Okay. Good afternoon, everybody,
and welcome to scarily what is the last physics Friday afternoon colloquium this academic year which seems to have gone in a flash.
It's a great pleasure today to welcome our old friends for lunch on the patio, who is a very distinguished accelerator physicist.
So Swapan has had his finger in most of the big accelerators which have been built over the last 30, 30 years.
In one way or another, he's been associated with those.
He's held a number of senior senior positions at just one lab at Lawrence Berkeley in 2007 eight,
he moved to he moved to become the first director of the Cockcroft Institute in Liverpool.
And where he was has been responsible for pulling together a large part of the UK's accelerated science efforts.
And of course the other part of that is here at the John Adams Institute, part of the John Adams Institute.
And so following his retirement from from the Cockroft Institute,
he's now a distinguished scientist at Fermi National Accelerator Laboratory, and he is a visiting professor here.
So it's a great pleasure to welcome him today as he's keen to talk to us about quantum sensors.
So forget. And you'll hear me, you know.
Okay. So I give my top ten accelerators last week, so today is not going to be anything to do.
It actually is because I can afford and I think after 40 years of being in that field,
we are kind of hitting the wall and maybe you should think a little bit differently to address
the same questions with the same expertise that one needs for particle beams and lasers,
but slightly time differently so that you can do something in a reasonable length of time with a finite amount of money.
But that means a bit more thinking in a slightly different way.
So Quantum Sensors is a topic today. So I simply introduce you to that idea which is not new to many of you UK and very strong quantum
technologies activity and I'll talk about that a little bit on the roundtable that I chaired very recently,
which may lead to a new initiative in the American side about how to compliment particle accelerator based particle physics astrophysics,
cosmology by quantum sensor based particle physics,
astrophysics and things like that give you a I don't have time to go through all the examples, but to give you a couple of examples,
one from a particle physics, cosmology, dark matter, dark universe sector,
one from gravitational wave sector, which also connects with inflationary cosmology a little bit.
The just hint that we can also existing for many, many other things like, you know, neuroscience, material science, geoscience and bioscience.
And so I probably would not have time to talk about quantum computing, but the whole idea is that countries like UK, USA,
Canada, they're spending a lot of money in quantum information science, hoping someday they will have a quantum cryptography.
From my perspective, that's probably 100 years from now.
But on the way as you go there, you can actually pluck some of the fruits of the scientific R&D that can benefit basic and applied science.
So okay, so I just want the whole bunch of people you can see is a very mixed bag of people,
not all particle physicists, not all affiliated people, but people of different mix that have helped me.
I also want to thank Andre for sitting here.
Ian is missing and John who introduced me for for giving me the extended offer to come here every year I enjoyed last year.
This is my second year and I hope to continue next year. Okay.
So I will start with this slide that says I am a builder of instruments and I
believe in this philosophy that if you just if you build a new instrument,
you have to understand what is being built for the science.
You do not have to be an expert in the science because you have to interpret it and understand it enough
that you can give the scientist you are into that they are science the best tool that they can have.
And then you can advance the science and it gives the feedback, just like Galileo and his telescope, right?
So Quantum Sensors is actually a new tool that's like particle accelerators with drives.
Quality beams are tools is a new tool,
a new instrument that actually fundamentally depend on a quantum phenomena or quantum entanglement at the very core of it.
And it has a promise for very weak to to detect very weak processes.
So it can give you very precise and high resolution information about very weak
with processes that can enhance this very good start for fundamental science,
quantum information, science and computing. So what is actually a quantum sensor?
Everything that you sense ultimately is classical is giving you a charge or a electric current or voltage,
which is all classical, of course, and measure with some real instruments.
However, if the source of that signal is fundamentally related to a quantum system,
and in particular if it relies on superposition of quantum states which are entangled,
then in principle it seems to us the instrument that you been with on that principle tend to give you higher position or higher, higher resolution.
So hence the new initiative on how you can have fundamental and information science based through quantum limited macroscopic sensors,
or you can actually have macroscopic computers based on Quantum Limited or performance.
So I'll give you some examples of quantum.
So, for example, here is a squid invented by Professor John Farquhar actually from Cambridge originally, but then I started from him at Berkeley.
