 And many, many thanks for the invitation and I'm really sorry that I didn't manage to go in person. So, and this is a long title, as you, you can see where I'll try to make you an update of a theme we've been working in in the last few years already. This concerns the persistence of cohere or the possible persistence if you want in a conservative manner of coherent effects in in a very noisy environment. I want to be dealing with a type of systems that perhaps are not our natural habitat normally I come from a quantum optics background, and these are complexes of different types that are hosted in membrane proteins of different organisms. The denominator they have is that they are involved in different processes of interest in biology, following irradiation, and then an ultrafast process that is going to be performed with a very high quantum yield. So we can be talking about photosynthesis in implants, algae or bacteria, and the primary steps of photosynthesis may also refer to radical pair formation that is a type of spin reaction that is suspected to to be relevant for belt navigation, but a candidate is the process of of retinal isomerization initial steps of completion. So what is that. First of all, I will sub select the type of pigment protein complexes that have been more investigated experimentally so I will, I will be referring to photosynthesis and then at the end will tell you how much we we can extrapolate. So the reason we started being interested in this type of complexes, having a background in investigating which conditions are generally necessary in order to have coherent and entanglement persisting or long and longer time scales. Is that there was a sequence of experiments that I will tell you the the gist of it that show that actually on time scales that are already relevant in biology. So we're talking about a few because a content scale, the seems to be a persistent coherence name lonely coherence in a way that we have to understand what does exactly meaning. The core of the talk is to deploy methods with being developed in open system theory in order to understand whether indeed we can benchmark as quantitatively as possible that indeed some coherent dynamics is present on those those timescales. Right. So this is a little bit to the James Cummings model of one biology. This is a complex involved in the photosynthesis of greens for bacteria. So let's say for biochemistry standards relatively simple and so was in fact the first one to be crystallized and fully assessed in x-ray spectroscopy, but it exhibits already the the ingredients that will be essential for our discussion. Having a network of pigments that you can really think of them as two level systems where the only thing that we are interested on is whether they are in the ground state of half experienced and electronic excitation. And then we have a coherent coupling term in between pigments that allow excitations to migrate across of this network, which is hosted in a phonon bath. The phonon bath that is provided in this scenario both by intramolecular modes and also slow emotions that come from the protein background that holds the thing together. Right. So we have in this complex in particular an enormous body of experimental information. Experimental information that comes from different forms of spectroscopy linear spectroscopy stopping from absorption with spectrum to linear and circular dichroism and then supplemented by nonlinear spectroscopy. That let's say allows us to start putting numbers in the type of theoretical description we will want to accomplish. So what are the energies of the different sites, what sort of coupling do I expect to have in between different models? So one idea that is relevant is that the way we start building up Hamiltonians, right, and possible ways of describing the coupling to the surrounding phononic modes come from a combination of first principle mutations and also reduce models that try to provide as complete as possible fitting to the different forms of spectroscopy. Okay, so it's a little bit like the models astrophysicists do really a lot of parameters that need to be fitted in the light of more and more experimental information. And what is very relevant to keep in mind because it's going to be very important later on is that these fittings, right, that set the ground for me to use this type of numbers in my theoretical description come from performing different adjustments to the spectral densities that characterize the fluctuation of the phonons, right. As you will see, this is a very complex function, the one that's measured or calculated by molecular dynamics and typically they do require some forms of embeddings. So, besides linear spectroscopy, the transfer of the multidimensional techniques that were developed in NMR to the BISI ball then allow to complete the picture by means of performing two dimensional electronic spectroscopy. And I think, well arguably, these two experiments performed in the group of Graham Fleming probably were the ones that really captured the attention of communities beyond photosynthesis. So, let's say that the conclusion that was put forward following these experiments is that there were signals signatures in the spectral response showing oscillatory behavior in the picosecond time scale. So let's try to understand what sort of experiments we are talking about and why people were argued that they showed quotation marks, longleaf coherence. So, these are experiments where one uses a sequence of laser