10:05:03 Okay, um, as our next speaker, we're very happy to have Andrew Tracy, and he'll be telling us about experimental tests of novels short range forces with a demo methods.
10:05:16 Okay, well, I'd like to thank the organizers very much for inviting me to speak at this really exciting workshop I really enjoyed a lot of exciting discussions, both today and on the previous two days and hope to have some more later on this afternoon
10:05:26 as well. So I'm going to say a little bit about the experiments that were involved with using a ml methods to look for new physics in particular, looking for some short range, new forces.
10:05:38 And I'm going to say a bit about the work we're doing now in an experiment to test gravity at short distance possibly may be uncovering something related to quantum gravity depending how you interpret it and then I'll talk about how the same technology
10:05:52 we're using there can also be used for gravitational wave experiments. And in the second half of the topic I'll shift gears to looking talking about our experiments looking for ultra light, dark matter, including both scalars and axioms.
10:06:10 So, if you look at the Standard Model of particle physics we have this huge disparity in energy scale. So for example, the gravitational force between two protons in the nucleus is about 36 orders of magnitude smaller than their electromagnetic repulsion.
10:06:24 And so this this hierarchy problem has plagued particle physicists for quite some time now to try to explain this apparent desert where there's no known physics between the electricity scale and the inferred energy scale of quantum gravity attended 19 GV
10:06:54 or so. And so one solution is of course supersymmetry which is still being searched for at the Large Hadron Collider. Other ideas have been proposed for example, perhaps that there are large extra dimensions in space where this high scale of gravity is
10:06:56 really just an illusion and the true fundamental scale of gravity might be actually much closer to the electronic scale where gravity would basically just look diluted because it has its propagating out into extra dimensions.
10:07:05 So either of these models whether you have supersymmetry or large dimensions can suggest signatures that the gravitational Newtonian force law may may change its character below some characteristic link scale, and a theoretical link scale that seems to
10:07:18 come up naturally here is sort of the submillimeter range. And so in this case you can look to see whether there be some new exponential form or perhaps a power law change in the gravitational interaction we bring two masses together like close distance.
10:07:32 And so you can look at sort of the landscape for tests of this sort of correction to the Antonia potential so this is the one of our are familiar with the potential, with the addition of an extra you call a type correction which could be produced to do
10:07:47 some of this new, new physics. And what I'm showing here are the current the current landscape for experimental constraints on this sort of a correction.
10:07:54 So here we're going all the way from laboratory scales down below micron up to astrophysical kind of planetary scales on the x axis, and then on the, on the y axis we have some coupling parameter which basically describes the strength of this interaction,
10:08:08 relative to gravity so if alpha was one that would be something of gravitational strength. And as you can see from the graph here, if we look at sort of Earth moon distances.
10:08:17 We have these precise, loser lunar Laser Ranging experiments which really tell us that the one of our from what the potential is holding to better than a partner billion level.
10:08:27 But, but notice the contrast, if you go down to below micron here on the all the way the left edge, you could actually have an interaction here that would be a 10 billion times the strength of gravity, but experimentally there would be no, there'll be
10:08:42 no constraint on such new force.
10:08:43 And so this is difficult because if you just look at how the gravitational force scales. For example, if I have to test masses that are spherical and have a certain radius, and I bring them as close together as possible you can figure out that the Newtonian
10:08:59 force between the masses is going like the positive fourth power of the size scale here. And so if I shrink this system down.
10:09:08 This these forces get very weak very rapidly. And so for material that is about as dense as one can discover on earth around 20 grams per cubic centimeter at the range of theoretical interest say 10 microns the magnitude of this forest you're trying to
10:09:21 measure is about 10 to the minus 21 Newton's, which is, you know, quite, quite tiny.
10:09:29 At the same time, you have to be worried, with the fact that other other scanner metaphors are actually much stronger than gravity as we've already pointed out, and so there are many electronic background forces that make these type of gravitational test
10:09:41 short distance particularly challenging. In particular, there's the Kashmir effect, which is an interesting effect in and of itself. If you just have nearby services you can have flood back and fluctuations, which can cause attractive forces between metallic
10:09:56 services for example. And we also have the possibility of kind of dirt force effects where you have things like electrostatic patch potentials or even though conductors are supposed to be perfect conductors in fact they have local potential variations
10:10:07 and these can produce spurious type electromagnetic signals and those experiments.
