Some Thoughts On Quantum Computing

Some remarks by a speaker at a recent professional event inspired me to rant a bit on the topic of quantum computing. For sure, it's not my area of expertise, but I do have a dilettante interest in quantum physics, plus I took a short course at University of Denver a few months ago that was a kind of "Quantum Computing for Dummies", and it is the area of expertise by the Ph.D. physicist who taught it.

[1] Quantum computers will not replace conventional computers. There is a lot of interest in QCs because it is believed that they can do calculations that are not feasible for today's computers. But those calculations are only possible for problems for which there are known - or believed - to be QC-type algorithms. You will never be running a web browser or a spreadsheet on a QC.

[2] One example is Peter Shor's quantum algorithm for large number factorization, which could be used to break encryption schemes that rely on the difficulty of such factorization. Shor is a theoretical computer scientist who developed Shor's Algorithm while at Bell Labs. This is why governments are interested/concerned about QC. A lot of encrypted secrets have been stolen by hackers (theirs and ours), but are just useless bits until they can be decrypted.

[3] Not all encryption is based on large number factorization. Maybe there are as yet undiscovered QC algorithms for the "trap door functions" that those schemes use instead of large number multiplication and factorization. Maybe not. Until then - if ever - such schemes are described as quantum resistant. Switching to such schemes is probably a good idea for sensitive data, just in case QCs eventually work.

[4] QC may never work. Although scaling up quantum computers is talked about as if it were an engineering issue, the people trying to do it are - in my opinion, and whether they realize it or not - trying to solve what physicists call the measurement problem. What constitutes a "measurement" in a quantum system - an action that causes the wave function describing a superposition of states to collapse or decohere into one state - is unknown. QCs work by causing the superposition created by the quantum algorithm to collapse into a state representing the answer, possibly solving a problem what would take a conventional computer years, or centuries, or ... Engineers working on QCs are trying to prevent a measurement - whatever that is - from occurring and the system decohering until they want it to. Defining what constitutes a quantum measurement is Nobel Prize territory, a problem that reaches into the very definition of reality in the transition from the realm of the very small to the realm we perceive. It is a problem that may never be solved, despite what investors are told.

I hope quantum computers do come to fruition. Not just for the practical reasons of solving some very difficult optimization problems and such, but because of the light it would shed on the measurement problem in physics. But I remain cautiously pessimistic.

NIST Time and Frequency Seminar 2025

Once again I attended the fire hose of information that is the U.S. National Institute of Standards and Technology (NIST) Time and Frequency Seminar. This three day, typically annual, event, held at their Boulder Colorado laboratories (commuting distance for me), covered such wide ranging topics as optical atomic clocks, practical measurement techniques for time and frequency, how to characterize and analyze frequency and phase errors in data, ways in which television and radio broadcasters might augment GPS for timing and positioning, and much more.

In honor of the event I wore my Rolex Milgauss. Felt cute, might delete later.

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My understanding is that virtually all national time and frequency metrology laboratories, including NIST (civilian) and the USNO (military) in the U.S., use an ensemble of cesium beam atomic clocks and hydrogen maser atomic clocks, the average of which is used to determine their contribution to the measurement of the SI second and the international definition of UTC. These are commercial devices, not laboratory experiments, and aren't astronomically expensive.

They use a combination of both because, even though the cesium resonant frequency is the (current) definition of the second in the international system of units, cesium atomic clocks suffer from jitter (short term variation), while hydrogen masers are more stable. The jitter in commercial atomic clocks is well understood, and the difference between a rack-mounted commercial cesium beam clock and a much larger and far far more expensive cesium fountain atomic clock in labs at places like NIST is all the extra hardware to try to reduce that jitter.

The image below is of the NIST F-3 cesium fountain clock. The collection of commercial cesium beam standards are kept locked up in another room.

Here's the thing: all hydrogen maser clocks suffer from drift (long term variation). And they all drift by a different amount. And it is not understood why. One hypothesis is it's some mechanism of aging of the components. If the manufacturers could eliminate this, they certainly would (and charge more).

The image below is of a decommissioned commercial hydrogen maser clock that I saw at NIST in 2018. You can't typically find one of these at NIST where it can be photographed because the running ones are kept locked in temperature controlled chambers adapted from commercial egg incubators.

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The blinking 1Hz LEDs in this brief video clip literally represent the real-time manufacture of the UTC(NIST) time scale (the U.S. civilian time base) and the U.S. contribution to the international determination of UTC.

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Next to the toe of my shoe is a survey marker embedded in the floor of one of the NIST labs. Atomic clocks are so precise now that centimeter changes in altitude have to be adjusted for, thanks to general relativistic effects.

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This was my fourth (2018, 2023, 2024, and 2025) and probably last time attending the Time and Frequency Seminar. It is so popular that not only does it sell out, but the waiting list is lengthy too. Could be time to let someone else become a certified Time Lord.