For almost forty years, we’ve been hearing about advances in quantum computers. Unlike the “classical” computer you’re using to read this article, quantum computers use the theory of quantum mechanics to change classic computer information into quantum states and back again. Just as classical computers use “bits” to store one piece of information at a time, a quantum computer has its own unit of memory: a “qubit” — which is like a combination of both. In theory, the advantage of this kind of computing is the ability to quickly solve problems that are too difficult for classic computers. However, the science of quantum computing is still in the early stages of development. Here are the five biggest breakthroughs so far:

## 1. Quantum computers first proposed and described

In 1980, Paul Benioff introduced the idea of quantum computers to the world, and demonstrated the math that makes them work. Basically, he transformed the concept of a Turing Machine — the abstract concept behind classical computers — into a quantum function using Schrodinger’s wavefunction. Over the next three years, Benioff continued to develop the idea and presented it at a major computation conference at MIT. Helping to popularize the idea was famous physicist Richard Feynman, who stressed the importance of quantum computing for solving problems specifically related to quantum mechanics.

## 2. Shor’s algorithm makes quantum computers more interesting – and dangerous

In 1994, Peter Shor discovered an algorithm while working at AT&T’s Bell Labs which generated more interest in quantum computers than anything had before. “Shor’s algorithm” shows that a quantum computer, if one could truly be built, would be able to break RSA encryption. As soon as Shor demonstrated his findings, motivation to research and construct quantum computers became much, much more motivated — and better funded.

## 3. D-Wave shakes up the quantum computing world with controversial claims

In 2011 a company called D-Wave Systems made an audacious claim: that they had already built a functional quantum annealing computer with 128 qubits. D-Wave One generated a great deal of interest among other companies and produced a lot of speculation that quantum computing’s problems had now been solved — a claim which many scientists said was bogus. Although papers were published calling into doubt that any quantum mechanics were involved in D-Wave One’s ability to solve problems, critics have become quieter over time as D-Wave seems to produce more and more results.

## 4. Solid-state quantum computer built out of dirty diamond

In April 2012, a multinational effort including researchers from California, Iowa, and the Netherlands built a quantum computer using “doped diamond”. The diamond structure intentionally contained flaws, which were used by the scientists to form 2 qubits — one using the spin of an electron, the other using the spin of a nitrogen nucleus. The advantage of this kind of solid-state quantum computer is practicality: unlike most previous designs, it’s easier to scale this one up to more and more qubits, it can operate at room temperature, and it’s resistant to “decoherence”, a problem that plagues the accuracy of quantum computing efforts.

## 5. Quantum Supremacy claimed by Google

In September 2019, Google AI Quantum made a powerful claim: that they had achieved “quantum supremacy”. Essentially, the idea is that they designed a theoretical computer problem that would be practically unsolvable by a classical computer, but would be simple for a quantum computer to finish. Google says their 53-qubit computer Sycamore has solved one of these special problems — in only 200 seconds! — which would have taken 10,000 years for a classical supercomputer to finish.

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