pulses, right, with controllable time separations in such a way that coherence can be created and probed at a later time. So, it's a complicated technique that will require some time to discuss, but I think you can understand what is underpinning it if you think of a much simpler situation where we perform Ramsey spectroscopy. So, think about the situation where I have a common ground state and a simple system where I only have two sides coupled to each other, yielding to a lower energy exciton and a higher energy exciton. And in such a way that the excitonic split it is this capital omega one two. So, by illuminating with the right power over two pulse, I can't prepare a coherent superposition of the two excitonic states. And this will pre says in this interferometric setup in between pulses in such a way that if I apply the second by over two and check, let's say, for the population of the upper exciton, typically, if these evolution is fully coherent, if there is no noise in between the two pulses, it will be a typical sinusoidal signal. If in reality you do the experiment as a result of the different noise sources that you will have, then you will have a damped exponential. Right. The denomination long live coherent concerns the behavior of what would be a superposition ground first exit on versus the oscillatory behavior of our excitonic superposition. So, this is a femtosecond time scale, there is a very strong local be facing bearers us observations that indicate that the lifetime of excitonic superpositions exceeds by large, the corresponding to a superposition ground excited. That's the origin of saying long is long as compared to this ground excited. Okay, so now you can take a very pragmatic viewpoint saying, what is going on, why is it possible that even at room temperature, I am able to have coherent remnants on a picosecond time scale, right. So, if you think an open system approach, and then beyond, it will come the far reaching question of saying, okay, if there is coherent pressing on a time scale, where things of relevant happen in biology, is this coherence actually instrumental or something is it facilitating assisting or making certain process more efficient, they can to account that you would like to go beyond qualitative and improving in the same way that teleportation is assisted by entanglement, you would have to find a proof a quantitative argument showing that certain processes happen more efficient if coherence is present than this is done when it's absent. While I would say that the second part is open to discussion, and I think we have a nice understanding of why what sort of mechanisms are at play that could indeed facilitate that on those timescales we have a form of coherence that is not going to be purely excitonic as it was initially solved, but actually more, more involved than that. What is interesting is that a characteristic behavior of these molecular complexes can be achieved already if you do even a back of the envelope calculation where you describe the effect of the phonobath in terms of just the Imbladion dissipators. If you would do that you would already unveil that this type of complexes like to be sitting in the fence in such a way that neither the dynamics is dominated by the coherent part of the evolution neither is fully dissipative. In such a way that if our figure of merit, for instance, is the amount of excitonic energy that is conveyed to a certain part of the network as a function of the defacing rate, then we encounter this typical non-monotonic behavior where there is an optimal value of the noise where actually the task of transferring is completed more efficiently. This can be nicely seen in experiments, this is a transport experiment performed with an array of 10 qubits in the ion trap group of blood and a cause, and of course, given the let's say the required conditions this phenomenon would manifest. But the issue is whether this is actually what is happening in this type of complexes. Because if we look at the spectrum of the fluctuations, if we look at the typical forms of spectral densities that will be characterizing our environment, we find functions as you can see that have all the typical features for traditional master equations of limb platform not being applicable. So, in principle, we could try to look for reduced models, right, where you embed certain environmental features within the definition of your system and treat the rest as a Markovian background. But in the presence of such a structured environment, this is a protocol where you can get into trouble very quickly. So in order not to be ransom of the approximations one makes in order to derive different forms of Markovian or non-Markovian master equations, it would be good to actually see how far we can go with numerically exact techniques. And this is precisely what we did already, gosh, almost more than 10 years or 10 years ago, right, and that concerns the using of exact numerics to be able to analyze the behavior of a modern system that is just dimeric. Actually, the numbers used were inspired by the lowest energy excitons of the initial complex I showed you, the phenomethiological complex, but we consider the effect of the environment exactly as far as vibrations that were almost resonant with excitonic transitions are concerned. If you write down what would be the total Hamiltonian of the system environment complex and you rewrite it. Taking local defacing, let's say as a dog information that comes from molecular analysis calculations