10:10:13 So if I zoom in on kind of the laboratory and now of that parameter space here now going from about 100 microns, down to about 10 nanometers, the area here in yellow is what has been ruled out by different experiments and the area on the left and pink
10:10:29 and green or some of the predictions from some of the theories that I mentioned.
10:10:34 So at the longest link skills here the best constraints are from Precision towards unbalanced experiments that are done at the University of Washington.
10:10:42 At slightly shorter distances there are micro cantilever experiments that I was involved in for my PhD research and sort of a 10 micron like scale. And then even smaller scales the best measurements come from sort of a adaptations of measurements that
10:10:56 And then even smaller scales the best measurements come from sort of a adaptations of measurements that are designed to look at cashmere effects.
10:10:59 So all of these all of these experiments, you know, are plagued with the same problem they need really high sensitivity and they also have these background signals to contend with and they're all based on sort of some sort of mechanical force sensing
10:11:10 device, whether it's a cantilever or torsion fiber or torsion pendulum or something along this and these mechanical sensors are limited, from one fundamental fundamental mechanism which is just thermal noise.
10:11:23 So, So, in particular, if you have a oscillator in contact with some thermal bath, at some kind of temperature, you can just write down the acquisition theorem and figure out that in the presence of sort of random thermal kicks from the thermal energy
10:11:35 of the bath. There's a minimum force that one can resolve in the presence of those random kicks in it, it goes like the thermal energy Katie, times the spring concept of the oscillator, times the bandwidth of measurement, times the product of the mechanical
10:11:49 quality factor, and the frequency of the oscillator. So, one approach then to improve the sensitivity is to improve the mechanical quality factor or eliminate dissipation in the system.
10:12:00 And these type of sensors whether the torsion fibers or cantilevers tend to have different mechanisms for for mechanical loss including clamping mechanisms as well as surface imperfections and just heat transfer flow and materials for example from thermal
10:12:13 elastic dissipation while these materials flex. And so this limitation can actually be overcome, using techniques from the atomic physics community where we actually can use radiation pressure from light to suspend mechanical oscillator rather than having
10:12:27 a clamped sort of solid state system. And so here if we have a dielectric object, and shine a laser at it, it requires a dipole moment induced from the light, and you want can get a potential where there'll be a minimum of energy at at the focus of the
10:12:50 a particle will be attracted to to a bright spot if you like in the light field and have a sort of confinement around that around that point. So now if you were to observe the motion of this particle.
10:12:56 Now its, its motion is very well decoupled from the environment, there's no more clamping mechanism or, or I'm not as concerned about the materials properties of the particle itself because I'm just looking at how the center mass of this thing oscillates
10:13:05 around in my container essentially made of light in this case.
10:13:10 And so in this way we can really improved the mechanical quality factor and get very good for sensitivity. So, in our, in our group we we trap nanoparticles that are silica glass spheres in in standing weighted optical traps and high vacuum, and this
10:13:24 is some of our earlier forced demonstration sensitivity demonstration where we were able to show that these systems actually can can conduct calibrated for sensing measurements at the level of a few zap do Newton so this episode is 10 minutes 21 degrees.
10:13:38 For those of you not familiar and this is actually right at the level where I was same claiming at the beginning that these interesting gravitational signals might start to surface.
10:13:48 And so, in our experiment. Then, what we're doing is setting up a nanoparticle next to a conducting mirror surface, and then behind the mirror surface we have a DR mass device that has different density materials and in our case gold and silicon.
10:14:03 We move that Dr NAS device and when we do that we modulate the gravitational signal on the nanoparticle, the conducting mirror in between is there to screen out the electromagnetic and chasm or background forces that should not very as I move the mastermind
10:14:17 behind the screen.
10:14:19 And so using the system both with its really good sensitivity and with the ability to position a particle really close to the surface here using the fact that we can put it in a number of anti nodes of our bright spots of the standing wave in this in
10:14:31 this optical cavity, one can expect to do many orders of magnitude improvement on previous limits and start to search into some of the other interesting theoretical primer space at the link scale.
10:14:43 micron, or so.
