The possibilities that emerge from a true quantum computer are to computing what fusion is to energy generation. It’s a field of active research, one in which many scientists have spent their lives, yet the promised land still seems to elude us. Just like fusion though quantum computing has seen several advancements in recent years, enough to show that it is achievable without giving us a concrete idea of when it will become commonplace. The current darling of the quantum computing world is D-Wave, the company that announced they had created functioning qubits many years ago and set about commercializing them. However they were unable to show substantial gains over simulations on classical computers for numerous problems, calling into question whether or not they’d actually created what they claimed to. Today however brings us results that demonstrate quantum speedup, on the order of 108 times faster than regular computers.
For a bit of background the D-Wave 2X (the device pictures above and the one which showed quantum speedup) can’t really be called a quantum computer, even though D-Wave calls it that. Instead it’s what you’d call a quantum annealer, a specific kind of computing device that’s designed to solve very specific kinds of problems. This means that it’s not a Turing complete device, unable to tackle the wide range of computing tasks which we’d typically expect a computer to be capable of. The kinds of problems it can solve however are optimizations, like finding local maximums/minimums for a given equation with lots of variables. This is still quite useful however which is why many large companies, including Google, have purchased one of these devices.
In order to judge whether or not the D-Wave 2X was actually doing computations using qubits (and not just some fancy tricks with regular processors) it was pitted against a classical computer doing the same function, called simulated annealing. Essentially this means that the D-Wave was running against a simulated version of itself, a relatively easy challenge for a quantum annealer to beat. However identifying the problem space in which the D-Wave 2X showed quantum speedup proved tricky, sometimes running at about the same speed or showing only a mild (comparative to expectations) speedup. This brought into question whether or not the qubits that D-Wave had created were actually functioning like they said they were. The research continued however and has just recently born fruit.
The research, published on ArXiv (not yet peer reviewed), shows that the D-Wave 2X is about 100 million times faster than its simulated counterpart. Additionally for another algorithm, quantum monte carlo, a similar amount of speedup was observed. This is the kind of speedup that the researchers have been looking for and it demonstrates that D-Wave is indeed a quantum device. This research points towards simulated annealing being the best measure with which to judge quantum systems like the D-Wave 2X against, something which will help immensely with future research.
There’s still a long way to go until we have a general purpose quantum computer however research like this is incredibly promising. The team at Google which has been testing this device has come up with numerous improvements they want to make to it and developed systems to make it easier for others to exploit such quantum systems. It’s this kind of fundamental research which will be key to the generalization of this technology and, hopefully, it’s inevitable commercialization. I’m very much looking forward to seeing what the next generation of these systems bring and hope their results are just as encouraging.