He was there for a long time, is still there. And nowadays he could have squid that can grow up to 20 miles 16.
That's the pursuit of Hertz type of sensitivity in magnetic fields, power spectrum.
You can have accelerometers, which uses atomic beams of some sort,
that can give you a ten to the -13 g of go to the earth giving that field of acceleration.
These are incredible numbers. You can have superconducting cavities, microwave cavity that had a few factor of ten to the ten.
And using quantum information technology, you can actually put a qubit inside a cavity and measure a single photon,
which is not a noise photon from the amplifier.
You can, after the couple come out of this cavity and make gravitational distortion of the space time metric,
and you can look to the electromagnetic field of the superconducting cavities and measure strain at the level
of 20 -18 people that are talking about superconducting follow metre photon to their superconducting circuits.
Of course, if you look at the quantum optics of the circles, they actually deal with a fluctuating electromagnetic field which is still coherent,
but due to the very small number of photons, like five or ten or one that microscopically correlated.
Here's an example of a coupling of mechanical motion with optics.
You have transducers, and if you if you look at the space and from KG to central brands to Hertz to ten gigahertz,
you can actually have all kinds of opto of two mechanical actuators that can operate in the nano micro macro domain,
fantastic sensors that one can build. And finally, people have used, of course, atoms, molecules and trapped audience, and they've actually can.
So yes, these are actually if you look at starting from a centimetre all the way to an angstrom,
which is the atomic level with MRI, nothing like squids.
I'll quote now, this is nitrogen vacant diamond.
Well, actually, you get down to very, very small resolutions indeed.
So all these sensors, all they are actually they are either they exploit quantum effects,
including the entanglement aspect of it, either in solids or in atomic systems or in some kind of a cavities geometry.
And you actually use all these things to actually help the field of quantum information science.
But as I said along the way,
you probably can pluck the low hanging fruit and some of the areas where you could find applications are like you can sense new particles.
They're everywhere. They don't have to be just created in a collider.
If you are sensitive enough, have a very good hearing aid, you can hear a particle without being created in a collision.
New types of interactions with gravitational waves can be used to probe the very, very, very early universe before even the event horizon.
During inflationary phase, if there was some kind of some kind of inflation nature of the dark universe,
biological signals of extremely weak signal from the brain, neuroscience, geosciences, all so.
So that's quite a bit. So the whole idea is that the funding agents in my field,
which is accelerators and some other fields like atomic physics, laser physics, defence theory, they work together.
I think that people are, you know, pursuing different disciplines in different areas.
But at least in my field where everything is driven by very large scale science,
either you do space borne experiments or you do a certain base experiments.
They're expensive because you have to create energy density in a laboratory to actually get the effect.
But the whole idea is that experiments have been done already and somebody did it and we already have all the things around us.
We just have to be smart enough to search for, like in archaeology, rather than trying to recreate all the stuff to find the easy way out.
The easy way is not easy anymore. The laws are expensive and so we have to think a bit differently.
That means things we have been. Investing in for the last 50 years.
Maybe we have to think a little bit differently, and that's the whole idea.
And with this idea in mind, there was a roundtable that was held at Department of Energy.
I was asked to chair co-chair it together with two others.
I guess I was there because I'm coming from the traditional laser beams physics side of it that have benefited particle physics for the last 56 years.
There was also two more people.
One come from the photon side, Roger from Tony from Berkeley on one come from that really quantum sense aside from Harvard.
And we were supposed to have a one day roundtable and we actually had it.
And this was supported by the entire complex of various agencies,
high energy physics and mass computing B And basically the sciences that funds all the light sources in America National Science Foundation,
which governs metrology of things. It's kind of similar, but quite different from the ones.
And you had a one or two year long quantum technology hub discussion?
I was part of it in the in a very painful way.
And that also, you know, brought out a few roadmaps for quantum technologies that stressed the technologies of various things like atomic clocks,
new materials and stuff. And the main difference here is that we had a whole bunch of particle physicists, computer scientists,
basically energy scientists who actually want to use the sensors to do basic science.
And so that's that's the major difference. Eventually, the composition of this people, the very hand-selected people, about 14 or 15.
