 Hello and welcome to the 2021 Martin Meyers and Berkeley faculty research lectures. My name is Jennifer Johnson-Hanks and I have the pleasure of serving as the tradition that has endured for 108 years. This afternoon's event marks the second of the two lectures of 2021. Thank you so much for joining us. The Berkeley Academic Senate selects members of our faculty for this prestigious lectureship each year, which recognizes the scholarly work of those who are among our most distinguished faculty members. Before we begin one housekeeping note, you can submit questions for Professor Whaley by clicking on the link in the lecture description at the bottom of your YouTube screen. Now, before I invite Chancellor Carol Christ to introduce today's speaker a few words about our Chancellor. Carol Christ joined the faculty of the English Department at Berkeley in 1970. She's a first rate scholar of Victorian literature. Between 1985 and 2000 Chancellor Christ served as department chair, dean and provost at Berkeley. In 2002 she became president of Smith College and served there until 2013. Chancellor Christ returned to Berkeley and did a second turn as provost before becoming the 11th Chancellor of UC Berkeley in 2017. She is a fellow of the American Academy of Arts and the American Philosophical Society. It is my great honor to welcome Chancellor Carol Christ. Thank you, Jennifer. It's my great pleasure and honor to join you all today for the second of this year's Martin Byerson Berkeley Faculty Research Lectures, a truly special annual event in the life of our campus. For more than a century, Berkeley's academic senate has singled out members of our faculty whose research has changed the trajectory of their disciplines. These lectures bring to the fore an essential part of our mission, the creation of new knowledge, the innovation and creativity that fuel the quest to know and understand more are at the heart of our university's antipathy toward the status quo, and our shared interest in making the world a better place. Being selected to deliver the faculty research lectures is one of Berkeley's greatest honors. For members of the campus community and the broad public we serve, this is a unique accessible forum for the presentation of scholarly research of the highest caliber. This also represents an outstanding and almost unbroken Berkeley tradition. Since its inception 108 years ago, the faculty research lecture was suspended only once in 1919, also a pandemic year. This year, our gathering may be virtual, but our admiration and respect for those we are honoring could not be more real. Some individuals chosen by our academic senate to give the 2021 faculty research lectures are Franklin Zimmering, who gave his lecture last month, and Brigitte Whaley, who will speak this evening. A professor of chemistry, Brigitte is also a faculty scientist at LBNL and co-director of the Berkeley Quantum Information and Computation Center. She received her bachelor's degree from Oxford University in 1978, spent one year at Harvard on a John F. Kennedy fellowship, and turned her doctorate in chemical physics from the University of Chicago in 1984. She was a postdoctoral fellow at Tel Aviv University and the Hebrew University of Jerusalem prior to joining the faculty here in the Department of Chemistry in 1986. Brigitte's research program spans a multitude of quantum realms with a particular focus on the intersection of chemistry, quantum physics, and biology. It should come as no surprise that her peers and colleagues consider her to be one of the most interdisciplinary theoretical chemists working in the United States today. Her most important contributions include developing algorithms, allowing quantum computers to efficiently solve computationally complex problems, including those of quantum chemistry. And she's played a key role in the development and application of quantum control for the realization of physical schemes for quantum information processing. As I prepared these remarks, I came across a remarkable description of what seems to have been a major inflection point in Brigitte's research. After learning that there are bacteria with the ability to biologically control quantum mechanical effects, she realized that understanding how living organisms are able to efficiently process quantum information could be directly relevant to her interest and involvement in the development and design of a robust quantum computer. Even as a professor of English, I was struck and transported by the curiosity, imagination, and creativity that must be marshaled to find and explore connections between some of the simplest forms of life and the most complex technological tools. As one of Brigitte's colleagues conveyed to me, Brigitte's perspective is expansive, spanning all the way from the practical to something bordering on the whimsical. And he said, I mean that in the most positive sense, for her work confronts the reality of what is possible now, while also envisioning, preparing for and inspiring what will be possible in the future. If that doesn't capture and embody Berkeley at its very best, I'm not sure what would. Simply put, as a theorist, Brigitte operates on the foremost frontiers of knowledge. She's authored over 240 scientific publications throughout her career, and her work has been widely recognized with numerous honors and awards, including to name just a few. The Alfred P. Sloan Award, the Alexander von Humboldt Senior Scientist Research Award, and several visiting professorships in the US and abroad. She's a fellow of the American Academy of Arts and Sciences, the American Physical Society, and the International Academy of Quantum Molecular Science. And as another testament to her scholarly prestige, Brigitte has served as a member of the President's Council of Advisors on Science and Technology in the area of quantum science. Brigitte has also shown outstanding professional and academic leadership over her career, and she's proven herself to be one of the campus's most dedicated citizens. She's served on important academic Senate committees, and several Chancellor's Advisory Committees. She's been a member of the Board of Directors of the Women's Faculty Club. Her commitment to her colleagues, her students, and our mission are beyond compare. So without further ado, please join me in welcoming our colleague, Professor Brigitte Whaley, who will present a lecture entitled Can We See Quantum Mechanics at Work Around Us. Thank you very much Chancellor Chris. So it's a great honor for me to present this lecture