10:50:05 So for the next talk. We'll be back to the table top four or less, and it will be Holger Mueller from Berkeley, who's going to talk about Michigan to the final structure constant and entanglement of masses, or perhaps has changed his title we'll find
10:50:21 out Peter, it's all yours. I'll give you a five minute warning.
10:50:46 One is a measurement of the fine structure constant, and the other is using atom interferometry with atoms held and an optical lattice, and what you can do with it.
10:50:51 Okay.
10:50:52 After Jason's excellent talk this morning I do not need to spend a lot of time and introducing atom interferometry, so that's just remind people that these are the trajectories, often atom on its way through and that's I'm into from it to the x axis is
10:51:09 time the y axis as height. The Atom comes in at a time t not there's a matter of a beam splitter and the form of a laser pulse to split the atoms between an upper and the lower interferometer arm.
10:51:24 We use Mira pulses to move the interferometer I'm spec together and then they interfere at the final beam splitter. Here's an actual picture of atoms and our lab, and the interference fringes at that moment are such that most of the items are in the lower
10:51:40 output and if the face changes by 180 degrees, then they will all be a via the face difference between the two and two from our arms is determined by the engine of the padlock integrated along those arms, and the laser baffling acts as a ruler for reading
10:52:00 out the interference fringes leveraging the precision of laser frequency stabilization for the face readout.
10:52:09 I want to drive home one important point and that is directly into from it escaped their enormous sensitivity from.
10:52:17 They get that from the fact that the face difference between the arms can be millions and even billions of Radiance Lion of one radium change and the face leads to order unity change in the detected atom number, meaning apart per billion change or even
10:52:35 less leads to nearly hundred percent change in the detected atom number at the detector to drive that home I have plotted those interference for ingest the content item number is function of face to scale using Mathematica.
10:52:50 And you see about the have to zoom and many many times before we see the fringes.
10:52:55 And this here is actual data taken by Kenya, Chang at Stanford.
10:53:02 Many years ago so this is not my data and this is not even state of the art data. And of course as Jason has explained in the future everybody will be trying to make this even better.
10:53:13 So interferometry gives you a long level arm to measure a tiny changes and convert them into a large change of a measured atomic population.
10:53:25 What's it been used for. They've already seen that it's been used for testing gravity and quantum mechanics and the stem for 10 meter atomic function.
10:53:35 It's for another example have been used to measure the gravitational constant big g by geometry union Florence, and we'll be talking about the fine structure constant.
10:53:46 What is the fund structure constant why is it important and how is it measured. Well, there are two types of fundamental constants the most well known ones, unfortunately are really only unit conversion factors the speed of light has units meters per
10:54:03 second. and it would be useless to remember its exact value.
10:54:08 And for physicists, because the numerical value would be completely different using different units in fact the theorists can get away with not knowing the speed of light and meters per second but just set it to one by choosing appropriate units.
10:54:22 But then there are fundamental constants that are the same and every system of units, and they are statements about nature, rather than our measurement standards, the fine structure constant is one of those as well as one over 137 and change in any system
10:54:40 of measurement. And it is the ratio between measurable quantities such as for example between the board level splitting the find structure or between the rest mass of an electron and the board energy.
10:54:57 These are all given by various posts of the fence structure constant, because the fans structure constant is important in all of physics methods from all of physics can be used to measure it.
10:55:06 This shows the situation of a couple of years ago, measurements has been done by spectroscopy, or may only using neutrons, measuring proton magnetic moments and by the quantum Hall effect.
10:55:19 But the most accurate of the model are either come in two flavors, either measurements of the electron gyro magnetic anomaly, and Washington and Harvard by Jerry Gabriel's or measurements of the ratio of the plan constant and the mass of atoms.
10:55:38 Before it showed you how to do that here a little footnote on the International System of Units. The International System of Units has recently decided to assign a fixed value to the plan constant.
10:55:51 Okay.
10:55:53 So in some sense that would justify me saying that we're measuring the mass of cesium atoms and not just HR MCs, but fortunately physics is independent of such semantics.