And there are some people who could not participate but give us contribution in a
remotely in a whole bunch of agency people that you can see them the top heavy,
all the funding agency. And then there are some international people you see and want to hear it, you hear in audience.
Is he supposed to be so good at that?
Oh, yeah. Uh huh. I've been trying to catch him.
Oh. So we included him. Of course. He was very busy, did not have enough time to contribute.
But we are getting contributions from all these people. And the whole idea to come up with a blueprint and a short report for duty and then
then interact with the international body of people to see what we can do with it.
So some of the things I'll tell you that came out of it before I give you some examples of that stuff which are really fascinating,
is that we came up with the thing that if we did it right,
we probably should be able to, by design, put effort into quantum systems of five, ten, 15, 20 years that are not only for the technology of it.
We should definitely spend a lot of benefit to society,
but we probably can make a big leap through in physics of processes at very high or very low energies, either very high meaning rather than TV.
I've never done to the precise measurements we go beyond what we know about systems today.
It could also help us explore the understanding of the so-called Dark Universe gravitational wave,
which cannot be saved by lasers very long remnant low frequency gravitational wave,
which controls all of the cosmic history, quantum materials, all kinds of new materials,
quantum simulation of chemistry, which is very, very difficult. But our bio sensing, geo sensing and also quantum computers themselves,
meaning networks and machines that can be engineered and truly put in programming if I put a little one
line are almost everything and also the reason that we can be involved in this kind of an activity.
And of course there were some observations that in order to do this, you have to think differently.
You have to probably follow the appropriate interdisciplinary community for them to talk to each other.
You have to kind of deliberately pump prime so things can be advanced,
actively continue and sustained effort not yet to year effort, which America does every year to change our budget.
Five years of year, 5 to 10 years sustained effort to a bunch of teams that can more progress identify impact on other areas.
Importance of you know collaborate with with international partners like UK Quantum Technology Hub and so on, optimising resources.
We don't necessarily have to have more resources, but obviously analyse the same metrics,
but the diagonal to be out of a different axis, meaning the precision probing then high energy radiation of high, high density.
Okay. So now let me give you a few examples. I cannot give you very many, but let me just give you a few examples of how exciting this would be.
One is the cavity electrodynamics coupled with quantum information science algorithm
that can actually make probably make a big dent in understanding dark matter,
we believe, without really going through a collider or space.
And the second one is actually this technology of atomic beams instead sort of lasers,
which have to be reflected by mirrors and mirrors, inertial objects that are subject to all kinds of vibrations.
If you are free falling atoms which do not have any vibrations in their fall,
but they simply sense fluctuation on the metric which is the space it is vibrating.
A space is undulating that way. You should be able to sense it by that on the wave function, by the phase factor of the quantum information.
So those two are very good examples.
I skip this too, and then maybe they are brain mapping, not the details, but people are looking into functional mapping of the brain.
They will map the brain in terms of neurones and axons and all the networks through very complicated,
coherent synchrotron radiation and terahertz imaging. But that physical mapping, what I'm talking about now,
the functional mapping of different functionalities through magnetic and electromagnetic activity of the brain.
Very, very small magnetic fields. Many of them occupy responsible point about the list you have, which is Google.
Certainly you can do dark energy tests using that laboratory scale.
It's worth remembering that that's not correct.
Not that I'm familiar with the artificial waves. Definitely yet.
So intense dark energy that is large. Well, it's always there's a very nice result in the place where I can talk to you about it later on.
I think the gravitational wave test must connect somehow to dark energy in a very conceptual.
I do not know how to do that. We can talk about it. Okay.
So let me just quickly, those of you guys from students that I know if got not do something for those of you who know all this already,
I'm also a student but but basically the standard model of amateur, inquisitive, incomplete, completely normal people.
I've seen classically, if you look at the the rotational velocity and look at the mass inside this,
then we know that it doesn't quite match to obviously there's some kind of a matter which is not visible,
but still interacting in a major way, gravitationally and through for lack of imagination.
We call it dark matter. So that's there.
And then also standard model of cosmology is incomplete because we have discovered by the
expansion of the universe through supernovae that probably there is acceleration of this,
of this, of this expansion and probably there is some kind of a field or dark energy.