today, and I'm going to talk about quantum mechanics, quantum mechanics, and how we see the influences of quantum mechanics today in the world around us. Quantum mechanics has been with us for nearly 100 years now, but it still seems to many people, and just as it was to its developers, quite exotic and esoteric, and often very counterintuitive, as exemplified by the picture that you see in front, which is indeed a whimsical picture. And I'll come back to that towards the end of the talk. But yet quantum mechanics is increasingly in the news these days as new quantum technologies are being developed appear and they impact our lives, and they even talk of the Second Quantum Revolution. So today I'm going to discuss some of these counterintuitive principles and then show you how in our daily life we make use of these. And then I'll also say show a little bit about how going forward, we want to use these unique aspects of quantum mechanics to do new things and hopefully make our lives better. So the first one, first principle I'm going to talk about is wave particle duality. Yes, quantum duality, wave and particle. And what's shown on this beautiful picture is a different kind of duality. It's actually a classical duality. What's shown here are droplets of water falling into a pond, and it's a very beautiful picture because it illustrates the water has droplets, particles, and yet water down below here can make waves. And of course, this isn't the kind of quantum duality where water is a particle and a wave at the same time, which is what we're talking about with quantum mechanics. So to illustrate the quantum duality. I'm going to show. Take you through the basic steps of the classic to slit experiment, which was originally a Duncan experiment but now all parts of it has been performed experimentally which illustrates personally on this slide the difference between classical waves and classical particles. The next slide will coming after this will show how quantum particles and waves combine these two kinds of features. What we see here on the pictures on the top are two pictures for classical waves, like the waterways I showed you on the second slide. If we have waves coming in with wavefronts shown as the vertical lines here impinging on some green barrier in which there's a hole. The hole will cause the wavefronts to bend and will have circular wavefronts emitting from going towards the right. And then if we put down a barrier parallel to our green barrier here. We'll see the intensity of the waves or the pressure if you like is a ways crash up against the this wall will have a smooth distribution like this. But if we now make two holes in our green barrier, we will have now sources to sources for circular waves coming out on the right and these circular waves will interfere. And they will interfere in its following sense if we look here with you but my cursor is. You see my cursor right. Yes, you see the cursor here. It indicates that there are circles intersecting two circles one from each of these two slits. And that means that we have constructive interference of the two waves the waterways, the crest of the waves will be higher in this region, and we'll get to maximum. And then the similar will be the case here where you see again there are two wavefronts intersecting. In between these, there's a region here where one way from only a single way front crests at one point. And that's actually on top of a minimum between for the other way front. So these are regions of destructive interference and the intensity of the wave against this black boundary here are there is then much lower. So this is clap these are what look these are often called coherent type of phenomena and they are coherent because they rely on waves having certain relationships with respect to each other. But these are classical coherent phenomena. Now, if we have particles, things are even simpler. If I take pellets, they could be dried peas, they could be rabbit pellets if you have a pet rabbit, or little balls of birdshot. And if I take a supply of these and I shoot them towards this green barrier and I shoot them towards the place where the, the hole in the wall is, and the holes big enough, they will go through and some of them may be scattered off the edges of this hole. So they won't have all land right exactly opposite the hole, but they'll be distributed fairly smoothly around that location. And then if I make two holes in my wall, and I shoot my pellets towards it. So the ones which are coming out in direction towards to the hole or the bubble hole or the lower hole, they will go through and they will each produce a smooth distribution located with a maximum at the center of the hole. So this is all in accordance with our classical description or classical intuition. But now, if we say, okay, so I've got pellets that pretty small. So let me go much smaller. Let me go to electrons. Electrons, we tend, if we're not thinking very hard, we tend to think of electrons as particles after they have mass. They have charge, you know, these things, and we think of them as whittling around the nuclei in an atom. And we can produce a source that will send off electrons. Notice I haven't put a little big block here. But we can produce a source that will emit electrons and we can hear them arriving on a screen. So we think they're particles. So we put them through a slit like this and we get a distribution just like we saw for the pellets, and indeed just like we saw for the classical wave with one hole in the wall. But now if we look at sending our source of electrons or beam of electrons in towards a double slit, we see that we get something very surprising. We get, instead of the two peaks from a classical set of particles going through the slits, we now see an interference pattern, just as we did for classical waves. So it appears that the electrons are behaving like waves in this case. Whereas in the first case, with only one slit, we can't really say whether it's wave or particle because it gives us a similar distribution. So then it's disturbing our intuition that electrons are particles. So we think, okay, so let's lower the intensity of this flux of electrons coming out from here. Let's make it much lower intensity, slow down, and let's reduce the volume of the number of electrons coming out. So then there's my controllers down here. So then what happens is if we see this kind of pattern on the right, on the left here, which is actually an experiment. These experiments were done quite late. They're starting in the 