10:56:06 Why measure it very precisely, and well defined structure constant and the magnetic moment is kind of a lucky case and physics.
10:56:14 If defined structure constant is measured for example by atom into from a tree to extremely high precision theory can calculate the electromagnetic moment to extremely high precision.
10:56:28 can be combined and compared to another accurate measurement. So we have three ingredients here in this comparison between theory and experiment, and they are all enormously accurate, in some sense, This is the most precise comparison between theory and
10:56:51 experiment in science.
10:56:54 And why is it important.
10:56:55 This graph shows you some of the contributions of the standard model, and really not just quantum electrodynamics but the Antichrist and that model to the prediction of G minus two, there's of course the first five artists of quantum electrodynamics.
10:57:11 But then there are the famous hydraulic contributions that are so thorny to evaluate for the me on the week interaction is only about an order of magnitude away from mattering.
10:57:23 If you look at this, then the hope of course, is that maybe we have overlooked a particle or a fundamental interaction. And if that's the case, then maybe an enormously precise repetition of this theory and experiment comparison can uncover the missing
10:57:42 element.
10:57:43 That's the hope here.
10:57:46 We've all heard about the Mian g minus two mystery I will not say too much about it but for the longest time, it looked like there was a four sigma or so discrepancy between the Standard Model prediction of the Mian magnetic moment, and the electron and
10:58:04 the theoretical prediction and this has most recent has recently.
10:58:09 And this measurement has been repeated formula.
10:58:13 And the significance of the discrepancy is not stronger it's 4.2 sigma has been called one of the strongest pieces of experimental evidence for physics beyond the Standard Model back singly.
10:58:26 There is also a new theoretical result that claims to explain why the G minus two is on this side and that opens up interesting questions of its own. Let's just say that a lot of interesting physics can be done.
10:58:40 I should say that the electron. The both theory and experiment for the electron is way more precise than for the neon because the electron is lighter that makes it easier to evaluate some of these effects at high precision, but it is, I would say, equally
10:58:57 interesting.
10:58:58 All right. How do I get the fine structure constant from Adam into from a tree, I'm looking at this equation parts of which are familiar to my students and my quantum mechanics class.
10:59:10 This is nothing else but the energy of the electron and the lowest bore orbit, and as low energy physicists, we wrote right that sh time see times the Ripper constant, whereas the high energy people would write it as one half alpha squared MC squared.
10:59:27 Those two are by definition of constant the same.
10:59:32 And I can solve this for alpha, and use that to determine alpha from the ratio of the plank constant, to the mass of the electron.
10:59:44 But that's not very well known as the electron mass and kilograms is not well known enough to apply this, but it's very well known as the ratio of the electron mass to the masses of atoms thanks to the measurements of class Blom and Heidelberg and other
11:00:02 people. If we can measure. Therefore, if we can measure the ratio of the plank constant to an atom mass and combine it with the ratio of the electron mass to the atmospheric console for alpha, and then make the theory and experiment comparison, how to
11:00:18 measure Hm.
11:00:22 He has that Ramsay birthday as a mentor for amateur and rich. One matter of a packet stays at rest, subject only to gravity hence the line is curved, and another partial matter of if packet is kicked up flies for a time t and this then kick back down,
11:00:37 while the second wave packets are separated, they accumulate a measurable face difference that is written here and the term of interest is this first term proportional to the required frequency.
11:00:50 That's the kinetic energy of the atoms motion in hertz.
11:00:55 And it's given by the plan constant times the vape number squared over to, em, so if I know the wave number then I can recall measurement will give me HMS desired.
11:01:09 Unfortunately, elegant as this scheme is, it is actually enormously sensitive to gravity and one man signal is another man's noise. Right.
11:01:18 Various the experiments that we've heard about by Jason are looking for this gravity term we are trying to not measure the gravity term. Unfortunately the gravity term is larger than the records from so we have to find a way to suppress it.