And so we do not really know what it is. And that, again, basically very simplistic model of that.
For those of you that know that there is this model of field manipulation based on the size of a typical universe
and you try to balance out of gravitational force with the pressure of of the system and you try to balance it out.
But actually, when you observe the actual motion of this of this galaxy, they don't quite match up.
And they have to you have to introduce a little number here to actually match numerically the
field of the supernova expansion and the actual thing to try to measure this object very,
very precisely. And it's not going away. And so it is.
And so this object either is a fundamental object or there's some physics behind it.
And the whole idea that I'm talking about is without questioning whether it's real or not,
we are telling my take on it that is their way of testing anything that is associated with this extra term physics behind it.
Okay. So let me now, so this this whole thing, then this to today's pie chart, you've seen this for many talking.
We talk about this thing, which is our ignorance of most of the world, except for 4%,
which is a baryonic matter, which I have been working on for 45 years, three accelerators.
So this is not provocative. After all these years, we have not really been touching this 96% of the thing.
So it's probably time for us to think about we can probably never get there by
particle accelerators because it's just impossible to take because there were.
So maybe we should think slightly differently to sense phenomena that are in the laboratory already, but very, very weak.
So and if you just put some numbers in there,
I'll just put some numbers for for undergraduate and graduate who actually know this energy density of expansion.
You know, if you if you imagine how much is the dark energy density that actually corresponds to this number?
And if you imagine this is not actually electromagnetic, but if it were,
then Maxwell's would be square and the electric field that corresponds to that actually corresponds to 12 square metre dark matter,
of course, is even more much, much denser. Right. Dark matter, if you look at it, is actually ten kilovolt, familiar kind of feet.
So these are non-trivial numbers of the actual energy that we are talking about that
one should not think that one come a do something in the laboratory to sense them.
The problem is if these are fixed DC.
As a background DC bias of some voltage or some energy or background mass.
It's very difficult to see something without a bias or if somebody fluctuating or changing it.
And you know, we are looking at AC effects over a DC background and in a sense everything is a fluctuation of a vacuum anyway.
So it is actually the proper way of thinking about what level of fluctuation above these levels can we expect conceptually,
theoretically and can measure them no matter how small are these are the quantum sensors which are actually turning out to be extremely sensitive.
So. And in order to do this analysis, fluctuations are not sufficient unless you can measure them at two different points and correlate.
So the whole idea is actually you have to be able to do this in space and time in a
coordinated fashion so you can actually get a measure of the strength of the power spectrum,
of the fluctuation and the entire thing behind it.
So here I will just tell you my philosophy.
Some people, some of my friends, I coming from the instrument side, I do not question the observations as much.
Let the people who take the data make them more and more precise.
But I'm going to say that at some point, maybe they are real effects.
How come we actually do experiments to prove, to verify?
I have one example from the past.
If you look at the plants law of Blackbody radiation and the plans constant, it was simply, simply used by planning just to fit a curve,
a bar of just a fitting power, an indefinite lambda in a fitting pattern of the expansion of the thing.
Right. However, it is not that because pretty soon there was photoelectric effect, we saw the light come from packets and each contender.
And then there was the spectra of the hydrogen atom which are each.
It turns out that H was not just a fitting parameter, it was something more.
If there is a fundamental contradiction. So far we are just too early.
Lambda is not turning out showing up anywhere else, so it may be a constant given to us.
Not what you can do about it. Or maybe there's something that generating it. We are.
So we are going to leave that judgement for future. I'm not going to assume that is just a constant given to us by nature.
So so then the question is how do we how do we measure this?
And so if you look at the dark matter universe, it just it's all over the place then many, many theories.
There's nothing really has been observed today. Some people thought the massive particles could be detected in Large Hadron Collider.
There is no indication of any massive dark matter candidate.
Some people are saying amazing light particles, maybe light photons,
which are dark like for every particle of light as a dark particle of light of the ring for particle connections which could be generated.
And these are all very light mass particles, but no one one can imagine to look at how do these particles couple the first couple of gravitationally,
which we know, because that's how they got the heart of the couple.
Even if the very feeble coupling with the standard model in some interactions, how do you measure these these couplings by their very small DC effect.
