The STM in a surface chemistry lab I worked in for a while was inside a box, and hanging from the roof of the box. By choosing appropriate springs to hang the sensitive bits from and sound proofing the box, it could adequately isolate the scanning table from its environment.
I've started searching for "dilution refrigerator" and found this video, explaining a little bit how ³He–⁴He mixture cooling works and what the applications are. I think the video also helps putting the Wikipedia article in a perspective and vice versa.
Quantum Cooling to (Near) Absolute Zero (2013): https://www.youtube.com/watch?v=7jT5rbE69ho
http://iopscience.iop.org/article/10.1088/1681-7575/54/1/S1/...
But I don't think this is relevant here.
EDIT: Yeah, pohl answered it. Vibrations are not relevant.
With the 2018 SI change, Avogadro's constant will be defined as an arbitrary number without any physical basis, and the amu will be a constant multiple of the kg. No more 1/12 the mass of carbon 12.
Of course we'll still need a way to represent large numbers, but there's no fundamental reason it has to be such a complicated number. It could be exactly 10^24, for instance. Again, I agree this isn't going to happen because of legacy inertia.
Naively, there seem to be multiple approaches to derive temperature from other, more fundamental units. Like using the thermodynamic definition, 1/T = dS/dE, or using Boltzmann's law to approach temperature from the mean kinetic energy of gas particles. Are none of them suitable for precise measurement?
The effort to redefine the Kelvin would probably use an acoustic thermometer to measure the speed of sound in a gas. This would fix the Boltzmann constant. It seems a bit silly to do this when the definition of the kilogram is expected to change, though.
In the meantime, triple-point cells are pretty convenient, much more convenient than the international prototype kilogram, or the infinite length of wire used to define the ampere. Also remember that laboratory temperature measurements tend to be much less accurate than voltage or mass measurements. ITS-90 is apparently good to within 100ppm, but 1ppm or better is no problem when you're measuring voltage, mass, or length.
Here's a presentation on thermometry, the acoustic thermometer described is what's used to accurately measure the Boltzmann constant: https://www.youtube.com/watch?v=Irr8fOLtiWc
However, you have to make sure the definition can be made into an experiment, unlike the old Ampere definition from the article. A definition that mentions perfect gases wouldn't work, if no actual gas exists that can provide a better precision than the triple-point experiment.
Edit: the Kelvin is changing too: https://www.eurekalert.org/pub_releases/2017-04/pb-rft040517...
You can define entropy directly without reference to other units, although it's a bit awkward. Entropy is the log of the number of microstates that correspond to a system's macrostate. Concretely, if you put n mols of ideal gas molecules in a box of volume V at a pressure P and temperature T, there is some large number of microstates corresponding to all those parameters. Entropy is the log of this number.
In classical mechanics, there's a normalization problem if you try to get an actual number out of this type of problem -- the microstates and all the macroscopic parameters are continuous. In quantum mechanics, though, this issue is solvable, although it's still awkward.
I can imaging a different type of system in which entropy really can be calculated, though. Imagine a particle that can be in exactly one of two states that are macroscopically identical. Now try to cool the system so that the particle is in one of those states of your choice. To do so, you will need to dump exactly 1 bit of entropy.
1 bit of entropy is tiny, but adiabatic demagnetization refrigerators work kind of like this, albeit in reverse, and I could imagine an experiment that would use a device like an adiabatic demagnetization fridge to remove a calibrated number of bits of entropy from some object. From this, you could, in principle, define entropy directly.
Kelvin is considered one of the 7 base SI units, as described here: http://physics.nist.gov/cuu/Units/units.html
I think the mean kinetic energy of gas particles is impossible to measure directly. You can compute it by measuring the temperature though :)
Acceleration due to gravity is a nice number between 0 and 10 if measured in "kilogram-meters per second squared".
On the bright side, the changes to the kilogram might begin to address the obesity crisis.
Not really. Detecting the voltage or current differences that you need for detecting an electron spin, that's a very different thing than doing the quantitative measures you need to redefine the ampere.
For example for measuring a single electron, you can use avalanche effects, which are relatively simple to realize, but would not be suitable for the quantitative approach you need to define an SI unit.
I'm not very well-informed regard quantum computing, but the problem with it seems to be more in realm of keeping the quantum states stable and controlled, and less on the measurement side.
