The microscopic and macroscopic worlds currently operate using two different standards -- general relativity governs the macroscopic world while quantum physics rules the microscopic. In our macro world view, thermodynamic (entropic) processes only move in one direction. That is, using an egg analogy, you can't uncook an egg much less get it to hop back into its shell and seal the crack. But in the subatomic world, many of these processes are "time-symmetric" -- essentially, they're reversible.
However, what Tiago Batalhão and his team at the UFABC discovered actually runs counter to our expectations. Their experiment sought to measure the entropy change within a closed system of carbon-13 atoms submerged in liquid chloroform while they're subjected to an oscillating magnetic field. The idea is that polarizing the field should cause the atoms' nuclear spins to all rotate one direction, while reversing the field's polarity would make their spins flip and rotate the opposite direction.
Now, if this process were time-symmetric as our current understanding of physics dictates, the atoms' spins should flip back and forth without issue and return to their initial states once the magnet was turned off. But the UFABC team found that the atoms' spins couldn't keep up with the magnet's oscillation rate and some would eventually fall out of sync with their neighbors. This means that entropy within the closed system was actually increasing -- precisely the opposite effect from what should be happening. It effectively proves that thermodynamic processes are not reversible at the quantum level. What's more, it reveals a disconnect between the current laws of physics and what we're actually observing.
The team has much more research to conduct into why, exactly, this dissonance exists and what physical aspects at the quantum level prevent these entropic reactions from reversing. Eventually, they hope to leverage this discovery into practical (and powerful) quantum computing systems.
"Any progress towards the management of finite-time thermodynamic processes at the quantum level is a step forward towards the realization of a fully fledged thermo-machine that can exploit the laws of quantum mechanics to overcome the performance limitations of classical devices," study co-author Mauro Paternostro at Queen's University told Phys.org. "This work shows the implications for reversibility (or lack thereof) of non-equilibrium quantum dynamics. Once we characterize it, we can harness it at the technological level." Their research was recently published in the journal Physical Review Letters.
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