10:14:46 And so I also want to mention there's some similar experiments that are based on different geometry approaches also being developed by groups at Stanford and Yale that are looking for similar things but it a little bit bigger, bigger link scales.
10:14:59 So in our experiment, we collect a 300 nanometers diameter silica glass particle This is the test pass. We hold it in a laser trap and then we can laser cool the motion the center of mass motion using laser feedback willing, and then can find it in this
10:15:15 standing wave trap where the particle is next conducting mirror and behind the connecting mirror we have a actuator device that moves this driving mass, sorry up and down to modulate the gravitational signal.
10:15:28 So this is a picture of kind of the guts of the drive mass in the middle of its fabrication process we have this silicon wafer. So we're using semiconductor processing technology to basically create this density modulation of golden silicon by catching
10:15:41 some teeth into a silicon wafer filling them up with gold, and then kind of smoothing the surface down at the end to create this buried density modulation on the device.
10:15:51 So, so it's not only sufficient to have the sensitivity, but we also have to be able to place this nanoparticle very close to the connecting mirror in particular micron scale distances to really, you know, be sensitive to forces that exponentially die
10:16:06 off at the micro scale. And so the way we load the particles near the surface is using a retro reflected optical lattice. Here's a demonstration of one method that we've developed to do that.
10:16:17 So we're here you have a nanoparticle that's initially held in a an optical focus trap here we can insert a mirror membrane into the into the trap and then transfer the particle into a anti note of that trap which is close to the mirror surface.
10:16:47 So when we do that, then you can see how the spectrum of the particle changes where we have a much tighter confinement in the, in the axial direction, compared to the initial trap, which which shows that, you know, in fact we are now seeing the lattice
10:16:50 optical lattice structure of this trapping potential. In this case the the particle is 408 nanometers away from the surface which is the first anti note of the trapping potential.
10:16:59 And so once the particle is there now we've demonstrated that you can actually scan the particle around in the plane parallel to that surface and also adjust the distance to the surface at this sort of micron range.
10:17:10 So this is a demonstration now that's sort of a just a proof of principle that one can do this type of scanning for sensing at the Adam Newton level, and you can sort of scan the plane you know at various points here along along the thing which is really
10:17:24 useful because now we can characterize some of these various backgrounds signals like electronic patch potentials and other things that may have some sort of distance dependence profile along along the surface so this will be a useful tool in our, in
10:17:38 our tests and then ultimately when we put the laser cooling back that we've previously been using it in principle we should be able to get all the way down back to this afternoon level of sensitivity for the ultimate measurement so we're excited to now
10:17:50 now put these put all these pieces together and hopefully sometime soon have some new results on test of gravity at micron, or so thanks Gail, but I wanted to mention sort of more some upcoming and more speculative things that we're also excited about
10:18:05 about developing here in particular, we're looking at whether you can use these, these nanoparticles actually as a detector for gravitational waves trying to take advantage of this SEPTA Newton kind of for sensitivity in terms of applications such as
10:18:19 this, and this I think is a really exciting time and we've already heard several talks about some of the really interesting physics that we've already learned from radio waves and some of the stuff that we still are yet to learn.
10:18:29 And in particular, I want to kind of amplify one of the comments that Hartmut made before I mean we can think about gravitational detectors as sort of a tool if you want more probing the Dark Sector or dark matter and the application that we're looking
10:18:40 at in particular would be to use these levitated particles to look for Dark Matter candidates like ACCION, or perhaps other sources signal that, for example being familiar black holes in their sort of sub solar mass range.
10:18:56 So already, there's some work from the Lego group on some constraints on primordial black hole dark matter. And we think that these levitated centers can really say something to the story here potentially here as well.
10:19:08 So here's the basic principle, if you want for how that how that measurement would work. So you can kind of think about this as sort of an optical version of the old style.
10:19:19 Joe ever type aluminum bar detector. So in that in that case you have a gravitational wave coming along and in striking the detector and causing it to ring like a bell.
10:19:27 And then you observe you know the strain caused on that on that object. So in this case we imagine we trap a particle, a dielectric particle inside of an optical cavity and think of now a cavity that's much smaller than the cavities of Lego so say ranging
10:19:40 from meter scale up to maybe 100 meters. And now the gravitational wave will will will essentially change the physical distance between the end mirrors of the cavity.
