08:04:51 Otherwise, please wait until the discussion, starts. And let me start by announcing the first speaker of the day is tailor it to keep up Jake UI and Jake is going to tell us today about tabletop experiments for quantum gravity.
08:05:01 Okay, please go ahead and share your screen.
08:05:06 First I'll mute myself and say, thank you very much to the organizers, it's really exciting to actually have this group of people together to be exploring this direction.
08:05:16 A lot of what I'm talking about today I'm going to call it speculative, in the sense that there are substantial technical and physical challenges that we're going to have to address before testing key concept sync quantum gravity only be achieved in the
08:05:34 laboratory.
08:05:36 But I feel like it's an aspirational goal that is worthy of the effort.
08:05:44 My name by the way is Chuck Taylor, I'm at the joint quantum Institute and the Joint Center for quantum information in computer science or quicks my homie agency is NIST the National Institute of Standards and Technology.
08:05:54 And you can find me on Twitter at quantum underscore chick.
08:06:00 So, first of all, what do we mean by a test.
08:06:03 When you talk about testing quantum gravity I usually think about two different pathways.
08:06:08 One pathway is kind of a bottom up, pathway in the other you might call a top down pathway.
08:06:13 And I apologize for the way I'm in the office right now. We have a massive vertical. And so, if you will, hard to hear me. Please accept my apologies and they don't hesitate to raise your hand asked me to say it again.
08:06:25 So, one approach basically is to sort of bottom up like hey, let's choose a theory. And from that theory, make a prediction so some years ago for example in the world the loop quantum gravity there is a prediction made that high energy photons might go
08:06:39 slower.
08:06:41 You can disagree with the calculation. Or you can try and measure that that effect.
08:06:48 And then the other is sort of more top down approach in which you suppose a principle of the theory, without being specific about theory and then find some testable contradiction.
08:07:00 So for example, we don't know whether gravity would cause sort of spontaneous wave function collapse. But if it did a massive superposition should go here.
08:07:09 And so you could look for 60 coherence.
08:07:11 And if you don't find it you would say well perhaps this spontaneous wave function collapse needs to needs to go away.
08:07:18 In either case, you can use improving theoretical knowledge to restrict theories, which then improves both of these types of tests.
08:07:27 And I think it's also important we talked about gravity we're talking about quantum gravity, and we have to come to some sort of agreement about what we mean by quantum gravity.
08:07:36 So, I don't have all the answers. We talked about this quite a bit and he's from about two years ago now in classical quantum gravity that Dan Carney metal postdoc and until Stanford I wrote.
08:07:46 So if you want to kind of get the, the depth of this talk in paper form I do encourage you to read that paper has a lot of this material in it.
08:07:54 But I think the fundamental point is that you know you can kind of say what you mean by quantum gravity is really does there exist, renewable so theory of metric fluctuations that recovers Einstein's equations in the appropriate limits and it's compatible
08:08:07 with the standard model.
08:08:09 So you can say this is those there exists and effective field theory of gravity is generally agreed. And since many in theory theoretical and experimental community that both gravity and gravity waves are the expected flat metric portion of the theory,
08:08:23 and should be detectable obviously we've seen gravitational waves through the Lego experiment.
08:08:29 But gravity. I've been much trickier could also ask really is gravity of fundamental theory is an immersion theory I see that to Jacobson's on on the call he's obviously one of the great progenitors of the possibilities there.
08:08:43 And also, is it even quantum you always there's some other interpretation of space time.
08:08:48 And some two key aspects, one is what is interrupted in space time but then the other is quite simply does gravity actually entangled things.
08:08:57 And so I'd like to now, dig into these two different ways of thinking about what we mean by quantum gravity. Either that, is there a effective field theory which has grabbed a tons.
08:09:07 Or alternatively, can we even say that gravity and tangles or we proved that it doesn't.
08:09:12 So let's talk first about the fact that field theory tests, and the basic premise is that there exists.
08:09:18 So in the sort of flat metric limit so low curvature limit.
08:09:23 The grabbed hands are really analogous to photons.
08:09:26 Do the quarter gravitational waves.
08:09:28 And just like, if you have a dipole emitting, the couple of electromagnetic field, you have spontaneous submission.
08:09:35 If you have a mass quadruple coupled to the gravity to the metric whichever mask logical is.
08:09:41 You should also get spontaneous mission.
08:09:43 And this is a type of linear as field theory effective gravitational coherence.
08:09:49 So, the key government constant for electromagnetism is of course defined structure constant.
08:09:55 Right, which is a dimensional quantity that's essentially a given the coupling strength squared, and natural units of electromagnetism.
08:10:03 So if you know the structure constant, you can also calculate the radiation rate from an atom, for example, with a vitamin D.
08:10:10 Obviously if you're measured in light use the planks and divided by electron charge.
08:10:17 The final structure constant and then a ratio essentially set by density of states, and the fact that it's a dipole transition.