1960s. If you start with the high intensity electron beam, that's the bottom curve here, and you see plots here. You can see the strikes of intensity maxima here and here. And in between there are these minima regions. And so this is basically the picture that I have here on the right that turns on its side. And so you can actually see the intensity in the vertical direction. And then this is on the left is indicated how many electrons are sent out per second or per minute. And this is being reduced in the panels going up to the top. When you see once you go below about a thousand, you really can't make much sense of any kind of strikes here at all. In fact, the position at which electrons hit seems to be completely random. In fact, when you go down to 10 or so, it really is just random positions on the screen. So this is a second very, very important point about quantum mechanics is that intrinsically, though we think on the one hand, that's coherence, we know what coherence means very regular motion of waves. At the same time, there's an intrinsic randomness. So each electron, yes, is behaving as a wave and as a particle, because as wave it can contribute to this to making this interference pattern. But when it behaves as a particle, it will basically just collapse this pattern and will only strike the wall at any one point. And that point is impossible to predict. We have no way of predicting with any of the equations of quantum mechanics, but which point on the wall that electron will hit. And that's something that's very disturbing for a lot of people about quantum mechanics. Einstein was very unhappy about this. His famous statement, God does not play dice, referred to this intrinsic randomness in quantum mechanics. Moving along. Okay, so we can do one more thing with this experiment. It's a wonderful experiment, both in reality and in Gedanken. Before I move on, let me just say, you could also do this kind of experiment where you go down and reduce the intensity with light. And in fact, this experiment with light was done back in 1909 as an undergraduate research project. From by George Taylor, who became later a very famous hydrodynamicist. You went into ways, but waterways more than lightways. But his first very first research was to do essentially this experiment with light, namely turning down the intensity of light. Slowly, slowly, slowly, slowly, until there was such a low intensity of light and he did this with a light bulb. That there would be only very small number of photons on the screen at a given time. This experiment was carried out after Einstein had first suggested that light somehow was corpuscular and Taylor then verified this. So now we have this duality going in both directions. We have electrons, particles behaving as waves and light behaving as photons. So that's yet another thing we can do with this, which is we can take our electrons. And we can see, well, if I'm looking at single electrons going through this double slit, then if they seem to be coming out randomly at random positions on here and each individually, then why don't I put some little observer, maybe a light source behind this green wall to see which slit did each electron go through. So we can do that. We can set up a strong light source here such that if an electron goes by, it will scatter a bit of light off it. So if electron comes by here, we'll scatter light off and this detector will click. Or if the electron goes through here, it will scatter light off it in this direction and this detector will click. So then we expect that we should be able to regain our classical distribution because we're measuring single electrons. But actually, we don't, well, sorry, we see this. So we see this, however, when we should be expecting a diffraction, an interference pattern. So this says that by the act of observing those electrons, because we should be observing, we should be observing individual electrons. We're in this regime here where lots of electrons are going through. And when we do that, instead of seeing this pattern at the end, we see we regain this classical pattern. So it's as if the observer here has perturbed those electrons, it's disturbed them and put them on a different path than they were on originally going through to create this distribution here. Instead, they have created the classical distribution that we expect from pellets. And pellets, if we put a light source here, that's not going to affect what that's going to have a very weak effect and their distribution remains the same. So this is this very famous experiment that illustrates the wave particle duality. It also illustrates the randomness, intrinsic to quantum mechanics, and also illustrates the feature that if we look at a system or quantum system, we will perturb it. It changes properties quite significantly. And of course, measuring a quantum system or measuring any system does mean that we are perturbing it. We want to see what it's doing. Then there's Yin and Yang in quantum systems that we want to really understand what it's doing. We have to try to perturb it as little as possible when we're trying to measure it and figure out what it's doing. So this is all with electrons. So this is very far from our everyday life. And this has led to this kind of picture here where people, this is from a well-known physicist, a boy, Jake Zurek, who's constructed this cartoon type of picture with a sharp boundary between a quantum world where we have photons, electrons, atoms, things very small, too small to see with our naked eye, maybe going up to some more speculative things like gravity waves, but we don't know about those yet. And then everything over here is very fuzzy, very wavy, and there are these strange cats that seem to be doing two things at the same time. We'll speak more about those later. And on the other side, this is where things appear normal. This is a classical regime. Here we have the sun, the planets, us, and we know what's going on. We can use Newton's equation, the second law of thermodynamics. And the scale here from behind this boundary is one in terms of quantum particles. And if we just increase the number of those quantum particles, we start going into atoms from electrons and nuclei, and then we go up to 10 to the 23, Avogadro's number, this is billions of billions of atoms. This is where we believe that we live. But it's a question, is there really a, and then we, if we're living here, we think, well, we really don't have to worry about what's happening over here, unless we happen to be studying