08:47:16 Yeah, so our next speaker will be Igor Perkowski, and he'll tell us about low energy interface of quantum and gravity.
08:47:48 Right. Well thank you very much. So first of all I really want to thank the organizers, not just for inviting me which I really appreciate. But also organizing this extremely interesting workshop after say now the last day.
08:48:00 It's like the the breath and span of topics is very interesting and I think very topical. So she's really been enjoying it so far, very much.
08:48:16 And my own background is in theory in quantum optics theory. In quantum information theory, but the last decade or so or even longer I've been most interested on the interface between quantum systems and quantum control on the one hand, and gravitational
08:48:19 And here. What I want to talk about is the so called low energy interface of quantum of gravity.
08:48:30 phenomena and possibly quantum gravity signatures on the other.
08:48:35 And so this talk is a bit of my own my own a subjective perspective on this field, and in some results during. And I'll talk a little bit about some of you know a small selection of results that we have seen with collaborators along the way.
08:48:50 Okay, so briefly as I mentioned in my group so we are interested in. On the one hand, kind of bread and butter quantum optics are upon a more physics, and in particular was.
08:49:02 And in particular, what's, what's interesting is the wide range of available novel systems hybrid systems and just novel quantum systems that can be controlled in different regimes of physical scales.
08:49:12 And so the spans from opted mechanical systems, and it can be atomic meta surfaces that you recently looked at atomic clocks, of course atomic found as many things that we heard here as well.
08:49:24 So this is on the one hand I think very exciting topic on by itself, but at the same time, there is the second kind of strong interest of mine and, which is the study of gravity related defects in the interface with low energy quantum systems.
08:49:40 And this could be you know novel phenomena that appear or women in includes gravity possibilities of novel experiments to test some models such as we just heard for example this test of some possible holographic principle or, or other ideas, and also
08:49:55 given can experiments were just conceptual questions that elucidate some of the foundational issues that when we overlay quantum gravity.
08:50:05 And so what I think, for me personally supposed to be exciting is that there's something very close interlinked between those two.
08:50:17 So on the one hand, if one has this new systems and they push the boundaries and entirely new skills and regimes and precision that allows you to start thinking about these ideas and how they really affect quite experiments that could be probed, and you
08:50:26 know this is of course the motivation for this workshop. And it also goes the other way, which is that studying these systems, or these kind of questions about gravity.
08:50:39 It gives some novel ideas of where the systems need to push and what kind of motivations terrorists for really truly fundamental physics and really explore regimes of physics that we don't know much about.
08:50:45 So really, kind of enjoyed this interface and just as a side remark. If you know any students are postdocs that they're interested in that, we might group, probably have open positions from fall as well so please, you know, would be nice if the preacher.
08:51:01 Okay. So, here let me just give a very brief kind of summary how this fits this low energy interface with between quantum and gravity. So this is taken from just my PhD thesis from for many years ago.
08:51:16 And this is just kind of a very simple diagram of how physical theories developed in on the red here in the red we have classical theories in the culmination of them being general relativity about 100 years ago which combined many of the concepts into
08:51:29 classical framework of gr. And then on the other hand here we have quantum mechanics and that has of course you know culminated in the quantum field theory we should call this is all interactions we know except gravity.
08:51:40 Now, the interface between those two is very interesting and there's different aspects of it in this is I think what that what I'm trying to stress here.
08:51:48 So for that, let me just distinguish conceptually even though they're interlinked but conceptually here two things. One is the notion of test article so geodesic motion on a curse background space time, and the other is the dynamics of gravity itself
08:52:02 and the gravitational field, which is governed by Einstein's equations.
08:52:09 So if you just look at test systems, then we can combine it or we can understand it in some limit in the context of quantum field theory and that's of course the very big field of quantum field theory curve space time.
08:52:20 And there's some effects that the right, so we can pull it up on the perfect grounds space time and and study it in very similarly and, and this is I think one way to phrase it very similarly we can do something with quantum optical systems, a more systems,
08:52:34 systems, so we can place low energy quantum systems on a curve background space time. So the one hand we treat the a most systems, actually not realistically because we're interested in atoms of the mechanics and molecules and so forth.
08:52:48 But we place it on the craft background space time and include some gr effects, which then can lead to novel phenomenon. And this is what I'll talk about a little bit here.
08:52:58 And then there's other interfaces, for example, the linear eyes limit of gravity, and in fact that can be context and it's known since the 30s. Since my to a project I actually am 34 I think, and with this a framework that we can study, and there's also
08:53:16 very interesting questions related to experiments that many we have heard also here so far. So that's kind of a combination of these different contexts with quantum mechanics, and then going beyond that starts to be difficult, but there's one very fruitful
08:53:30 Avenue, which is what, what I would call quantum gravity phenomenology, and this is trying to study maybe some expected behavior, like what we just said about holography and see how it might fit into some of the experimental frameworks that we have, and
08:53:45 it's based on some maybe speculative suggestions, but it's trying to incorporate things into known frameworks and try to find experimental signatures, because we have a lack of the food theory that can really gives us definite answer.
08:53:58 And this whole theory this giving a definite answers quantum theory of gravity. Well that's of course the Holy Grail.
08:54:04 But that is beyond my intellectual capability.
08:54:09 And in fact, it's a very interesting question but so far it has not been much focused on experiments.
08:54:15 And so I think the experimental overlap is really the three parts here Linda is quantum gravity economy phonology and quantum mechanics of space time.
08:54:24 And this is something that I've been very interested in in the last decade.