08:10:21 Now what's interesting of course for gravitational radiation. The current structure constant here is Newton's big G, rather than to charge the electronics the mass of the electron.
08:10:33 And if you look at this individual students, you can also rewrite this as a massive electron compared to the plank mass quantity squared.
08:10:39 As you may expect this is a very small number. So if this is 10th of my students is 2545.
08:10:51 And that means that while you can in principle, have some sort of gravitational coherence, the coupling constants here are really really hard to work with no one band you have is that the quadruple here is a mass quadruple so units of mass times like
08:11:01 squared.
08:11:10 And you're comparing massive something big. To electrons that's going to be a big number but you still have to beat this 10th of minus 45 front, and you can run the numbers and essentially you need something that where the gravitational background is
08:11:11 a high temperature you're working for frequencies there's a large political moment, it really starts to look like the coherence mechanisms for neutron stars, and I just don't see a way of doing it on Earth.
08:11:23 Nonetheless, if you could observe this difference between stimulated emissions spontaneous remission of gravity.
08:11:31 You're good.
08:11:32 We just don't think that these numbers are accessible on Earth, why not.
08:11:38 Well, so it's called the sun dismal science of gravity gravity on Earth, which is that if you look at the natural combination of units for terrestrial experiments you basically take Newton's constant big G and the physical parameters like material density,
08:11:50 and this defines a gravitational coupling strength. Is it which is units of frequency. It's just the square root of big times density, and it's about a million hurts.
08:11:58 In, for you that for materials like tungsten, which is a high density, high quality material.
08:12:05 I claim that this is actually a fundamental skill that's going to govern any of the gravity experiments that we can see on Earth. So, going back to that gravitational radiation.
08:12:14 You can rewrite it in the following form, l being the size of the mass quadruple lambda being the wavelength of the associated gravitational radiation.
08:12:23 Here's your coupling Constant Data squared divided by frequency that gives you an overall units or frequency.
08:12:28 And then we had the length compared to a harmonic oscillator length. So the small fluctuations of the particle.
08:12:38 And then you also have the length compared the wavelength. In a similar way, if you look at the quantum mechanical coupling between two harmonic also just couple fight gravity.
08:12:43 So this is a linear as expansion of the Newton's interaction.
08:12:48 And you can see that you write this time harmonic oscillator length you pull one mouse over left or right, this quantity is your zero quandary square and this quantity is just h bar over omega, this is units of energy as you expect.
08:13:03 And you see that the cup of constant in units are frequency is going to be typically less than a million hurts at best.
08:13:10 So I hope this motivates this data parameter and I would encourage others to think about data as a way of characterizing just so hard and experiments going to be
08:13:21 So a nice thing to do with me to show that gravity doesn't act entangle things. So that would say that you have to have some quantum theory of gravity you can't just get away with something somewhat possible.
08:13:33 And I think that I like the fund and other object based on the data parameter which is the idea of entrepreneur appearance so ultra coherence.
08:13:40 It's a massive object that has a positional coherence time. That's an excess of this sort of theoretical quantum gravity limit terrestrial quantum gravity limit.
08:13:48 And so, is gamma Q is the quantity coherence time you want to be less than data for some massive super positions. I will say though we're actually getting a little bit closer to this than I expected from 10 years ago.
08:13:59 You know the key frequency of them is for project materials are getting pretty good, and he actually if you look at free falling particles like trapped particle that you let go and a high vacuum, and you look at the effect of background gas and the black
08:14:13 body radiation inside the object. You can start to think that you might actually be able to get well below this value.
08:14:18 It's not inconceivable that with further advances in mechanical systems in isolation from background materials and in vacuum systems, it will actually get to this ultra coherent regime, and of course of the next decade.
08:14:30 So for me, This is the biggest motivation to explore this direction.
08:14:35 Now, but why would massive superposition do here.
08:14:40 We don't really know.
08:14:42 We can speculate though, right. So, one speculation is, is what I call the 10 rows conjecture with sort of DLC Penrose theories, and what you assume that to make gravity work, you have to some classical gravity work you have to have some deep coherence
08:14:58 of the systems, which leads prevents the contradictions that would be an inherent in semicolon classical classical gravity and one of mechanics.
08:15:09 And you can come up with like equations like the Newton Schrodinger equation, which is a sort of guests that how does everything might work. You can come up with theories of gravitation to coherence which become quite interesting and involved.
08:15:20 I will note that you know we have some additional reasons to be suspicious funded Insurance Group.
08:15:25 Because if you have this sort of non linear equation governing quantum mechanics, then key assumptions in computational complexity collapse for example dQp become empty space to come equivalent so you can solve any computational problem.
08:15:37 It's similar in some respects to the problems you get when you allow for clothes time my curves. So, the time travel, where you get much more computational power than we expect should be there.
08:15:47 Nonetheless, you should look for this and if you don't see it, declare some level of success.
08:15:52 You know there's other questions about equation of state gravity and my call it saying hey this is really a thermodynamic ensemble perhaps there is no entanglement bit gravity.
