Back of the Envelope

I've been bouncing around an idea in my head of starting up a second blog, a group blog devoted entirely to Quantum Computation. The idea would be to despin the quantum news in order to help the layman understand the true state of progress without trying to convince people that every incremental step is the next revolution in computing. It would also help readers keep up withthe real news in quantum computation, looking at important advances which appear in the scientific journals but which lack the proper PR department to impress the MSM.

The problem is, aside from my lack of time to take on yet another project, the fact that I lack the expertise to effectively do this. I am, as I have said in the past, not a physicist, theoretical or otherwise, but an engineer who has done experimental physics, and I'm not even in the field of quantum computation anymore. Thus the need for this to be a group blog, where my role would primarily be Token Engineer and Substitute Layman, trying to get the real experts to explain it in terms the rest of us can understand. Of course, to really do this, I would need to recruit real Quantum Computation experts, of whom I know a couple. I'm not sure they'd be interested--some of them are bloggers, but they may rather write their own blogs than participate in a group one. If one of them were doing the job, I could just link to them and not worry about it, but some prefer to use their blogs for non-technical things, while others are way too technical, and most of them are not very regular bloggers. We'll see.

There's a great post on well-tempered numbers at Zeroth Order Approximation:

In doing quick approximate calculations, you certainly do not want to do actual multiplication or long division. Heavens! So you take short-cuts and round things off pretty severely. But you want to round things off in a uniform and consistent way, to keep your errors under control. To do this, I find that I naturally begin using a well-tempered set of numbers.

The idea is to choose a set of numbers that are separated by equal ratios -- like the notes in the well-tempered scale. Instead of filling the space between 1 and 2 (one octave), though, you fill up the space between 1 and 10 (one decade). Basically, the numbers you pick are evenly spaced on the slide rule scale. How many "notes" should you have in your scale? Not too many, or the system will be cumbersome; not too few, or your calculations will be too approximate to be useful. The exact number of notes in a decade will be chosen so that the individual steps have very convenient, easy-to-remember values -- even if you have to cheat a little to get the right "harmonies".

This is why engineers, at least those working across many orders of magnitude, such as radar engineers, often use units of decibels. Of course, thinking this way tends to skew your thinking, especially when you look at a circuit and think, "Okay, it's only a 3 dB loss in power, so I'm okay." The problem is, 3 dB of loss means you've lost half the power.