There has been another recent advance in quantum computing, which may be an important step towards the development of large scale QCs.

The QCs developed thus far have to work at very low temperatures in order to keep the energy of the system low enough that the qubits remain stable. Very low temperatures, which means close to absolute zero. In practice this means below about 0.1K, or within a tenth of a degree of absolute zero.

A paper last year outlined how in theory this minimum working temperature could be raised to around 1.5 Kelvin. Still absurdly cold, but in relative terms this is a huge jump up from 0.1K. This is a quantum-dot-based system, and the mechanism by which they can work with the higher temperature is by isolating the quantum dots and then using magnetically-controlled electron quantum tunnelling to read the qubit state. (As an interesting aside, it is the phenomenon of quantum tunnelling that sets a barrier to the size reduction of traditional processors, which could end Moore's Law.)

Why does a change from 0.1k to 1.5K mean a big reduction in the difficulty of producing large scale QCs? Well, each time you make the machine bigger, and more powerful, each time you add more qubits, you are introducing extra energy, higher temperatures, which means even more cooling is required. There is a several orders-of-magnitude difference in the dollar cost between cooling to 1.5K and cooling to 0.1K. As one of the paper's authors stated: "This [1.5K] is still very cold, but is a temperature that can be achieved using just a few thousand dollars' worth of refrigeration, rather than the millions of dollars needed to cool chips to 0.1 Kelvin."

So this was the theory, an increase in workable temperature for QCs from 0.1K, up x15 to 1.5K. The big advancement is that this theory has now been experimentally verified, by the team at Delft that I've mentioned in previous posts.