Traditional computing is bound in binary data, the world of zeroes and ones. This constraint was originally born out of a engineering limitation, designed to ensure that these different states could be easily represented by differing voltage levels. This hasn’t proved to be much of a limiting factor in the progress that computing has made however but there are different styles of computing which make use of more than just those zeroes and ones. The most notable one is quantum computing which is able to represent an exponential amount of states depending on the number of qubits (analogous to transistors) that the quantum chip has. Whilst there have been some examples of quantum computers hitting the market, even if their quantum-ness is still in question, they are typically based on exotic materials meaning mass production of them is tricky. This could change with the latest research to come out of the University of New South Wales as they’ve made an incredible breakthrough.
Back in 2012 the team at UNSW demonstrated that they could build a single qubit in silicon. This by itself was an amazing discovery as previously created qubits were usually reliant on materials like niobium cooled to superconducting temperatures to achieve their quantum state. However a single qubit isn’t exactly useful on its own and so the researchers were tasked with getting their qubits talking to each other. This is a lot harder than you’d think as qubits don’t communicate in the same way that regular transistors do and so traditional techniques for connecting things in silicon won’t work. So after 3 years worth of research UNSW’s quantum computing team has finally cracked it and allowed two qubits made in silicon to communicate.
This has allowed them to build a quantum logic gate, the fundamental building block for a larger scale quantum computer. One thing that will be interesting to see is how their system scales out with additional qubits. It’s one thing to get two qubits talking together, indeed there’s been several (non-silicon) examples of that in the past, however as you scale up the number of qubits things start to get a lot more difficult. This is because larger numbers of qubits are more prone to quantum decoherence and typically require additional circuitry to overcome it. Whilst they might be able to mass produce a chip with a large number of qubits it might not be of any use if the qubits can’t stay in coherence.
It will be interesting to see what applications their particular kind of quantum chip will have once they build a larger scale version of it. Currently the commercially available quantum computers from D-Wave are limited to a specific problem space called quantum annealing and, as of yet, have failed to conclusively prove that they’re achieving a quantum speedup. The problem is larger than just D-Wave however as there is still some debate about how we classify quantum speedup and how to properly compare it to more traditional methods. Still this is an issue that UNSW’s potential future chip will have to face should it come to market.
We’re still a long way off from seeing a generalized quantum computer hitting the market any time soon but achievements like those coming out of UNSW are crucial in making them a reality. We have a lot of investment in developing computers on silicon and if those investments can be directly translated to quantum computing then it’s highly likely that we’ll see a lot of success. I’m sure the researchers are going to have several big chip companies knocking down their doors to get a license for this tech as it really does have a lot of potential.