physics or chemistry, or what? Well, or, or we go to a hospital and we have to have an MRI taken. So there are instances, MRI is a very beautiful instance of somewhere where a quantum technology is really here and really impacting our daily lives and certain instances of healthcare. So let me tell you a little bit about MRI. So this really is, it's called magnetic resonance imaging. It's really a quantum imaging tool. So on the left, you see a magnetic resonance machine. Many of you have probably experienced this. It's a huge magnet. The person gets lit inside. And inside that magnet, there is a very, very large magnetic field. So the, the whole imaging is based on properties of a very mundane molecule. That mundane molecule is water. We have a lot of water in our bodies. Water is this little model represented by this little molecule here, this ball and stick model with the red ball being the oxygen atom and the two white balls being hydrogen atoms or protons. And these protons have a uniquely quantum mechanical property called referred to as spin, which has no, there is no classical degree of freedom like this. There is a classical analog, which is often used for us to the help, help mate to try to understand to get some intuition about what spin does. You can spin in the kind of rotational motion has properties of an angular momentum, which is the rotational motion. So you often see this kind of picture. This is specific to a proton. The proton we know has massive has some volume. So then here it's quite natural to think of the proton spinning on its own axis. That gives it some angular momentum. And the property of the quantum spin is that it generates a, because the proton is charged, this will generate a magnetic field, which is indicated by these curved lines coming up. And then the magnetic moment pointing with this indicated by this arrow pointing out and that magnetic moment will interact with the magnetic field. And if you put a strong magnetic field on one of these spins, then those, that spin will align. And if it's, if it happens to be a spin down, it will align against the field. If it's been up, it will align with the field. So the spin up will go, sorry, the spin in this case spin down will be aligned with the field and that will be the lower energy. In the other state, the spin up will be the higher energy. And the most important thing for the MRI application is that the energy difference between these two levels of that little quantum spin is linearly is proportional to the magnitude of the magnetic field. Now, so then enter the big magnet in the MRI machine. So it's possible in this huge magnet that you are sent into to bury the magnetic field strengths over different parts of your body. It's shown here in extreme case, varying over the entire length of the body, but it could be just over a small part, for instance, over the knee of the person. And this in fact is on the right and MRI of my husband's knee. And I will explain to you what this feature is here is it's a torn meniscus. And let me tell you how this image is formed by interrogating these quantum spins. So here again are the water molecules with the protons here and the spin indicated. And so there's many, many protons in your body attached to water. And it says no magnetic field. They were all just randomly oriented. But if you put on a magnetic field, they line up that they showed on the previous slide and some of them aligned, most of them are lined up, aligned parallel to the field and aligned with the field and some of them are anti aligned. But most of them are up. But then exactly how many are up or down depends on the local environment that the automolecules field. And then we can interrogate those spins by applying little pulses in the so-called radio frequency regime. These are very low energy pulses to flip those spins and to look at their dynamics and by measuring the energy release when the spins relax back to their natural situation, we can measure the concentration locally at the spins. And so what's then the ability to make this gradient is very important because the gradient ensures that the spins in one region of the body will have a very small energy splitting and so they will be detected at one end of your energy range of a detector. And the spins of the other end of the region you want to interrogate will have to have a very high, relatively high frequency pulse to flip them and that would be detected as a higher energy when you detect the relaxation. So then on the right you see this image of a knee and the black areas are low concentration of water so this is one bone here and one bone there. And then in between the two little black triangles represent the meniscus which is cartilage and essentially has no water and in this little region here there's a white region with lots of water. And that is a tear in the meniscus that has to be diagnosed in this way, very non-invasive way and has to be repaired. And this is a true quantum technology, very commonplace now. So that's the first example. Let me carry on with some molecular examples. What about the shapes of molecules? Well electrons we know are confined to spatial regions around and connecting nuclei because of the Coulomb interaction with the nuclei. These are what we call bonds. And there's a very deep and completely non-trivial theorem, very absolute theorem about properties of spin for electrons. So electrons also have spin but now you can't really visualize it as rotation because electron is a point particle. The power show that you can only have two electrons in each bond because you can only have two electron in each bond. That's what gives rise to the shape of molecules. If you could put as many electrons as you wanted into each of these bonds, we would not have molecules with shape. We would basically be like blobs of fluid and we wouldn't have biology or life. It's really this very non-trivial principle of pairing of electrons and bonds that gives rise to these localized shapes we have of molecules where the shapes are determined by the topology, the connections between the nuclei and these connections are formed by pairs of electrons. So this, now the question is can we actually see this structure? Well we can actually see this with another quantum tool. So in 1981, Benjamin Rohert IBM developed what's called a scanning tunneling microscope, which is shown here, which is basically device that allows one to put a voltage between a metal tip and a surface. And if you put your sample, so this molecule over here is very flat, you can