So imagine a very shielded volume where ordinary light or matter cannot penetrate, but dark matter can penetrate.
And then you could actually put a sensor inside this volume that can detect the very small coupling of the dark matter with ordinary matter,
giving you a real particle of light from light. And that's the kind of detection that we are talking about.
And here is where this clarity and superconducting qubit technology comes in.
I give you a simple picture here. If we imagine a shielded volume and inside there's some kind of a electromagnetic circuit,
which is a oscillator which can measure something coming in,
something the sensor is completely shielded by ordinary electromagnetic radiation, so no ordinary matter can get in that.
But dark matter, of course, can get in.
And you have to detect the coupling of this very, very weakly coupled up to this internal circuit at this level.
Okay. And if you see a single photon that is coming inside this volume that resonates with the resonance frequency,
and that photon could not have come from anywhere else, and that photon must be a real, real photon coming from from copying from the real particle.
And so so that so that way you can do an experiment where you just have a cavity and the flux of hidden particles or dark matter is going through.
And you convert that flux of hidden particles with the oscillating fields into the oscillating fields of the cavity.
And there comes a question of even not know the coupling of these two fields, how strong, how weak.
And so we need to really know that we need to assume in the field the extremely weak so that you could actually have a chance of detecting it.
And so and this is where we are. We are talking about electromagnetic cavities, which are superconducting.
And so let me give you an example of even that. Up the line resonators, which are not unfortunately very high IQ.
They don't ring for a long time. Then they have superconducting aluminium cavities, superconducting niobium cavities, a very high IQ.
Nowadays they are going over ten to the ten.
But there's a lot of noise inside the volume coming from amplifiers, even when they are cool to zero degree temperature.
So we have to eliminate that noise spectrum.
Just to illustrate for those of you why superconductivity in this particular application,
if you look at the normal conducting RF cavity, of course you pump in some kind of power, could be any kind of religious pulse.
And of course, because it's normal conducting it does not stay for too long.
Losses and stuff decays and then you have the again.
And so if you have a very strongly coupled system which does not need renewing for a long time, that's okay.
But you've got a very weakly capital system you need for the ring for long time so you can cumulatively add up the interaction.
Right. So this is for example, superconducting this like for all action of dark matter, such people are looking into superconductivity.
This was kept on ringing where I tell you the ten, ten to the 11, if practically infinite, I want to talk.
Does it? So just to illustrate that a bit more, let me give you an example of a two very simple two pendulum,
which are very weakly coupled, and you will see the energy will be transferred from one to the other.
So I'm would put one out and that's going to very the connected slowly over time you will see energy transfer from this one to that coupler.
That oscillator will pick up all the energy and this one will be addressed almost.
And then that will transfer all the energy to this one.
Then this one will be addressed and so on and so forth. The different long time to build up information.
This is coming up positive. See this? It's almost definitely now and most of the energy is transferred to this guy
is almost stationary and all of that ticking again and it'll go up slowly.
So over many, many cycles the transfer of back and forth with us weekly double thing.
But if we have a strongly coupled thing is if.
I was beginning to transfer to the other one. Okay.
Let me now do this. And you will see very quickly within three or four oscillations the changes back and forth.
Very simple demonstration for this quickly as it done now.
So depending on the coupling of the this dark matter field,
which is oscillating in time with the cavity feel and depending on what you have to have very high kill systems.
And this is why most of the superconducting RF is used for dark matter.
Such is superconducting, not room temperature.
That is not sufficient because even if you get a signal inside the cavity at the same frequency of the cavity,
that will mean that you have seen a particle with a mass that is equivalent to the frequency because it could be a noise photon.
And this here comes a problem of noise that even if you cooled down classical amplifiers to very cold temperatures,
you still have one background photon, the zero point photon left after which the amplifier lies.
Now this noise, now it is. If quantum mechanics allows us to understand noise, and that is the tuition fees.
And people actually have been able to have technologies that can squeeze the feed.
Information of the knowledge is not important to us,
but we just want to know that there's one photon which is the right fork on a lot of noise photon as the what they do,
they simply mirror the entire phase and they have total, absolute, almost absolute certainty that that's a little photon.
So, you know, the photon number is a concert number, so you do not kill the photon number in that.
