Wednesday, May 21, 2026

Qubits, and Why Quantum Computing Is a Winner-Takes-Most Bet on Physics

What better place to start building an understanding of quantum computing than with the qubitThe basic unit of a quantum computer. Like a 'bit' in a normal computer, but instead of being only 0 or 1 it can be 0, 1, or a blend of both at once.? In the end, it all comes back to that. A regular computer runs on bits; a quantum computer runs on qubits. That is the whole sentence. But is it really that simple? Let’s open it up.

The physics underneath

As a physicist, this is the part I find most interesting. It is the purest physics layer; the engineering challenge begins from there. So, what is the physics of a qubit?

When most investors hear “quantum computing,” they think of IonQ (NYSE: IONQ). IonQ is one of the most visible pure-play quantum-computing companies in the public market. But on the science, it tells you only a slice of the picture. IonQ runs on trapped ionsA qubit made from a single electrically charged atom held in place by electromagnetic fields and controlled with lasers.. Other companies use neutral atomsA qubit made from an uncharged atom held in place by focused laser beams ('optical tweezers')., superconductors, semiconductors, photonicsA qubit made from particles of light (photons). Photonic machines can run at room temperature., defectsUsing tiny flaws in a crystal, such as a missing atom in diamond, to hold a qubit., topological states, or bosonic modesAn approach that encodes a qubit in the vibration patterns of light or sound rather than in a single particle..

That is why the physics matters for investors: choosing a quantum stock is partly a bet on which physical system scales first. For this note, I will group them by the physical field they draw from: atomic physics, solid-state physics, quantum optics/photonics, and topological condensed matter.

Nuclear physics belongs on the list too, in principle, but in practice it has become a legacy field, used mostly for demonstrations and teaching. It may be worth a note of its own one day. For this one, I will set it aside.

Public-company exposure, by physics field

The table below lists the tickersThe short symbol that identifies a stock on an exchange, such as IONQ or QBTS. most often associated with each modalityThe underlying physical approach a quantum computer is built on (trapped ions, superconducting circuits, photonics, etc.). Choosing a quantum stock is partly a bet on which modality wins.. Some companies appear in more than one row because the large technology firms fund or expose investors to multiple quantum approaches at once.

A winner-takes-most market

The key point is not that one box is automatically better than the others, but that each box fails and scales for different physical reasons.

I suspect quantum computing will become a winner-takes-most market, at least within the parts of the field that require scalable, fault-tolerant machines. There may be room for more than one approach for a while, but if one of them produces a decisive breakthrough, the funding, the talent, and the attention will move toward it, and the rest will be left fighting a much harder fight.

So, my goal in this notebook is plain. Understand the subtle aspects of each method, learn the benchmarks that actually matter, and be ready when the turn comes.