put that molecule on the surface here, that's molecule right here, and you lay that molecule flat, you can then force electrons from the surface over to this little tip here. And electrons going in a surface or in a metal, they are very happy, they are low in energy, they are surrounded by lots of nuclei, they have places to go, and they can hang out and be cool. Electrons do not like to be in their space because there's nothing there to hang on to. So electrons experience a barrier shown here on this little diagram, so on the left here there's an electron wave doing its wavy thing, very happy inside this surface. But here it comes across this barrier, this barrier is counter-intuitively maybe to our macroscopic eyes is actually the free space between the surface and the tip. So normally, electron with certain energy, the energy is represented by this gray line here, wouldn't be able to go through a barrier which is much higher. I mean, if a tennis ball thrown at a wall, you can't go over the top of the wall if you don't have enough energy. But in quantum mechanics, a particle can tunnel through due to its wave-like nature. And this, again, is a purely quantum mechanical phenomena. It allows us, though, today to actually take a picture of the molecule, to take a picture of the bonds, and that's what's shown here below. This is work from my colleagues, Felix Fisher in Chemistry and Mike Cromby in physics, who developed this technique, which allows them to resolve actually the actual bonds, not just the people that looked previously at molecular orbitals and the rough distribution of electrons, but they are looking now at these individual bonds connecting the atoms and defining the shapes of the molecules. So yes, we can see those with our extended eyes of the instrument. Another example is, and again, a very simple example, very important in chemistry, and to us also colors of nature. Why are plants green? There are a number of answers to this, but the simplest one is illustrated here, which is that the color of something that you see is the color of the light from the sun that's reflected. The colors are that are not absorbed. And what's shown here on the left is an absorption spectrum, which indicates how much of the light coming at a particular wavelength. This is wavelength in nanometers, I apologize, it's a little bit fuzzy, but how much is absorbed by different pigments in plants. And the most important pigment for photosynthesis is the chlorophyll, which is shown here in a ball and stick model, this shape. And you see that chlorophyll absorbs in the red, and it absorbs in the blue, but it doesn't absorb in the green. And that means that the light from plants is reflected as green, and that's why plants are green. Now another point here, what does it actually mean that lights absorbed? Well, this is one of the observations that was gave rise to the entire growth of quantum mechanics, starting in the 19th century. And people observe that spectra of atoms were very sharp, just specific energies. And that's illustrated here by this two level system, just like a spin, the two electronic energies, ground state and first excited state of a molecule. And to a lot of, for most of the rest of the talk, all you will need to think about are two level systems. But absorption lines are not sharp in plants. They're not like spins. They're not isolated. They have vibrations and rotations. They exist in complex and packed environments. And so, so in that situation, we have to think a little bit more carefully about whether we can see things. So what I'm going to first do before I go to that is explain one more quantum weirdness, which is very much involved these days, which is quantum entanglement. This is a term coined by Schrodinger in 1935, which refers to the ability of two systems. So this is an artist's sketch of what entanglement is here. And the idea is that one has two quantum systems and they are, they may be prepared by some interaction that's very important. And then they are separated. And the point is that when they are separated, they're in such a particular state that if I was to carry out a measurement on one of them on this one here, for instance, that that would automatically determine the outcome of a corresponding measurement on this one. And that sounds fine if they're close by, but this property of entanglement is a property of the state. And if I put these two objects together, and I create this entanglement and then I separate them without anything interfering with them or disturbing them. I can separate them in principle that one of them is on the moon and one of them is on earth. Then they would still have this property. There would still be that one person on the earth would measure a particular aspect of this object and the person on the moon, a person on the moon or something on the moon would then automatically have a predetermined in a sense measurement outcome for that. And this is very weird. This was not really explored for a long time, but starting in 1964, Bell started to think about this. And now, since then, it's been really very much explored and it's very important in all of our quantum technologies today. And here's a very simple example of this, an idealized example. If one takes a laser beam and puts it through a nonlinear crystal under certain conditions, one can generate pairs of photons where one pair of the photon is vertically polarized and another pair is horizontally polarized. And these two photons come out in different directions. Now, if you look at the points where these two cones intersect, then you can see that since one cone is horizontal polarized, the other cone is vertical polarized, so those points of intersection are shown on the right here in the green, this green light. One has no way of knowing which one is horizontal and which one's vertical. They came spatially from different regions, but if you're just looking at what's appearing at this point here, you have no way of knowing. And if you have no way of knowing, we call this, we have to basically say that they are horizontal and vertical at the same time. They exist in two states at the same time. And this is on the one hand an expression of superposition like waves, which have where we have two waves adding together, but it's also now because we have two particles, two entities. They are also, this is also what we call entanglement. So entanglement is a special kind of can be thought of as a superposition of multiple particle states, where there are very strange correlations. And