10:19:51 And then when that happens, the, the trapping potential the anti node or the particle is sitting will get displaced, and then the particle will get kicked.
10:19:59 As a result of that displacement and so, so you can arrange it so that the resonance frequency of the trap of the particle in the trap coincides with the frequency of a passing gravitational waves and this way it's sort of like, to enable resonant version
10:20:12 of the bar detector. And when that happens, then the particle will get rung up into a large isolation. And so you can get quite, quite good strain sensitivities at high frequency, with this kind of approach.
10:20:24 And so this type of approach wouldn't be competitive say for example with the Lego detectors that their frequency band, but it would rather extend the frequency range of Lego detectors into higher, higher ranges.
10:20:34 And the reason is that while ago is limited high frequency by laser shot noise. In this case we're limited by that thermal Brownian motion that I talked about and those noises have a different frequency scaling.
10:20:45 So, whereas Legos and cities actually getting worse at high frequency this technique actually gets better, high frequency so there's sort of a crossover point if you want.
10:20:53 So we're building now a one meter Michelson a prototype of this to sort of test, the noise levels and to a proof of concept, but so the basic idea is that we have these two arms of the Michaelson and under a spacetime disturbance will expect to see a
10:21:12 pattern of displacement of the two suspended particles in each arms in terms of the cavity. So, the signals that we could look for I mentioned already, promoted black holes the other signal I think that's really interesting would be signals from accent
10:21:21 annihilation through black holes within our galaxy so if you have lacks whole black holes you can accumulate clouds of accents through the super radiance process, and then these accents can annihilate with themselves being their own anti particle and
10:21:35 tonight can get a monochromatic source of gravitational radiation where basically the gravitational wave is twice the mass of the ACCION. And so for a gut scale axons this, this is sort of right in the range of 100 kilohertz frequencies which is nicely
10:21:49 you know in the in the range of our optimum sensitivity band. And so we could, in principle, look for these kind of ACCION signals, whether using this instrument of different, different sizes here and using different sort of levitated sensors for these
10:22:04 different curves that we're showing.
10:22:07 And so then the vision would really be to sort of this is now very similar to some of the plots we saw earlier and I should probably add the interesting Adam interferometer ideas and other ideas to this plot to extend fill in some of the gaps that low
10:22:21 frequency but we're hoping to do here is actually fill in some of the gaps at the higher frequency and and so using these levitated sensors, then we expect to be able to cover these dark matter related sources and sort of above the 10 kilohertz band instruments
10:22:37 of various sizes, as we develop the technology.
10:22:42 Okay, so I just just want to briefly mention so all of these applications are all sort of in the classical limit right so we're thinking about, you know, just a particle in a trap and we're thermal noise limited and we're not really in the quantum regime
10:22:54 necessarily of measurement in these cases, but in fact it's possible to to now get these particles into the quantum dream, this is something that's happened long ago now for individual atoms and ions, and as of about a decade ago even larger mechanical
10:23:07 objects using cryogenic techniques and other laser coaching techniques have now been able to actually be cooled into the mechanical ground state of some vibrational mode.
10:23:16 And so back in and this is sort of showing the rapid progress in the field over the past decades, but at 2019 now this has been proven also to be possible for levitated particles by Marcus as far as group in Vienna so this opens up some exciting possibilities.
10:23:32 I think for experiments reason ultra cold particles in particular for matter wait interference type experiment. And so, So the largest objects now that I've been demonstrated to show matter we've interference are these large molecules that are shown in
10:23:47 some exciting work for Marcus Arntz group, it should be possible to extend the size scale of these things by a few orders of magnitude to these glass nano spheres and if you do that, there are many interesting applications in particular you could perhaps
10:24:16 questions about what being able to see what role exactly gravity plays and entangled in quantum systems. I won't say much about this because I I'll direct you to and you Pam's talk who's going to say a lot more about this I think in detail shortly.
10:24:30 Okay, so let me just now switch gears for the last 10 minutes or so and talk about some of the other activities that we're excited about where we're looking for dark matter either scalar dark matter or, or dark matter candidates like axons.
