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 learn more than just: “quantum computing works because of superposition and entanglement.” The Quantum Edge newsletter will tell you what goes with superposition and entanglement and what those terms actually mean. 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: A closer look at the quantum processing unit and closing in on the workings of entanglement.

The prior issue brought a diagram of a quantum processing (QPU) unit with 49 qubits. The illustration (shown again here as figure 1, below) depicted several qubits in superposition, several entangled, and the rest not yet in superposition. Today, I’m going to dig into the actual construction of that QPU.

As I’ve said before, a qubit can be made up of a lot of different things. Anything, in fact, that exhibits quantum superposition and quantum entanglement has the potential to be used as a qubit. One of the most promising devices being used as a qubit is called a transmon. A transmon is a device that creates a very small quantum field that exhibits superposition and entanglement.

Figure 2 shows a set of four superconducting transmon qubits. The transmon structures are called out in B. C shows the control lines used for sending pulses for setting, tuning, and controlling the qubits. A shows the readout resonators.

Control signals are sent to the qubits via the control lines. These set the qubits to superposition and/or entanglement. When it’s time to read the qubit, the collapsing wave function travels through the readout resonator as a microwave pulse. The system detects the collapsed value based on how the output signals shift in the resonators. D, the return signals send results back to the supervising conventional digital computer.

The “+” plus sign part (figure 3, a) of the qubit is a capacitor. The capacitor is wired in parallel with a squid (superconducting quantum interference device) shown in figure 3, b. The squid is formed out of two Josephson junctions, one of which is shown in figure 3, c. The Josephson junction has two crossing conductors with a very thin insulting layer between them. I’ll skip the physics for now, but the combination of everything shown in figure 3 exhibits that same quantum properties of superposition and entanglement as a single electron does. Therefore, it can be used as a qubit.

Everything in figure 2 leading up to the transmon is support structure. It is related to communicating with the qubit, setting it to superposition, entangling it, reading it, and keeping it stable. The hypothetical 7 by 7 QPU in figure 1 would have control lines, resonators, return signals for 49each of the qubits.

In figure 1, I have illustrated qubits in positions A1, A2, B5, C1, D2, D4, and F6 as having been set to be in superposition. Qubits A1 and A2 are entangled with each other as are qubits D2 and B5. When this QPU reached its superconducting temperature of 0.01 Kelvin, the supervisory computer sent a series microwave pulses down the control lines to those seven qubits.

Step 1: Cool the QPU down to 0.01 degrees Kelvin.

Step 2: Send instructions to qubits A1, A2, B5, C1, D2, D4, and F6 to set them to superposition. The instructions are in the form of microwave pulses of a frequency and energy level that causes the qubits to go into a superposition state.

Step 3: Send entanglement instructions to A1/A2 and D2/B5. These entanglement instructions are microwave pulses of an appropriate frequency and energy level (different from the superposition instruction pulses) to create an entanglement state.

A more complex real-world configuration would have many more qubits in superposition and many more sets of entangled qubits. They would be arranged to form quantum logic gates and, in total, a quantum circuit capable of calculating a complex math problem.

In figure 1, two of the entangled qubits (A1 and A2) are right next to each other. The other set of entangled qubits (D2 and B5), however, are not next to each other. The entanglement has to cross some distance with several qubits in between. Entanglement with the qubits next to each other seems logical, but entanglement between particles that are not next to each other does not.

However, quantum entanglement has been demonstrated in laboratory settings with the particles being widely separated. Mathematical simulations have shown that quantum particles can be entangled at any distance apart - even light years.

The math works and experiments have proven distant entanglement, but the concept begs a lot of questions. Like, if the particles are a very long distance apart and the entanglement action takes place virtually instantly, does entanglement mean that faster than light communications is possible (No. It does not.) Or, how do they connect up instantly over even vast distances?

The answer may come from Einstein’s special relativity.

Special relativity states that as something approaches the speed of light, the passage of time for that thing slows down. If you are in a spaceship approaching the speed of light, time will pass slower for you than it will for outside observers that you are moving away from. In the “science fiction” classic example, you leave Earth at near light-speed. You return after ten of your years, but 10,000 years have passed on Earth. You have a few more grey hairs but back on Earth, everything you know has been gone for ten millennia. This phenomenon is called time dilation.

Even time dilation doesn’t seem like it would help entanglement happen at vast distances instantly. But it’s not just time that dilates. Distance does too. If your ship is 100 meters long at rest, it looks 100 meters long to you and to people on the outside. When the ship is traveling at near light-speed, it will appear shorter to the outside observer. Inside, to you, it will still appear 100 meters long, but to an outsider, it may shrink to 50 meters in length. And the mass of the ship will also get proportionally larger.

If you continue to try to get to 100% of light-speed, your ship will shrink to infinitely short, it’s mass will grow to infinitely heavy, and time for you inside will essentially stop. You can’t quite get to light-speed because infinities don’t really work well with objects that have mass, but when you are very close to light speed, time virtually stops ticking. The effect is that travel distances essentially shrink to near zero. You travel the distance in no time at all (from your perspective), so effectively, there is no distance at all (from your perspective).

The star Proxima Centauri is about 4.25 light years away from my house. If you travel there from Earth at 99.9999999% of light-speed, Earth viewers will see you arrive there in about 4 and a quarter calendar years. From your perspective, you will get there almost instantly. Time compressed for you and so did distance because space and time are interlinked.

Time dilation is usually discussed with speed being the focus. However, it’s not necessarily speed that gets messy. Mass may be the problem. A photon, the elementary particle that caries light and other forms of electromagnetic energy has no mass. Photons can and does easily travel at the speed of light. A photon’s natural state is to travel at the speed of light.

Caution: Brain twisting ahead

Logically, if distance compresses to zero at the speed of light and time compresses to zero at the speed of light, a photon should be able to go anywhere instantly, from its perspective. Since there is no distance, a photon isn’t really traveling. One photon is in the same place as any other photon.

We, as outside observers, see a photon as traveling at 299,792,458 meters (186,282 miles) in a second. We call the speed “C”. But inside the photon (if you can imagine that there is an inside to an elementary particle), time and distance have no meaning. To the photon, everything is in the same place and travel anywhere is instant.

Before I end today’s newsletter, I’d like you to consider the possibility of the following:

That may not be the exact mechanism that allows entanglement to work, but I submit that it is a plausible explanation.

Until next time…

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.

Coming soon: Volume 2, collecting newsletter issues 11 though 20 is in the works. Look for it on Amazon soon.

In the meantime, you can order the Volume 1 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.