08:16:00 And that will be a very interesting to show that you can't make it technically a gravity.
08:16:04 I did mention that this master equation via gravitational waves also creating massive super positions, think the words my colleague a lot, who is the way to prove space time, texture, at the quantum mechanic level so these are very interesting questions
08:16:16 but I don't know really how to formulate and others will probably do it's better than I can. single particle massive superstitions.
08:16:24 I'm much more interested in the two body kits.
08:16:27 So let's talk briefly about disentangling question for two bodies.
08:16:30 I want you to imagine I have two amount of oscillators, want to come here by Alice one here by Bob.
08:16:36 Each of these behaves locally quantum mechanical, and we have an induced gravitational interaction between them so for small displacements from the equilibrium position, we write the gravitational interaction in a multipolar expansion.
08:16:47 This pre factor here is that data parameter squared times the mass times x one next to where this is again small displacements right so you could try and entangle these two oscillators via this interaction.
08:17:03 Now, when we think about what's going on under the hood and chill stamp has some disagreements about this slide here I'll just say that off the get go.
08:17:10 But nonetheless, this is a helpful way to think about how you get a local a non local interaction, like Newtonian interaction of local events and variant theory.
08:17:19 And the idea is that you have some gauge particle, like here at represented by a Masonic operator a.
08:17:25 And this gauge particle media interaction between next one the next to so in the simplest possible limit.
08:17:32 If you have this gauge goes on here with some frequency omega, and a coupling, which is just given by x one times the displacement of the field, and x two times assessment the field.
08:17:43 You can try integrate at the Foursquare so you say let's look at frequencies much lower than this back and forth time omega.
08:17:50 And you can make a unitary transformation of fuller on type transformation in which you're essentially saying, Well, I'm going to remove the linear eyes coupling between the fields and look at what happens afterwards.
08:18:00 This is also similar by the way to what happens when you make the ministry transformations. for the dipole approximation electromagnetism.
08:18:06 So when you do this, the vacuum fields actually displaced by a small amount that depends upon the positions of these two oscillators.
08:18:12 So in this new frame.
08:18:14 You have an effective interaction between the two objects mediated by the field, and no object field interaction that's left.
08:18:22 And that would seem to be a kind of a nice way to create this interaction.
08:18:26 But these are mathematically equivalent in the limit of high frequency.
08:18:31 And so, you can use this construction to create a similar interaction, but one that doesn't entangle, the idea is very simple.
08:18:40 So over time what's happening here is Alice and Bob are exchanging, if you will, virtual gauge bosons.
08:18:47 But if you add a screen, so that the gauge was on before it's allowed to propagate from Alice to Bob undergoes, some screening interaction that removes any entangling character.
08:18:59 You can recover the semi classical limit of the interaction, but not have any quantum information communicated through the screen.
08:19:07 And so, if you think about the properties we're looking for one is we wanted to sort of reproduce the classical dynamic so they are interested in which, if you will.
08:19:14 At the same time we want to let note entanglement through so about eight years ago, my student recovery and I sort of looked at this problem in some detail and solved it specifically for the case for Monica oscillators.
08:19:26 And what we showed is that over all possible non entanglement channels. So all possible screens, you could put in the middle.
08:19:33 There's a upper bound the lower bound on how much the variants of the momentum these particles changes over time.
08:19:42 If the channels on penguin to G here is the quantum mechanical coupling between the two objects which we said there's going to be less than the middle hurts.
08:19:50 And the point is if you can show that there's no it's below the threshold vendor actually exists a protocol but what you can arbitrarily. Well, purify the entanglement produced between these two masses.
08:20:01 So this is a type of test. You're saying let me look for this noise, if I do not see this noise. I have to confirm that there is some entanglement happening.
08:20:10 And you can propose now so for example I think we're gonna see a lot of different examples of this nature of the course of the week. And what you have to, for example, I'm on a call center she represented by tours last letters, these are oscillators they
08:20:20 can spend about their access as dumbbells, if you will, and it's really motivated by the original Cavendish experiments were measuring G.
08:20:28 And then you have some sort of superconducting shield that screens, non gravitational interactions between them.
08:20:34 Because you just want to the gravitational part.
08:20:37 You may come out of something very dense like platinum in order to measure this coupling.
08:20:41 And then you read them out the optical your electrically. And the idea is you're looking for sort of an anomalous heating event in which the coupling between them.
08:20:50 causes an extra phone on about once every few thousand seconds for the race to be calculated platinum.
08:20:56 And of course you have to contrast this to the thermal background for these objects which we calculated using the best source oscillators for the last group out that university Washington will be in the order of one fun and every 10 seconds.
08:21:08 You know, so that's not so great, in principle, you can kind of try and run this experiment.
08:21:12 You have to do several things one, you have to verify a couple things actually do the graphic on it confirmed one of our law, not confirm the density dependence.
08:21:22 And you also need to estimate the heating rain over a long time, with a very high level of accuracy so that you can repeat it many, many times to look for a discrepancy.