11:01:34 The first is to make the signal that we want larger, and we do that by large momentum transfer atom optics as Jason has talked about in particular by multi photon BRAC diffraction by the atom absorbs for example five photons from the first beam, and is
11:01:49 stimulated met five photons into a second team, so that it receives overall 10 photons of momentum kick.
11:02:01 Because the kinetic energy goes like the momentum square, this doesn't just give us a tenfold enhancement over a single photon atom optics gives us 100 fold enhancements so that's very useful and gives us this factor of level and squared here.
11:02:17 The second way to improve the situation is to cancel the unwanted gravity term and we do that by what because simultaneous conjugate interferometer is just lower atom interferometer, the one I've just shown.
11:02:31 And then there's an upper atom interferometer which is essentially an upside down version of the lower one.
11:02:38 And by adding the two phases together, the gravity term cancels out, and the recall term doubles. So now we are ready to measure the fence structure constant without being limited by our ignorance of how strong gravity is exactly.
11:02:53 I should mention that this interferometer is so sensitive that the standard vibrational noise in our lab, makes it impossible to see interference fringes.
11:03:05 But fortunately, the two can be correlated to form an ellipse, so the scrambled phase of the first interferometer together with the scrambled face of the second interferometer form an ellipse, the stochastic le bearing face due to vibrations determines
11:03:22 which point on the ellipse we get in a particular run of the experiment, but the shape of the ellipse can be fitted to determine the needed differential phase
11:03:34 final ingredient is necessary to improve the sensitivity of the answer from its are sufficiently and that's blah oscillations at the center that used to accelerate the upper interferometer further up and the lower interferometer further down that increases
11:03:52 the face, and so that it looks like this equation at the bottom and the nice thing is the number of block oscillations can be made very, very large so that the resulting signal is very large.
11:04:07 Another nice thing is that the number of blood oscillations can easily be very right. And we can use that to repeat the experiment at various numbers began to look for systematic effects.
11:04:20 Here's what the setup looks like it's a standard atomic fountain it does indeed fit on a table top its height foot and theory enabled us to use a time of light of up to a second but an actual fact we never do with that.
11:04:34 The reason for that is that the systematic effects. Go up for the time of flight faster than the signal we're looking for signal we're looking for is proportional to the signal from gravity gradients is proportionate to Tq so in actual fact we never fly
11:04:53 the items for longer than about 200 milliseconds.
11:04:57 Here's some data.
11:04:59 When we measure our alpha we scan through past separation times from five milliseconds to 80 milliseconds and fitting that to the expected phase as function of time of flight gives one determination of alpha, and then we go through that for days and days
11:05:16 and days.
11:05:18 One day of the beta roughly gives one estimate of alpha and in the end they are combined to a global average going through with these in real time allows us to spot misalignments of the setup that would give rise to a deviation of the expected behavior
11:05:38 as function of tea.
11:05:40 Okay. It's very important and precision measurement to not be biased by knowing, and by comparing your data to other people state of you therefore adopted applied analysis, and even after we were done with the arrow budget, I will talk more about the
11:05:58 arrow budget later so skip this slide for now.
11:06:02 Even after we're done with nailing down all the terms of the era budget. You still repeat the experiment, over and over again and look for variations of alpha, birth,
11:06:16 with all sorts of variations for example your run the experiment for the lower contrast on purpose and see if the value of alpha shifts and so on.
11:06:25 And only after you're satisfied that all these experiments, either here, no variation of alpha, or they reappeared a variation of alpha that you understand quantitatively and that you can take out.
11:06:38 Only then you I'm fine.
11:06:41 And when we unblinded, there is a look like this.
11:06:45 So let's look at only the three most recent This is the previous atomic physics measurement of alpha point six six parts per billion accuracy.
11:06:55 This is g minus 2.24 parts per billion accuracy and this is us point, 2. billion accuracy.
11:07:04 You see that we are fully compatible with the previous atomic physics measurement but there's a two and a half seek my discrepancy from G minus two.
11:07:13 And I would say the bottom line, the zero or the message here is the two numbers determined by completely different ways.
11:07:22 Agree to the park pavilions level of precision which is great, but very curious and we want to know what could the two and half signal be due to.
