Is the world’s only commercial quantum computer really a quantum device, or a just regular computer in disguise? Controversy has long swirled around the computer produced by D-Wave, a company based near Vancouver, Canada.

Now a paper published on the arXiv preprint server takes a step forward in showing that it really does operate on a quantum level, Nature News Blog reports.

In 2011, a group led by scientists working with D-Wave published a paper in Nature with evidence that their 8-qubit system was working on a quantum level: it responded to temperature changes as expected for a quantum device.

Now, a group of independent scientists follows that up by showing that the 128-qubit version of the D-Wave computer (or at least the 108 functioning qubits in the specific computer that they analyzed) also seems to be behaving quantumly.

Scott Aaronson, a theoretical computer scientist at the Massachusetts Institute of Technology in Cambridge who has historically been sceptical of D-Wave’s claims, says that he is fairly convinced by the data, but that there are plenty of important questions remaining — including whether the current or future versions of the D-Wave computer will actually be any faster than classical machines.