Quantum computing is one of the first great technologies of the 21st century, but the details are still shrouded in mystery. I can explain conventional digital computing down to the electron in a MOSFET, and with this newsletter, I have made it my mission to do the same for quantum computing.

Welcome to the Quantum Edge newsletter. Here you will read about the physics, chemistry, and all sciences that create the foundation for quantum computing. Join me in my quest to translate the mysteries of the quantum world to the language of the dinner table and the coffee shop.

In today’s newsletter: how temperature works and how lasers can cool things down

When we last talked qubits, I explained how, as a variable, a qubit is a container holding a vector number rather than a scaler. As a reminder, a scaler is a one-dimensional number. It’s just a quantity, like 1, 6.5, 70, or 0. A scaler 70 can mean 70 oranges, 70 miles per hour, or 70 of just about anything. Without the label (oranges, miles per hour, etc.) it is not real meaningful, but it is a number.

Even with a label, like “miles per hour”, the scaler number 70 isn’t super meaningful. 70 miles per hour, where? In what direction? When? 70 is the number. “Miles per hour” is a dimension. Direction would be a second dimension. “70 miles per hour, traveling due south” has two pieces of information, or two dimensions: speed and direction. Having more than one piece of information makes it a vector rather than a scaler and it becomes more useful for describing things in the physical world.

If you were to give “70” the label: “speed”, you could say speed = 70. Since your speed can vary, “speed” in this case is a scaler variable that, at the moment, equals 70. When the traffic cop asks you what your speed was, you would say “70.”

If you gave your speed and direction the label: “travel plan”, you could say travel plan = 70 miles per hour due south. Your travel plan is a variable because it can change, and it is a vector because it has more than one piece of data.

Lasers. Yes.

But first, let me talk about heat, temperature, and a scientist that discovered what happens when things get really cold.

I recently read an article about John Bardeen. Mr. Bardeen won his second Noble Prize in physics for his work on superconductivity (the principle that some materials will conduct electricity with zero resistance when extremely cold). Bardeen’s work did not directly lead to the creation of qubits, but it came close. His first Nobel prize, by the way, was for co-inventing the transistor.

Quantum computers (QCs) are cryogenic devices, meaning they only work when super cold. Current quantum computers require temperatures as cold as 0.1 to 0.01 degrees above absolute zero on the Kelvin scale (-459.49 to -459.652 Fahrenheit). For comparison, water freezes here on Earth at 273.15 degrees Kelvin (K) and boils at 373.15 K (32 degrees and 212 F respectively or 0 degrees and 100 degrees C). You may note the difference of 100 in the Celsius range. The Kelvin scale matches Celsius in terms of the temperature difference per degree. Regardless, 0.01-degree Kelvin is very cold. At absolute zero, heat does not exist, and, in theory, all movement of atoms and molecules stops.

Quantum computers need to be super cooled to reduce the movement of the qubits. Heat is essentially movement of particles. The more movement, the higher the temperature.

While qubits do require some motion in order to exhibit spin up and spin down properties, they don’t need much movement. Less movement means that the spin state is more stable while more movement means that natural vibrations become more of a factor than the properties of the qubit and it can’t reliably hold or process data.

Random qubit movement can change the value of the qubit or just make it impossible to set or read. The warmer the qubit, the less stable it is and the less useful it is as a computing tool.

As I was jumping from article to article related to Bardeen and superconducting, I ran across “laser cooling.” Now generally, lasers are thought to heat things up. Some lasers can create so much heat that they cut steel and other high temperature materials. Lasers can also be used to cool things but to explain that requires some background on how heat and temperature work.

Heat, which is quantified on a temperature scale, is really just atoms, particles and molecules vibrating and moving around. The more heat energy a particle has, the more it moves around. The more it moves around, the hotter it is said to be. If particles are not moving at all, they don’t have any heat and their temperature is zero on the absolute scale, which is called the Kelvin scale. Our scientific world has created temperatures close to 0 K but not exactly 0 K.