08:21:30 I basically think this is almost impossible, it is over embarrassingly parallel and principally can do many of these devices.
08:21:37 So, I will mention just now briefly a new thing that we've been involved in, in collaboration with Mila group at Berkeley, which is what I call a single sided testament hanging with via gravity.
08:21:49 So, one of the big challenges in this type of experiment is that you're looking for entanglement between two different massive objects, both of which are hard to make fun of mechanical.
08:21:58 And while you can come up with interesting attainable witnesses as bucko and those have done, and others that measure both of these things, if you can reduce it to a problem where you just measure one object that you know that you do very well quantum
08:22:12 mechanics, and then the other object which becomes less important will make your life a lot easier so we figured out the simplification just over the summer, but the paper up in the archive in January.
08:22:22 But the idea is you can actually test under certain constraints which I'll talk about the idea of entanglement your gravity using measurements, only on one of the two systems.
08:22:33 And the idea is actually to use what you call entanglement induced collapse and revival of coherence.
08:22:38 I'm certainly seeing this type of plot in which you have two systems interacting, you may have some sort of Ramsey fringe for example some oscillations but over long times the overall coherence of isolation goes down, and then recovers.
08:22:51 That's called revival.
08:22:54 So, what we're thinking about in this case was a scenario where I have a harmonica player with a big mess. This isn't a pendulum, for example, and I have an atom in a trap.
08:23:05 This is a type of Adam interferometer which I'm going to split the atom into two pathways, hold it at some distance l.
08:23:12 Now, if it's on the left side, this thing season force this way, right, so let's use the force that way.
08:23:17 And so over time, this pendulum starts to move.
08:23:20 And then, then we try and recombine the atoms and measure where they are.
08:23:25 And again, that would produce the signal so the fast oscillations are due to the difference differential force the atom sees, and the slow oscillations are due to the entanglement of the atoms with the mass but when the mass makes a full circuit of its
08:23:43 dynamics of goes out and then back again, it actually becomes disentangled. And so, in principle, you can recover the atomic cohorts.
08:23:51 So what are the assumptions that make this into a test.
08:23:54 Well, I've Allison I had Bob and I have some channel on channel two between them.
08:24:03 And the idea is that this channel, we have to convince one it generates time evolution and America consistent with time translation and variants and obeys the CME Group composition law.
08:24:12 So that is that the channel from TTD double prime is equal to the channel from two different and followed by the channel from TT double prime.
08:24:20 for any ordering have to just nature.
08:24:24 The second key point is that the observe obsessive substance and this level is qubit if you will a has a dynamics generated by the channel, which is a trace over the other system, which preserves the population the two states and non monotonic Lee changes
08:24:39 interfere metric visibility. So, that is to say that k on sigma sigma sigma z, and the visibility changes sign for example by oscillating periodically.
08:24:50 If both of these are true, then l is not a separate little channel.
08:24:54 And that means it can it can convey entangled.
08:25:00 So, by the way, this summer group means that Allah has a liquid form. So if generators are limited form.
08:25:06 And this revival is equivalent of a coherence transfer from one system to the other and back.
08:25:12 So here's that again harmonic also their concept, you can think about the following way. So I started the center.
08:25:17 I put the Adam and supers in two locations that effectively produces a force which is a displacement on these two objects. It evolves over time.
08:25:25 And if at the end, I put the atom back that on does the displacement. And then I can say is this thing far away from that thing, these are the two from pathways that the mask could have gone through and the overlap between is what the term the coherence.
08:25:42 So that really good we'll talk about this a little bit later but but basically you can imagine a scenario where you set up some masses you have Adams like this.
08:25:43 So I think part of it.
08:26:01 experiment is they have animate Frommer's here's a cloud of atoms they hit it. This is in time, space is a Z axis here.
08:26:05 They hit it, it goes into superposition two locations, it has to be different.
08:26:11 And then they hit the sort of inflection point so that they go to the same point of the apex of their trajectory upward in Earth's gravity.
08:26:20 And then they turn on an optical lattice, and not to the last will trap the atoms for an extended period of time on the order of say 20 seconds, and then they will recombine the items in our influential signal at the end of the experiment.
08:26:33 And so, if you if you run the numbers.
08:26:37 You find that this thing, first of all, actually essentially behavior, it can improve with temperature of the massive system. So, random the massive random but strong motion that the masses is better requires high density that's we have to talk fast as
08:27:00 three factor, as you may expect works better with a bigger atomic masses works better with our larger superstitions here. And with longer times.
08:27:02 But what we discover is actually if you're doing on the order of 10s of the four experiments with tended to seven items each principle, you can actually test this the five sigma level and about two months of running.
08:27:11 So now we went from something like 3000 years of runtime for the two sided experiment to two months with a one sided experiment so very excited about that.
08:27:20 Now, I have not that much more time left. But I want to talk about the third sort of test for quantum gravity here on Earth.
