Schrödinger's Water Bear?

Long story short: Scientists are about to attempt to create a life form existing simultaneously in two quantum states.

Here's Marcus Chown's fascinating September 15, 2009 New Scientist story about the quest to observe living superpositions in the lab.

I intentionally didn't write "the world's first quantum life" because it may turn out that we are all, in fact, quantum states masquerading as people.

Here's the article.

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Could We Create Quantum Creatures in the Lab?

Quantum weirdness could soon invade the living world, if a scheme to give a flu virus a strange double life comes off.

In quantum theory, a single object can be doing two different things at once. This so-called "superposition" is a delicate state, destroyed by any contact with the outside world. The largest objects that have been superposed so far are molecules. It is hard to put a much larger object such as a cat or human into a superposition because air molecules and photons are always bouncing off it.

But it might be possible with a small life form, according to Oriol Romero-Isart of the Max Planck Institute for Quantum Optics in Garching, Germany, and his colleagues. They hope to prove the concept with the flu virus, which exhibits some properties of life, because it can survive in a vacuum – solving the problem of pesky air molecules.

Laser Hold

Their scheme would use two laser beams, whose light exerts a gentle force on matter. Where the two beams cross they form an "optical cavity" holding the virus in place.

By adjusting the frequency of the beams, the laser photons can be made to absorb the vibration energy of the trapped virus about its centre of mass until it is slowed to its lowest possible energy state. In this "ground state" the virus is ready to go into a superposition.

Sending a laser photon towards the trap should do the trick. Since a photon is a quantum entity it has more than one option open to it. Thus it will be both reflected and transmitted at the trap, putting it into a superposition.

By impinging on the virus, it forces it into a superposition of both its ground state and next vibrational energy state. Now the virus should be doing two different things at once – the equivalent of you simultaneously mowing the lawn and doing the shopping. "They have come up with a really neat experiment – inventive and I think feasible," says Peter Knight of Imperial College London.

Romero-Isart and his colleagues speculate that they could pull off the same feat with a tardigrade, or water bear [top], an animal less than a millimetre in size that can survive extreme temperatures and a vacuum for several days.

Big Questions

Making a living thing do two things at once is more than a physicist's tour de force. It could answer fundamental questions about the nature of quantum theory.

Most physicists believe that the reason quantum behaviour manifests itself only in small things is that objects are difficult to isolate from their surroundings. But the prominent physicist Roger Penrose of the University of Oxford believes instead that there is a critical size, or mass, at which bodies cease to become quantum.

According to Knight, experiments of the kind proposed by Romero-Isart's team could finally offer a way to distinguish between the mainstream view and Penrose's.

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Below, the abstract of the latest paper on the subject from Romero-Isart's group.

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Towards Quantum Superposition of Living Organisms

The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. Up to now, the existence of such states has been tested with small objects, like atoms, ions, electrons and photons, and even with molecules. Recently, it has been even possible to create superpositions of collections of photons, atoms, or Cooper pairs. Current progress in optomechanical systems may soon allow us to create superpositions of even larger objects, like micro-sized mirrors or cantilevers, and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high--finesse cavity at a very low pressure. Our method is ideally suited for the smallest living organisms, such as viruses, which survive under low vacuum pressures, and optically behave as dielectric objects. This opens up the possibility of testing the quantum nature of living organisms by creating quantum superposition states in very much the same spirit as the original Schrödinger's cat "gedanken" paradigm. We anticipate our essay to be a starting point to experimentally address fundamental questions, such as the role of life in quantum mechanics, and differences between many-world and Copenhagen interpretations.