Sciency Words: Qubit

~ J.S. Pailly

Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of science or science-related terms so we can expand our scientific vocabularies together.  Today’s term is:

QUBIT

I’m starting to think I can get used to just about any weird quirk of language.  When I first saw the word qubit, referring to the quantum bits inside a quantum computer, I’m pretty sure my eye twitched.  The spelling of that word… it just looks so… so wrong.

And I’m not the only one who to feel that way.  In a paper titled “From Cbits to Qbits,” American physicist N. David Mermin laments that “the prevailing ‘qubit’ honors the English rule that q should be followed by u but ignores the equally powerful requirement that qu should be followed by a vowel.”  Mermin would prefer the spelling qbit.  I would prefer the hyphenated form q-bit.  Unfortunately, neither of those options seem to have caught on.


So who is responsible for this crime against English spelling rules?  It was another American physicist by the name of Benjamin Schumacher, who originally introduced the term in this 1995 paper on quantum information theory.  In the brief acknowledgements section at the end of the paper, Schumacher explains: “The term ‘qubit’ was coined in jest during one of the author’s many intriguing and valuable conversations with W.K. Wootters, and became the initial impetus for this work.”

As a writer, I kind of identify with Schumacher here. I’ve had the experience many times of either learning a new word or inventing one, and having that spur fresh and exciting new thoughts.  But still, why is the word spelled that way?

Several other sources (including Wiktionary) say the word qubit is formed by analogy with cubit, the ancient unit of measure equal to the length of an adult male’s forearm (from elbow to fingertips).  There is a certain inherent uncertainty involved in cubit-based measurements, given the amount of variation there can be among adult male forearms.  So I guess connecting that to all the inherent uncertainties of quantum science and quantum computing makes a sort of sense.

I don’t know.  Maybe I’ve gotten so used to seeing the word spelled the way it’s spelled that it doesn’t bug me as much as it used to.  And knowing a little about the word’s history, and its apparent association with the cubit, probably helps to make the weird spelling a little more palatable for me.  But what about you?  Are you okay with qubit, or does that weird spelling make your eye twitch when you see it?

16 thoughts on “Sciency Words: Qubit”

  1. To the best of my understanding, quantum computers don’t even use qubits the way a classical computer uses bits. They can’t, as information is not conserved in superposition. These qubits get treated as invisible microstates that get coarse-grained into macro states, much as we coarse-grain the invisible positions and velocities of the atoms in a table to the useful thing we can see.

    The difference is we seem to believe the atoms in the table actually do have positions and velocities, whereas for qubits we don’t. Not sure this bodes well for the qubit table.

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    1. Sounds like you’re better informed about this than I am. The way it’s been explained to me is that qubits represent zeroes, ones, or zeroes and ones at the same time, and that that allows a quantum computer to work through multiple solutions to a problem simultaneously. But I haven’t dig too much deeper into the science behind the idea.

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      1. What representing zeroes and ones at the same time really means is that you don’t know if it is a zero or a one, and the erstwhile computer can’t know either. The qubit doesn’t even know. Without this information problems do not get solved. This is why efforts so far focus on trying to tease out macro information, like is it a qubit table or a qubit chair.

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  2. I think they’ve missed an opportunity in not calling it a ‘quantum bit’. In terms of clarity, it seems like it would translate better into different languages. That said, If ‘qubit’ is a universal scientific term, then English language rules need not apply.

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    1. You’re braver than I am. That’s a cute name for a quantum computer, but I totally get why some people wouldn’t like it. I’m kind of nervous about using the word at all in fiction, unless I can include an explanation so the general audience know I’m not the one who came up with the spelling.

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