and seems that the main source of defacing is local nodes. And we rewrite the total Hamiltonian in the excitonic basis that results from making diagonal, the coupling, the dipolar coupling between pigments, then let's say a qualitative picture starts to emerge where we can see that the effect of localized modes can actually be an in-built driving force that could potentially be able to restore the coherence that is lost as a result of all the other broadband modes that are far of resonant. So, to do that, in the case of a dimeric system is now is possible, right, to employ TD-MRG techniques well known in contents matter that allow us to transform a typical configuration, right, given the spectral density, what's the spectral density is provided into a geometry that is amenable to do the MRG, given that it only involves coupling between nearest neighbors. So then we can provide what would be exact calculations for being in the presence of a background that contains quasi-resonant modes. And then being able to see it again to account that in this case I can propagate the whole universe then trace out the modes and in fact access what would be the dynamical properties of the excitonic state, right. And what I encounter is that the values of the excitonic coherences can indeed be sustained by these quasi-resonant modes. More relevant, this will even be present when I operate at room temperature. So the presence of this structured background can actually be good news as far as the persistence of coherence is concerned. As I said before, qualitatively we can understand it in terms of saying this is very much like being defacing while driven, right. So then these quasi-resonant modes are able to pump back, right, the defacing effect due to all the other background. Fine, that would be nice, but if we look at the actual form of the spectral densities for all complexes, then we encounter that this calculation may still be simplistic, right. In the sense that depending on the type of complex, right, if I represent what is the value of the excitonic splitting calculated in terms of the coherent dipolar coupling, then I encounter that, A, I can have many modes in the vicinity of that resonance, and B, I may have very long tails in the high energy region. So what is the effect of those? Can I really smooth them out? Can I perform embeddings that is, as I mentioned at the very beginning, the technique that has been used to do the fittings to the linear spectroscopy? Well, this is actually, this is the more recent results I'm presenting you on just this week, we got them accepted for publication. So the thing is that we have to be very careful, because if we look at the different parameters that characterize the couplings to the different localized modes, we encounter A, a large variation, and B, the maybe cases where the couplings are very weak, but we have many modes. So then indeed, the effect of considering the full spectral density can actually be highly non-trivial. I don't know how I'm doing with the time. You essentially have three minutes. Okay, perfect. So then I will focus, there is here a lot of information. I'm going to focus only in showing you what are the results of doing exact calculation of absorption spectra, carrying all the 55 modes that characterize another model complex. I'll show you how does the spectrum changes. So this is figure C here in the middle. And then you can see with the green dots that would correspond to the measured spectrum. And in the other colored lines, I have a representation of the exact calculation. When I perform embeddings in such a way that I only consider 20 modes in red, you see that is pretty far from the actually measured spectra. When I include 40, right, still not okay. And you see in black what happens when I consider the full distribution of these 55 modes I have present in the spectral density. So in this type of environments is risky to perform the typical tricks we do to try to encompass in a reduced model the effect of the vibrations. And what is relevant is that, in fact, actually I can do an estimation just using perturbation theory to see that I may have very significant long shifts in some situations. But what is very relevant is that if I go back to trying to analyze two dimensional spectroscopy where I can access the lifetimes of the different coherences that can be present. Then, as a result of the strong renormalization I may have in the presence of the complete the spectral density, then the allocation of who is responsible for whom changes. So, despite there has been a lot of controversy, and arguing what sort of coherence is the one that we are observing. Is it just ground mode coherence in the ground state. Is it a purely excitonic coherence in the excited state manifold. We strongly argue that, in fact, we are witnessing by chronic coherence that has contribution both from electronic and vibration and degrees of freedom. In fact, one of the more striking effects of considering the full spectrum of the fluctuations is that the electronic coupling can be strongly renormalize so actually the strength of the electronic interaction, maybe larger than initially thought. So, take home message is very tricky when we are dealing with noisy, noisy situations with a complex environmental fluctuations is very tricky to link a spectral response to the actual dynamics taking to account that here we are not amenable to perform full spatial tomography. And so, accessing, for instance, the excitonic state is not possible. And