Surviving quantum superposition

A tardigrade on a silicon nitride membrane which is in a state of superposition of two eigenstates (groundstate plus first excited state). This is a sketch; the size of a real tardigrade has to be much smaller than the size of the membrane

Gröblacher is also interested in experiments involving living creatures. He is currently working on putting a sheet of nitride into a superposition of states. By using a laser, it is theoretically possible to get a barely visible membrane of silicon nitride measuring around one millimetre across into a superposition of vibrations ….. Gröblacher reckons they are within a couple of years of achieving this superposition of vibrations.

“A superposition state of these membranes would allow us to demonstrate that objects that are visible to the naked eye still behave quantum, and we can really test decoherence – the transition between classical and quantum mechanics,” he says.

He then hopes to extend the experiment by placing tiny living organisms called tardigrades onto the membrane of silicon nitride, putting them into superposition too.

This is an idea with a high outreach potential. A first quantum vivisection, a Scroedinger tardigrade…. These micro-animals (official title) are famous for being tough: They can enter a ‘hibernation state’ of near complete dehidration and metabolism rate decreased by factor 1/1000, and, being in this state, survive an exposure to outer space (almost perfect vacuum), high-intensity radiation of all kinds (including gamma rays), and pressure up to 1,200 atm. Therefore, they can withstand cryogenic environment required to achieve ground state cooling of the membrane. In short, if there an animal able to survive superposition this must be a tardigrate.

What is interesting is the survival statistics similar to that obtained in an experiment in 2007: …dehydrated tardigrades were taken into low Earth orbit on the FOTON-M3 mission carrying the BIOPAN astrobiology payload. For 10 days, groups of tardigrades, some of them previously dehydrated, some of them not, were exposed to the hard vacuum of outer space, or vacuum and solar UV radiation. Back on Earth, over 68% of the subjects protected from solar UV radiation were reanimated within 30 minutes following rehydration, although subsequent mortality was high; many of these produced viable embryos. In contrast, hydrated samples exposed to the combined effect of vacuum and full solar UV radiation had significantly reduced survival, with only three subjects of Milnesium tardigradum surviving. Would there be any difference between just the groundstate and superposition of the groundstate and first excited state of the membrane? Or it would be negligible on the background of the mere exposure to the cryogenic environment?

The problem is that the typical size of silicon nitride membranes Gröblacher (and other teams) currently dealing with is <= 0.5mm. This is also the typical size of tardigrates. I do not know masses but expect them to be comparable. It is not possible to maintain the extra-high quality factor of such membranes after placing on them a tardigrade – unless the membranes are on-purpose designed and curved, with ‘nests’ for tardys (a-la seats of Space Jockeys).

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