11:07:35 Well, first let's put it in context of the Standard Model theory. These lines are the current accuracies of G minus two and alpha and you see that the accuracy is good enough to see the contribution of the moon on at about 10 sigma.
11:07:48 To see the fifth or the acuity effect at a couple of segments, and to see those hydroponic shifts that are so thorny and the Mian measurement. Also at about 10 sigma, but we're still an order of magnitude or wave or so from seeing the talent from seeing
11:08:04 the week interaction
11:08:07 that to describe discrepancies between me on me the Standard Model MP electron and the standard model can be plotted and common coordinates and then if you look at how good a job that's the standard model do at predicting laptop magnetic moments you'll
11:08:24 find that the standard model is about five sigma of, which is actually quite a lot.
11:08:30 The signs of the discrepancies for the mayor and the electron or opposite, and so there have been theory papers and this is way above my pay grade, I was just mentioned that for completeness.
11:08:41 There are theory papers that say here's a model that explains, both discrepancies and there's also been theory papers that argue that the two discrepancies must have different reasons because they have different signs.
11:08:57 Anyway, future of alpha, what to do from here.
11:09:02 Well one important element of the future or of the present actually is a new measurement, done by the Paris group, the same that whoops what's happened.
11:09:13 The same that had measured this data points here. Okay. And they now find a value of alpha that is slightly to the right of the GM minus two derived about you.
11:09:25 We can speculate for a bit by that might be and it could have to do with the fact that the way the laser beam is pretty parents but on the whole I would say they did a solid job here there is nothing that would say oh this is the reason, obviously, and
11:09:41 and science but we need is not speculation, we need data. So if we want to improve the measurement of alpha even further.
11:09:50 I will say one thing.
11:09:51 When our experiment, and their experiment reconstructed scientists did not understand the imperative to create very clean speck of free laser beams, very well.
11:10:08 And so our new experiment they'll be the first experiment that has been constructed from the ground up to create an extremely pretty laser beam. And now let's look at the budget.
11:10:21 A large number of error terms for example the gully face Bayfront curvature and so on, scale with the size and smoothness of the laser beam, the more close the laser beam as to an ideal client base, the better.
11:10:35 So all those terms and the Arab edge, it can be dealt with by making the laser beam larger and cleaner.
11:10:42 About terms and the Arab budgets, such as the gravity gradient can be dealt with by better characterizing them.
11:10:49 And so even though there is a large number of terms in this era budgets, we expect that a new experiment can address many of them at the same time. And they're ready for an order of magnitude improvement.
11:11:03 This is how it looks like they have constructed, and recently baked, a large diameter vacuum chamber, that is very suitable for giving us a clean laser beam because it minimize the scattering of the beam at the walls.
11:11:19 There's a new atom into from it a geometry to cancel the gravity gradient, and they're working on a several hundred watt laser system to fill the enormously thick laser beam in this chamber with intensity.
11:11:33 If.
11:11:35 With that, I want to close the fight structure part of this talk by thanking the people working on it sec pagan met ben stein and jack Roth, our grad students here is sick if it's a postdoc who has recently joined us from bytes man and there's a host
11:11:59 previous people also collaborators at Lawrence Berkeley National Lab that I'm indebted to. Before I close, I want to spend a few. How much time do I have from here on.
11:12:07 Let's see if you could finish in seven or eight minutes that would be good. Okay, I'll try to make it seven and a half, I want to talk a little bit about a new paradigm and as a mentor from a tree, very well not measure things by dropping out of time
11:12:22 spent by holding atoms.
11:12:24 So I've talked about cavity and so from a tree.
11:12:28 Let's build an optical cavity around the ultimate perimeter, what are the benefits we get bigger higher laser intensity, we get smoother and more well defined laser beams.
11:12:40 So let's try that,
11:12:43 the cavity is actually very pedestrian it's about 40 centimeters long, and has a fitness of only about 100. The reason as we want the cavity to act as a good mode filter, but we want the line birth to be large enough so that we can still drive ramen transitions
11:13:01 and practice direction without trouble.