And so you introduce all kinds of phase kicks to distribute the phase so that you are allowed to measure the photon count.
Precisely. And so this technology is actually being used.
We just found out last year very successfully in quantum computing community and being funded by Department of Defence laser.
And we have never been able to use this in the setup of a cavity that we use today, particle accelerators dealing with dark matter,
people searching for it, but they never been able to put this kind of a cubic circuit inside it, what we can do.
So now we have a collaboration with University of Chicago Cubit Group and a superconducting RF affiliated group
and the Dark Matter Action Group at Fermilab to actually do the next generation cavity based search for Axion.
If you put down the numbers, you can immediately see that so far people have been getting all these small areas.
If you look at the mass of that's the only large logarithmic scale on the microwave scale and the coupling thing.
Even after in one sweep,
if you could have a major large volume of a cavity and the superconducting cavity would tend to return to the level kind of a cu.
And if you can put the stupid circuits inside, Discovery will actually wait long enough and you can actually discriminate and
you can actually count and see if there's a foregone that a certain mass and
not so clearly for dark sector photon for epsilon four actually allows it becomes
a bit more difficult because it is not sufficient to just have a cavity.
You also have to have a magnetic field coupled to the quantum numbers of the actual and RF cavity.
You do not like to be living inside a very high field, so this is a problem,
but we think we definitely can address the question of hidden photon very accurately in these in this paradox,
but it is still a little 100 times bigger face space than what we have to do.
Epsilon requires magnetic field and we are actually looking into it.
How to how to make that a separate problem, isolate the cavity from the field problems.
And I just want to give you some example of that.
This is actually a real work in progress, taking into account a collaboration of parking further people,
detector people, quantum gravity people and dark matter.
Such people are Fermilab to do this experiment.
So next generation admits three or four will definitely take advantage of the quantum sensors to sense dark matter inside a superconducting cavity.
Okay, now let me. So, therefore, Galileo told you about it.
Really? That is a very funny collaboration. We are not used to it.
We are learning this collaboration for the whole idea of this workshop was to bring us together
so that we can actually do this lesson is controversial and this is atomic being part of it.
And the whole business is you know, we just saw recently the gravitational waves, right.
And when I was a graduate student give talk and everybody came, there was talk of black holes and stuff we saw.
And I never thought that you would see gravitational wave like that, two black holes merging, but actually saw it.
Right. And this was a coherent wave. That was.
That was emitted by the merger of two black holes at a coherent rate.
And you see it propagates. It probably here they probably give them a decent enough order.
So that's, of course, all good and legal did it.
But Labour had a frequency which is very high and long for a short lived and compared to what it needed for particle physics connection.
I'll tell you what, if you look at some people have computer experts here who know better,
that signals of gravitational wave from sources that are out there in the cosmos,
merger of other types of binaries that exist between the mini hertz and the ten hertz.
And what's more important to me, at least, is because I have some background in stochastic noise and feedback systems,
is that if you believe this theory of intelligence,
which I was just trying to understand, it is probably it's a matter of faith or not, but inflation has not been tested.
It's a very elegant theory.
However, if it is true that you want to probe something beyond this horizon and the inflation came to an end and then start to grow slowly,
then no other probe than gravitational waves that are coming from that era.
And you can imagine that having such an interesting heart and you begin to slowly extend.
There was some tremors, felt gravitationally.
So the metric of space was disturbed. And we must be still feeding that rumour.
We must be still feeling that earthquake. Our empty space today coming from the crunch of inflation and people have computed what's the measure?
What kind of what strength could that gravitational background noise could be?
And then can we then? So this is really a demonstration that these are really actually these are fuzzy lines we
got this will build me a new is not quite three metres is three metres plus or -227 metres.
Right. How do I measure that, that thing.
And so we want to use atoms because atoms are inertial objects and we don't have to hang them from something.
And we want to measure the first shift of a falling atom over a long distance to measure whether the spacecraft is historic or not.
And that's the whole, whole idea.
And I think calculations show initially that you can probably get to a frequency range of 1000000 hours to ten hertz if you use atoms,
and hence all the excitement about atomic beams. Okay,
so here is the scenario I just borrowed from particle physics finds that out that this range of Largo and so this Largo here and
we are talking about this range and this is basically you are trying to understand and the coupling of gravitational physics.
