbers into prime numbers, which is called ‘factoring’. Factoring for ordinary computers takes time, is expensive and often impractical.

Quantum computers can perform factoring easily, but this means that it could put our data (even more) at risk. In response to this problem, quantum encryption keys would protect data, making it unbreakable and impossible to hack.

When will we all have access to quantum computers?

Don’t get us wrong, the next iPhone probably won’t have a quantum chip. As amazing as quantum computers sound, they’re also incredibly sensitive to interference. They have to be kept isolated from any other form of electrical interference and chilled down to a temperature colder than outer space. Long story short, you probably will never have access to a quantum computer—sorry about that.

We still have quite a while to wait before quantum computers can do all the things they promise. At the moment, the best quantum computers have around 50 qubits, which is enough to make them incredibly powerful. However, they also have incredibly high error rates resulting from interference problems.

What is quantum supremacy?

Quantum supremacy, which is the point at which a quantum computer can outperform a classical computer, has not yet been achieved. In 2019, Google published a paper suggesting it had achieved quantum supremacy. Soon after, IBM disputed the claim and said that Google had not yet tapped into the full power of modern supercomputers.

Quantum computing is here to change the world, but, for now, the devices themselves still require a lot more work. Until then, using a ‘simple’ computer remains the easiest and most economical solution for tackling most problems.