The scientists published their findings in the journal Science[1,2] and in pre-prints in arXiv.[3,4] It’s been theorized previously that there are many obstacles to quantum computing, such as the fact that certain quantum particles, like photons, have behaviors that are impossible to predict using ordinary computers. In the most recent studies, researchers have injected four identical photons into a network of beam splitters on a chip.[1] Thanks to quantum interference, which happens when photons strike a beam splitter simultaneously, the photons take a different path through the optical maze each time the experiment is run. Detectors spot the particles at the end of the run, revealing the probabilities of arriving at all possible destinations. Without the device that the researchers constructed, calculating these probabilities would be mathematically difficult, yet not impossible. Every added particle doubles the computational difficulty. If 100 photons were put in such a device, the most powerful supercomputer on the planet wouldn’t be able to crunch the numbers. The experiment could be scaled up to that size, but generating large numbers of identical photons will require getting the timing just right and this won’t be easy. Thankfully other teams are working on similar projects as well. A team in Australia unveiled their own prototype[2] and two more groups, in Austria and Italy, describe similar experiments.[3,4] These machines are proofs of principle, and their construction has only been recently possible thanks to the ability to produce simultaneous batches of identical photons with high reliability. References:
