An Introduction to Quantum Biology - with Philip Ball

thank you very much well good evening ladies and gentlemen wonderful abs packed house um so let me say a few words about the speaker this evening Philip ball is a freelance writer previously he was an editor nature for over 20 years he writes regularly both in the scientific and popular media and has written many popular science books I haven't read all of them but I've read several of them I promise so some of his books h2o a biography of water bright earth the invention of color the music instinct curiosity how science became interesting interested in everything he won the 2005 Aventis Prize for science writing for his book critical mass in fact I think that was the first occasion I met Phil I was sitting at his table my wife and I was sitting at his table so obviously we would cheer hit cheering him on do you remember that and then and then so we walked with delight as there somehow we could share and reflected glory when his name which was announced as the winner he's been awarded the American Chemical Society's greatest stack award for interpreting chemistry to the public he was the inaugural recipient of the Lagrangian Akay ting complexity science he trained as a chemist at Oxford and as a physicist at Bristol so this man is not a hack this man is very very smart and he covers a wide area of science he was one of the first people we sent the draft of our manuscript to my book life on the edge when we wanted some expert opinion someone to cast their eye over it a filter latest book by the way is invisible the dangerous allure of the unseen he wrote the article in nature switch that that picture is associated in 2011 but as as early as 2004 I think 10 10 or so years ago for wrote an article in nature about how quantum mechanics plays a role in the action of enzymes so this is essentially before many even many in the world of science let alone in the wider public had even heard of the subject of quantum biology so now that this field is is really emerging and and a lot of people are getting very very excited about it I think there's no better person to provide an introduction to the to the field than Philip ball Phil over to you thank you very much thank you Jim it's very flattering to be entrusted with this rather daunting task I'll see how I get on I guess like most trendy fads in science quantum biology is actually rather old and I want to suggest to you that it begins on the 15th of August 1932 with this man this is Niels Bohr the Danish physicist and he gave a talk at a rather unlikely sounding meeting the International Congress on light therapy in Copenhagen and boards title was light and life and he offered some thoughts on what the new theory of quantum mechanics which he had just helped to formulate in Copenhagen during the previous decade what it had to say about biology about life well what was the right man for this job not because he had any real understanding of the answer to that question but because he wasn't someone to let ignorant get in the way of speculation and I mean that in a good way because when smart people like Bohr are prepared to stick their necks out and say something on a topic about which they know rather little there's always a chance that they'll spout nonsense but I think there's a better chance that they'll spark something valuable and I'm trying to say that without looking in Jim's direction in his talk Bohr asked I quote whether some fundamental traits are still missing in the analysis of natural phenomena before we reach an understanding of life on the basis of physical experience by which he meant physics but he left that suggestion rather vague and it's not really what or said that matters but who was in the audience because Bohr had been very anxious to make sure that among the audience was a young German theoretical physicist named max delbruck here he is and soon after returning from Copenhagen to Berlin delbruck decided that the kind of missing trait that Bohr had eluded to might be found by studying the physical and chemical nature of genetics and by that delbruck didn't that physics might help to explain genetics but rather that my studying genetics he might uncover some new principle of physics now remember that at this stage virtually was nothing was known about the molecular origins of genetics people had begun to understand how genes evolved in a population according to Darwinian principles but they really had no idea what genes were they didn't even know that they were associated with DNA and in 1937 delbrück went to America where he began to investigate the genetics of bacterial viruses since they were very simple form of life and this work eventually won him a Nobel Prize for his work on how viruses replicate and Delbert established the idea of genetics as an information science it was all about transmitting information he also helped to stimulate the interest of other physicists in biology and one of them was this chap Owen Schrodinger who in Dublin in 1944 after having fled the Nazi regime he published an extremely influential little book called what is life and here Schrodinger pondered the question of how an event at the atomic scale a mutation in the molecular structure of a gene how this while being governed presumably by the laws of quantum mechanics could potentially cause a profound and visible change in the structure of a living organism and Schrodinger speculated that these genes must be something that he called an a periodic crystal that is an arrangement of atoms that was highly specific not random but that didn't have a regularly repeating structure like that of a crystal now another physicist lured into biology by Del Brookes work on replication with Francis Crick who of course in 1953 with Jim Watson showed that Schrodinger was right that genes are made up of very specific sequences of molecular components along the double helix of DNA according to the eminent molecular biologist Gunther stent Brigham Watson's disk brought about the wedding of the informational School of delbrück with the structural school of crystallographers who were looking at the atomic scale structures of biological molecules like DNA in proteins and that stent says made molecular biology what it is today so there you have it it wasn't just that physics created modern biology it was specifically quantum physics that started it off well that's all very satisfactory for smug physicists but it doesn't say anything about Bohr's intuition that quantum physics has any actual role in biology now of course in a trivial sense it must do because as Bohr himself showed in the famous papers in 1913 where he laid out his theory of the atom quantum mechanics can explain why it is that atoms bond together to form the molecules like proteins and DNA and RNA of which all life depends so in this sense quantum theory is at the root of everything and we need it to explain everything we need it to explain why I'm standing here talking to you tonight now I know that quantum theory can seem scary or mysterious to some people who are not so familiar with it and here one is usually supposed to reassure you with Richard Feynman's famous quip that no one understands quantum mechanics anyway and that if you think you do then it shows you don't now I think that that's true at the level that Fineman intended but it doesn't mean that quantum theory it's hard to understand it's just hard to understand what it means the challenge isn't so much in understanding what quantum theory says it's in accepting that bad information so let's see how we get on it was known by the early 20th century that chemical bonding is all about the electrons that atoms contain Ernest Rutherford had proposed that atoms are like a little like tiny solar systems for this dense very massive nucleus and electrons orbiting around it and Bohr said that those electrons can only have specific energies and no others and that they can therefore only adopt some orbits and not others and they can jump from one orbit to another by absorbing or emitting energy for example by swallowing up or spitting out a photon of light with a particular wavelength which is related to its energy when electrons do this they are said to make a quantum jump and Bohr outlined how electrons can adopt quantized orbits that link two or more atomic nuclei and that will join them then together in a chemical bond here are some of the early sketches that were made of that idea well this quantum theory of atomic bonding has got a lot more sophisticated since then and it now gives a very detailed a precise description of the shapes and the properties of molecules that explains for example why grass is green and why blood is red questions that John John Donne asked in the 17th century they that they have these particular colors because the energies of the electrons quantum states in chlorophyll and in hemoglobin are so are what they are so that they're they're the right energies to absorb red or blue or yellow or green light whatever the case may be so in this sense molecular biology depends on quantum physics but when we talk about quantum effects in nature and in science we generally mean something different from this quantum mechanics is notorious for producing effects that defy everyday intuition particles can behave like waves they can be in two places or in two states at once they can pass through walls and apparently communicate with each other instantly over vast distances now we tend to be insulated from actually experiencing these odd behaviors on the whole either because they only appear in rather specialized conditions such as a very low temperatures or because their operation at the scale of single atoms and molecules becomes washed out when averaged away for objects at everyday scales that contain trillions trillions of of atoms this is why we can generally rely on the pre quantum classical physics classical mechanics of Galileo and Newton to explain and describe how things behave in the everyday world quantum biology explores the possibility that some of the strange quantum effects can happen in biological systems where they might in fact turn out to be essential for the way the system does its job now this seems on the whole be very surprising and unexpected if physicists want to study quantum effects then very often they need extremely sophisticated equipment they have to cool things down to maybe within a few degrees of absolute zero they might have to create extreme vacuums greater than the more empty that is than the vacuum of interstellar space they might have to take great pains to make sure that things aren't disturbed by the environment biology in contrast the world of the cell is warm and wet and messy cells are little bags of countless different types of interacting molecule all colliding and reacting and expecting to encounter quantum effects here is a bit like expecting to be able to sit down and meditate peacefully in Waterloo station in the middle of rush hour and yet it happens there's good evidence that quantum effects like this do matter in biology and I'm going to tell you about some of them but I want to stress that to what extent they matter whether they happen at all and if they do whether they're biologically relevant this is something that's still being intensively debated these effects seem to be well attested in some cases and seem to be uncertain in others and extremely speculative in others now this is natural quantum biology is still in its infancy and we can't yet say whether it amounts to just a rank bag of oddities and quirks of nature or whether it's a profound aspect of how life happens well let me start with waves wave particle duality is probably one of the least helpful Russians in quantum theory but what it strives to convey is that very small particles seem in some experiments to show the characteristics of particles with particular positions in space let's say and in other experiments to behave like waves which has spread out through a large region of space the particles of light called photons do this and so do electrons that's how electron microscopes work by making use of the wave-like character of electrons and so do atoms now here's a picture of atoms this is a real picture of atoms where each of these blobs is an individual atom I mean sure they've been colorized and you know tidied up to look this way but really that's what you're seeing here atoms arranged on the surface of something like a metal into these patterns and yet here is what happens if you fire atoms through two narrow slits in a screen first of all you see that the atoms seem to appear on the on the screen pretty much at random but as you look and see more and more of these impacts you start to see this pattern of bright and dark bands appear this is due to the interference between atoms acting in a wave-like way and this wave-like behavior has even been seen for some quite large molecules containing dozens of atoms and some researchers are aiming to show it for proteins to show that whole protein molecules can also behave like waves now there's no indication that that sort of wave-like property of molecules is relevant to biology but that's not the point I want to make this smeared out character the atoms and subatomic particles can possess have some strange consequences it means that in quantum theory you can't speak of particles like this as having a definite position in space but only of the probability that they will occupy a particular position in space and this probability can depending on the conditions and such as the way you look can be quite tightly constrained as it was in the atomic snapshots that I showed earlier or it can be rather spread even if you put an obstacle in the way of a quantum particle that should be unable to get past it to get across to the other side there's a small chance that it still might spread out and be found on the other side of an obstacle like this in other words the particle can tap seem to tunnel through this what ought to be impenetrable barrier and in fact that's how the earlier pictures that I showed you of atoms were made they used instrument called the scanning tunneling microscope in which a very fine metal tip is brought close to a surface and if there's an electrical voltage between the tip and the surface because a very small chance that electrons will tunnel across the gap between them and if the tip and the sample are connected in an electrical circuit this gives rise to a tunneling current a flow of current because of the electron tunneling and because that current is extremely dependent on the precise and separation between the tip and the sample any small obstacle on the surface like a single atom just poking up from the surface can produce a large change in that tunneling current and in this way the current measures the topography of the surface as the tip is scanned over it now loosely speaking the amount of quantum smeared out Ness of a particle it can increase the greater that the smaller the particle is so very small particles tunnel more readily than larger ones atoms can tunnel in principle but the probability that they will do so is generally only significant if they're particularly tiny atoms and the smallest tiniest lightest atom that there is is the hydrogen atom it has only one proton in its nucleus now moving around hydrogen atoms from place to place is immensely important in many biochemical processes there are several enzymes in our bodies that do just that here's a couple of them they're involved in things like the generation of energy and in respiration in general the reactions involve moving hydrogen atom that's to say in effect a single proton from one location where it's bound to perhaps one part of an atom or a molecule moving it to another location and that costs energy because the proton has to be transported over an energy barrier it's a bit like plucking an apple off a tree you have to target it to get it off but it seems that in some perhaps most processes of biochemical proton transfer like this the process is made easier by tunneling that's to say the proton can tunnel across this gap rather as if the apple on the tree suddenly vanished from the branch and just appeared in your hand now how do we know that that happens well as I say the ease of quantum tunneling depends on the mass of the particle the heavier it is the less it tends to tunnel so if we replace an ordinary hydrogen atom in a case like this with an atom of heavy hydrogen the isotope deuterium which has about double the mass of an ordinary hydrogen atom because it has a neutron in its nucleus as well then we should alter the tunneling rate significantly but at the same time the chemical properties of that of the hydrogen are virtually unchanged here different isotopes of elements which differ in the number of neutrons they have in their nuclei are chemically identical so all we change in this case is the mass and therefore the tunneling rate and when once I just when chemists first did this experiment in 1989 for an enzyme called alcohol dehydrogenase they found that indeed the rate at which protons are transferred is different for deuterium in a way that fits with what we'd expect from a change in the tunneling rate and that's something that's now been confirmed for several other enzymes so tunneling makes biological proton transfer easier and faster does this mean that biology uses quantum tunneling well it probably sounds though that just what I've said but actually tunneling is almost impossible to avoid in a situation like this in fact even how hydrogen atoms or more strictly hydrogen ions protons move around between water molecules in ordinary liquid water even that involves a degree of tunneling so while you could argue that tunneling is useful for biology it's not clear that enzymes have evolved to make use of it they may be just stuck with this thing that happens whether they like it or not some biochemists such as the Nobel laureate Arielle Wartell believe that quantum tunneling is not only a rather minor importance in biology because it only speeds things up typically by factors of maybe two to ten which is not a lot for an enzyme but also that it's just a side effect that it's not something exploited by evolution as one theoretical chemist has put it tunneling is a fact of life but life has no special effect on tunneling our protons aren't the only particle to tunnel in enzyme reactions some of them involve transferring an electron from one molecule to another for example this is a crucial aspect of photosynthesis in which an electron is kicked off a chlorophyll molecule by sunlight and passed along a chain of molecules in the chloroplast membrane and electrons tunnel even more readily than protons because they're lighter and it's been known for years now that tunneling is also significant in biological electron transfer too but one of the most celebrated candidate systems for quantum biology involves electron tunneling in a much more unexpected manner and the idea here is that tunneling within the receptor proteins involved in our sense of smell enables us to detect and identify molecules from the way they vibrate so in the olfactory bulb in our noses where smell takes place there are membranes studded with protein molecules that have cavities where the smelly molecules get lodged now of course these molecules aren't intrinsically smelly they smell precisely because they can slot into the sites on the receptor proteins and tree some nerve signal that signaling process is quite well understood now but what remains unclear is exactly how the odorant molecules molecules like these how they start the process off the conventional idea has been that the odorant and the receptor are like a key and a lock with complementary shapes that fit each other but it can't be quite as simple as that for one thing we can smell many more molecules than we have different types of receptor but also some molecules with very different shapes and smell similar here are two groups like that while some molecules with all those identical shapes like these two forms of the molecule carvone can smell very different in 1996 the scientist luca turin who is a specialist on perfumes and in fact once set up his own company to advise the perfume industry suggested that smell might not work primarily on the lock and key principle instead he thinks that odorant receptors are a bit like vibration sensors that they can smell the way molecules that they bind are vibrating molecules with very similar structures can have very different vibrations while differently shaped molecules can have very similar frequencies of vibrations just as a saxophone and a trombone can play the same note even though they're very different shapes so in effect the idea is that the vibration has changed the distance between the odorant and the walls of the cavity in which it sits and thereby help electrons to jump the gap to tunnel across the gap and it's this electron current that the receptor then senses to trigger a smell response now if tune is right it should be possible to distinguish an odorant molecule containing ordinary hydrogen atoms from one in which they've been replaced by heavy hydrogen by deuterium that's because the heavy hydrogen at our isotopes that have twice the mass vibrate more slowly even though the molecules shape it's pretty much changed and there's some evidence that this can happen there's some evidence now that fruit flies can tell the difference in 2011 a team in Greece collaborated with cheerin on experiments on fruit fruit flies where they placed them in a t-shaped maze like this with two attractive odors wafting from from each passage one of them just a deuterated form of the other and they found that the Flies preferred the ordinary stuff over the heavy stuff the researchers could train these flies using mild electric shocks to actively avoid the deuterated odorant which is something they could only learn if they could tell them apart in the first place and what's more flies trained to avoid one kind of deuterated molecule would also show an aversion to a quite different um deuterated molecule that happened to have a similar spectrum of vibrations now another team has since shown that bees too can be trained to discriminate between ordinary and deuterated odorants there's no evidence yet that humans can tell the difference although I have been told there's a group of chemists in Prague who are trying this out in their lab and they do tell me that they can get used to it smelling that the distinction between the two now unfortunately none of this actually proves that Luca Turin's idea is right for one thing the the doubling of the mass for ordinary and heavy hydrogen means that they're not quite as chemically identical as isotopes of other atoms are where the mass ratio is is smaller so it could be that these creatures are actually detecting very small differences in chemical bonding rather than in vibrations and even if they're not I've been told by one of the leading specialists on fruit fly behavior and fruit fruit fry Olaf action scott waddle at Oxford that there could still be more conventional explanations of these sorts of experiments in any event some heavyweight supporters of the conventional theory of old fraction including some Nobel laureates are bitterly opposed to this vibe idea even though physicists and bio physicists have shown that it could work in principle my own opinion for what it's worth is that whether it's right or not it deserves to be taken seriously as a splendidly inventive and stimulating proposal now as well as having electric charge a negative charge electrons possess another feature a quantum mechanical feature called spin now whereas electrical charge is a familiar property from classical physics spin is is purely a quantum phenomenon the name is misleading it doesn't mean that the electron is it's literally spinning although sometimes that analogy is loosely made because spin is related to the electrons angular momentum which in classical physics comes from an object's rotation an electron spin can take two possible values which can be imagined as the electron spinning clockwise and anti-clockwise an electron spin was first introduced into quantum theory in the mid 1920s by Wolfgang Pauli and he based these idea his ideas on ion theories that had just been formulated by Schrodinger and Heisenberg and this led Pauli to propose the so-called exclusion principle which states that no two electrons can share the same quantum state and it's because two electrons can have opposite spin that two of them can share the same orbital in an election in an atom and this picture of how electrons share orbitals can explain the whole of the periodic table of the elements in terms of the array the arrangements of electrons how the electrons fill up the available orbitals so this idea of spin is central to understanding the whole of chemistry and because of their spin electrons are magnetic you might again crudely think of this as being a little similar to the way the spinning earth has north and south magnetic poles for this reason the spin states are often referred to as spin up and spin down although again you shouldn't take those labels too literally one way to it the spin of an electron from up to down say is to put it in a magnetic field which can realign these poles now in recent years there's been a lot of interest in constructing a form of electronic technology that makes use of electron spin in ordinary electrical currents the electrons have a mixture of these two spins and it's not an important factor at all but if we could control the spin states of electrons say using magnetic fields then we might be able to use spin as another variable for encoding binary information and to carry out digital logic like that used in computer circuits in a new way and this my dear is called spintronics and it depends on making electric electronic devices that can do things like allow electrical currents to pass depending on the electrons spin now this is hard to do because it's it's very hard to stop the spins from getting randomized and so far we really only have a handful of spintronics devices at least one of them is hugely important though and there are because the magnetic effects on electron spin can create an effect called giant magneto resistance where the electrical conductivity of a device becomes highly sensitive to the presence of magnetic fields and devices that use this giant magneto resistance are used in the readout heads of computer hard drives to read the information of the magnetic disk but it seems the biology already knows how to do spintronics Ron Naaman at the Weitzman Institute in Israel and his co-workers have found that various biological molecules and systems such as some of the membranes involved in photosynthesis can conduct electrons selectively depending on their spin this is something that DNA in fact can do also it's not completely clear whether this happens in real organisms or if it does whether it serves any role in biology but it could be useful for spintronic technology there are some proposals for using biological molecule or tricked learn from them in these devices what's more Luca Turin and coworkers have recently presented evidence that anesthetics whose molecular mechanism of action has long been a mystery might act by changing electron spins so as to enable electrical signaling between certain kinds of protein molecules but there's an even more striking way in which electron spin might feature in biology the fact that spin makes electrons magnetic has long been thought to account for the fact that some chemical reactions can be sensitive to magnetic fields you see electrons generally tend to pair up in orbitals that lowers their energy and that's how electric that's how chemical bonds are formed by the pairing up of electrons on on different atoms and these electron pairs in a single orbital have opposite spins that that's Pauli's exclusion principle and so the the pair has no net magnetism in that case they cancel out but some reactions including some important ones in biology involve the splitting apart of chemical bonds to form pairs of atoms or molecules that eat has a lone unpaired electron and those molecules are called radicals and because they have a net electron spin they feel magnetic fields and that this means they that the the reactions can be sensitive to magnetic fields radicals like this are generally very reactive they don't stick around long before they find some other atom or molecule to combine with now for many years it's been suspected that this might help to explain the magnetic compass that some birds seem to possess which allows them to migrate by using the Earth's magnetic field lots of birds do this robins do some sparrows do and homing pigeons and the idea is that the geomagnetic field despite being so weak somehow influences the rate of some biochemical process in the bird's brain so that the Neuros near the neural signaling depending on how the bird is oriented in the geomagnetic field and this this seems to be very probably what's going on what's more controversial is a recent idea that this avian magnetic compass uses perhaps the most bizarre effect in quantum physics which is called entanglement now in Schrodinger who gave entanglement its name proclaimed that it's actually the central concept of quantum theory that he said it quantum theory isn't too much really about quantum jumps or wave particle duality or particles being in many states at once it's about entanglement the irony is that the possibility of entanglement was first identified by the man who having more or less started quantum theory in the first place by the 1930s have become one of its greatest skeptics that's Albert Einstein now it's um it's not that that Einstein thought the quantum theory was wrong he just thought that it was incomplete according to the idea of Niels Bohr and Verner Heisenberg and their colleagues in Copenhagen in the 1920s quantum theory imposes fundamental limits on what we can know about the world and in their so called Copenhagen interpretation or you can know is what experiments tell you so the fact that experiments seem to insist on some uncertainty about quantum states or that different experiments might tell you different things wasn't because of some limitation in what you could measure it was because there was literally no deeper truth beyond that to be found so when quantum mechanics failed to predict say whether an electron would have one spin or the other until you measured it this wasn't because the theory was incomplete but because there was simply no meaning to that question before you had made the measurement so this is the Copenhagen interpretation and it's what Einstein couldn't accept he was convinced that there had to be a deeper truth what became called hidden variables which assigned everything with a definite one or the other value even if we couldn't find out what it was and with two younger colleagues in 1935 Einstein published a paper showing why in his view the Copenhagen interpretation had to be wrong he imagined an experiment in which two particles would be generated with quantum states that had to be related to one another let's say a pair of electrons in which the spins would be would be opposite one spin up and one spin down and the idea is that the electrons would be spat out in opposite directions from some device now we don't know which of them has which spin until we measure it whereupon we know so we make a measurement on one of them when we figure it has that spin and so we know that the other one must have the opposite spin and because of the it's because of this correlation between spins that we know that this must be the case and and and that that in that sense this pair of electrons is said to be entangled now if the Copenhagen interpretation is right then it's not just that we don't know which spin is which until we make the measurement it's actually that the spins are literally undecided until then and when we make the measurement that decision is made by the universe at random by making the measurement of one electron we force the choice to be made but then it would seem that that choice has to be communicated instantly to the other even if they've become separated by vast distances Einstein called this spooky action at a distance and he said how can this information be sent instantly across such a distance in fact that idea seemed to violate his special as the theory of special relativity which said that no signal can travel faster than light now in his view there was not there was no need for something as weird a bit as this because he said the spin states must have been assigned to the electrons all along it was just that they were somehow hidden from us he's challenged to the Copenhagen interpretation stimulated lots of discussion but there was no obvious way at that time to test it and it wasn't until the 1960s that the Irish physicist John Bell proposed an experimental way to do that I don't have time to explain what Belle proposed but his theory was put to the test in the 1980s by Allen aspect in France he's got this splendid the start with sort of invites jokes about entanglement that I won't try and get into he made measurements on entangled pairs of photons coming out of a laser and he measured not they're not spin States but their states of polarization whether they were horizontal or vertical and these experiments showed that there can be no hidden variables after all that entangled photons really behave exactly as if spooky action at a distance is real now I need to qualify that statement first of all there are various loopholes in the argument that excludes hidden variables from this picture and that they've only been very recently closed off second entanglement doesn't actually violate special relativity because it can be shown that although there seems to be this instant correlation between the particle States it's interrelation we can't establish that in any way that that transmits the information faster than light and third this doesn't amount to saying that this spooky action at a distance is real it only looks that way if we're thinking in terms of einstein's idea in which particles really do have locally self-contained states what entanglement really shows is that quantum theory involves so-called non-local effects meaning that situated that there are situations like this where we can't think of what is happening here of being independent from what is happening here it's a non-local interaction between them okay back to the birds this magnetic sensor then that they have is activated by light striking the bird's retina and the best guess at the mechanism for how it happened seems to be that the energy deposited by each incoming photon creates a pair of these radicals in which the unpaired electrons that they contain both have the same spin and as the radicals move apart they experience and magnetic fields they both feel the Earth's magnetic field but maybe one of them also feels a magnetic field from a nearby magnetic atom and the difference in the fields shifts the radical pair between two quantum states with different chemical reactivity perhaps some signaling chemical are synthesized in the bird's retina it happens at a different rate when it's in these different states and the relative balance of those states would then depend on the orientation of the bird relative to the Earth's magnetic field so that's that's the general idea Simon Benjamin in Oxford and his co-workers have proposed that these two unpaired electrons being created by the absorption of a single photon have spins that are in a state of quantum entanglement and although entanglement is usually quite delicate at ambient of room temperatures the researchers calculate that it's it could be maintained in this avian compass for at least tens of microseconds which is considerably longer than it's usually possible to sustain it in artificial systems in the lab they argue that this entanglement is essential for the extreme sensitivity of this system to very small magnetic fields because magnetic field effects experienced by one of the radicals can be in some sense felt by the other one some distance away well that's all very interesting but it won't be proved unless we can identify what the radical pairs involved are at least you know at least if we can't show that magnetoreception in birds and also in some other magnetic field sensing organisms like fruit flies seems to be mediated by a kind of protein called a cryptochrome which will produce radical pairs no one is quite sure how this happens in detail recent experiments in flies have seen have pretty much established that this is the sort of conventional idea and you see this shifting around of electrons here that essentially creates radical pairs this is the conventional idea for what's going on but it seems that recent experiments have rule without this particular pair of radicals as the ones that that can be involved one of the experts in this field Steve Reppert at the University of Massachusetts Medical School tells me that any explanation for this process is going to have to come up with a different way to generate these radical pairs so there's still a lot to be understood here now I talked earlier about how quantum effects seem to depend on size they might appear on very small things like atoms but not in big things like us no one yet knows whether that's a fundamental fact or not that's to say the reason footballs can't tunnel might not be because they're big but rather because they're so complicated because they're made up of so many atoms each atom has a wave-like nature but the waves all get jumbled up and out of step so that these wave properties get averaged away like soldiers marching out of step the technical term for this jumbling is decoherence and according to one view the reason why quantum behavior at small scales becomes classical behavior at big scales is because of decoherence and so this is a relative thing the more atoms and object contains the more decoherence kicks in and the less likely it is that we'll see these quantum effects if we want to make use of certain quantum effects then we generally have to control and suppress this process of decoherence one way to do that is to isolate a quantum system from its environment the jostling that it would receive from all the atoms around it is something that would cause this decoherence now an area where this is important is quantum computing and here the aim is to encode information in quantum states just as we currently encode information in say the magnetic domains on a magnetic disk or in arrays of light scattering dimples on a CD or a DVD the advantage of a quantum computer is that a single quantum bit could be placed in several states at once not just one or zero but a bit of both and this is a so-called superposition state this means that quantum bits could in effect perform many calculations at once at least that that's the simplistic explanation is what I'm going to give tonight the truth is that actually no one is yet really sure where the sort of speed-up that quantum computers are thought to to offer we're quite where it comes from but it's really hard to do this because these coherent states of quantum bits are generally delicate and easily disturbed they're very vulnerable 2d coherent and that's why so far we have quantum computers with only a handful of bits and why generally they need to be cooled to very low temperatures even the one quantum computer currently available commercially this one made by the Canadian company d-wave is it looks like one of the old mainframe computers it's the size of a room and that's because of all the cryogenics that is needed to keep the quantum bits cool I should say that some that there's a real debate at the moment about whether D waves quantum computer really uses quantum effects or not but that's another matter so you can imagine then perhaps why people were so astounded by a claim made in 2010 that coherent quantum superpositions of energy states can be created and sustained in bacteria and algae and perhaps in all green plants that use photosynthesis and that this is what makes photosynthesis which is really the font of nearly all life on Earth what makes it possible photosynthesis starts when a chlorophyll pigment molecule absorbs sunlight and that energy is then transmitted through a forest of pigment molecules around it until it reaches the so called photosynthetic reaction center and there it causes an electron to be spat out and sent down a relay of molecules where eventually it's used to split water and produce the energy storing molecules of the cell and the standard view was that this energy bundled into wave-like packets called exit ons that are spread out over several pigment molecules that this hops at random between the pigment molecules until it finds its way to the photosynthetic reaction center and as you can imagine finding at this path by random hopping is pretty inefficient and it's time consuming during which some of that captured energy may be wasted as heat but researchers in America reported experimental evidence that they said showed that photosynthetic about our bacteria and algae contain exit ins that move not in these random hops but as coherent waves of quantum superposition states if the Ekta stones are in this coherent superposition then they can explore many paths at once and this should allow them to find the best route much more efficiently and quickly it was suggested that this was in effect the same as the same as of the way a quantum computer would perform many calculations at once that in effect photosynthesis is a kind of quantum computation which sounds pretty amazing right but is that really how things are well since those experiments were conducted 5 years ago there's been a lot of debate about the interpretation and some researchers now think that the results originally interpreted as quantum coherence might have other explanations in particular that they might be caused by more conventional interactions between the actor tones and the vibrational states of the pigment molecules while we need some quantum theory to understand that process in any event it's not at all clear that what the researchers are calling coherence here is indeed the same as the quantum coherence that is being sought in quantum computing so in fact we still don't yet really know if photosynthesis truly is a manifestation of quantum biology and even if it is we have again to ask the question has biology adapted to make use of this effect or is it inevitable it's all too tempting to attribute it to the wonderful power of natural selection to find good solutions to problems but we can't simply assume that that's what's happened it might be that if you need to pack together pigment molecules densely in an array to get the to maximize light absorption something like this coherence of exit on States is unavoidable that it's just a by-product not an adaptation after all most photosynthetic organisms are spoilt for light they don't need to worry about conserving every last bit of photon energy and so there's not obviously any selective pressure to get them to make use of quantum tricks like this well then I hope you can see that there are some extraordinary possibilities in quantum biology but also many uncertainties about how far it reaches nearly all of the the Prize candidate systems in quantum biology still have plenty of questions to answer but some speculations about quantum effects in life go much further and I want to end by just mentioning a couple of them one of the biggest questions facing the life sciences today is how the brain works and in particular the origin of human consciousness in his 1989 book the emperor's new mind Roger Penrose suggested that the the that consciousness may have something to do with quantum theory he suggested that the choice that seems to happen when we make a measurement on a quantum system a choice called wavefunction collapse because it collapses all the possibilities into just a single outcome that this might underlie processes that are non computable once that a computer can't calculate or simulate and he suggested that the human mind is capable of dealing with processes like this and and that wavefunction collapse might therefore be important in some way for thinking and for consciousness that in conjunction with the physician Stuart Hameroff he later suggested that entanglement between electrons on protein structures called microtubules in the brain could be at the root of this process now like most Oh like many I should really say of Penn roses Wilder ideas this one is tremendously inventive and like many of them there's also not a shred of current evidence to support it but some interpretations of quantum theory imply far far more profound consequences for biology than any of this the collapse of the wavefunction is in fact a very puzzling thing because there's nothing in conventional quantum theory that explains or predicts it it's something that has to be put into the maths by hand and some physicists are very dissatisfied with that they think it's much more parsimonious to assume that in fact there is no collapse of the wavefunction at all instead they say all the possibilities contained in the equations of quantum theory correspond to real situations none of them goes away when we make a measurement instead the world meaning really the entire universe splits into alternative alternative worlds when this happens and that they are all real but that our consciousness can only be present in any one of them so you could say in one of these worlds Schrodinger's famous cat survived and the other one it died and both happened this is the so-called many-worlds interpretation of quantum theory it was first proposed in the 1950s and it's now advocated by some of the most influential physicists in the world including Stephen Hawking and Frank will check as well as well-known popularizers like Brian Cox and Max tegmark and Brian Greene in this view quantum physics offers you another way to replicate it's a whole lot less fun than the conventional one but but you can't avoid doing it more times a second then you can possibly imagine every time a quantum event occurs anywhere in the vicinity perhaps anywhere in the universe you split into multiple selves well I felt obliged to mention this idea my own view which I don't have time for CH initely to justify is that this idea richly merits Wolfgang Pauli's famous put-down it's not even wrong in another youniverse I'm going to dash out right now and go to the pub in this universe I'm happy to stay and ask questions thank you very much is the cooler temperatures to slow it down so that we can observe it more or do they simply not work is in a quantum computer would they not work it sort of higher temperatures

Channel: The Royal Institution

Views: 611,989

Rating: 4.8486791 out of 5

Keywords: quantum biology, Quantum Mechanics (Field Of Study), biology, physics, philip ball, Jim Al-Khalili (Academic), entanglement, Science (TV Genre), Royal Institution, royal institute, Science Communication (Literature Subject), Education (TV Genre), Ri, Quantum (Literature Subject), talk

Id: bLeEsYDlXJk

Length: 54min 42sec (3282 seconds)

Published: Wed Feb 18 2015