10:24:43 And in particular, one of the efforts we're building up is similar to one of the efforts that Hartman also mentioned this morning where we're looking for really light scalar dark matter so we have this sort of natural division of whether Dark Matter should
10:24:53 be thought of as a particle or a wave sort of with the boundary given sort of at the one EV or so level. Dark Matter could be if it's a wave you know all the way as light as 10 minutes 22 up and still fit inside of the dwarf galaxies.
10:25:08 So, in particular, If you have this ultra light scalar field background.
10:25:13 It has some energy density, or has to amplitude this radio to energy density in dark matter row dark matter and then it has some frequency that's the constant frequency of the Dark Matter field which could be anywhere in this range all the way down to
10:25:26 10 eight hertz or so, which is corresponding to this 10 minutes 22 EV level. And so, in particular, this can cause fluctuations, as it's been pointed out in different parameters and the standard model for example the mass the electron, or the fine structure
10:25:40 constant. If you have an oscillating electron mass then you have an oscillating war radius of the atom. And so if I have a rigid object like an optical cavity, then the size of the apple cavity will actually breathe or strain as that massive electron
10:25:53 fluctuates but as it interacts with the passing Dark Matter field and so we're doing an experiment now to try to measure this using a comparison of cryogenic optical cavities.
10:26:05 So the idea is you have one rigid cavity with a with a solid spacer which is going to be undergoing this breathing effect, as the dark matter interact with it.
10:26:13 And we compare the length of that against a suspended cavity which is not able to respond quickly enough to respond to that passing Dark Matter field as it as it shakes the ceiling above it, or strains the ceiling above it and so this should have Enough
10:26:28 sensitivity to get into this kind of theoretically interesting natural ranges for these, these parameters for modulation of the for example electron mass in a tabletop size cavity type experiment.
10:26:42 And there's also some exciting work from other experiments that are also showing some constraints now in different parts of frequency space, as well as the work that hard but mentioned from the geo experiment that we heard about earlier this morning geo
10:26:58 600. And then finally, one one exciting thing I wanted to talk about it more in the realm of new short range forces is, we're doing an experiment to look for.
10:27:08 Not mass coupled but rather spin coupled forces in particular from from the key city ACCION. And so there are a number of experiments that are looking for the ACCION or x sound like particles as dark matter candidates.
10:27:21 We want to exploit the fact that axons are actually forced mediator which can cause interactions with between spins and nuclei of distances as small as 30 microns.
10:27:33 The nice thing about this is that we don't need to make an assumption about dark matter or the amplitude of the local ACCION background field at Earth, we can just try to see directly as whether the ACCION exists as a force mediator.
10:27:47 And so our experiment is the axion resin interaction detection experiment or Ariadne for short. It's a collaboration between folks at these institutions.
10:27:56 And so, in terms of the parameter space for the QC ACCION it's kind of a nice theoretical target because it has sort of only has one parameter the mass is related to the, the concept for the QC ACCION and so you can really look at describing the parameter
10:28:10 space just in terms of the mass of the ACCION. So there's a number of current experiments that are running to search for for ACCION, we know from astrophysical limits the axon is lighter than about 10.
10:28:21 million EV, and then depending on the model of cosmology the axon could be light also be lighter than 10 micro micro EV level and so there's heard of a range between kind of nano or Pico EV up to, Millie EV which is really the allowed window for for ACCION.
10:28:39 And so, this is sort of a blow up of some of the recent really exciting work kind of filling in the microwave the range.
10:28:45 Well, there are a number of puzzles and experiments that are developing now to kind of fill in some gaps here on the lower end our experiment is trying to fill in the gap here on the upper end kind of looking for axons from several micro EV up to several
10:29:00 milli. And the way we do it is looking again for this fifth for so this is like my original cartoon where I had two masses it's now. One is a mass and the other is a nuclear spin.
10:29:08 And so, ACCION will mediate a potential that looks like this form, it's called a monopole dipole term, where you have a sigma car coupling between the spin of one fermion and the mass of another.
10:29:22 We have these coupling constants, one is a scalar coupling one is a pseudo scalar coupling. And then there's this one of our r squared type dependence, because it couples to the spin and the spin is proportional to the magnetic moment, we can think about
10:29:34 this as sort of a fictitious magnetic field if you want, which is acting on the spin that only turns on when the mass is brought within the competent wavelength of the axon so lambda ex fiance is fed by the mass, the axon.
