"This blueprint tells us how to start and how to keep going all the way to millions of qubits," says the university's Professor Andrew Dzurak​, who led the team. Several companies, including IBM, already have machines incorporating up to 50 qubits, the quantum units at the heart of quantum computing. But any practical computer would need to incorporate millions. The new chip could easily scale to that number, says Professor Dzurak. "It's kind of swept under the carpet a bit, but for large-scale quantum computing, we are going to need millions of qubits. Here, we show a way that spin qubits can be scaled up massively. And that's the key." Quantum computing is the next big step in electronics, and promises devices enormously more powerful than our current generation of hardware. "It's certainly one of the most keenly fought tech battles going on around the world – and the rewards are potentially enormous, both financially and in terms of the type of problems that can be solved," says Professor Dzurak.

But quantum computers don't work like normal computers. They are not really useful for all the sort of things we use computers for – playing video games, for example. What they do is specialise in probability. Imagine a computer model of atoms in a cloud of gas. Each atom moves randomly. Each time an atom hits another atom, they spring off each other in random directions – increasing the randomness. Computers can model a few atoms. Quantum computers can model a whole cloud. They have this power because they are, essentially, built using probability. Normal computers run off bits, small pieces of information that can either be a zero or a one. Quantum computers use qubits, which have a probability instead of a value – for example, a 50 per cent chance of being a zero or a one.

By chaining enough qubits together you can quickly calculate all the possible answers to a math question, something a normal computer would take years to do. A special algorithm can then be used to sort through all the possible answers to find the right one. The University of NSW's new design, published in Nature Communications on Friday, takes all the parts needed for quantum computing and puts them on a single silicon chip. Silicon is the material used to build our existing computer chips; this chip could theoretically be manufactured using existing equipment. Theoretically is the key word, however. "This is not a demonstration of the design, it's just a design. It has not been proven. There are plenty of designs for quantum computers. Everyone believes they have a scalable architecture," says Christopher Ferrie​, a researcher at the Centre for Quantum Software and Information, the University of Technology Sydney's competing quantum venture.

Scott Aaronson​, a top international quantum computing researcher at the University of Texas, puts it even more bluntly. "It's sort of a running joke in the field that scalable quantum computers were already built more than a decade ago – at the level of impressive-looking PowerPoint animations. "The challenge is to make it real."