A discussion of quantum computing is not what many people expect from a blog about magazines, but then they forget that magazines have a habit of going anywhere and discussing anything.

Back in 1986, I commissioned an article for *Acorn User* magazine, which was later dubbed ‘Spider Power’, from David Johnson-Davies and David Deutsch. The blurb on the contents page read: ‘The Davids present their Spider curve-plotting program to plot almost any equation.’

The Spider was an incredible BASIC program that really did do what it said it would. It was my favourite program – even over the breakthrough fractal routines and Mandelbrot listings we ran. You could type in an equation – even a mix of cartesian –* x* and *y* – and radial – *r* and *θ* – and still it would print the equation. Raise *x* to the power of *θ*, *y* to the power of *r*, whatever you typed in, the Spider plotter went away and did it.

One example it plotted was a a set of circles arranged at regular intervals. Don’t ask me to remember the equation. But get hold of a copy of *Acorn User* from October 1986, issue 51, on eBay and you can see it all there. Type the listing into a BBC Micro emulator and you can run it too.

It was worth buying a £400 BBC Micro just to run this program. There was nothing like it on a £3000 Apple Mac. You’d have had to go to a minicomputer. The only problem was the time it would take – days, weeks even. I gave up on several plots. Even with a second processor attached (which probably tripled the processing speed).

But what about quantum computing? Well, the Davids behind the program were the MD of Acornsoft and a researcher at Oxford University. David Deutsch, the latter David, was tricky to get hold of because he never got up till 3pm (typical student I remember thinking!). When you did get hold of him, you learnt of his theoretical world of computing using the states of atoms for computation and data storage. Given the billions of atoms in a grain of sand, the possibilities are incredible.

Deutsch had recently published his landmark paper on the topic – ‘Quantum theory, the Church-Turing principle and the universal quantum computer’ – and today he’s regarded as the father of quantum computing. The only problem with such machines, I’m sure someone told me at the time, was that they might disappear because they had moved into another dimension (unlikely, but theoretically possible).

All this has been sparked by *The Economist*‘s quantum computing technology quarterly (QC in TQ). The TQ is entitled ‘Here, there and everywhere’ and I read it on a a plane from from Sydney to Hong Kong. The theme of the articles is that the technology is at the stage where it is about to be commercially exploited.

But keep hold of that 1986 *Acorn User* magazine because it gives an insight into the thinking of one of the greatest minds of this century. When Dr Deutsch wins a Nobel is probably the time to sell it.

Tags: acorn user, bbc micro, David Deutsch, David Johnson-Davies, quantum computing

## Leave a Reply