10:29:46 And so, in this case, this is different than a regular and I feel that doesn't couple to Angular men are moving charges and doesn't obey Maxwell's equations for the experiment, it's important that it is not screened by magnetic shielding so that we can
10:30:03 block ordinary magnetic noise but but but this interaction persist. And so the mass so the ACCION is less than say about 6 million EV so that gives you the link scale here you want to get your objects together and sort of 3030 microns or larger to look
10:30:18 for lighter axioms. And so the principle of detection we're using is Mr. Basically you take the nuclear spin in our case it's a helium nucleus spin one half.
10:30:27 You put it in an external field, and now there's some energy level splitting between spin up and down that's basically given by the nuclear lahmar procession frequency.
10:30:35 And now we use a resonant technique where we take a mass and we bring it closer and farther away from the spin. But at the resonance frequency at the numeral nuclear long procession frequency and so when we do that, then we will drive you the axon potential
10:30:49 will actually drive the spin procession so sort of act like a transverse excitation field here and Mr. And it's driving that procession then we can pick up that processing spin.
10:30:59 Using a squid magnetometer and take advantage of the fact that there's a really high IQ here and here the IQ is from the large to time or transverse the currents time of helium three nucleus and so this gives us a nice handled to get a big resident enhancement
10:31:14 that gives us a large field that can be picked up for example with a squid magnetometer.
10:31:19 So the experiment, it's still in cartoon form but it looks a little bit more like this. In fact, we have to modulate the accent potential is mass that's shaped as, like gear with teeth in it.
10:31:31 And so as the different teeth pass by then we turn on and off essentially this ACCION potential at the period of the nuclear alarm prevention frequency and so then we do that then the passing teeth of my of my own polarized tungsten wheel here are the
10:31:50 is the device that's been driving the sprint procession. So we use laser polarize helium, to get a high polarization then we have a squid pickup loop to measure the magnetic field in the system.
10:31:57 Fundamentally, we expect to be limited by the quantum spin projection noise in the sample.
10:32:02 And so this is more getting a little more realistic now looking at the design for the bottom.
10:32:23 can tune depending how fast we stand and what a field, we apply and separation distances here on the order of a couple hundred microns for this first round and experiment.
10:32:27 Here's a picture of the prototype tungsten source mass which is about four centimeters across.
10:32:33 So then using this system this is what we're trying to achieve, as our goal for searching for an axon. So this is now the premier space with the mass of the axon at the top going for Emily v down to micro wavy.
10:32:56 the bottom, from the 30 microns up to about 10 centimeters. And then the product of these two couplings on the y axis. Current experimental limits are in this shaded blue range.
10:33:01 If you add in some astrophysical constraints combining them with experiment you get this shaded tan area, but the QC the axon if you ask where it's expected to be is actually in this darker band here at the bottom, the upper edge of the band is because
10:33:14 we have a limit on the neutron EDM we know theta QCD is less than about 10 minutes 10.
10:33:20 There's a lower band here because we know there's some CP violation already in the standard model and so we would expect data QC to be bigger than about 10 to 16.
10:33:27 And so we're aiming somewhere in this range we think in the first round of our initial experiment we hope to be able to get now to probe really into that parameter space, depending on what kind of tea to time we can actually achieve in the lab.
10:33:40 And then in a future experiment if we scale things up we're projecting we should be able to take out about half of that parameter space on this log scale.
10:33:48 If you look at the sensitivity just limited by the magnetometer by the square than it would have principle allow you to carve out almost the entire parameters pace.
10:33:55 So using other techniques where we take advantage of quantum coherence in the long term future. Our spin squeezing or something like that might even be able to Let us push down all the way to that limit in the, in the, in the far future.
10:34:06 So with that I think I'll just wrap up so I talked about a number of different MMO methods that we're developing to look for new physics kind of standard model including gravity gravitational waves testing different aspects of quantum mechanics, as well
10:34:21 as searches for Dark Matter candidates like ACCION or other wave like dark matter, and I wanted to just acknowledge some of the people doing actually all the hard work and then thank our funding.
10:34:33 Thanks for your attention.