08:27:28 And that is actually connecting, some of the theoretical knowledge we have what happens in the early universe with searches for dark matter.
08:27:38 And in particular, you can ask, can we make documented it only interactive gravity.
08:27:41 And there's a beautiful talk by Andrew long, get up from last year which I encourage you to take a look at, and some of this material. This slide and the next in particular were drawn religion has worked.
08:27:52 So you can ask what types of dark matter is created in the early universe, so one thing is that near inflation if there is coupled to the standard model.
08:28:10 onto a Dark Sector with this vertices way to buy the mask. But actually, even if there's no standard model coupling. just the actual inflation itself so in the LR w metric.
08:28:19 In the early universe, you can break down the old regime for this type of scalar field theory, for example, and what you get is that there's an effective mass, which has the reach of curvature in it, and also the reseller in it and also has the conformal
08:28:33 growth constant a, and the consequence basically is that in the early universe, effective massive scale our field is changing in time.
08:28:42 And when the effect of massive changing and time the grace that we have function has to adjust to changing maps, so you know, very very viscerally here's a tight confinement and I have a totally can find him on the hospital a functioning.
08:29:03 become much more weekly can find this spreads out. But the problem is that this may not be able to just add badly to that because this is growing exponentially. And the consequence is that you let behind you leave down some expectations in this in this system.
08:29:08 And those could be the dark matter.
08:29:10 And so if you can. I will say that the consequence by the way is that there's a national scale, given roughly speaking by the early universe of a constant, which gives you some of below plank mass but close to the plank mass production matter particles.
08:29:22 And so you could try and say hey, is there very heavy so plank mass scale, dark matter, sometimes called with dealers.
08:29:30 And how would you measure this. So, if it's only interacting by gravity, you have to measure its gravitational effect so if you have a test mass here and the dark matter particle here with some impact parameter B, and momentum, mass times this last two
08:29:42 years is taking the non realistic limit, as it comes by, it'll have a small deflection, because the gravitational interaction right so it goes by and this thing gets an impulse laterally, you can calculate the deflection angle in terms of My Little Theater.
08:29:56 Remember that's the square root of big times the density now with this mass.
08:30:01 You can also calculate the impulse how much momentum is transferred to this object and it's basically given by the zeta parameter squared times the interaction time which except that they interact parameter times the initial momentum.
08:30:13 Turns out that we believe you can actually measure this level of impulse. If you're careful.
08:30:23 Let's give a little impulse background so if you have a five milligrams dark matter so that's substantially heavier than the black mass black mass being about 20 micrograms, then you have a five milligram sensor the impulse delivered is in the order of
08:30:31 10 minus 19 now. That's actually not so bad we can already do a billion optical photons and a pulse, which is also tend to the minus 18 kilograms meters per second.
08:30:44 You know, if you're in the article here and regime. You can see that actually the thermal noise background for five milligram mass is actually below, well below the impulse that you get at this level for reasonable amounts of integration time.
08:30:57 You can also ask what happens if your background processes systems are preventable single helium out of it for Kilbane hitting a mass produce an impulse but 10 to the minus 24.
08:31:06 If you go down to the sort of sub, sub like mass level now you really getting interested in really challenging, you want to make a sensor kind of small as well for a variety of reasons but the biggest problem is that this becomes quite small, and you
08:31:17 really need to get that background gas load down below 10 to the minus 13 tour, so you know there's there's what you could probably do with current technologies is what you might try and focus on for the, for the future generations.
08:31:29 There's sort of a standard quantum limit for men to transfer and you need to actually get well below that we have some nice work on that recently.
08:31:35 But the this whole idea of trying to measure.
08:31:50 Dark matter is gravitational interaction and just trying to infer if there is such heavy dark matter is become a large corporation called the wind time collaboration spread across Purdue from the lab rice, Maryland, Oakridge Minnesota Berkeley and nest.
08:31:56 nest. And the idea is to create a basically a summit at the bubble chamber, but we're each of the objects in this thing's blue Matt pendula have been excited by dark matter particle going through, you look for correlated tracks of these excited about particles
08:32:04 You can read more about it in our proposal paper back from two years ago now, and some more recent work on the archive.
08:32:15 But it's very very challenging, I want to be clear about that. You know, you're looking for dark matter that's in like mass scale here. So, this by the way is the massive in the gv it's like masses right about there.
08:32:26 And this is now on the order of the two 110 billion 1 billion sensors forming in the array.
08:32:33 You can make the spacing large for which creates a number of detectable events for your to be higher which is good.
08:32:40 But then you'd have kind of a maximum and minimum mass you can measure which is well above like mass, make them more closely spaced. And you can now see to Laura masses.
08:32:53 At the cost and event rate.
08:32:55 You can go to lower masses, and then becomes more challenging I mean we think though that this stuff is really on the edge possible because now you're looking at the sort of, You know one to 10 events per year.
08:33:04 And this is assuming they're able to get through really limited so that means you have to have substantial backpack innovation in this type of effort.