11:13:04 Okay and the sweet spot is a fitness of about 100.
11:13:09 And this is how the machine looks like when it's finally assembled, this is fake a show she's been grad student on this project will not join the Lego group as MIT as a postdoc, and what can you do with that two applications, I want to mention briefly
11:13:24 the first SB, use the machine to measure force induced by black party radiation gradients. If there's a hot object inside your vacuum chamber. This metal cylinder heated by a laser from outside.
11:13:42 Even that's hundred degrees see it emits black body radiation most of the black body radiation is ready tuned with respect to the atoms, and the gradient of that causes an attractive force of atoms two boards, the heated object.
11:13:59 This was stunning to us with hindsight Of course it's completely clear that this should be expected but stunning is that this causes microns per second squared accelerations,
11:14:11 which is thousands of times higher than the intrinsic sensitivity of atom interferometer is. And so this shows, if you actually want to measure gravity very precisely without some into from access.
11:14:27 You have to control the temperature of your vacuum chamber very well.
11:14:29 The second application is detecting fifth fifth forces caused by exotic theories of dark energy for example that committee on particle.
11:14:38 And you can see that they've repeated this experiment twice and each time, had about a factor of hundred improvement and sensitivity relative to the previously known limit.
11:14:51 Okay.
11:14:53 But let's move on and how can we use cavity interferometry to realize long interrogation times. I don't need to spend time to cost to talk about very long baseline interferometer such as this one on construction and Hanover, or the one and Stanford.
11:15:10 There's also efforts to run atom interferometry and free fall on the space station. Because long interrogation times are good.
11:15:20 But you reach a point of diminishing returns.
11:15:23 What if you want to hold the atoms 10 seconds, you would have to build hundreds of meters tall.
11:15:30 Or, maybe we can hold on to the items, and this is an idea indeed that was first realized by others in 2012, and then repeated by the Tino group and they got a whole time of up to one second, limited by the in homogeneity of the optical lattice used to
11:15:52 hold the atoms. And so we thought great, we have a very homogenous laser beam and the optical cavity maybe we can improve on that.
11:15:58 And so here's what we do. The autumn starts like a standard Ramsey birthday item interferometer only now, we use the cavity mode as a beam splitter.
11:16:10 Then when the atoms are addressed, be turned on an optical letters were restored the atoms for a while, and then be turned the optical lattice off and repeat the beam splitter sequence to bring the two partial vape packets to interference.
11:16:27 And here are some interference fringes that be obtained early on the face difference, actually, unlike the standard mentor for amateurs they face their friends and this outcome is a formatter is almost completely determined by the free of illusion face.
11:16:45 During the lattice hold, which is essentially given by well the difference in the action between the two paths. And I will note that curiously it is proportional to the proper time difference between the two locations.
11:17:01 And then let's see if we can gain the whole time so French after point two seconds still has 80% of the theoretical the expected contrast.
11:17:11 The one second, it's going strong.
11:17:14 Five seconds. Contrast starts to drop a little bit, but not too much.
11:17:27 After 10 seconds contrast has dropped further but the fringes are still very clearly visible in the first talk I presented that ever I presented this in real time so now we're at about 50 seconds, 15 seconds, Mark.
11:17:35 And finally we could demonstrate interferences, even after 20 seconds.
11:17:40 So here are two spatially separated based packets, hell it's separated by the article that says, for 20 seconds and you still have fringes.
11:17:52 One practical aspect right this is a good thing is that, in a standard atom interferometer you flush the laser on at three or four times, and only and those times, do the atoms, interact with the environment, meaning if you have time dependent perturbations
11:18:10 such as vibrations, you're going to alias them, and you have way more noise than you should have.
11:18:16 But thanks to the lattice hold the lattice hold interferometer averages over those vibrations and so if you plot the vibration sensitivity as a function of frequency, you will find a very strong suppression of the unwanted sensitivity to vibrations.
