The ArXiV Blog and several other sources last week linked to a new paper titled 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 Schr\”odinger’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.
I’ve had this open in a browser tab since last week, but I’ve been struggling to find something to say about this. It’s kind of an odd paper in a lot of ways, starting with the format– I’m really not sure where they would be sending this. It refers to itself as a “Letter,” but is longer than most journal articles of that type. It also contains surprisingly little technical information in the main text, pushing all the details and math into appendices, whose total length is about the same as the main text.
Formatting details aside, though, I’m really not sure what the point is.
Don’t get me wrong– on a technical level, it looks solid. The idea here is to use laser cooling and trapping techniques to select a single virus and transport it into a high-finesse optical cavity, where it can be trapped in a standing wave laser inside the cavity. By choosing appropriate laser wavelengths, the cavity field can be used to cool the particle down to the vibrational ground state, at which point its behavior should be very unlike that of a classical particle oscillating in a trap. With a little more work, it can be put into a superposition of the ground vibrational state and the first excited state, and that superposition can be detected.
There’s nothing there that obviously won’t work (it’ll be difficult, but the basic techniques have all been used before). But I’m not sure what this adds to our understanding of “the quantum nature of living organisms.” Viruses only barely count as “living organisms,” given that they need to piggyback on the cellular machinery of other organisms in order to reproduce themselves. They’re basically just really big organic molecules, and we already know that large-ish organic molecules show quantum behavior– the Zeilinger group in Austria has demonstrated diffraction of fluoridated fullerenes.
Saying “we demonstrated quantum behavior with influenza viruses” has more cachet than “we demonstrated quantum behavior with fluoridated fullerenes,” granted, but is that enough to overcome the additional hassle of the precautions needed to handle biological specimens?
It’s not like you’d really be shedding light on the effects of consciousness on quantum measurement, or anything. I’m fairly confident that you would need to have a nervous system for that to work. It’s not even like you could monitor the behavior of the virus before and after the superposition– it’s a virus. Absent a cell to infect, it just sits there. I suppose you could try to infect cells with viruses that had been put in superposition states, but that seems ridiculously complicated.
So, while it’s an eye-catching title and a clever idea, I’m not sure you learn anything from this that you wouldn’t learn by using tiny little glass beads, or other non-biological objects of the same scale.