08:54:28 So this is, I think, where it really theory and experiment, go together there's a lot of interesting questions to explore.
08:54:34 So just to give you some examples if you have novel conference the steps and then new insights to gravity of this range there's new questions that arise and possibly experiments.
08:54:42 So for example, a very, very famous and now very topical Of course and we heard much about it and we will hear in the next talk but animal.
08:54:53 sorry, I apologize.
08:55:08 And and that it can tell us something about the possible quantum nature of gravity and so there's been some proposals about in recent years some more recently, and also also some very interesting proposals by Jacob Taylor, who we heard.
08:55:14 But, so we'll hear about this of course more detail and this is this test of gravity as a mediator of entanglement.
08:55:14 Now, many years ago about possible maybe classical channel of gravity. So that's one example, there are some new ideas that we had not so close the experiments, but about trying to study the quantum nature of causality.
08:55:28 And if I can maybe perform some type of experiment in order to see if your time itself has to be a quantum motion without definite definite features.
08:55:39 And then there is, for example also bright future was just mentioned. Here's a very interesting. Recent result on quantum noise of grabbing tones. and even though it's far away from experimental durations today that's very interesting to think about this.
08:55:53 And what kind of noise of of gravitational waves look like.
08:55:57 Okay. And then in terms of quantum gravity from the knowledge in terms of speculative theory I think the most famous example is the rotational wave function collapse the idea that maybe quantum mechanics breaks down at some skill because of the inclusion
08:56:08 of gravity.
08:56:09 And there's been actually many proposals that I think this is one of the starting point I would say of this field where people show that you can actually do experiments to try and prove it.
08:56:18 About 20 years ago Randy and Dave, it's been since, you know, many efforts in this direction.
08:56:24 And then we had an example at where we showed there something entirely different you can prop it up to mechanics and namely a possible a generalization of the uncertainty principle which has been proposed in the context of many models of quantum gravity
08:56:36 and under some conditions and interpretations, it would have a signature enough that we can because systems as well, which one can constrain other ideas, for example quantum for making a call back and say for example propose to test.
08:56:50 So this is just a small selection of things then of course you know we heard many more in this talk, but just to kind of categorize it a little bit and how it.
08:56:59 And then finally there's this quantum mechanics occur space then which is non speculative but in a regime of physics which has never been proved, namely quantum dynamics and the presence of course Newtonian features.
08:57:10 And for example, there's a very nice proposal by actually diagram, we heard also Jason Hogan, and colleagues from from 2013 years ago, looking at phase shift and post this on your corrections phase shift and so next generation atomic interferometer is
08:57:25 is hopefully we'll be able to pick that up.
08:57:28 And then another class of signatures in, and in experiments, is what Mike collaborators and I worked on and proposed. And there's a sequence of works on that which is that what I call a quantum interference of clocks, and then do something similar here
08:57:48 And so at this point, I will mainly focus on that, and talk about what novel features arise there with number of signatures, come about also conceptually, and how you know what experiments can do to probe.
08:58:06 Okay, so the overview of kind of their target is, this is maybe a bit optimistic overview but so I'll say a few words on patients that mental belief, and then a small detail because this has also been mentioned I don't want to.
08:58:18 I thought about talking more about this here but it has been mentioned so I won't spend much time but I also want to talk a little bit about our work with Judy and collaborators on clocks and how we can use them to test gravitational wave is to better
08:58:32 test gravitational waves. And then in the kind of the second half of the talk, I'll focus on this interference of clocks and proper timing from its rate introducing it talk a little bit about how it can also lead to the experience of competence systems,
08:58:44 and what kind of, you know, experimental challenges are. And finally I wouldn't have time. And this is just a different type of what I mentioned before a different research area which is a test of quantum gravity inspired committed from issues without
08:58:59 the mechanics, but that only for, for another time.
08:59:04 Okay, so of course phase shift is used by gravity a very well known and very the heart of many talks we already heard. Now in this workshop, and to understand at the very basic level, it really is just the fact that in the trading equation, we just include
08:59:22 the gravitational potential. And if you do that, then there is a position dependent term in the evolution of our unitary evolution, which means that we have a matter wave which has mass, and it's D localized and position.
08:59:33 And then this will be a superposition state with which you are quite a relative face. And so this is assuming this in all the paths are fixed but just for simplicity, this is the core of the, of the whole of the whole effect.
08:59:47 In this phase shift depends on the height.
08:59:51 And of course at the time is how long this system is into position. And the fact that it's observable has been actually noticed by Cordell over Hauser and Bernie narrative first time in 1975.
09:00:03 And the reason for this even though is gravity is extremely weak. The effect is divided by h bar. So you actually have a strong signal, and really hold a mirror of course made this point very very nicely with many fishes that you obtain.
09:00:15 And so the first experiment was with nutrients from a courageous rotator setup and you see the screen shift in 1975. And of course now atomic fountains and matter with interferometer switch, pick up this critical phase shift, are all based on the same
09:00:27 principle here an example of like a half a meter scale fountain, or even precisely this type of setup in fact by Holger religious group, which he just talked about.
09:00:39 Now, just to say the following what did we learn conceptually about it because there was also a question in fact about it, au I think yesterday. So on the one hand what we learned is that we can add the gravitational potential into the shedding of Jesus
09:00:50 we can add any other potential. That by itself is non trivial I'm sure we can do that. But gravity is different from other interactions and so maybe it would work but but it does.
09:01:01 And so everything is fine exactly as we expect and what we see is that the cook pure quantum effect. So it's, it cannot be described classically and it's really quick here and faced induced by graph.
