On Monday, Canadian Prime Minister Justin Trudeau explained to a crowd of vaguely disinterested reporters how quantum computing works. The National Post calls it “the math lecture heard ‘round the world.” Lovely! Except, it’s actually physics. But still, it’s fantastic that so many people are talking about it. However, it is important to clarify exactly how they function.
The problem is that in actuality quantum computers are a bit more complicated than the Prime Minister would have us believe. His basic explanation of computing is correct – that computers have bits, which use a value of 1 or 0, corresponding with electricity flowing or not flowing. Computers use bits, short for binary digit in the form of little groups called bytes (there are 8 bits to a byte), which can store data and execute commands. This is why computers’ hard drives are measured in gigabytes.
However, his portrayal of quantum computing is at best simplistic. The basic idea is this: while a normal computer uses binary ones and zeros called bits, a quantum computer can use values of one, zero, and in-between, called qubits. Which is weird. Obviously, it’s impossible for a wire to have electricity and no electricity flowing through it at the same time. As Mr. Lebris loves to tell us, though, quantum mechanics is weird. Photons are examples of particles which abide by quantum mechanics, which is to say, they’re also really weird.
This means that photons have a lot of really interesting information about them – like how tall the waves are, or how often the waves come – the same as waves in the ocean. Two photons can combine their waves, creating what’s called a superposition. This superposition allows photons to take on values of things like their height and frequency that can range between the value that would be yielded by a single photon, and the value of the two added together. Using the wave analogy, if two boats sail next to each other, their wakes will hit each other. The resulting new wave can range between the height of one individual wave, or two waves combined. Photons are the same way.
So what? Well, a quantum computer takes multiple values at once, and can work on them separately. A traditional computer can do one thing at a time (newer computers can do a handful, but still not many). A quantum computer blows that out of the water. It can work on lots of little things at the same time until you’re ready to see your answers, then you get them all at once. Estimates suggest that, for a specific application, a quantum computer has the ability to “work in parallel” more than a million times faster than the device you’re reading this on.
The problem is building it. In reality, qubits have to store information using atoms, smaller subatomic particles, or photons. Which is great, except that the machines we use to mess with those things are absolutely massive. You would need mechanisms for containing these particles, and also for interacting with them in order to store and read information.
Fact is, quantum computers are really far off, and as of now they only have very specific applications. Who knows where traditional computing will go in the next 50 years? It’s still in it’s early days, so for now quantum computing remains far-off and largely theoretical. Check back in 2100 – maybe we’ll all have them in our laps.