A couple of weeks ago, I visited the London headquarters of IBM in the UK and Ireland for discussions about possible areas of collaboration in research and education.  At the end of our meeting, we were taken to see some of their latest developments, one of which was their Quantum System One computer.  We had seen its casing, a shiny silver cylinder about half metre in diameter and a metre and half long with a hemispherical lower end, hanging in a sealed glass cube in the lobby of the building.  The computer we viewed was also suspended from the ceiling of a sealed glass cube in order to isolate it from vibration, but was without its cylindrical cover so that we could see its innards which need to be cooled to cryogenic temperatures.  The room in which it was displayed was darkened and a soundtrack of the computer operating added to the atmosphere – it sounded like birds chirping.  IBM are already operating quantum computers, starting in 2019 with a 27-qubit processor and achieving 433 qubits last year with plans for 4,158+ qubits in 2025 in their roadmap.  There are about 80 companies focussed on quantum computing worldwide, including Universal Quantum who are working on a million qubit computer.  Qubit is short for quantum bit and is the quantum mechanical analogue of a classical computer bit.  A computer bit works in binary and can only have a value of 0 or 1.  Whereas a qubit holds information about the probability amplitudes for 0 and 1 which will always have a sum of 1.  The use of probability amplitudes allows complex systems to be described more efficiently and larger solution spaces to be explored.  IBM’s quantum processors are thin wafers about the same size as the one in your laptop but their need for cryogenic temperatures and vibration isolation means we will not be using them at home any time soon.