Einstein, as Schrodinger said, this is referred to entanglement as the true characteristic of quantum mechanics. It's one for which there is no, there can be no classical analog, unlike superpositions where we have classical waves. So we pose the question, can there be coherence and entanglement in biology. And here's an example of a biological system, the photosynthetic system two, which is responsible for the growth of plants, which managed to do this with a very small amount of chlorophyll over here. Samurai's over here. And then the process of photosynthesis starts with photons being absorbed, they out here in these harvesting areas, and being transmitted by some path to a region called the reaction center where this electronic excitation is converted to free electrons and then chemistry happens. So we're very interested in this first step and recall coherence. Let me just remind you what we mean by coherence is that waves are moving together, whereas it's a start moving all the difficulty, then they will be incoherent. That's what we mean by incoherent. So the question here that was posed was whether the excitation hops like a particle or propagates like a wave. So my colleague, Graham Fleming, started in the early 2000s and he showed in breaks for experiment, I'll show you in a moment in 2007, showed that there is indeed coherence in excitation energy transfer over pathways of such systems. And in particular, he looked at a protein called FMO after the people who worked out its X-ray structure. So very well studied, very well characterized protein. And even though it comes from a very unprepossessing green bacterium here, it's been very widely studied because we know exactly where each of these chromophores sit and what their relative orientation is. And so we can just understand this in a very quantitative manner. This protein acts like an antenna connecting the, acts like a wire connecting the antenna which absorbs where the photons are actually absorbed to the reaction center. So it serves to transmit excitation energy through here to the reaction center. So what Fleming's group did was constructed a very sophisticated multi-pulse, one, two, three pulse, later time result, time to second later experiment, which would allow them to probe at some arbitrary location here in reciprocal space. It allows them to probe the polarization of the sample due to absorption of these different beams. And that gives them access to actual amplitudes, which will show, in this case, show oscillations, which reveal the coherent transport of the excitation energy as it goes through this set of chromophores. So these oscillations and also the smaller ones here are understood to be oscillations of the polarization and evidence of coherence. So we did theoretical work on this and showed that that was indeed accompanied by entanglement in here, the case, there's a signature of the entanglement here. And also then we show theoretically that one can do calculations, modeling, accurate modeling for these larger systems to show that there is indeed coherence over the entire path. That's not yet. Okay, so entanglement is coming in a moment. One more thing we could do here, which is now in progress, is another aspect which relates to the random nature of quantum mechanics, which is quantum jumps. So quantum jumps have been mentioned for many years and was first seen in the 1980s for isolated atoms in vacuum. Now we're seeing this in a very wet, dirty biological system. So what is a quantum jump? A quantum jump refers to the fact that when a light is absorbed, it occurs in one step, one jump of a photon taking the ground state to an excited state. But the picture that people often use is that light and energy is absorbed in complex systems in a stepwise process in requiring many, many absorption events. And it's only after maybe hundreds or thousands of photons that you would actually get enough energy to release another photon or to create, which is a proxy for electron hole pair. So this experiment generated is an experiment which, like the source of pairs of photons, generates two photons. One goes onto the sample, which is here, another one of these light harvesting systems. The other one goes into a detector and sets a clock. And what we did was we counted the number of photons of the blue type, the clock photons, that had to be absorbed in order to see one photon coming emitted from this complex. And if you see a peak here at one, then you have evidence of a quantum jump. If you see nothing here, it's no quantum jump. So what did we see, and this is very recent work from Fleming's lab, is we see this beautiful distribution with a peak at one showing a quantum jump. So this is another example that even in a very complex system, there is a true quantum process happening. I'll skip the vision. This is the burst. I will skip the burst because it's a little bit late, but this is, I can say more about that if people have questions. And let me say a little bit about quantum information processing. So the power of these quantum systems has been recognized over the last 30 years increasingly as a means of processing quantum information. And this is really a technology that's coming soon to us, in fact, very soon. And so the idea is that we can take any two level system. It could be a spin or it could be two electronic states. And because the system can be in both of those two states, that's what we call a superposition, it can be a zero and a one for information processing rather than a zero or a one as a classical magnet would be in the computers that we know today. And all of these, so we can have an infinite number of states like this, they're all represented by points on the surface of a sphere. So we can make superpositions of states from multiple two state systems, and we can then use these to do various kinds of information processing. And there are several centers at Berkeley now, one from the NSF, one from the DOE, and under the BQAC, which has been around for longer, and the Center for Coherent Quantum Science. And with all of our colleagues in these, we are investigating primarily issues of computation, but also simulation, and to some extent, the sensing and communication. What I'd like to just give you an idea of a couple of slides here is what's involved, why this is, what's involved in this and why it's hard. So if we put these quantum bits together, these two level systems together, we need to have many of them, but once we have say any of them, we can make superposition states of all of them. And that