08:33:13 Nonetheless, and what are the scientific frontiers here so actually one of the questions that we have is, is, you know, what are the fundamental limits for the small detection of horses and impulses, it's going to be critical for both entanglement tests,
08:33:25 and also for this dark matter type test.
08:33:29 I think the answer by the way is yes we could probably detect dark matter if it's heavy enough through its gravitational interaction, but this road course along the way you should also be asked, as we build all of these different apparatus, what are the
08:33:41 other physics targets that we can look for what are the other physics that will learn so I'd like to think about that as you go through the talks about the work today.
08:33:48 And then finally, you know, what can you learn about quantum effects and gravity so I've laid out two different pathways, but I think there's a lot more out there so I'm really looking forward to the rest of the talks.
08:33:56 And I want to thank everyone for the time, I just want to mention at the end here, my call up my old postdoc Dan Carney who's now at Berkeley at Lawrence Berkeley laboratory, who drove a lot of this work, my students so so he gosh and john Goodman, who
08:34:07 have been doing a lot of the calculation work on my new postdoc Jeff Epstein, who has come from Berkeley, and is joining the group to work on more of the semi classical theories of graph, thank you so much for your time and I'm happy to take questions.
08:34:19 Thank you, Jake for the very nice and stimulating talk is so I have seen already.
08:34:27 Henry said a Diego, do you want to go ahead and ask the question.
08:34:34 Thanks a lot. It was super, super nice talk. I guess my question is going to be shared by other participants is like what happened with other models of dark matter where you have direct direct interaction with the, with the sample right.
08:34:49 I guess you're able to do to see the gravitational
08:34:53 company and you also will be able to have super strong constraints on data coupling. Thank you.
08:35:00 Yeah, so when it comes to dark matter the has the center model coupling.
08:35:05 We have two different interesting things. So first of all,
08:35:09 it's going to be harder to say it's a tester quantum gravity.
08:35:14 Right, because it's not gravitational motivate this center mothership.
08:35:21 But nonetheless, if you're building these detectors you want to know Are you also sensitive to, for example light or dark matter, or through standard medical billing The answer is yes so we wrote some papers about it.
08:35:28 For the ultra light, dark matter.
08:35:31 And so you can read about it but but in terms of you know what we're focused on today.
08:35:36 It's really only this very high mass regime, where gravity is implicated for the ultra light, dark matter for for light, dark matter and other types of wimps.
08:35:50 It's hard to say the gravity is necessarily part of the story, but gravity has to be quantum whereas if it's purely gravitational coupled, and you create it in inflation.
08:36:00 It's got to be metric fluctuation. That's all we got.
08:36:03 And so you know I would say that if we can show that you see these things and they have no center mall across section which, if they had a cinematic cross section it would change the size of what the sensor sees you know that's that's a smoking gun.
08:36:20 Alright, so let me go to the next questions, am I think the next one that I saw was ARCA me.
08:36:30 Hello So, since we're talking more emotional was a question because our plan, like to follow the idea about just discussing, you know, granted it seems to me a little bit.
08:36:45 Kind of interchange. It was a point that if you can see the normal TV stick objects. And I believe that it was consideration. In this first part about nano diversity culture them
08:37:00 become just what is called instantaneous interaction, which is a normal potential imagery. And in this sense, I mean,
08:37:11 relation to exchange by the way with them for example they with appeals when you're trying to, to make it consistent with loans in various but let's say say is that we are talking about nominally system.
08:37:23 Okay, certainly just a normal quantum mechanical system, this certain type of interact potential. Okay. So is this a spec.
08:37:31 It is the same as for example for electromagnetic interaction, which is also kind of longer range.
08:37:37 But, and then you know all these questions about, he is in fact he is it's not specific for quantum logins I suspect. So, so what I'm trying to say is that when we are going to flip the song delay with you when deviation from flat plate Mrs is a can,
08:38:08 exempt and indeed, we can discuss what is quantum what is non quantum and how to interpret this and, but classical field care for you know gravitational field.
08:38:11 If you are talking about this small, small, small MP to towards the field. I do not see any, any specific PC deals is because every single to be done in a centered way.
08:38:19 So, okay, this is where I am. Okay, and the confused about that yeah I will say, I'm very fortunate that little stamp has a recent paper that digs in executive the question you're coming but which is.
08:38:35 So if I'm looking the relativistic limit.
08:38:38 You know what, why do I need to have some sort of local theory in the limit.
08:38:45 And you know, in another way to think about it right is it but if you choose it and engage.
08:38:51 Because these are gauge theories, be choosing appropriate gauge. Then there's a direct matter matter interaction.
08:38:57 It's not that I disagree it's not simply because again it's it's a normal image of the system in the military agreement, then it's not, it's getting the pendant in the military, basically.
08:39:10 No. Okay, I agree, I agree.
08:39:12 And
08:39:16 so, the thing is what I'm trying to say, though, is that if you, if you have a theory.