11:18:34 We have demonstrated that with data. Unfortunately, the data is not shown here but that matches the theoretical curve beautiful the
11:18:46 current state of the artists that the contrast decay is the slowest for very small spatial separations and as faster for longer spatial separations and a model generated by my postdoc Chris panda explains that as a result of atoms thermal orbiting in
11:19:07 the lattice potential I won't have time to explain that in detail.
11:19:14 So in the future we'll try to make this better longer holds better contrast and then we can either use that as a compact vibration insensitive perimeter.
11:19:24 We can try to measure gravity of smaller masses to explore gravity at smaller scales, we can go for gravitational a higher enough boom effect and try to show that there's a face difference generated by gravity in the absence of classical forces.
11:19:42 And finally, and versus an idea that really is due to Jake Taylor and den Carney, we can try to do the old to answer the question if I have an object in a superposition of being at two places.
11:19:59 Which way does the gravitational pull from the object pole is the gravitational pull also in a superposition If the answer is yes, then that would show that gravity is a quantum field, or is it not, in which case gravity would be classical various all
11:20:14 the rest of the road is quantum and that's a very strange prospect. You can find the details in this pre printed by Jake Taylor and then Carney.
11:20:24 For now I want to thank the people I'm working on the cavity atom into from it's very here's some of the people of the early hours met Jeffrey he's now a postdoc at University of Chicago, Vicki I mentioned, Chris panda is the poster right now.
11:20:40 Logan used to be our postdoc until he got door by the green pastures in finance and James ego half is now a grad student Miquel Andhra undergrad students.
11:20:53 Thank you very much for this fantastic workshop and for listening to my talk.
11:20:59 Well thanks for a great talk you pretend a lot of results and a lot of future directions as well. So what questions what comments what suggestions do we have.
11:21:21 Let me ask one.
11:21:23 Can you speak more about future plans for doing the classical versus quantum gravity experiment, the last one you mentioned on your previous slide. Yeah.
11:21:34 So what's the.
11:21:36 So this is an idea that's obviously not our idea, and has been talked about at the very least since Fineman, but the elegance of this new proposal and I'm bragging about it because it's not my own idea I just claim credit for it.
11:21:52 Right.
11:21:55 If I misrepresented Jake Taylor is here I might be able to correct me but the idea is this.
11:22:01 If they're gravitational interaction is capable of generating entanglement.
11:22:08 And that question, that it's a question, not a statement because classical gravity such as described by general relativity is not right.
11:22:17 If that's the case, then that can use it to entangle.
11:22:22 I have an atom that's in a superposition of being in two places. And I can entangle that state with the state of a classical harmonic oscillator close by using gravity.
11:22:34 I could try to demonstrate this entanglement by conducting both measurements at on the atom and measurements on the harmonic oscillator, but the scheme described in this pre print shows that it's not necessary to do both measurements, you can prove the
11:22:51 existence of entanglement by showing that the atomic interference fringe has a modulation and visibility in particular this collapse and revival of the interference.
11:23:04 Yes. Now the contrast is not very large, It is determined by the strength of the gravitational coupling.
11:23:23 But and this is the other great idea of Taylor and Carney, it can be enhanced by a running the interferometer at a high temperature. This is an intuitive result and I spent a lot of time, verifying it and I'm convinced that this is right.
11:23:31 And it can be enhanced by.
11:23:35 Let's say biasing theatre from itself by generating an initial entanglement using non gravitational forces, because now we have an effect that's linear and the gravitational interrupting string.
11:23:50 Joe Welcome to Ask follow up questions but I'll leave it at that for now. Yeah. Why don't we go to Andy, who's had has been up.
11:24:00 Hi Holger very nice talk. So I had actually a question on the same proposal, so I just wanted to get a sense for what kind of separation distances, you're imagining between masses and things like that for this.
11:24:15 Quantum gravitational test that one sentence answer, but don't forget to get a second sentence to the one sentence answer is smaller is beautiful.
