Questions tagged [metrology]

The study of measurements

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How do measurements of $G$ account for variations in the local gravitational field?

One of the notable discrepancies of modern physics is the current disagreement of measurements of the gravitational constant $G$, well beyond reported uncertainties (and agreeing only to about 1 part ...
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42 views

Why is there a Moore's Law for atomic clocks?

From the NIST website: If you add the more recent data points, like this one in 2019, which achieved $~10^{-17}$ fractional instability, the trendline continues. Why should there be a Moore's law ...
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68 views

What is the difference between quantum sensing and quantum metrology?

The title is mostly self-explanatory. Both terms get thrown around a lot. I used to think quantum sensing uses harmonic oscillators / bosons and quantum metrology spins, but this doesn't seem to ...
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23 views

Quantum Fisher information for Gaussian states without eigenproblem?

Given a Gaussian-preserving interaction (including a unitary operation and losses) for a Gaussian input, I want to know if there is an "easy" way to compute the Quantum Fisher information without ...
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57 views

How did Henry Kater measure distances down one part in $10^5$?

Wikipedia says that in 1817, Henry Kater was able to measure distances accurately enough to get at least five significant figures in a measurement of $g,$ suggesting that he could measure a distances ...
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116 views

How can I estimate meta-uncertainty?

A type A uncertainty estimate is derived from repeated measurements. For example, I may estimate the uncertainty on a measurement by repeating the measurement $N$ times and then calculating some ...
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75 views

How are energies determined in gamma ray calibration standards?

In operating scintillation gamma ray detectors, certain gamma ray standards are used for calibration: Energy (KeV) Na-22, 511 Mn-54, 835 Co-57, 122 How are ...
1
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1answer
96 views

New S.I. and the second definition standard

The new SI defines the second as the hyperfine splitting transition time associated to the frequency of that transition of caesium-133, 9192631770 Hz, that is 12 decimals precision, but...I wonder two ...
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68 views

Does the New SI spoil the nice Coulomb law in Gaussian units?

Now, after the redefinition of SI, the elementary charge $e$ and the reduced Planck constant $\hbar$ (and also $k_B$) are exact quantities in the SI units, as is the velocity of light $c$. The ...
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2answers
40 views

Source for updated values of physical constants

Looking for the value of the Molar Gas constant. I am unsure because NIST has 8.314 462 618 J/(mol*K) while Wikipedia says ...
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1answer
29 views

Electrostatics, measurement of charge

How did physicists come up with a standard for measuring charge? How an electrical measurement of charge was made?
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32 views

Uncertainty in length measurement

I am trying to measure the length and the uncertainty in length of a fiber optic cable for measuring the speed of light. So far, I have measured it the standard way: Using a standard meter scale. I ...
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37 views

Saturability problem about the quantum Cramer-Rao bound for the multi-parameter quantum metrology

I was studying the multi-parameter quantum metrology these days. And I was confused about the saturability of the quantum Cramer-Rao bound for the multiparameter problem. If all of the generators are ...
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16 views

Effect of variation in day length on timekeeping

I was reading about atomic clocks when I came to know that precise measurements of time have shown that the time for earth's rotation is slightly more that 24 hrs (on the order of 10^-3). I was ...