To particle physics coming from the evolution of the cosmos be inflation.
And so you need to have some kind of a probe.
And we think that these atoms are the probes and that, of course, they had in the paper, something that some of you may be familiar.
I'm not going to question the inflationary physics of it or the calculation of the expected distortions of the gravitational
wave background noise coming from this tremor that might have happened and then an internal impression that might even be real,
I don't know. But if there is some level of gravitational jitter in the space metric, we are trying to detect that by recently.
That's the whole idea. And the other purpose of the I'll just show you what that proposal is, is basically it's not following interference.
I'll just show you the picture first and then I'll I'll come back to that.
Well, what it is so basically the proposal is to have two atomic interferometers, not laser interferometer,
because they said you don't want to be diverted by the, by the vibration of of inertial mass separated by a kilometre.
And you measure the distance fluctuation of this kilometre from the rock, from the gravitational wave background.
And actually there are possibilities because at Fermilab we are building this huge, very high power neutrino.
We with very heavy megawatt protons, which of course are helping them get these neutrinos of what I think I'm contributing to the traditional karma.
However, this new thing sent it along is too big, came to five kilometre back.
And so, you know, if people know the technology of atomic beam interferometry 1015 metres,
if we can handle it up to a certain level of sensitivity, it should not be infrastructure.
Why is that difficult to put two of them on the shaft and see if one can get an atomic interferometry reading of gravitational waves similar to Largo,
which measures the infrared things coming from pre-invasion.
And we cannot say no, we have to look into it. Right.
And that's the whole purpose of of of doing it, not just to be very naive and explain the thing to my junior colleagues.
So so here the atomic beam interferometry is basically this.
We have an atomic beam.
Did you prepare it to very close and high performance dates and then by laser you manipulate this atomic being as it falls under gravity,
it goes to two different parts. And then you bring them together and you look at the atomic beam interferometry at the bottom.
And so it looks kind of like this from being the wave function.
Let the fallout go up against gravity or fall, and then they come back.
Then the laser beam, they been together and you create a little interference level here.
So the phase of the atom changes to the fall through the gravitational distance being changing.
All the stuff is recorded in this thing. And of course, as I said, to do it properly, you need correlation.
It's not enough.
Just what you want is a fluctuation of this thing and not just so you need to know the fluctuation of whatever is fluctuating at different points.
And so there you need to have two and hence you've got to have those up and bottom.
And you actually, if you are naive and you just made you don't get anything out of these because these signals are so small,
they add up in in root mean to zero.
But if you wait long enough and if you collect the fact that there is nothing is constant in life,
everything is changing, the metric of space is changing.
And hopefully if you if you have proper data analysis anyway, you probably will get a zero phase between the two interferometers.
And then you have to interpret this is not coming from anything other than what you are trying to look for.
It may not be gravitational wave that is causing it. It may be something else.
Maybe some inertial stuff happening on the on the highway and on a49 or whatever the whole task is.
Then to understand the noise sources that can get an effect of that on being as it falls the gravity.
But people are looking into it and like other people of course have done extensive job of lasers being affected by mirrors and stuff.
They have created very fancy mechanical suspensions that can cancel out noises so atomic beams have their own problems.
Again, this is a technology never, ever been pushed to this limit because in order to do this,
you have to get a sensitivity of ten -15 G, not generally -12.
That's a that's a three or four magnitude more. So the atomic beams people who are getting funding.
From Defence or other agencies are doing up to 20 months, nine months, ten months, 11.
The challenge for them is can they do it? And are the two, three or four magnitude benefit could be useful for gravitational wave search.
The Stanford guy you look, I've done it out of the previous people. I'm doing it.
Here is a little laboratory set up often that we can see the problem.
These are running, being set up and it takes a lot of effort to do these.
It's not just a simple mechanical thing. You see, the beam is going to be formed.
It coalesces and you see it last for a certain length of time.
And then, you know, the lifetime is not really long enough to do everything in a lifetime.
When the beam is produced, you drop it. Initially, you know what, ten metres, nine metres.