08:39:25 With this interaction.
08:39:28 There will be dynamical corrections to that theory, in order to ensure Lawrence in France.
08:39:34 Right. And so, you know, when you talk about what we can do here on Earth.
08:39:40 We have, we're going to run into problems like there will be loopholes.
08:39:44 So the loophole that I would think about in that context right is that while you could, for example show that you're not able to make entanglement through this gravitate What do you think is a gravitational channel.
08:39:56 What you really want to do is show that the numerical correction doesn't work either.
08:40:01 Right.
08:40:02 And so that's that's why it's, like, I can't say that there's way to get around loopholes. Now, not that I can see it today.
08:40:10 No, it's not a loophole because in this way, you can ask the same question is magnetic interaction and you know just various requests that we do have, say, photons like in here we, kind of, you know, propagating object which is called Word GLAMAZON until
08:40:29 it is obvious in in in zz Simic Lesko Lynch, in this is so so user is a new kind of deviation what they would would be your answers.
08:40:41 So I guess the point actually is that this is why I said the beginning right. Many people believe linear as gravity is a great starting point. Yeah.
08:40:48 And the point of these entanglement tests, is that they're actually asking their ass asking is it asking about linear as gravity first like, do we even have proof for linear as gravity of the quantum mechanical level, that's what they're asking.
08:41:00 I see I understand that, but there's no doubt about the existence of.
08:41:11 So in this way, I said it can be solved solvable problem, it doesn't meet experiment.
08:41:12 Okay, except that if you if you do the experiment and and never untangles then you learn something.
08:41:17 Sure. Well, thank you. Great, so I mean we will have more discussions later so I'm going to take a break I want to stick on thanks I'm going to take two more questions and then we will have more time for the discussion that's that's the idea.
08:41:30 So, I think that next person, I saw was gone.
08:41:34 I'm trying to feel. Keep the order hopefully I'm okay Cindy brightens it.
08:41:39 Yes. Thank you, Tom chicken. And so I have two questions. I mean, this proposed test using the full sentences, you have to suppress and the third one is and other things tremendously, by, by, do you have any realistic expectation, you can get a 50 decibel
08:41:53 suppression.
08:41:55 They'll actually, the 50 decibels of back action evasion in the light is or in order to get to the thermal limit.
08:42:03 Let's be clear, so Okay.
08:42:07 Yes. Okay.
08:42:09 And people have demonstrated the thermal limit side of that actually in the past but without good enough readout.
08:42:15 So there's this balance you have to be able to see enough signal, but not have too much noise.
08:42:20 And the problem is that you're looking for something it's happening at high frequencies, so dark matter, we think is not a little bit decoupled from our gravitational rotation rotation in the galaxy.
08:42:30 So stuff comes by very fast.
08:42:33 You know, some not not relativistic no no point 005 C or something you know so it's like it's fast,
08:42:43 it's tend to the minus three See, that's what I Well okay, I said to my three times that are free.
08:42:53 But it goes by quickly. And so you have to have a sensor that sees this, but you need to long enough integration that because when you want something massive at same time so there's this balancing act.
08:43:00 Because it's hard for large master respond quickly.
08:43:04 And that balancing act basically ends up putting you in a tight corner and the measurement side.
08:43:09 So you can move yourself to easier spot and measurement but making things lighter.
08:43:13 But then you're the number of sensors you need goes up.
08:43:17 So, My take is that 50 dB of combined back action evasion and quantum non demolition is the very outer limit of what we can achieve with a 30 year program.
08:43:28 That's my take.
08:43:31 Okay, it's time I brought this other there's other purity gravitational production mechanisms, other than inflation with Zillow, I mean, that gives you a wider range of message.
08:43:40 I mean, that gives you a wider range of message. So there are there are a whole bunch of other gravitational mechanisms out there, I agree, I agree. I think the point is that if you, if you create dark matter from gravity, one way or the other.
08:43:50 It really is a smoking gun that high curvature gravity has to be one of them. I mean, that's my take a know there are mechanisms don't require gravity to be quantum I disagree with that, we can talk offline about that.
08:44:02 Yeah, that'd be great.
08:44:04 Great. Hey, I think the next one is unopened.
08:44:10 So, thanks Jake is a lovely talk I just want to ask him. So what's the acceleration Do you require. Because it's all working with the because of the relative acceleration which is impacting on your mass.
08:44:23 So, it's effectively a building of the world class sensor which is very beautiful. This is what we want. but what is the relative acceleration can measure.
08:44:33 Yeah, so, so I put things in terms of impulse, rather than acceleration, because the scene comes through like a shot and you're looking for a change in momentum from the impulse.
08:44:43 But the corresponding noise force that you're looking for are actually something that we've achieved that lower frequencies.
08:44:50 So it's in this sort of Pico De Pere route hertz levels of sensitivity. And those are the world's best accelerometers.
08:44:59 You can actually get away with worse if you have more sensors, up to about an energy brewers I've actually built the sensor that works in the energy Bruce or it's not a theorist, I mean, but no more seriously.