09:01:11 But what we've done learned about is anything that goes beyond the neutron, namely the Newtonian limit everything seems simple it's just a potential and so forth but beyond that gravity symmetric theory so there's interesting questions that arise and
09:01:23 how the book, and also of course we don't know anything about the consumerization of the gravitational degrees of freedom themselves.
09:01:31 Okay, so what we looked at is a specific aspect of the metric nature of gravity which is unique to it, and that is the time dilation.
09:01:41 And we focused on that because it's an interesting, like I said unique aspect which really separates it from other interactions in that gravity also changes University the flow of time.
09:01:51 And you know of course time glaciers know gravitationally very well.
09:01:55 Basically, clocks closer to a mass, take slower than clocks further away. And that is because all clocks pick up proper time at the proper time depends on the Newtonian gravitational potential.
09:02:04 Okay and so this is be tested Of course with cesium clocks first time directly.
09:02:10 Many years ago, and then more recently with is trying to Iron Cross on the 30 centimeter height and the clocks are so good that you can catch it. Pick it up but in any.
09:02:19 And then you experiments even now on sooner millimeter scale.
09:02:22 Okay, and so small detour. With this development of cops, and I apologize my kids just came home so if it gets a bit noisy. This is the background, but the atomic clocks, because they're getting better and better.
09:02:37 What we studied with collaboration with experimental groups of Pune and me show looking around was worth. Also the human called glitz and the glam tree in a few years ago, is to see if they can be used at all from gravitational wave detection.
09:02:50 A few years ago, is to see if they can be used at all from gravitational waves detection. And at that time, it was just before the language detection.
09:02:57 In fact, and it was just projection about what kind of possible. Students one could get in the next decades. But there was also interesting proposals by atomic found the fountains and, you know, Jason talked about it as well.
09:03:04 And so here we wanted to see how things would work out for atomic clocks, and, and, basically, the bottom line of that study is that once you get a narrowband detector, with a relatively competitive sensitivity in the sense of if you project technology
09:03:18 to the next, you know, 2030 years and put space, but most importantly you get that universal detector in the millionaires to hertz range, using quantum control and the atoms, that's really the interesting aspect.
09:03:30 And so just very briefly go through it, the signal that we detect for example in life is allied signal and what like measures is just the effective distance between two masses.
09:03:42 So, if a distance is D in flat space time in the presence of the gravitational wave light has to travel effectively a distance which is modulated by the presence of the gravitational waves by h of t.
09:03:54 And if the distance is for example much smaller than the gravitational wave gravitational wave wavelength. And then this expression can be approximated Taylor expanded and then we get this very famous strain sensitivity namely that the change in this
09:04:08 effective distance and the photon sees divided by total system is directly proportional to the anti liberation weeks. So this is why you want a long baseline but we just one comment here, the longest and of course, only works in this limit.
09:04:22 So at some point along baseline for example in their space it's not that important anymore.
09:04:31 Okay, so this is measuring strain by changes in the optical face, and now something similar can also be done with atoms. Namely, if you have the following set up with the effect to free floating masses also just as a license proposing and on the each
09:04:43 of them you place an optical lattice atomic clocks. And then what you do is you actually connected. So you use a single laser to face lock both clubs at one in the same laser, then what you're doing is you're just doing a quarterly clock spectroscopy
09:04:58 between both of these systems, so you don't know total time, but you can just compare them very precise. And this coronal correlated spectroscopy this link between them on it is imprinted this precise change of discrimination wave, and how the clock speaking
09:05:12 it up as an effective doctors. So it's an effective Doppler shift instead of an effective phase shift. Let the clock Speak up. And what's interesting is that the signal for a specific Ramsey time looks in the following way so you get to the frequency
09:05:24 signal between the clocks, and it has two factors. One factor here is due to the transfer factor due to the baseline of the system. So how's the frequency of graduate compared to the distance, and the other factor, and that is really I think one of the
09:05:37 crucial aspects is due to the transfer function in, in terms of how do we actually accumulate a signal and the clocks. So depends on the documentation time or Ramsey spectroscopy time bt and, depending on what actually spectroscopic this week was your
09:05:53 CLI, you can change that. So when you get this you really get some kind of detector which not only operate slightly differently, but also allows you to control and changes.
09:06:04 And so basically your fundamental limit is a projection noise, and and So here for example for this baseline of really kilometers and using strontium atoms to their coherence time hundred 60 seconds, and many many add some more items that we can look
09:06:19 today. But then, projecting that one gets extra sensitive to window which is the competitive with, with the Lisa proposal. And then, one could change this sensitivity window by using dynamic of the complex sequence is here this purple one and so I can
09:06:35 shift this around the peak is narrow been paying so effectively if I'm hesitant spacewalking shifted in the frequency.
09:06:42 Okay, so this is kind of a small detour on that and I'm happy to, you know, answer questions about it if there's interest, but here the rest of the talk, I really want to focus on something very different.
09:06:54 Namely, this notion of time dilation in the context of quantum mechanical matter wave in front.
09:06:59 So, going back to the slide I said that clocks differently across different scales. Now, what is important is the clocks that we use to measure it actually quantum mechanical systems.
09:07:09 So there's nothing special about. In other words, we know that the shredder equation evolves with respect to proper time.
09:07:17 So that's an experimental fact that i don't think that has ever been really kind of stressed.
09:07:30 Clearly or. But, but this is actually what's happening because we know that the training equation evolution of internal clock states. According to quantum mechanics is accumulated with respect to proper time because the proper time is different between
09:07:34 systems. So, the clock mechanisms can very well be quantum and that's well tested. But what's different has been tested, or improved is if the actual g localization localization of the system is a quantum mechanical freedom.
09:07:46 And this is what we looked at. So this is kind of, yeah, just to put it, it's just kind of in this context of quantum mechanics of curve space then we'll post Newtonian corrections.
09:07:55 This type of clock in the front. And the bottom line of this whole you know it's there's many works in this and then you follow us but the kind of the really core is very, very simple.
09:08:05 The core core is the following what we call this quantum between paradox, and namely instead of taking two clocks, two atoms you take a single system like a single atom, and then you put it in superposition of two different heights.
09:08:17 Now on this superposition of different heights, it will evolve according to different property types. That is the prediction by gr in the presence of Max, but the prediction of quantum mechanics is that if there is some degrees of freedom, which pick
09:08:30 up, which way you're going and then the ference, then the interference will disappear. So this the quantum complementarity principle and Emily is there is which way information, and there is because of GRNGR only.
09:08:42 Then the interference will wash out. And so really that kind of the signature expensive signature is that there is some modulation that change a few interference contracts depending on if you are, how gr changes your internal degrees of freedom.
09:08:55 And so this is the interference of proper times where you effectively place a single system if being a superposition of younger and older than itself.
09:09:03 And the experimental signature is that there is a change in the park.
09:09:07 And so this is we first proposed that a more than 10 years ago, and it was inspired in fact by the you know some theoretical ideas by Danny Greenberger and very interesting discussions, but also by interesting observation of hope a millionaire and his
09:09:32 competitors is Steven Chu at that time, namely about that the face in in an optical so in Adams parameter depends on the proper time. And so there was a debate about as you know it came on interpret this the content clock and so forth.
09:09:39 And that means that think about a more deeply about the notion of infant has an operational clock. That is there, what novel effects arise. And basically what really arises is entanglement in which we information it's acquired by cook.
09:09:52 Okay.
09:09:56 So, how do we capture it in this. Okay, I'll go just very briefly towards the end. So basically what you would really want to study the field is quantum dynamics in the presence of posting Tony corrections.
09:10:04 So we need one of the C square corrections to the dynamics of our systems, and what is really useful for us is of course the Hamiltonian formulation because we want to look into quantum optics.
09:10:14 And so there's many different ways we can start with the relativistic equation. And you know look at the interesting energy Hamiltonian of that system.
09:10:23 And very importantly, is the following. Okay, so this this looks like that roughly but very importantly is that we want to lower energy, namely that in the rest of the system and also with respect to its proper time.
09:10:33 But what is the crucial addition here which hasn't been done previously because of course all of this has been done in four point particles and just massive is the realization that one needs internal composition of the particle and internal rest Hamiltonian,
09:10:47 such as the governing for example that two levels and their oscillation. In order to see this additional effect, and that's why it has been actually overlooked until until.
09:11:01 Until then, so you know when my death, one of the things in the effect of Hamiltonian with one hour c squared corrections which works fine at this level.
09:11:06 And you know there's these known relativistic corrections AGR corrections that are well known, but then there's this additional term that arises, which coupled with internal degrees of freedom to external degrees of freedom, namely to liberation potential,
09:11:19 and to the, to the moment. And it's really just capturing the notion of proper time, and that the fact that clocks, is the tix was h zero. It's just a universal Newtonian that governs clock local clock evolution.
09:11:33 That depends on proper time, and the proper time depends itself on these coordinates.
09:11:39 Okay, so this gives us Hamiltonian to study this, and you know just for simplicity we can forget all of these other things we can just fix path political momentum to zero and so forth.
09:11:55 And then really we just end up with an effective interaction Hamiltonian between the position of the system and our internal habits. So now we can really just do a more physics, and that makes it easy, and a different approaches to derive the same thing
09:12:03 as luck Roger information and this works well.
09:12:04 And just, it just kind of exercise.
09:12:06 Okay. And so the core is the following.
09:12:09 Classically is Hamiltonian really just captures what I said before it's just the gravitational rich, so he has have been turned on Hamiltonian from oscillator.
09:12:20 And then you have this Newtonian potential, and that's true but then on top of that you also have this a redshift have this internal Hamiltonian as a first order correction relativistic correction.
09:12:28 So, you know, the ratio is you know gx or c squared. So this is gravitational redshift per single system. And the difference in quantum mechanics is just simply that they put hats on.
09:12:37 So we quantifies the position, and the internal degrees of freedom, and then and then and only then, a new effect the Raiders are disaffected year after it rises namely, that this interaction Hamiltonian now in tangles the path degrees of freedom and
09:12:51 your intelligence of freedom. So if you have not just the matter wave, but you have a matter wave with internal clock states that are also in superposition and are evolving in time, such as atomic clocks, for example, and then you split this matter wave
09:13:03 to go either on a higher or lower path than your effective way function is not just simply a superposition with a relative face, but it gets entangled with a internal clock states, like I said before, because they take slower on the lower part and faster
09:13:16 and higher. And this entanglement is gr induced. And so this is a way to see what kind of curve space and that's on the quantum mechanics, and the signature is if you then do your interference experiment is that actually your visibility of your face is
09:13:32 now reduced. So you're not look, you don't look at the face shift which is just a Newtonian potential or possible corrections, but now you look at this visibility which is really probing time dilation in front.
09:13:43 And this depends on this overlap if your clock stick figures you wish for information.
09:13:47 Okay, and then.
09:13:49 Okay, I'll try to speed out I guess I have five minutes or so, what to say is ok there, it was actually it's a, you know, an interesting research effort since then.