And then they disappear. And then and then you're not sure what are the sources of this Philae floating at them?
They're not quite free. They're not mechanically suspended, but they're trapped by certain electromagnetic fields.
So you have to understand those noises. And so. Okay.
So I think I motivated that.
And I think the reason people are optimistic is the tremendous progress in atomic physics, atomic clocks, and that is incredible.
So there's optimism that maybe if I put some directed effort into it, we can get to it at some stage.
Simultaneously we are looking into can you simply used to superconducting cavities?
Just cavities are a coupled but they are gravitationally captured in the sense that gravitation introduces strain into these and then that strain
transfers into all kinds of more transfer between these two cavities is not quite the same as the reverse cylindrical receiver of gravitational waves.
Slightly more complicated if they had to regain circuit of two superconducting oscillators that are talking to each other.
I'm told that some people are doing to work on it and that's a long way to go.
But again, to measure the signal, we probably have to use cubic type of technology.
Finally, let me close by something where I have no expertise,
but I know some people are working on measuring very, very small magnetic fields around your your neural activity.
So people image your brains physically,
which give you a map of the neurones and excellent stuff and the basis of intelligence or creativity in a very complicated subject.
We used to think you'd have to do that for your ability to do logical things.
Mathematic is not quite true to all kinds of other things come in that creates an entire thing called some kind of intelligence or creativity,
and people are trying to try to understand it. And of course we all know why it is important for us.
The first thing that comes to mind, you can create new science and innovate and enter society into so the very, very primitive mapping of the.
So people have done very detailed physical mapping of the brain and it's like protein crystallography.
But unless you connect it to the function of the protein on the membrane, you don't quite get to the biology of it.
So people know kind of the two hemispheres and the connectivity of different human activities and so on.
But each one of these activities comes with a very specific set, may I say lot of the normal modes of magnetic field configuration, they don't.
It's like when the protein folds, it does not fold arbitrarily.
It falls to a certain set of problems.
Similarly, when some activities are happening in the brain, these are not arbitrary magnetic field patterns acting systematically,
the magnetic field patterns which have different modes of functionality.
So the idea is to map out those modes magnetically numb destructively, because you could destroy them many if not destructively.
How can you devise a magneto instead from a graphic helmet with quantum sensors in it?
And you can actually you can actually stimulate certain activity in the brain.
And this is a big, big field, actually. It's very, very light field, probably very, very profitable field also.
So I just plug there.
I think so I think I've said this and similarly, geo signals, biological signals and people are working on new types of materials, all kinds of stuff.
I don't have time to talk about it, but here is my basic thing is that there is real potential, at least in my field,
where we're dealing with very large scale experiments and missions to maybe to think a bit cleverly in a medium scale.
That's a scale, even the very clever listening capability. And actually it is very exciting science and you can engage in a lot of very
young people and getting fruitful results in three or four or five years time,
a lot of it four, six, seven, eight, nine, ten years to get data and then get to know.
So I think it will be very important to keep our field active.
And yet so there's some creativity and.
We have come back here just to tell you that the problem we have with the quantum thing is that if you have one particle,
you can control it very well, but you don't get much signal.
If there are many particles, you get a lot of signal of how to control.
So how can we get quality information? And quantity of information from the quantum sensors is a term of struggle.
And so while you can have a quantum sensors of some sort, this competition between quality and quantity is always going to be a problem.
I'll end up with a simple analogy, which is very provocative,
but I'm using it quite a bit because what we have been doing in our field is this thing we don't know what there is.
That's the [INAUDIBLE] out of it. If you are never comes out, catch it.
Hey, look, I got this and that, but maybe there's a better way of doing it.
A lot of smart people conjecturing, theorising very good theories as to why not do this.
Very elegant, you know, fly fishing instrument. That means that the theorists are going to tell you,
but you have to have the ability to throw the thing in the right place, in the right position, to get the right fish.
And I think it's time that we put some effort into that direction.
I told him, See, that Oxford particle physics definitely cannot afford just to do colliders and and fixed target beam physics at Fermilab or Japan.
And you guys have all the expertise in optical physics to actually do this double work for particle physics and astrophysics,
cosmology and for material science and all of that stuff.
Thank you for listening. Thank you.