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 12.0, August 7, 2025

Today, I’m looking inside the quantum computer. My most recent full post covered quantum superposition. Superposition is the state in which a qubit can be both 1 and 0 at the same time. It’s one of the key concepts in the operation of a quantum computer. Today’s issue steps up to a broader, higher-level, view and covers the quantum processing unit (QPU) and the structural part of the system that holds the QPU.

A quantum computer, unlike your common laptop, is a part of a bigger system. It can’t do anything alone. A quantum computer requires a powerful conventional computer sitting on top. I refer to that as the supervising computer. Quantum computers also require a system to cool the QPU down to extreme temperatures and keep it there. This is the cryogenic system. The cryogenics consists of an external cooling system and a set of successively colder chambers inside of chambers that contain the processor. Read on to see just what those two systems are and then read about the QPU at the heart of it all.

The Supervising Computer

The supervising computer is a large conventional computer (CC) that controls the quantum computer. It’s as powerful as a few of the most powerful high-end gaming computers put together and is responsible for the following:

• Connects the quantum computer to the outside world.

• Governs the systems that make up a quantum computer.

• Translates between normal speak and quantum speak.

• Takes the instructions given it by a programmer and creates the quantum configuration.

• Reads the quantum results and converts them into a useable form.

• Makes the results data available to the operator.

Next comes the cryogenic chamber and multi-stage cryogenic cooling system. It cools the system in multiple steps down to near absolute zero.

The Cryogenic Chamber

Quantum computing news often comes with a picture of something that looks a bit like a brass chandelier. Figure 1 below is an IBM quantum computer. On the left is the computer sealed up and ready to run. The right shows it without the case. The picture on the right - the brass chandelier - is what most articles about quantum computing show. If you’ve been paying attention to the subject in other media, you most likely have seen this or a similar image.

To me it all looks pretty complex and mysterious. It will be less so if we break it down into smaller parts.

The round metal plates (right side of image) spaced out from top to bottom are thermal isolation plates. Isolation plates lower down are smaller because they are contained by nested layers of smaller cans, each at a colder temperature.

Again, looking at Figure 1, right image, all of the braided cables and tubes between layers carry the signals back and forth between the QPU and the outside world.

The white container on the left side of figure 1 is the system with cryogenic containment installed. It’s a series of nested cans that are each cooled more and more until the final can with the QPU is at near absolute zero.

The actual computer part is a very small chip down at the very bottom. See the call out “A” in figure 2 below. This is the Quantum Processing Unit, or QPU. That’s what does all of the work.

The QPU needs to be super cold. So cold that it must be held at near absolute zero and it must get down to that temperature in stages.

The Quantum Processing Unit

The QPU in the picture is cooled to a temperature of 15 millikelvins. Absolute zero Kelvin is -459.67 degrees below zero Fahrenheit. Divide a degree Kelvin into 1,000 little sections and take 15 of those above absolute zero. That’s how cold a QPU must be to operate.

The QPU chip is not really anything at all like a conventional CPU (central processing unit). A CPU has a number of sections with different purposes. It fetches instructions and data from memory. Other CPU sections store the data. Some perform arithmetic. Other sections keep track of memory address and instruction locations. Each part works in concert to perform operations based on the instructions in the computer’s memory.

CPUs can solve many different problems by being given different sets of instructions (a set of instructions is called a program or an app). Load a different app and the CPU will do something different. CPUs can often work on multiple apps at the same time by quickly jumping from one to the next.

A quantum processing unit is not at all like that. Before it is powered on, it has no functions and can’t do anything. It is simply a two-dimensional array of qubits - like a graph paper grid with nothing written in it.

Once powered up and cooled down, the supervising computer sends instructions to the QPU to configure the qubits as quantum gates or as data. The supervisor sets up superposition and entanglement. It turns the empty grid into a quantum circuit designed to solve a specific problem. As configured, it will only perform one specific problem. It can be later configured for a different problem, but not more than one at a time.

The reason quantum computers have the promise of calculating things in minutes that a conventional computer might take years is in the quantum circuit. A quantum circuit is designed to perform an extraordinarily complex calculation in one step. Such calculations in a conventional computer may take millions of lines of code executed millions of times.

In a later issue, I will get into the specifics of how a quantum circuit can solve such complex problems, but for now, it is just important to accept that rather than performing a trillion small operations in sequence, like a conventional CPU, a QPU will perform an operation that is maybe a trillion times more complex than a CPU operation, and the QPU will do it in one step.

More to Come

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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About Positive Edge LLC

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.