09:13:58 So this was our first realization that you know this effect takes place and this is for periodicals, and so if you have any clubs which ticket some frequency, then you get this modulation which depends on the proper time difference that this accumulated
09:14:11 by you are better ways in position.
09:14:14 So this is the prediction, but also effect will be surprisingly but it was interesting is, it actually happens also for mixtures of our parent o'clock so if you have many systems and you don't actually even have clocks that you can use, but even have
09:14:27 thermal states. They will also see a reduction visibility and there is kind of this defacing that takes place. And this can cause complete loss of coherence, even in Mrs complex timescales so that actually leads a novelty coherence mechanism that has
09:14:41 been, you know, not known previously, and which takes place due to the background space time inducing time to finish.
09:14:48 And you can also tested with photons if it's looking at Shakespeare again.
09:14:53 Okay, and now just just two words, two slides on this big coherence phenomena, and it's the same principle as I said before, and it relies on the fact that the stage, not that I showed his true that's a local Hamiltonian is arbitrary.
09:15:08 And for example, you can even think about the failure modes of your system. And these are many degrees of freedom, you don't even control your internal state, you don't even think about I'm talking about.
09:15:20 But instead, you don't even have to come over here and so you can even have thermal.
09:15:25 Sorry my. Yeah, my toddler is hungry so I hope it's not too too disturbing but anyway so there's no coherent.
09:15:36 And then basically one can still study the same problem in one can, you know, see how this interaction effect of time really should use interaction changes.
09:15:45 Your dynamics of like a complex molecule that's in superposition for example here, and eventually the outcome is that, you know, just a simple model system, it doesn't depend on it but just to get some numbers, if you have been in harmonic modes of a
09:15:57 molecule state, and you places markets position of different gravitational fields, so you just say it's in superposition almost our thermal and so forth.
09:16:05 You start off with a product state. So the center of mass is completely decoupled just in the presence of mass of a big mass like Earth, what happens is that these internal thermal vibrations will actually be slow down exactly the same way as any other
09:16:20 than.
09:16:21 And so you get to kind of thermal vibrations which are slower closer to the mass and faster further away. And there is enough to lose coherence and one can compute this effect among get an effective the coherence time and it's a Gaussian decay it's a
09:16:34 different, different type of its antimicrobial
09:16:39 mechanism, but you get an effect of the coherence that which depends on the many modes so many how many particles do system consist of, and then mostly just a lot of fundamental constants.
09:16:47 So it's a very interesting kind of combination of a quantum effects of relativity, gravity and and even thermodynamics.
09:16:55 And so you get the documents time here from this interest to different members, and this is the main motivation 3d care of the experimental questions.
09:17:08 And here the numbers are for example for like a micro scale object on Earth at room temperature. If you can also create a micro meter or a larger separation in.
09:17:15 In superposition vertically, then it was equal here after about a millisecond.
09:17:18 So these are extremely challenging numbers to achieve Of course experimentally but conceptually is very interesting numbers because they are Mr. Scott, and so kind of you get this intrinsic the coherence time, just from within quantum theory in the presence
09:17:31 of evolution so it's a novel effect that arises when you include post Newtonian effects in trading equation, but more interestingly for experiment is this initial entanglement induced effect, which is the time dilation it uses entanglement between your
09:17:47 controllable internal clocks stereo very fast, and the position degree of freedom. So for example, if you look at numbers such as atomic fountains, and then if on top of this fantasy that we have today you also have optical states which hadn't superposition
09:18:00 along each path. And then these, it depends on the frequency this effect and so there are five, you know optical frequencies, then you know what's achieved is, you know, something like two orders of magnitude away from when this effect will Kiki, or even
09:18:13 a bit less. So it's a factor hundred or so away. So, so really next generation atomic fountains and also some that be heard here will be able to start and see this effect, and why it's interesting is because the never has the regime of physics being probed
09:18:28 Also some that be heard here will be able to start and see this effect, and why it's interesting is because the never has the regime of physics being probed where you look at quantum dynamics across space.
09:18:38 And this gives you a window for doing that. And namely a particular feature which is not present in electromagnetism name the package.
09:18:39 Okay. Finally, this is my last place to connect to the experiments, a little bit also so all of it is very inspired by experiments obviously but I, you know, I am a there's been a lot of studies done for concretely, looking at experimental efforts and
09:18:54 is of course challenging, but one thing to say is, for example this effect has been simulated already many years ago, where the population was stimulated by in homogeneous magnetic field on sprint procession.
09:19:05 And this has Vito has been exactly the predictions that we gave you get the self interfering clock in around finance group.
09:19:14 Then what's very interesting is this will become relevant, even in atomic clocks as Johnny talked about as they become more and more g localized quantity localized.
09:19:21 So there was, I mentioned it here because there was precisely the question I think by Jake Taylor, but what is different about measuring redshift just with ID localized quantum clock and just individual systems, and this effect that I'm describing here
09:19:33 is precisely the difference, you get an additional pure quantum effect which is entanglement of this degree of freedom of clocks, and it's good spatial degree of freedom, which does not take place either classically nor in Newtonian physics.
09:19:48 Okay and then you know it's proposals to do some space based assistance but i you know i don't think i don't think they will fly, he can soon. And then of course it's very relevant I think for these developments that Jason talked about.
09:20:03 For example, matches 100 for when you really start getting 10 meter, Quantum positions.
09:20:09 Then, you know, if, if you have a proper time difference that's really the important point so it's not just a high difference you really have to look at what the geometry so you really can capture a proper time difference between different class, then
09:20:20 this effect will kick in.
09:20:22 And then of course you know the first set up the tiger talk about what do you really hold out them so position for 20 seconds.
09:20:29 The separations here are much smaller so the effect is not yet relevant, but hopefully you know in the future installments of that one maybe could be able to probe it directly, and I hope that's the case.
09:20:39 Okay. And with that, I apologize if I've been a little over time. So just a brief summary here. One thing was atomic clocks are interesting and they of course open new high precision frontiers and one example is relational detection but it's not just
09:20:52 simply they have high precision. They also open new possibilities for, you know, quantum control and other type of things which are not necessarily possible within the parameters, at optical its parameters and, of course, a Jason's group knows very well
09:21:06 that an atomic interferometry you can do something very similar and he is, you know, very very interesting papers on that as well, which is directly related to these things as to.
09:21:18 And then, finally, kind of the main topic here was the interference of clocks and what I wanted to show is that there's new effects that arise, even at low energies.
09:21:31 When I'm combined post Newtonian gravity and quantum dynamics within the known frameworks. And so we can make predictions in this framework because it's fixed gravitational background nothing quantum about it.
09:21:38 But then there's some new effects arise, and it will be very interesting to probe exponentially because it's really completely experientially proved the spreadsheet, maybe things are completely different and these predictions are wrong.
09:21:48 And so the big prediction is that triangulation needs to entanglement between position and 30 degrees of freedom, depending on how much appropriate time is accumulated along each sucralose trajectory.
09:21:58 And so hopefully it's relevant for really short term. Next, future microwave interference experiments. And also, conceptually leads to some novelty coherence mechanism, which is probably still hard to read a long long time for one be able to see it, but
09:22:27 it's an interesting thing that appears. All right, and without. Thank you very much. Thank you for the great talk. And I'll open it up to questions, please raise your hand. Yeah, So last night thanks for the nice talk Igor.
09:22:33 I wanted to maybe take a little issue with the statement that there's no quantum field theory of gravity. I think there are lots of quantum field theories of gravity.
09:22:42 At least effective theories. That is, I don't think gravity has to be considered that that much different from the other forces.
09:23:05 it as a relativistic quantum field theory. The difference is that it has, you know it's not normalized well so you have to add higher dimension operators.
09:23:12 And then there's some ambiguity as to how you do that. But most of that ambiguity goes away in the low energy limit.
09:23:20 So, thanks yeah thanks for Israel right i mean i completely agree and I probably you know phrase did not very well.
09:23:29 I mean I completely agree and I probably you know phrased it not very well I. You're exactly right. I think what that were meant to say is that we don't have a full framework that we know kind of is the correct one for sure we're in all truth because
09:23:41 he's kind of, you know, smoothing it all out.
09:23:44 But I think it's extremely what you're saying is that a reasonable it's works, some extent but of course they're kind of conceptual problems or technical problems at some level, and you know have different approaches where some people take one or the
09:23:51 So you're right. Let's see my main interest is really not in any way to some or to the agnostic even about what what may be the correct approaches or what do you prefer and more to look at what kind of signatures arise at low energy from any of this and
09:24:06 and I think the framework you described is probably the, the best one even to to to figure out what the signatures are unless there are like degrees of freedom or extra dimensions of space time or something funny.
09:24:18 All these theories give essentially I think the same predictions that low energy, so there should be an ambiguous prediction from from this theory, but I think that's what I met with this linear as quantum gravity and if kind of these any of these theories
09:24:29 are good they should give the right prediction we should even now today no more or less, but maybe there's, you know maybe they're surprises, and you know maybe I'm not sure exactly what linear is quantum gravity means it doesn't mean that you don't allow
09:24:46 allow a gravity time to split that is to interact with itself. You only allow it to interact with matter.
09:24:54 And maybe it can still interact with it, so I don't know what the limit is. So it's kind of weak gravity. So I'm not sure I don't recall I think it's in this fine my lectures of gravity when it works well it does some level, and then you know the at some
09:25:05 point when there's food on the the heritage of ancient equations has to kick in, then you get into trouble.
09:25:11 So you know we don't even know if you take powder particles. So you want to scatter to matter particles, and they exchange gravity.
09:25:23 Gravity fans don't have to self interact. If you try to compute that full loop, it will also diverged. It has a divergence proportional to the square of the energy momentum tensor of the matter.
09:25:37 So, so that I guess it doesn't cause any from the mental, I mean what I mean here is Joe I don't think the fundamental difficulties either. So, I mean, I'm just trying to understand what's the benefit of linear eyes quantum gravity over the full a full
09:25:52 effective quantum field theory of gravity.
09:26:01 He says the question to me I mean I'm sure there are experts on quantum gravity, who will be able to comment. Okay, I thought you had worked on linear eyes quantum gravity.
09:26:12 No I though I worked on kind of signatures of tools such as for example you know entanglement of mass so forth. What do you have to look at the sessions with them, you got you got.
09:26:13 Know.
09:26:21 I also want to, I totally support what Lance said, there's actually a very well defined infrared quantum theory of gravity. In particular, some very nice papers by Donahue on exactly this.
09:26:37 And there are some effects which are not at all affected by what the UV completion is for instance, there are logs that you can compute the logarithmic corrections which are quantum quantum gravity corrections which you can compute, independent of any
09:26:58 And so, I recommend strongly you read these Donahue papers. Oh, I know that, of course, the signatures you get their experimental every smaller, we have but this, but but that's what you, that's what gr and quantum mechanics predicts their ambiguously
09:27:14 Smith. Yes. Well, but then I think my point here was, there's more to it than just this, namely there's a lot of interesting experiments that are interesting effects of the rise interface that that have been missed so far and there's too much to explore
09:27:33 the emphasis was not on this part because it's this way.
09:27:53 I believe that might be I got that wrong but my patient is that he tried to emphasize opponents that, for example, clock depends on the position. You're, you're measuring device that depends, I mean your cloak depends on say I was a five, and it's of
09:27:56 course, you can ensure to unionize gravity no problem.
09:28:00 However, I mean, statements that, you know, as this is, you know, influence on the measurement. I mean, how you define your clock. I mean, and it's it's not about the sky energy whatever just about, you know, this time dilation right.
09:28:20 But my point is, is, yeah absolutely but there's a complete prediction from quantum mechanics and gravity put together. And in fact that's already in, that's in the papers of Jason and Peter and Mark Kassovitz and I'm satisfied marvelous post Newtonian
09:28:35 parameters, and, and, and, and.
09:28:49 Precisely, not because they did something wrong or something, but because there's an effect it's missed, which only appears. If you have additional in terms of use of free.
09:28:50 Okay, let me jump in here, because I think that's exactly the point I want to make which is very very important, namely the prediction we have here is not in these papers.
09:28:59 So the predictions you get from that paper for example is when you look at these corrections here, which are perfectly fine. But that's additional corrections that appear, which entangle your internal systems external one.
09:29:12 If your mass is not just simply a mass of the atom, which is what you take usually in this approach, but you also allow for some kind of rest Lagrangian which allows for dynamics.
09:29:23 So I think this is an extremely important point I want to that's precisely what is what. Why this effect has been missed it is not speculative, it is not kind of postulated it is within the same framework.
09:29:34 Just namely actually looking at it in a from, you know, slightly with a slight addition.
09:29:41 I think that's really great if I understand it right you're saying you and you have internal degrees of freedom you have other frequencies besides the mass of the whole system associated with the different bounce dates and if those three phase in a particular
09:29:53 way you'll change the amount of interference. I guess I see my tangled in as well. Exactly, yes, and you wouldn't get the entitlement just if you only had the rest of this That's right.
09:30:04 That's right. Yeah, I think that's way, but is that something so just be clear you you were also talking about large molecules but is this something that's visible in, in, in principle in the atomic systems too.
09:30:18 And they haven't reached their level of precision I missed that part.
09:30:21 Yes, excellent Yes, excellent question. That's exactly right. So, it is feasible in fact it's best physically atomic systems, probably atomic in the parameters or, you know, maybe I taught my class as well but for example here just as an example, if you
09:30:38 have an atomic interferometer, it will be visible, if they can increase so the heights of operation today something like half a meter Meteor scale on a weekend of and failed for maybe a milliseconds.
09:30:48 So if that can be improved by one other two orders of magnitude, this effect would kick in, under specific geometry something from it.
09:30:55 Okay, it will be directly relevant for the system, precisely like you say similarly to this dimples proposal.
09:31:02 So similar is just kind of a slight different effects which appears if you also have this internal degrees of freedom, but you need similar skills, so maybe you know, hopefully a 10 meter separation, as in Jason's Fermilab fountain that better there,
09:31:24 Exactly and the prediction is to follow it. So, all these other things are phase shift so sorry I didn't even I didn't mention it and I think for this question.
09:31:31 So the face shifts are you know this difference in probabilities of detection is two different detectors of the output ports and you know you have this black curve which would be Newtonian and then post Newtonian, you get this blue curve which is a bit
09:31:42 shifted, so you get the spaceship, which is the usual signature. And this additional signature here is the modulation of the role phase shift with an additional kind of envelope.
09:31:52 And it's this modulation, and even the drop at certain times and then revival it. Other times, which is the unique signature of the, you know, you have this tabulation induce entanglement between the different branches as well.
09:32:06 But, can I ask you respect to these, these points. So if this is for a single particle so he reads the Hamiltonian for a single atom in the internal levels.
09:32:18 Yes. So, what about if you're having Dominion has something that goes in German levels with external levels to, so you are you have so many particle Hamiltonian is that also going to be affected or not.
09:32:30 Yeah, it's an excellent question, a very short answer and probably wrong one is, yes, in principle, it doesn't matter. Ah, not because of universality of triangulation is arbitrary.
09:32:39 In other words, whatever dynamics you have it will be affected the same way. However, that having said that, of course, I think anybody thinks and maybe other even coupling to external degrees of freedom will change the dynamics of grief.
09:32:53 And so I think it's an interesting question and I think it would be fantastic actually to, to, to, to look into it in more detail, but the short answer is the same effect will appear.
09:33:02 But how exactly to manifest itself. Depends maybe a little more on the details.
09:33:08 Okay. The mood.
09:33:14 Okay, I have two questions. One is not the question. This is just my observation about the map you'll make to, to show the branch of the physics and whatever.
09:33:19 Yes, yes.
09:33:25 So, you know, there's two things is that the quantum gravity so gravity cannot be quantified as we know like electromagnetism. The reason is that in fourth dimension.
09:33:38 gravity is not gauging very.
09:33:40 So only love of dimension, you can have this.
09:33:44 And this is something which we were, we were not some time thinking about it but for dimension for this season is hot, but my second this is the second one is more serious maybe about the quantum mechanics in terrorists space when you, when you show the,
09:34:01 the dynamic of the parts can uncover space. That's like.
09:34:06 So, if you can pass that yeah here.
