Until recently scientists thought that quantum entanglement, when particles such as photons and electrons interact physically and then become separated, was required to run a quantum computer. But although entanglement, a phenomenon famously derided by Einstein as 'spooky action at a distance', can be facilitated in the laboratory in near ideal conditions, outside the laboratory the process is fragile and transient, and therefore not ideal.
Now, researchers have realised that entanglement may not always be necessary, and new examples of technologies that can gain a quantum advantage without entanglement have been discovered over the past few years.
A new study, published in the journal Nature Physics, from researchers in Australia, Singapore and the United Kingdom, has focused on a technology called quantum discord. This phenomenon, far more robust and easily accessible than entanglement, can also deliver a quantum advantage: it could be harnessed to bring quantum technologies within easier reach than expected.
By encoding information onto laser light to demonstrate the unlocking of this quantum resource, they showed that it is possible to retrieve more information by using quantum discord than by not accessing the discord.
Another study author, Ping Koy Lam from the Australian National University (ANU), likened their experiment to 'decoding music from a AM/FM radio simulcast that is badly affected by static'.
They found that discord is similar to shared quantum static, and that more 'music' can be extracted from this simulcast with the right quantum tools.
Quantum discord has been shown to be present in many systems, and might previously have been characterised as unwanted noise, making some scientists sceptical about its potential usefulness, but these new findings suggest otherwise. The experiment carried out isn't considered a quantum computation, but it shows that discord has potential that can be unlocked for quantum technologies.
Researchers are now looking for other tasks that could be enhanced by quantum discord. The hope is that discord could prove an easier path to future quantum technologies than entanglement.
Their study 'hints towards the possibility that the requirements on certain quantum technologies could be relaxed'.