we do partial tomography if you if you want via these different spectral phones, but then connecting dynamics and spectral responses far from trivial. And so this is the reason that underpins the the the an ambiguous interpretation of the of the experimental results. But nevertheless, the picture that in this type of complexes, we have a nice interplay in between the coherent and the incoherent part of the dynamics seems to be taking more and more ground. The thing is that if we believe that indeed this type of analysis show that we would have coherence in a significant lifetime, then what would be the next to trying to breach the gap to see whether this has any importance in actual transparency, or even, even if it doesn't at all, right, what would be the lessons that can be learned in order to have bio mimetic or super bio devices that perform with artificial structures, energy and charge transfer. Obviously, I think on the basis of the results showing extraordinary normalization effects we need a next generation of experiments, and furthermore developing more efficient exact techniques that would allow us to compute exactly the spectral dimensional response beyond diamonds. And maybe from the purely theoretical point of view, maybe if you had a look at the at the post of Giovanni's paper, this is an approach that we followed recently with the aim of having quantitative tools that may not tell us exactly what the truth is, what actual dynamics is, but allows us to discriminate the ones that definitely are not able to reproduce the experimental results. With this, I conclude, and this has been a long story in a very small time, so this is the many people that have contributed and in red, they still the quarantine. Thanks a lot for your attention. Okay, so thank you very much. Thank you very much for for for the talk. Are there questions here in the audience physically present. I don't see. Let me check online. Let me ask you a strange question. How far are we from quantum biology? It depends on the, depends on the weight you want to, to give to the, to the term, right, I would say that for an argument that we have coherent effects in, in, in a picosecond time scale. I think this is certainly the case, right. Now, if the question is how instrumental that can be for actual processes in biology. I think this is not known. Right. The thing is that even, even, let's say, if the conclusion is that at room temperature and in natural conditions, right, is actually totally irrelevant. So it may be that these complexes actually are able to sustain coherence under the right conditions. So for instance, when they are manipulated with laser light. I think then the far reaching result could be how can we exploit them these phenomena in devices that are actually freed from the constraints you may have biologically. So exploiting these in technologies. Photos or tags, for instance, or any type of devices you can think who starts this to convey energy or perform chart separation. Nevertheless, I wouldn't give up yet on the issue of finding something that may in fact be relevant for biology, maybe nothing for the synthesis and that simply, I think is the more studied situation for historical reasons right but maybe other other processes and isomerization retina is one where actually hopefully we do have a nice one people through relation. Okay, okay, so thank you very much we have also some other question. Okay, one. One because we are running a bit late. So there is a question you mentioned the control over the phasing optical simulators can we also think about implementation in quantum gas microscopes and maybe control dissipative dynamics in interact. No, sorry, this was the wrong one. No, no. Okay, no, sorry. So, sorry, when you use a reduced number of modes to calculate the spectra, how do you choose them. One could imagine that some modes are more relevant than other and that they contribute differently to the spectra. Okay, taking to account that this 55 modes for WSCP is actually an exact form of the spectrum density there so this funny complex has these 55. So the form of the spectrum density is exact. Right. So now the issue is that indeed. Let's say if you want to do an open system analysis, typically what you do at the beginning is trying to see a, which of those modes, do you expect to be more relevant for the figure of marriage you are trying to explain. Precisely what has been normally done. People were trying to feed the measure spectra by means of performing saying well actually I put all these modes under the same Gaussian and so on. But the lesson we have learned is that that can be dangerous with so many modes and then performing reduced calculations may actually obscure many things. In particular, neglecting renormalization effects that in many situations indeed are not relevant, but the interacting systems they are. Right. So, this is a, I think the, the, the, the complete analysis of WSCP is that indeed chopping off high energy tails can be dangerous. We do obtain different values of the absorption spectra, depending on whether we take all or a few. Right. And this is a cascade, because these effects then what are the, the model parameters in your system Hamiltonian. And sometimes when you try to ascribe saying okay this signature in 2D is definitely vibrational coherence wrong, it may have an electronic component that you are disregarding. Okay. So, thank you very much. If I think there are no other questions here so we thank you again. Thank you very much for.