09:34:11 I think this format is looks very handy. I mean, you notice, you know, then evolution a question is presented this evolution a question is not the ransomware again so he still he is not related with sick is not even.
09:34:27 I don't know he's not even see it's a correction to any other things. I mean, that the format is we should present it is.
09:34:35 It's not very clear to me that you you see your your your evolution a question for the size started by the proper I'm tall and then victory of your past to these questions but this is even if you accept is that the interaction terms make me little worried
09:34:54 because this.
09:34:55 If I understood that you wanted to contest this right and make into format or whatever.
09:35:01 Find the face transition phase the difference or some whatever so that this time interaction is, you are dealing with a non parametric can have it.
09:35:11 As I see here
09:35:14 is how you how you simply talk about the quantum relations when your Hamiltonian is directed by the sun none of her mission terms which is fully, it's fully permission, it's fully hemisphere.
09:35:28 So this is you start with a client or an equation and then you look at the single particle sector is you know you can approach it with electromagnetism, and then you kind of, you know, do you do a full divorce that has formation and so forth.
09:35:42 So you can do everything standardized exactly the same as we operate relativistic corrections to the, you know, in normal, you know, electromagnetism, this is, this is the this is the same as a stutter or pylon for monies in 1960 or something, because
09:35:59 I work on that and I do not remember that the things goes like this simply, you know, just, I don't know, maybe, I don't know but this is not the things which I, I, it's not very fair to me that to go just simply from the poor vector, which, when you
09:36:19 didn't define it your character clearly and then just simply pass to the reclaiming your
09:36:30 memory. Yeah, okay.
09:36:38 Non related mistake. Yeah, that's the same know every field, you just take the architecture eg not not to expand.
09:36:39 So I'm happy, I'm happy offline I can send you some references and in life clarify, but but but only to say this is of course commission, and underlying to us of course fully Laurens invariant so it's just kind of a useful way to treat quantum systems
09:36:54 with.
09:36:55 Okay, Jason. Thank you. Thank you. Next question.
09:37:00 Oh, great. Yeah, thanks for your for the really interesting talk.
09:37:03 So I have a question on the proper time difference interferometry effects.
09:37:08 So I guess the I guess these are like gr you're saying gr effects, do the proper time difference and I guess I'm worrying about the equivalence principle.
09:37:24 Basically in the metric you gave, it's sort of a uniform acceleration to the gravity and so I feel like I should be able to, you know, transform into a different reference frame of really falling frame where it's it's it's a locally flat metric I can
09:37:44 of gravity. And then I would talk about proper time difference in some of the language maybe in terms of Dr ships or something. And so, so I guess what I'm wondering is, if in order to describe these effects which I'm sure the phenomenology is that you're
09:37:50 describing is there but in order to attribute them to gr, would I need to be in sort of a curved space time or another was I'm worried about sort of frame dependent interpretation of this result right because I can I can go in there freely fine framework,
09:37:59 there is no gravity. Whereas if I had a curve metric maybe that wouldn't be so I was curious on how you think it's an excellent question and I you know I'm glad to clarify this that you're exactly right and of course you know this effect, let's say, arises,
09:38:13 That, of course you know this effect, let's say, arises, the same way with acceleration. And the only thing that depends on this prototype. And so you can have proper time differences to to velocities do the acceleration due to gravity.
09:38:24 And then the second part is, yes, either. If you're in the homogeneous limit here, which had small distance as is fine.
09:38:30 Then you can always interpreted the homogeneous limit in terms of Einstein's 1907 paper. So not 1915 full gr but it's sufficient to take special relativity, add equivalents principle on top of it, and you get the gravitational Richard prediction.
09:38:44 And so it's kind of a special relativity plus equals prints were added to it, which is sufficient to have this next day, and I completely agree there's nothing.
09:38:52 If you can push it further. So the curvature does not matter for this effect on the proper time, if you can push it further maybe you can make it on them biggest yacht, but to just say, but, but I would say it's exactly the same as any other test of gr
09:39:04 the test the gravitational Richards, so you know, if you talk about traditional redshift as one of the pillars of test of gr which Einstein also labeled it is actually a test of this 1907 prediction.
09:39:15 And so we can always go into the fray and where this is just visual entity and this is fine, but it's only two minutes homogeneous them and in fact, I hope really to, we were just finishing a paper where we show how he can really increase the distance
09:39:26 We were just finishing a paper where we show how you can really increase the distance tremendously by looking at entangled systems and then you then want Can you don't have to be this purely to gr as well.
09:39:38 Yeah. And would you want to be in that limit in order to sort of make claims about quantum effects and curves FaceTime, you need to see some curvature, in order to say that I guess.
09:39:44 Would you exactly so this is not an effect you to current space them because the curvature does not enter, but is the effect i would i phrase it as if it was close to Tony corrections or the GR motion of proper time.
09:39:54 And so short, you can go to the regime where you also have furniture, and for the, you know, maybe we don't know much, you know, maybe, maybe betters, but from the farmers we have today that you know doesn't matter it's only the proper time work life
09:40:07 matters. And so you're right, that will be interesting too. but I think kind of conservatively I'm comfortable calling it like gr And who am overlap, because it's an executive team spirit is classical test of gr.
09:40:30 And so short going to curvature is interesting and will be even better, but for, for this particular effect, it's sufficient to have this kind of proper time contribution to to math.
09:40:32 Great, thanks so much. Okay, so we're entering the general discussion, but I'll continue to, because people have already had their hands up, Ted, did you have a comment I saw your hands up.