08:45:11 The range depends on some of the other choices.
08:45:15 But you're looking in that in that region.
08:45:17 So it's, it's the acceleration for is we're looking at are similar to what we can do today with the best sensors, but the problem is the bandwidth is much different, because you're looking for to measure something get a microsecond, not in the second
08:45:29 is my next point is that in order to really do this kind of like analogy which you said which is exactly the kind of regime you would love to perhaps you would you expect that the entire system to be kind of like a free phone system, somewhere, either
08:45:45 so there's a maybe underground free fall live oratory where you can get you to the seismic noise or surfing slithering pass through my experimental lab or something like that.
08:45:55 These are all great questions actually so there's two different pathways that we look at right so one is using systems which are cold, damp.
08:46:03 So basically you're measuring them reading them out and feeding back on them. So all the low frequency stuff is integrated out, and you only see high frequency.
08:46:10 And that's like the semiconductor industry approach like make it, many, many things purchase it many, many chips.
08:46:17 And then the other approach is to use levitated small objects with optical lattices levitate them all at once, and let them all drop.
08:46:28 And so, you know, Dave more yellow for example looking at that direction, whereas the project team is looking at the chip based approach, but in both cases you need many many sensors and the whole reason you sensors is to reject background, because you
08:46:40 you want to see a track correlated track from a long range force and not an individual new on the hit something and not that.
08:46:47 And so that's that's a key point.
08:46:52 Thank you very much. Great, I think we have time for one more questions I thought before I saw Lance I don't know if you want to or just wait until the discussion.
08:47:01 Sure I wasn't sure if you had time. That was very interesting talk.
08:47:06 Can you show your sensitivity plot again. I was curious about.
08:47:12 I mean, there should be a well defined line. That's your target for wimps and I wasn't sure if I saw it in terms of mass versus flux.
08:47:21 Also, yeah, I mean, while you're finding that maybe.
08:47:27 Yeah. So where's where's isn't there a specific events per year that you can just draw for the dark matter Halo here.
08:47:37 Yeah, so, so the event, so we're assuming the existing document of Halo is almost entirely at some mass.
08:47:45 Okay. Yeah.
08:47:47 And then the events for years how much of the Dark Matter Halo we actually see.
08:47:51 Okay. And if you see all of it.
08:48:02 Some of them go through our detector of that of those ones that go through a deck or some of them are above our threshold for notes.
08:48:05 Which one no I mean, what do you mean by see all of it like the point is this dark matter halos comprised of small particles the cars whizzing by the earth.
08:48:09 Right. So, if you ask like what is that what is the sort of cross section of these types of detectors. It depends on how many sensors but at the at the billion sensor scale the cross section is some sort of 10 meter squared.
08:48:23 Okay so events per year is just a function of that area of your detector or something like that is area of detector, the functional area.
08:48:32 And your sensitivity limit. Okay, anyway so I see how you phrased it okay so as long as I see something that's okay anyway. Now, question of whether if you see something in this mass range that it shows quantum gravity.
08:48:48 I mean, I think you can, you know, we have.
08:48:52 There could be some other secluded sector that produces heavy stuff that is made up of agglomerations of light stuff like you know neutron stars are two balls or.
08:49:02 or.
08:49:04 So, how do you know you haven't found that I just don't see that this is so I'm for quantum, I think what you're, there's two different things you're looking for first of all you're looking for the existence of this dark matter and second you're looking
08:49:15 for the fact that it didn't have a short range interaction.
08:49:18 You mean with our standard model but that's easy range you just have some, you know, something that it could talk to the Standard Model through 10 to the 10th gV suppressed interactions and it effectively be gravitational.
08:49:32 Yeah, so I don't I don't disagree with that assessment and I guess for me.
08:49:37 If you had a data constraint on the massive dark matter. I think we'd get a much better sense of whether or not the inflation driven scenarios the right scenario.
08:49:46 So I guess I would say it's a way to get closer to it.
08:49:50 But then you have other predictions which could be a contradiction so yeah I don't disagree, it's not a, it's an ironclad. Okay. But it would be very nice know if it is, you know, one, one TV or Planck scale or above until you hit macho limits and stuff
08:50:08 like that. Yeah, what would maybe be less appreciate it, but it's important to note here.
08:50:12 This this is the first time but I think that anyone had proposed that we could actually measure dark matter of in that range.
08:50:18 You know there you can measure dark matter of that sort of planet scale.
08:50:24 And you can measure Dark Matter down in the in the, sort of, you know, TV down through my creepy range right that's been proposed in many ways, but this sort of regime of intermediate spot where there's not that many in the heavyweight regime to have
08:50:39 some coverage for. Yeah, so we're excited about that, obviously.
08:50:41 Thanks.
08:50:42 Great, thank you very much. So thanks, Jake, for the very nice stuff, and then the let's move to our next speaker, that is money on a separate Nova from University of Delaware.