Physicists ‘squeeze’ light to cool microscopic drum below quantum limit

arXiv: <a href="https:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1606.08795.pdf" rel="nofollow">https:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1606.08795.pdf</a><p>By the way, this group achieved ground-state cooling of a very similar mechanical oscillator back in 2011.<p>&quot;Sideband cooling of micromechanical motion to the quantum ground state&quot; <a href="http:&#x2F;&#x2F;www.nature.com&#x2F;nature&#x2F;journal&#x2F;v475&#x2F;n7356&#x2F;abs&#x2F;nature10261.html" rel="nofollow">http:&#x2F;&#x2F;www.nature.com&#x2F;nature&#x2F;journal&#x2F;v475&#x2F;n7356&#x2F;abs&#x2F;nature10...</a> arXiv: <a href="https:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1103.2144" rel="nofollow">https:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1103.2144</a><p>Both oscillators were of roughly the same frequency (10 MHz) and size (~15 nm diameter aluminum disc). In terms of phonon occupation number, things improved from 0.34 to 0.19.<p>They emphasize in this new paper that they were able to get colder by using a squeezed vacuum state of laser light. I&#x27;m no expert, but I think the use of this technique is much more important than the improvement in the mechanical state they were able to achieve.

I&#x27;ve often read that absolute zero (0 K) is impossible to obtain, but never really understood whether it&#x27;s just for practical reasons or if there&#x27;s actually a theoretical background.<p>As far as I understand, there&#x27;s no reason why a particle having 0 kinetic energy can&#x27;t exist. Also, achieving it seems theoretically possible when a particle has kinetic energy equal to one photon, then emits a photon. Obviously it&#x27;s hard to experimentally produce such a situation, but not theoretically impossible.<p>So, would 0 K theoretically be possible or am I missing something?

For those curious of possible applications:<p><i>Sensors would become more sensitive. You can store information longer. If you were using it in a quantum computer, then you would compute without distortion, and you would actually get the answer you want.</i>

Fun fact: LIGO&#x27;s next big upgrade will be to install a squeezed light source to reduce quantum noise at higher frequencies.

It&#x27;s a beautiful image, I hope it&#x27;s not an illustration.

From the article: &quot;squeezed light removes the generally accepted cooling limit&quot;. Generally removing a limit in physics is a huge deal. What was this limit based on? Has some fundamental quantum physical property been disproven? Is this a breakthrough more significant than setting a coldness record? Was the generally accepted limit based on what would be &quot;really tough&quot; or something else? Anyone know?

How can something have a fraction of a quantum of energy? I thought energy levels had to be discreet integer multiples of Planck&#x27;s constant? The more I read about Quantum Mechanics, the less I understand!