One of the great challenges for quantum physicists is to find quantum behaviour in macroscopic objects. There are obvious examples of quantum behaviour on a large scale, such as superconductivity and superfluidity, but physicists want more.
Having created quantum superpositions of photons, electrons, atoms and even molecules, one of the current obsessions is to create a quantum superposition of a living thing, such as a virus. The question is how to do this and whether it makes any sense to say these things are living at all.
This is an experiment that will be hard. But today Oriol Romero-Isart from the Max-Planck-Institut fur Quantenoptik in Germany and a few buddies suggest that it is achievable with current technology and outline the challenges that will have to be tackled to pull it off.
The experiment will first involve storing a virus in a vacuum and then cooling it to its quantum mechanical ground state in a microcavity. Zapping the virus with a laser then leaves it in a superposition of the ground state and an excited one.
This works only if the virus behaves like a dielectric, can survive the vacuum and appears transparent to laser light, which would otherwise rip it apart.
As luck would have it, Romero-Isart and co say that several viruses fit the bill. The common flu virus is known to be able to survive in a vacuum, seems to have the required dielectric properties and may well be transparent to a careful choice of laser light. The tobacco mosaic virus, to all intents and purposes a dielectric rod, looks like another good candidate.
But does it make any sense to say that a large molecule in its ground state is somehow alive? It’s difficult enough now to define what life means. Throw a quantum superposition into the mix and the biologists who ponder these problems are likely to implode.
Nevertheless, many groups are currently looking to create superpositions of things like tiny cantilevers and micromirrors, so viruses certainly look achievable in the near future. And beyond that, why not bigger organism such as the tardigrade (or water bear) which can grow to 1.5 mm in length.
But why bother? Performing a Schrodinger’s cat experiment would be fun (although not for the virus). Romero-Isart and pals go further and say the work will “experimentally address fundamental questions, such as the role of life in quantum mechanics,and differences between many-world and Copenhagen interpretations”. Perhaps.
But their contention that it will also address “the role of consciousness in quantum mechanics” seems a step too far (although a flu virus may beg to differ).
Ref: arxiv.org/abs/0909.1469: Towards Quantum Superposition of Living Organisms