I can explain digital logic down to the electron in a MOSFET, but I can't come close to the same with quantum computing. This newsletter is a journal of my quest to learn the fundamentals of quantum computing and explain them on a human level.

Welcome to the Quantum Edge newsletter. Join me in my year-long journey into the weirdness that is quantum computing.

Issue 3.0, Feb 20, 2025

News about quantum computers keeps piling up. I’ve added a couple of links with recent quantum news in the “Independent Resources” section at the end of the newsletter. I suspect QC will be one of the more popular tech subjects in the news for the next few years. I’ll try to find a few of the most interesting and add them to the list below.

Back to Particles

As we discussed last week, an electron is an elemental particle, meaning it can’t (with our current technology and understanding) be split into smaller particles. Protons are composite particles and can be broken up. They are made up of three* quarks. Below is our beachketball representing a proton with a few more blanks filled in. Quarks come in different types and a proton is made up of two up quarks and one down quark. We’ll get to the meaning of up and down later. The quarks are held together by gluons.

* Probably three. Read Max’s article to hear an alternate view.

I only show three gluons on Figure 1. However, in reality there are usually 16 gluons holding together the three quarks. Gluons are so named because they act as the glue that holds quarks together to form composite particles.

One little detail. Quarks and electrons don’t look like little basketballs or golf balls. To the best of our understanding, they are points. That means they are as small as is possible to get. No matter how much you zoom in, they are still just a point. They are special points though. Around each is what I am calling a cloud of influence.

A magnet can influence something without touching it. You can push away a magnet with a magnet without the two touching by pointing the like poles (North to North or South to South) together. You can also pull things that are magnetic with a magnet without the things touching. That area where a magnet can influence something else without touching it is the sphere of influence. Particles have a similar “area of influence” property. It’s not magnetism, but it works much like magnetism.

While our elemental particles, the electron and quark, are just points, they operate like they are very small spheres. The sphere of influence gives particles the appearance of size and the polarities of the particles cause them to influence one another. Like magnets, particles can attract or repel.

With magnets, we talk about North or South poles. With particles, we refer to the polarities as positive and negative. An electron has a negative charge, and yes, that’s where a battery gets the labels “negative and positive” for its poles.

Just a warning. Things are about to get a little weird, but first we take break and look at another table.

Table of Elementary Particles

Electrons aren’t the only elemental particles. My 1979 high school science class had the periodic table of the elements as I posted in Figure 1 last week. We did not have a table of elementary particles as I have posted here in Figure 2. The table shows the 17 elemental particles currently known (as of 2/20/2025, 7:14 am, PST).

Particles, like atoms, are grouped in the table based on common properties. The important properties (other than the sometimes goofy name) are mass, charge, and spin.

Mass

I’m sure you’re familiar with what is possibly the most famous math formula every written down. Albert Einstein’s E=MC² formula for converting mass to energy and vice versa. Energy = Mass times the speed of light squared. Raise your hand if you EVER, in your wildest dreams, thought you would see this formula used in the real world. I’ll wait.

Hang on to your hat because you are about to see just that.

Look in the table in Figure 2 at the electron, third down on the left, in green. There are three numbers that describe the properties of the electron as an elemental particle. The first is mass, then charge, and finally, spin.

The mass for an electron is ≈ 0.511MeV/C². But, how do we get that number. An electron seems to be too small for my scale. This is where that math comes in because, while we can’t weigh an electron, we can measure how much energy it is made of. People have done so. An electron has 0.511MeV of energy. Let’s break it down and do a little figuring courtesy Mr. Einstein.

≈ means “about” or “close to”, meaning this is an approximate value as close as we can get with current technology.

0.511 is the number of MeV.

MeV means Mega (equal to millions) of eV (electron volts).

1 eV is the energy it takes to accelerate an electron through a vacuum to reach a potential of 1 volt. The electron has just over half a million eV of energy.

/ is the division symbol

C² is the speed of light (300,000,000 meters per second in a vacuum) squared (That’s 300,000,000 X 300,000,000, or 90,000,000,000,000,000). With numbers that big, you can see why folks like to use the abbreviations C and C² respectively. It’s a lot easier to write down.

Bring out the formula: E=MC²

E ≈ 0.511MeV, which can also be written as 511,000 electron volts.

511000

C² = 90,000,000,000,000,000

Substituting the actual values of E and C² gives the equation: 0.511MeV ≈ M times 90,000,000,000,000,000.

Substituting the symbol C² back because it’s easier to write than the big number: 0.511MeV ≈ MC²

Using algebra, I divide both sides of the equation by C² which cancels the C² on the right side:

0.511MeV/C² ≈ MC²/C²

0.511MeV/C² ≈ M

I move the M ≈ to the left for easier reading

M = E/C² or mass = energy divided by the speed of light squared

Substituting the actual values for E gives the equation: M ≈ 0.511MeV / C²

The mass of the electron is approximately equal to 0.511MeV/C², as is shown in the table below.

That’s a lot of energy for very little mass.

Charge and Spin

I think mass was enough for one day. We’ll get to charge and spin another day. Mass and charge are important, but spin is where we start getting close to quantum computing.

I will give you a parting exercise for today. Your assignment is to say the word “Lepton” three times fast. Don’t worry if saying the word conjures up images of breakfast cereal and cartoon leprechauns trying to steel an imaginary pot of gold. In our day-to-day world, leptons are no more real and probably less relevant. The important aspect of this exercise is that the more you say a word, the more familiar it seems. As it gets more familiar, it becomes less of a roadblock to understanding.

In Summary…

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