gives us access to very, very many quantum states, many more than with magnets. And then we can evolve these states in parallel with quantum circuits, and this is just, never seen this before, it looks vaguely like a classical circuit, just treat it as a nice piece of art. And then we interfere the amplitudes, recall the double slit, we have cleverly chosen measurements, recall collapse, but it's very important how we choose those measurements. And you put all those things together, you get a promise of significant speed up in scaling of computation with the size of the system. And indeed, recent experiments have shown that there is a real advantage for some problems with that can be implemented with up to about 50 qubits. But there's a real challenging going further than this. If you think about the kind of accuracy you require, 99.99% accuracy is way beyond any kind of accuracy that a biological system ever needs, or a chemical system. So the control that's required to put this together is enormous. So in a sense, and the reason that you need all this control is because of the environmental interactions which remove the quantum states, that's a decoherence. So, and this is, I'll come back to this in a moment, this is the reason why we in general don't see very large systems in a quantum superposition, because of the interaction with the environment. So one thing though that is a technology that is really right here now is quantum communication is much much further advanced and quantum computation and this is an example very impressive example from a collaboration between China and Austria, which is an internet continental quantum network, where photons single photons are being sent from one of these stations, either in China or in Austria, up to a satellite, and then extent down to the other station. And this allows a completely secure quantum key, a one-time keypad, because of the properties of quantum physics. In particular, it's impossible to copy a quantum state. So if there was an eavesdropper out there, they would not be able to copy any of these, the state of any of these single photons that was being emitted, because they wouldn't, they would be disturbing the system while they were measuring what the state is. And then, so we know then, the people in China and Austria will then know that someone was out there measuring their state. So then they throw that part of the key away. And with this kind of quantum key distribution, they managed to encrypt pictures on the one side, the Schrodinger flown over from Austria and on the Chinese side, Mekius, who was a scientist about the time of democracies, who actually had some thoughts about some comments about the first, about action and reaction, similar to Newton, and these pictures were shared in complete security. So this is something which is really very much on the table right now. And this is something which might be coming to us individually in the future. This is a project in the UK to make consumer QKD, which is to use that same technology but at a much, much reduced scale to make a completely secure ATM banking. So stay tuned for that. And I think I'm pretty much much time. I'm pretty much out of time to have a cup. Well, maybe I'll just put this slide up as the closing one. But one more after this. So the next question is really what limits quantum superposition. So, as I've indicated, it's very, very hard to build a large scale quantum computer. And that's this reason. But similarly, we might ask, well, so, so why can't we, why can't we have this absurd picture from of a skier? Is it the complexity? Is it just a size? Is there really a true boundary, firm boundary between classical and quantum? And this does have implications for the nature of the reality that we live in, which I don't have time to go into. And there's this famous example from Schrodinger that if I have one radioactive or small number of radioactive atoms in a box or something very microscopic, put a cat in a box. After I leave it for an hour, after an hour, there'll be, if I've chosen the radioactive element correctly, there'll be a 50-50% chance that the atom has decayed. But it's decayed in a quantum manner. And so if it's decayed, it's a Geiger counter, which there was a hammer, which hits a bottle and releases poison and the cat dies. But if it doesn't decay, the cat's alive. So we don't know until we open the box. So this is often stated as being a conundrum because do we get the quantum superposition? Quantum mechanics might predict we get the quantum superposition of live and dead cats. Well, fortunately, we will never be able to find out because in order to show that it's a superposition, we have to show some interference, like in the double slit experiment. And as far as we know, we cannot interfere live and a dead cat because to interfere, we have to be able to go convert from live to dead and from dead to live. So let's leave biology out of it. And instead, we have here an example, again with Berkeley work here from John Clark's group of magnetic flux qubits, which are little rings of superconducting metal, which where the current can go through in one or other directions, giving rise to magnetic field in one or other other directions. And these are like bits that they have large numbers of electrons. So the number of electrons involved in the current is approximately 10 to the 10. With some theory that we did, we showed that the number of electrons doing things differently is only about 10 to the three. So these are not macroscopic. So, can we really get macroscopic? So this is the very last, the last technical slide here. This is something which is a very active area of research right now, which is to see how large a system can we make that would show a true macroscopic superposition, meaning a particle that we can see by eye. So this is the 150 nanometer particle of silicon, silicate, which is visible through a microscope, not for the naked eye. It's about 10 to the nine atoms. It's in a cavity here. And these, my colleagues in Vienna, this Marcus Aspelmaier's group, have managed to basically low put this into its vibrational ground state, but then there's still some zero point motion, there's still some uncertainty due to the quantum mechanics. And this is of the order of now 1000 for the nanometer. The idea is if you let this fall, will it separate into a state falling to the left and a state falling to the right. In other words, will you have a, can you generate by this means a quantum superposition of a truly macroscopic piece of solid. And