Physicists Claim They've Quantum Entangled a Tardigrade With a Qubit. But Have They?

    (David Spears FRPS FRMS/Corbis Documentary/Getty Images)

 A team of senior physicists claims to have entangled a superconducting qubit and a tardigrade, working the freezing, tiny, and well-controlled world of quantum into the "hot and wet" systems of life. 

However, the results showed in this preprint paper are not quite so cut and dried, and many quantum researchers are arguing that the poor tardigrade wasn't entangled in a meaningful way. 

Quantum entanglement is when two or more particles are linked in such a way that a key quality they share – such as position, momentum, or polarization – are not independent of each other. 

To take a very simple non-quantum example, if you found a right-handed glove in your drawer, you could be sure the missing glove would fit your left hand: knowing something about one tells you something important about the other, and that knowledge is not random. 

Entanglement occurs in quantum systems naturally after particle collisions, or almost any other time particles interact. Although Albert Einstein wasn't much of a fan, physicists have demonstrated in the years since that entanglement itself isn't super hard to produce. 

Scientists have done pretty good entangling larger and larger things. They've entangled molecular ions, larger nanoparticles, and also teeny tiny diamonds. 

But all of those systems are still too much small, usually very cold, and well organized. A tardigrade by contrast – even in its dehydrated, 'unbreakable' state – is a comparatively large collection of frozen, messy biological molecules. 

In this new preprint research paper made available on arXiv, the researchers took a tardigrade species called Ramazzottius varieornatus, and put it into a dehydrated cryptobiosis. They then cooled it down to just 10 millikelvin over absolute zero, and place it under very low pressure of just 0.000006 millibars. 

Then, the team did experiments where they attempted to entangle the tardigrade with two superconducting transmon qubits, detecting that they "observed coupling" between the creature and the qubits. 

After about 420 hours of test, they heated up the tardigrade, and it went along its merry way. 

But after some initial breathless headlines, many physicists and science writers are pointing out that this is not really entanglement – or at least not something that hasn't been done before. 

For now, it doesn't shows we have enough evidence for the first living organism to have been quantum entangled, as electrifying as the idea of a quantum tardigrade may sound. 

We also don't really know how seriously we should be taking this study, and whether the researchers knew their work would get quite as much careful as it now has. 

This research paper is available on the preprint server arXiv. 

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