When I first started reporting on quantum computing several years ago, I had a lot to learn about the workings of these complicated, potentially groundbreaking machines and the cast of characters leading their development. Since then, I have been lucky to speak with many of them. But there is one person who has always eluded me – until now.
Everyone with ties to quantum computing seems to know the name Craig Gidney. I’ve also noticed that any study he has co-authored in recent years has made waves. Yet Gidney, who is based at Google Quantum AI in California, has written no books, gives no splashy keynote lectures to general audiences and rarely speaks to the press.
One of the few digital traces of him is his rather technical blog. It wasn’t merely my curiosity that was driving me to want to speak to Gidney, though. He is working on finding a way to run what could be the world’s most dangerous algorithm on quantum computers.
That makes him a hugely consequential figure, as if and when this algorithm does run on a real machine, it could unleash a crisis known as Q-Day, when it will suddenly become possible to crack the encryption systems that secure everything from our emails to our bank accounts. To understand Gidney’s story, it helps to start with encryption. Today, much of our private data is protected by encryption systems that can’t be broken without solving a difficult mathematical problem.
One common choice is factoring very large numbers. Another involves abstract mathematical objects called elliptic curves. Conventional computers struggle to solve these problems, so our data and savings remain safe.
But in 1994, theoretical computer scientist Peter Shor at the Massachusetts Institute of Technology discovered that a large enough quantum computer would excel at these challenges. The countdown to Q-Day, then, is really a countdown to a quantum computer successfully running Shor’s algorithm. In the 1990s, Q-Day seemed more distant science fiction than real threat, because quantum computers were themselves not real.
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