10:34:36 Thank you very much for the very nice talk, and I'll open it up to questions for Andrew.
10:34:49 Yeah, Ted.
10:34:54 Thanks for your interest in.
10:34:57 I have a question about the gravitational wave detect your scheme.
10:35:01 Okay.
10:35:03 I guess I would think the laser intensity would have to be highlighted as my ego.
10:35:09 But then all that energy would impinge on the class bead and heated up, so.
10:35:16 Is that an issue.
10:35:17 Yeah, so it's a great question. So actually, one of the technical limitations of these optical levitation experiments is actually associated with laser heating and absorption in the article itself.
10:35:29 And so you want to use materials that have a very low measure index so that they actually don't absorb as much heat from the, from the, from the laser.
10:35:39 So, what this effectively does is make some sort of upper bound on the frequency that you can achieve in these experiments so if you go above a certain laser intensity you will start to lose the particle or evaporated even if it's a visually high but
10:35:54 but for reasonable parameters and materials we think probably up to 300 kilohertz is pretty reasonable in terms of damage on the, on the actual material.
10:36:04 There may be ways of getting even higher frequencies, if you use special materials that are doped with crystals that you can actually internally. Cool.
10:36:14 So there's sort of solid state laser Coulibaly materials which may allow you in theory to get even higher intensities if you use particular wavelengths and particular materials for the levitated object, but just using kind of silica really pure silica
10:36:28 I think that's it. Yeah, thank you.
10:36:38 glass, it should be possible to get to a few hundred kilohertz before you start to really limit, yet let me from that was that your question or was there some other.
10:36:43 Alright, Mariana.
10:36:44 Thank you for great talk a little bit more over the which sources your normal gravitational a detector on with the sensitive for I missed the point about why would the actual deletion source gravitational wave.
10:36:59 Yeah, so this is a good question. Thanks I went over this kind of. So, so I think one of the most interesting things we are looking for here with this detector is actually accidental violations and so, so if you look at the Milky Way, you know, up to
10:37:10 say distance of maybe 10 kilo parsecs we estimate something like maybe 10 to the south intended a black holes within the Milky Way and so these are, you know, fairly close by.
10:37:20 If the ACCION exists, there's a process known as the Penrose super radians process where if there's a way of extracting energy out of spinning black holes and forming clouds of black holes that can be quite long lived around, sorry clouds of ACCION sorry
10:37:36 around these local levels that can be quite long lived. The ACCION, it's sort of you can think about it sort of like a gravitational Adam, if you want in the sky where you have, you could have level transitions between the bound axons, but you can also
10:37:47 have an isolation between the axons that are in that cloud, and the if you have axons that annihilate then they can produce a single gravity on with a with a frequency that's equal to twice the mass of the ACCION.
10:38:00 And so, that frequency for a gut scale ACCION is about 100 kilohertz or so, which is kind of in this range, where were you know would be sensitive.
10:38:11 I'm still probably one of the Why don't you just produce forums, where do you print.
10:38:16 Yeah, I mean I guess there's some process right where you can produce other other signals as well but this is just based on an estimate of the gravitation emission from this case and so, so you have some energy you know marine conservation conditions
10:38:29 right and you have the fact that you're around the black hole allows for this process to happen in a certain way with certain restrictions and so forth.
10:38:38 The have also been some predictions that gravitational just black hole mergers would actually produce winter light fields.
10:38:49 Would you be sensitive to something like this. Yeah, this is a great question yeah I actually, I have to do I think more analysis really I've been excited about that idea and I haven't had the opportunity to really analyze it in detail but in principle,
10:39:02 it would be interesting to see if there would be some kind of a signature here from that as well. I think with this high frequency detector. One thing also that I didn't mention is that when you do have these mergers, you know we have a fairly high sensitivity
10:39:15 at the high frequency and and so in principle we can also see kind of high frequency tails and harmonics and things like that of those type of mergers that might not be as, you know, visible in the larger interferometer kind of detectors.
10:39:29 Is there any reason you can actually the only reason why you would see signal.
10:39:38 Background gravitational waves from inflation at high frequencies.
10:39:40 I think it's very small, yeah.