this raises very fundamental questions, not only about macroscopic quantum physics, but what is the relationship between the quantum object itself and gravity. And can we make quantum superpositions possibly even a space time. So from. So that's basically the last slide I wanted to show you which really takes off in a completely different direction. But what I just to summarize, there's another picture of the famous cat with a nice lively tail and a sad tail. And it's under a sky of the sips of, sips of knowledge and these are the many, these are the various enigmas. Some of them are enigmas, some of them are basic facts that we accept and a part of our daily life discrete energies powerly pairing of electrons. All these things that quantum mechanics tells us, but did you see anything from what I've, but I've said there are still many mysteries we still don't really understand this and there's a lot of exciting things still to be done, but I think we know enough at this point that we recognize these. We can go about our daily lives and look around us and say, wow, this is quantum mechanics working. These are all these colors of the flowers and so on outside. This is, this is quantum mechanics. This is really cool. Thank you. This is actually this is the very last slide. And this is a quote from Goethe's house from the prologue. It's actually when God is speaking with the three archangels and he tells them to go away and figure everything out. So which is, I think, we aren't archangels, but as scientists, I think what a lot of our work is is looking at things that appear very vague and very fluffy and we're not really sure. And then we have to really think very, very hard, carry out experiments and then maybe we get a clear picture if we're lucky. Thank you, Dr. Waley. That that was just such a compelling and moving talk and just to connect so many things in so many ways. We're getting lots of questions in but unfortunately we're only going to have time for one and the one question I'm going to bring to you is almost immediately after you you moved on from the slide about the birds. We started getting questions about could you please tell us about the bird. Okay, very good. I can maybe go back and very quickly. Just say a little bit about the birds. Yeah, there they are. Okay, so this, this is a fascinating topic. I didn't dwell on it too much because it's still largely hypothetical. It's very, very difficult to do experiments on birds, but the problem is the following. The scientific problem is the following. We have birds we know migrate very large distances over from north, generally from north to south, south to north. And they do this, they navigate by using the declination, the angle which the magnetic field makes against the earth. So they're measuring the direction of the magnetic field in just the declination of that that's shown here on the right. So then that tells them whether which part of how far north and how far south they are. And so it's believed that they do this, or they can do this by several methods, but one method that's believed is active, possibly with others, you know, as for proof to be for proof. The one method is involves certain proteins that are in the back of the retina. These are cryptochrome proteins shown here, and they have inside them some special pigment FAD and another set of pigments here. And it's believed that that on light absorption of a photon, a single photon of light. So here's this FAD molecule here that one electron gets excited up to here. So suppose a purple electron with a spin up electron gets excited up to here. Then there would be nothing left here and then the electron transfer will occur from this molecule here. This electron over here will then pop over here and fill the hole here. So that means when it's then left with electron spin up on this molecule FAD and an electron spin down isolated on the molecule tryptopan plus. And this means we have two separated electron spins. One is up and one is down. It's a bit like the horizontal and vertical photon side that I described. And these two unpaired electrons are known as radical pairs, very Berkeley. And they can be entangled, meaning that they can have coherent dynamics which flip them from up down to down up. And also, in fact, from up down to up up and down down. And people have made models and also carried out chemical experiments with models. Making molecular, basically artificial analogs of this cryptochrome set of pigments to see whether the coherent dynamics can actually cause signaling to the brain of the birds. And it can do in the models, it appears to be able to do so by changing the reaction yield of particular signal signaling molecules. And then the net effect is the bird sees by some signaling process will see a particular pattern in the reflecting the reflecting the reflecting the the orientation the local orientation relative to the magnetic field of the earth. So it's a very complex multi step modeling process, but there have been experiments done in the lab. There have also been done a beautiful set of experiments. The couple of the which goes in Germany carried out for 20 years, behavioral experiments with birds. And they're very difficult to do they could only do 20 birds at a time or 12 birds at a time and it takes two years for each experiment so the data is quite limited. And so it's not, it's not, it's not a conclusive evidence right now that this is indeed the case and it is it's probably one mechanism among others, which birds use. That's just fascinating the these multiple ways in which something so difficult to understand and esoteric as, as, as quantum entanglement in quantum mechanics then comes through birds and MRIs and cryptography into our into our everyday lives it's just been an extraordinary extraordinary talk and I want to thank you so much for this enlightening presentation. Thank you to the members of the audience who submitted questions. I'm sorry we didn't have time to get to more of them. I'm happy to answer a question by email if people want to, they really want to persist. Well, thank you so much. It's, I hope we were able to capture a little bit of the questions to kindle your further discussion and reflection. So members of the audience, I want you to know this lecture will be available online soon following the event at faculty lectures.berkeley.edu. I want to thank everyone for being here. I hope you all have a wonderful rest of your evening or day or wherever you're joining us from and what time it is there. Thank you all and fiat looks.