Technology, Connected - Build Your Own Quantum Computer

Episode Date: November 22, 2025

What if someone handed you the recipe for a quantum computer?Coleman Collins of IonQ breaks down DiVincenzo's criteria—the five capabilities any system needs to be a quantum computer.Physicist David DiVincenzo created the checklist. Every major quantum architecture (superconducting circuits, trapped ions) follows it.The five requirements:1. A well-defined qubit (your basic unit of quantum information)2. Initialization (set every qubit to a known starting state reliably)3. Long coherence times (qubits stay stable long enough to compute without losing quantum state)4. Measurement (read each qubit's state at the end—ideally individually)5. Universal gate set (single-qubit control + entanglement = any computation you want)Mix them together. You have a quantum computer.We talk about:- Why these five criteria matter (the foundation of every quantum system)- What coherence means (how long quantum states survive)- Why measurement is harder than it sounds- How entanglement enables universal computation- Which quantum architectures excel at which criteria- Why trapped ions vs superconducting qubits make different tradeoffsThis is the foundation. Every major quantum company—IBM, Google, IonQ, Rigetti—is solving these five problems in different ways.Now you know what they're building toward.---Other ways to connect with us:⁠Listen to every podcast⁠Follow us on ⁠Instagram⁠Follow us on ⁠X⁠Follow Mark on ⁠LinkedIn⁠Follow Jeremy on ⁠LinkedIn⁠Read our ⁠Substack⁠Email: [e-mail]

This is a five minute short on quantum computing. If by the end of it, you haven't learned something, then email me personally at mark at thinking on paper.xyZ, and I'll make it up to you. There's a lot of different ways to make a qubit, right? All you really need, there's this list called Devin Chenza's criteria. You need five things plus two if you want to do networked quantum computing. As long as you have those five, you can use a photon.

You can use a non-abillion anion, which is the thing that's in the news with Microsoft recently. You can use neutral atoms. You can use superconducting circuits. So basically a loop of wire that, I mean, on the chip, that has this discontinuity called the Joseph's Junction that you use to then sort of create atom-like behavior. We use trapped ions. We use physical single ions of uteribium or barium,

depending on which generation of system you're talking about. And then we address those with lasers, and that does math, turns out. Okay, hold on. Right. we'll get to Microsoft later. Those five steps, we need to know what those five things are. Yeah, so Dr. Vincentzo,

even Vincenzo is a theoretical physicist. I forget where he works or worked. But basically, this is the list of the things you have to have to have a quantum computer. And so you need a well-characterized cubit. So you need a two-level system, a quantum system that you can either be in like a fiducial one, a zero, or somewhere in between, superposition. you need to be able to initialize those qubits to a single state to know where they are.

You kind of know where your zero is. And that's just like, so you have a reference point to then do all the other stuff. You need long coherence time. So what this means is you may be talked about this before, but many different types of two quantum states sort of relax over time, right? One of the challenges of quantum computing is that you quite literally need to isolate the quantum state from the universe. And there are many reasons why that stops being true. One is sort of coherence from interference of like electrical fields, magnetic fields,

you know, solar radiation. Cosmic rays is actually a real problem in superconducting systems. And you also just, depending on what kind of quantum state you're using, sometimes it's relax, right? So you start losing the ability to tell the difference between your one and your zero again. And you're just, you're going back to basically random. And so you need both kinds of coherence there.

That's three. You need to be able to measure, ideally, individually, but at least all of them. And then you need what's called a universal set of quantum gates. And so you need an entangling gate, and you need a single-quit rotation of some form. And generally, that's kind of enough. And that's basically so you can kind of explore the entire what's called the Hilbert space, the sort of the mathematical space that you're trying to compute in, kind of efficiently.

And so you need all five things. But there's a lot of different ways to do that. You can do that with photons. You can do that with squeeze states. You can do it so on. We use trapped ions. And the kind of the reason the logic behind this is that we, our cubits,

don't have any fabrication errors, right? They are made by nature. Good to go. All of the errors that come in are from environmental control, environmental interference, and then basically our inability to actually perfectly because like you can,

like literally we are trapping, ions on a chip. They're floating like, I don't know, it's like 40 microns above a chip that we design and then fad with a partner. And then we're shooting lasers at them. And they're effectively a single point source, but we need to be able to exactly hit those with exactly the right wavelength, exactly the right phase, drive these transitions between multiple ions to entangle them, all of which is, that's the engineering challenge, right? Like our founders like to say that, like, we have no new novel physics to figure out, just a lot of really hard engineering.

But to be clear, it's pretty hard engineering. Like, getting there, but. So we kept ions, and that's a philosophical choice, basically. There's a lot of, the way I like describe it is there are, everyone who is sort of driving, especially kind of in the big commercial space, everyone is picking the hard problems they think are the easiest. And we think that's sort of cubic control,

rather than cubic fabrication, which is what a lot of your kind of superconducting people are thinking about. I think that goes without saying like a lot of people focus on the easier thing than the hard thing sometimes just to get the things done. Look, we're doing things. We're doing things. A couple quick thoughts. Disruptors and curious minds, don't ever say we didn't give you anything.

We actually, thanks to Coleman, you now have the checklist to build a quantum computer. So brought to you by thinking on paper. All right. So what did we just watch? right there. We watch Thinking on Paper, bite-sized, a shot of technological tequila to your prefrontal cortex. It's just a taster, a smorgasbord,

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