10:39:43 Yeah, I mean I think at this frequency that at least the models I've looked at and I'm familiar with. I don't think there's too much prospect although there are certain kind of blue shifted models, I'm not sure if maybe other folks.
10:39:57 There was this workshop that Hartman had mentioned, where there's a paper that came out of that a white paper looking at some possible sources but my impression was that this is the ACCION signal is probably the lowest lying target here range.
10:40:10 Thank you so much.
10:40:13 Yeah.
10:40:15 Maria. I'm great, thanks. A very nice dog, Andrew, so I have one question related to the independent force. When you put the mass is very concerned with magnetic dipole dipole interactions or some type of other type of interactions that approach as you
10:40:31 approach a dipole mentality or magnetic typo.
10:40:45 Yeah, so actually there's an analogous potential term actually that where you'd actually would would have a real dipole dipole interaction even mediated by the ACCION, so the the challenge there, you know is that, sorry I'm too many things to click through
10:40:50 the challenge there is that now if you really have to magnetic, or, you know, to spin polarized objects you have the real magnetic signal associated with the spin polarized object.
10:41:00 I mean there are tricks people have done of making objects with, you know, with a lot of spin and not much actual organization you know if you arrange things in a clever way so you can kind of suppress the real magnetic field at some level, but but the
10:41:11 challenge in doing this Spin Spin experiment is that oftentimes you have to contend with the real magnetic background, much larger than you would have, in the case of and polarized object interacting with the polarized spin.
10:41:25 In our case, we're extremely sensitive to regular background magnetic field fluctuations from noise at our frequency range of interest and from a number of different sources, including things like you know magnetic impurities and and other other kinds
10:41:42 of effects and so. So, in this case, you know the the challenge of one of the big challenges here I didn't talk about the technical details so much on the screen but one of the big challenges is really to get a really pristine environment around the the
10:41:56 spin and that in the way we do that is using a superconducting shielding and closure to eliminate some of these magnetic backgrounds.
10:42:11 Ted Did you still have questions or comments or was that hand from before.
10:42:18 Okay,
10:42:24 there any more comments, questions for Andrew.
10:42:33 I actually had something I was curious about so when you talked about detecting forces that very short distances, what what kind of scales did you go down to.
10:42:45 Yeah, so we're looking primarily at kind of the micron, like scale so sort of one microns our object in our trap, I think I want to go too far into the object is about 400 nanometers away from the metal surface, in our case here, that and then that surface
10:43:01 The object is about 400 nanometers away from the metal surface, in our case here, that and then the surface itself is a few hundred nanometers thick so we're kind of talking mass separation distances at the micron at the micron range, and then in terms
10:43:11 of projected sensitivity. Something like here I say between hundred nanometers up to 10 microns, we should be able to make some kind of improve search, I think.
10:43:20 And are you looking for something specific like do you have to rule out backgrounds from known forces and stuff like that. Yeah, that's actually really the name of the game with these measurements is not only about getting the sensitivity but it's about
10:43:30 understanding what it is you're looking at that, that's on top of the signal. So the big the chasm mirror effect for example is about 10 to the five times stronger than we're trying to measure.
10:43:40 And the way we deal with it is by rendering it sort of a DC background that doesn't vary when I move my mass pattern, you know, behind the mirror, if you like.
10:43:49 There are other things like spurious patch potentials and things that can cause surface you know interactions between the nanoparticle and the and the surface and so as a way of characterizing that there's different tricks that we use.
10:44:01 So for example if we, if we change the location where that, that honestly mass is moving behind the mirror if we if we say very the equilibrium position of that isolation, we would expect to see a particular pattern in the force if it's really due to
10:44:15 to the density modulation, where it would kind of get strong and weak and strong and weak again depending on whether the heavier gold pieces next to the nanoparticle or the lighter silicon pieces next in that program so that's one that way we can kind
10:44:26 of scan, what's going on behind the surface to kind of tease out those effects. The other effect is the approach that I showed you where we just demonstrated this scanning method where you can actually move the particle kind of over the surface and kind
10:44:39 of map out the local area in terms of how quiet is in these terms of these, you know patch signals and other kinds of backgrounds, with trapped typos and things like that.
10:44:51 Okay.
10:44:57 Okay. Um, so
10:45:01 thanks thank you Andrew again and we'll move on to the next talk.