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Sparked by this video with Microsoft's quantum chip: https://www.youtube.com/shorts/9SBVZr3lbS0

The video mentions how to get the array to work each atom had to be lined up exactly and that it took 17 years for them to get it to do so. But if quantum physics is fundamentally random (this was from a Kurzgetstat video about time) then how are they able to line up atoms, or place them I guess, so precisely?

Qmechanic
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BoltStorm
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2 Answers2

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Notice in that video:

enter image description here

Here the two curves represent the so-called wavefunction of the electrons. This is written as $\psi$ in quantum mechanics, and the absolute square $|\psi|^2$ corresponds to the probability of finding the electron at a given location.

Therefore you can see that:

  1. Quantum mechanics is fundamentally random - you can't say the electron is at a particular spot, only that it is within some distance of that spot with a particular probability Y. But -
  2. You can still say that there is one electron on the left and another electron on the right. That's because the two electrons are overwhelmingly likely to be found on the left/right.
Allure
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In classical physics the evolution of a measurable quantity, like the $x$ position of a particle, is described by a function $x(t)$ so that if you measure $x$ at time $t$ you get the value $x(t)$.

In quantum physics a measurable quantity is described by a more complicated mathematical object that can be represented by a matrix:

https://math.libretexts.org/Bookshelves/Linear_Algebra/A_First_Course_in_Linear_Algebra_(Kuttler)/07%3A_Spectral_Theory/7.01%3A_Eigenvalues_and_Eigenvectors_of_a_Matrix

The possible results of a measurement are the eigenvalues of that matrix. Quantum theory predicts the probability of each of those possible results. The probability for a result can vary from 0 to 1. If you want to understand this better you can read a quantum mechanics textbook such as "Introduction to quantum mechanics" by Griffiths and Schroeter.

All that has to happen for a bunch of atoms to be in a row is for that result to have a probability of 1 or some good approximation to 1.

How could that happen? When you do an experiment in which quantum effects are important in general what happens to all of the possible outcomes contributes to the probabilities of the possible results. This is called quantum interference. For an example see Section 2 of this paper

https://arxiv.org/abs/math/9911150

The particular kind of experiment conducted by Microsoft is more complicated than the one depicted in the above paper but nothing about quantum theory prohibits arranging atoms in a row. You can read about the theory and the experiments behind Microsoft's chip in the papers below

https://arxiv.org/abs/0707.1889

https://arxiv.org/abs/2401.09549

alanf
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