11:24:27 But the key experimental challenge is how close can I get the harmonic oscillator to the atoms, without screwing up the performance of the atom interferometer, and the limitation here that I can see right now is really that anything close to the laser
11:24:47 beam because optical diffraction and that will mess up our beautiful optical that is also, if that's messing up up the off the lattice is dependent on the possession of the harmonic oscillator, then this alone will generate an interactive effective interaction,
11:25:07 many times stronger than gravity. So there needs to be some sort of shield between the mass and the atoms.
11:25:14 And I want to put in a plug for beautiful result by one of my former postdocs Charles you learn who's working at Nanchang University in Singapore. He realized, an atom interferometer inside a hollow core optical fiber.
11:25:31 So that shows that at least in theory such a shield is feasible, even on a small things.
11:25:38 So to make the experiment happen people try to see how close can we get the oscillator to the atoms, and then go from there. All other dimensions like the optimum splitting between the vape packets and so on, scale that that distance.
11:25:54 But what to mention one feature of the signal here.
11:25:57 It goes like the whole time of the atoms to the fourth power.
11:26:02 Okay. So by having 20 seconds, we have already come a long way to making this term big, and by even improving the 20 seconds but just the fact, but just 50%, or, or maybe doubling it.
11:26:17 That would make this sector a whole lot larger too.
11:26:24 Thanks.
11:26:26 Okay, a new pam,
11:26:30 panko very nice talk and I just wanted to touch upon the last point, what Andy asked. So, if I recall from our paper which is, and is also involved in I think we would require massive roughly of the order of 10 years to minus 14 kilograms.
11:26:47 And you have to create a shortening your cat state with the separation roughly around. microns, hundred microns. Now, then only you would get an entanglement phase you to gravity would be roughly of the order of one.
11:27:03 So, so that's the reason I think perhaps Andy was also asking this question that what exactly the you know shorting jacket and estate you want to create and how massive your system should be and how long will you be able to measure or observe the entanglement
11:27:19 phase to make it something somewhat observable, maybe yes so the answer to all these questions is, there is no safe approach here, there is no separation, there is no duration that I can promise that would make the experiment definitely feasible.
11:27:40 All these parameters have to be improved, relative to what we can do now, the pre print outlines scenario, assuming hold times have around a minute. But let's things are fair grounds 100 micron, read the numbers do work out.
11:27:57 And I should say this gives rise to a visibility modulation, less than a part per million so it's barely measurable. Right.
11:28:08 But even those numbers, even if this number sounds scary. The reality is more scary still because, for example, while we have demonstrated 20 seconds whole time so that 60 seconds doesn't sound terribly much longer, right, that has all been done without
11:28:27 any objects, close to the optical lattice. So, getting the same whole times and extending them will get a lot harder.
11:28:36 But, but neither kind of shielding.
11:28:39 And, by any chance Did you also study the recurrence rates and how will the system has to be.
11:28:44 Yes, and I had a slide that I showed on the very briefly so here's the measured contrast as functional full time for various separations.
11:28:57 And here's an outline of the model, imagine that the article letters as a pancake shape potential so imagine you're a partial faith Packard's in one of those pancakes, your temperature isn't zero you have a kinetic energy and so you describe one of those
11:29:15 orbits inside that potential.
11:29:18 Right, carpets could look very complicated, or they could simply be circular and your part though, partial packet and the lower pancake is describing a similar orbit.
11:29:32 If these two orbits.
11:29:35 Separate too much from one another, then upon interference that contrast will be very low.
11:29:41 And so this model does a good job at explaining these curves, and it also points out what we need to do in order to improve things even more smooth optical lattices will obviously help.
11:29:54 And what will also help is to make the two pancake potentials more similar to one another by putting the fitness part the rest of the laser beam in the middle between the two five packets and not to the side.
11:30:11 I'm sorry if I'm not very quantitative here maybe Christmas and the audience and he knows those numbers.
11:30:19 It's okay.
11:30:20 Thanks. Thank you very much. Sure.
11:30:24 Yeah john Mark Russell you had a hand up Do you still have a question or suggestion. No, it is exactly the same question was asked us okay that's fine.
11:30:32 Yeah.
11:30:33 Okay. Um.
11:30:37 Any more on Tigers talk or related things.