In our home, we experience heat when the air molecules bump into our skin molecules. The faster the molecules are moving, the hotter we feel. When two moving particles bump into each other, some of the heat, in the form of movement goes from the faster moving particle to the slower moving particle. We can use the game of pool to show this.

If you hit a cue ball toward a stationary eight ball, you could say that the cue ball is hot because it has motion and the eight ball is not hot because it doesn’t have motion. When the cueball bumps the other one, the cue ball will end up losing much of its speed to the eight ball. The cue ball energy transfers to the eight ball. The eight ball takes that transferred energy and starts moving.

The movement energy didn’t go away. It was transferred to the object with lower vibration energy (in the example, the eight ball). Energy can be changed, moved, and transferred, but it’s always there. Heat energy works the same way. Heat always goes from hotter to colder.

The same phenomenon happens all around us. If you walk outside in the winter, the cold air molecules will be vibrating slower than your warm skin molecules. When the air and skin molecules bump, some of the vibration / heat energy is given to the slow air molecules and your skin molecules slow down a bit. Your nerves and brain interpret that as “brrr. cold.” During the summer, the air molecules are moving faster, so we feel more heat.

Now for the lasers… Pew. Pew. Pew…

Not those kind of lasers. Well, yes. Those kind of lasers, but less powerful. A laser is a concentrated beam of light that is all the same color. Color is set by the frequency of the light, so a laser can also be described as a beam of light that is all the same frequency. As we have mentioned way earlier in this series, light works both like a wave and a particle. Light particles are one of the elementary particles - can’t be broken into anything smaller - and are called photons.

Photons move, so they have momentum, but they don’t have mass. They are just little packets of energy. If a laser is emitting a lot of photons, it can heat things up, even to the point of cutting metal (or imaginary space battles). If it is emitting a small number of photons, a laser can be used for other things like cooling atoms down to near absolute zero.

Now let’s look at a quantum computer that uses individual atoms as qubits. Most of our QC discussions have used electrons as qubits, but some types of atoms can be used too. The quantum processing unit (QPU) in this example is chilled with multiple stages of supercooling cryogenic refrigeration systems. But the atoms qubits are still not cold enough to be used as qubits. Lasers can be used to reach the lowest temperatures.

When a photon hits an atom in just the right way, the atom will absorb the photon. Shortly thereafter the atom will release another photon out in a random direction. Laser cooling systems will point two or more lasers at the atoms to be cooled. The atoms absorb photons that are coming toward them. By doing so, the momentum of the photon cancels some of the motion of the atom. The atom will then release a different photon in a random direction, releasing the energy from the photon.

As long as the laser photons are coming from the same direction and the released photons are leaving the atom in random directions, the atoms movement will slow, thus cooling it closer to absolute zero (0 K). Current quantum computers operate at between 0.1 and 0.01 degree K. The colder a qubit is, the more stable it is and the better it works for computing. QC experts are looking at lasers and one possible way to try and get qubits even colder.

New to the Quantum Edge newsletter?

Thinking about re-reading it but want a more transportable format?

I’ve wrapped the first ten issues of The Quantum Edge newsletter into book form. The collection, called “The Quantum Computing Anthology, Volume 1”, is now available in Kindle and paperback on Amazon. The book collects newsletter issues 1 through 10 and has some additional material and edits for continuity and clarity. I will add another volume to the series every ten newsletter issues, so look for Volume 2 (newsletter issues 11 - 20) in early 2026.

You can order the Kindle or paperback editions on Amazon today: The Quantum Computing Anthology, Volume 1

Check your email box Thursday - probably. (Okay, some of these weekly issues have come out on Friday, or not at all. But, in a quantum world, how can you tell?)

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Positive Edge is the consulting arm of Duane Benson, Tech journalist, Futurist, Entrepreneur. Positive Edge is your conduit to decades of leading-edge technology development, management and communications expertise.