“Nature Relies on an Interplay of ‘Noise’ and Quantum Mechanics”
(February 13th, 2015) Recently, about 40 researchers gathered in Brussels to discuss an emerging subfield of biology, quantum biology. Martin Plenio, physicist at the University of Ulm, explains how quantum biology can give us new insight into a world we thought we knew.
For the past decade, scientists have become increasingly fascinated by how quantum physics - the science of the incredibly minute – may affect biological systems. In the past, the principles of quantum mechanics have been confined to chemistry and physics, with biology being the odd one out. Yet, recent data show quantum phenomena do occur in living organisms. It turns out the behaviour of complex structures such as proteins - composed of hundreds of thousands of atoms - can be explained, at least partially, by quantum mechanics. This idea has opened up an entirely new field at the intersection of biology and physics.
LT: How did your interest in quantum biology start?
I received my PhD in quantum optics a long time ago, 20 years, and I've been working in quantum information theory and its implementation into real devices since. My interest in quantum biology started in 2007 at an editorial board meeting of Contemporary Physics, when a colleague pointed out a paper about oscillations in photosynthetic systems. They had made some claims saying it could be a quantum search algorithm and so I started to look at it. A year later we published our first paper.
LT: Do you consider quantum biology a new field or has it just been hidden?
The founding fathers of quantum mechanics were already thinking about this. In particular Pascual Jordan, the person who wrote the second paper ever on quantum mechanics, thought about it in the 1930’s and he wrote a book about the relationship between physics and biology. In that book, there is even a chapter entitled quantum biology. But the problem was that, at that time, there was just no experimental technique to study the ideas. So one could only speculate and that was it! It was a slow burner for a long time. It was only very recently - in the last 5-10 years - that experimental technology has advanced sufficiently. Now, one can actually examine some of those theories.
LT: Photosynthesis, sense of smell and how birds sense the magnetic field are the three phenomena, which can be explained by quantum biology: what do these examples have in common?
These three phenomena surely have a common basis: in each case, if the dynamics was determined purely by quantum mechanics - an isolated system - they would not work at all or they would work with much less efficiency. The additional ingredient is that biology may have quantum systems and they follow quantum dynamics, but at the same time they're interacting in a constructive manner with the environment. That’s really a new viewpoint. Nature has found a middle ground: there's quantum dynamics and there's a bit of this "noise", both roughly of the same order of magnitude. Biological systems can live in this intermediate zone between pure quantum mechanics and pure classical behaviour, and at this interface that's where they're most efficient. This is really the key point: Nature relies on this interplay of “noise” and quantum mechanics. That's really different and is common to all these mechanisms.
LT: Are there any more mechanisms to be added to the list in the near future?
It's fair to say these are the three phenomena that people already acknowledge because there is some experimental evidence, sometimes direct sometimes indirect e.g. via behavioural studies. There are some thoughts that maybe in DNA, quantum mechanics might play a role, but in my view, this is very speculative as there is no experimental evidence at present. I think the best chance to find new mechanisms involves searching for processes, in which either electronic dynamics interacts with vibrational motion or in which electron spins interact with their environment. The scientific community really has to find new places in biology where these kind of processes may play a role.
LT: Do you think quantum biology will have an impact in our understanding of how life works?
Yes, I think it will make a difference. Biology focusses very much on our everyday experience of classical physics, and there are many things that are either inefficient or not possible in classical physics. However, they are certainly possible in quantum physics. So, quantum biology may give new insights into our understanding of how receptors in cell membranes work, for example. Then, there might be a possibility that we can design drug molecules that interact with those receptors, perhaps, more efficiently. This is speculation, of course, but if this would work, it could have a major impact.
LT: What do you think is the way forward for quantum biology?
We can develop theories but we always have to test them. In quantum technology, if I have an idea to create a new realisation of a quantum information processor, for example, I can say whether it’s feasible. It may cost 5 million dollars but it can be built. Every parameter is very well determined, and so I can predict what is possible. In biological systems, this is different. We might know protein structures with a certain resolution but it may not be good enough to be able to predict all the quantum behaviours in the system. And many proteins do not even have a known structure. This is one problem we’re experiencing already and this is why we really need practical experiments. We also have to understand more about the quantum dynamics in this "noisy" environment. We have found some basic principles but we have not found everything. The current challenge is to bring together biologists, physical chemists, chemists and also theoretical and experimental physicists because we need tools from all these areas. Biologists will not normally be able to recognise a quantum phenomenon because they have not been trained in quantum physics. Theoretical physicists might come up with "funny" theories because they don't know what the relevant questions in biology are. We have to work together and we have to bring people together at this interface between biology and quantum physics. That's a big challenge!
LT: How about education?
This is a multi-disciplinary field and progress will not be made if just some physicians or some biologists do the work. It's hugely challenging to talk to each other because of the very different modes of thinking and it might be good to educate people so that they don't only know theoretical physics or biology but they know about both fields. I think we have to find ways to strengthen the education so that students are taught both subjects. These may be new doctoral or masters programmes or it could start even at an earlier stage. Students would learn a bit of biology, a bit of chemistry and a bit of physics.
LT: Where would you like to see the field of quantum biology in 5-10 years?
I'm sure more people will get involved. In ten years, I hope we can establish strong direct evidence to support bird navigation and olfaction and that we have found many more biological phenomena in which quantum mechanics and noise interact to benefit biological function. We have indirect results and we can make predictions about how the system should behave: for example, we can subject Drosophila to an odour and then see how it reacts. But we would like to make experiments directly on the receptors that are responsible for this phenomenon and really show that quantum mechanics and electron transfer play a role. Ideally, I would like to show results not by looking at the behaviour of an entire animal, but by actually looking directly at the protein. This would be a huge boost.
Photo: Ulm University