How they did it: 410 nm laser, Doppler, Stark shifts, simulations

1:25:26>> This is going back to our bigger stadium instead of our muonic smaller >> stadium. Now we're trying to do the same thing but with our bigger stadium. And with a bigger stadium there's a lot more problems. >> Yes. Yes. >> And it's just incredible some of the stuff that they were dealing with. Dude, >> it's it's actually insane. Okay. the the transition that they were trying to figure out was this 6p orbital to 2s. So all the way up there to like down here there's that transition. That transition releases >> violet light at 410 nanome. >> Okay, >> that's the first issue. >> Okay, >> violet light at 410 nanometers. That's really short wavelength. We've got

1:26:06lasers at like blue and green and red. We don't have lasers in violet. Okay. You can't just buy that off the shelf. You got to make a laser at 410 nanometers. Okay. >> Okay. >> So, that's something that they had to do. They actually took like a titanium sapphire laser which operates at the infrared at 820 nanometers. >> And they effectively did like a trick where they um stuck that inside a nonlinear optical crystal. And what this crystal did was, you know how when you like play guitar and um you like strum on one of the strings, but then if you like clamp down in the middle, then

1:26:48you're going to get the octave higher. Yes. >> Right. That's what this crystal is doing. >> Okay. >> It takes in a laser light at 8 820 nanometers, but then effectively squishes the wavelength by by half. So the frequency goes up by two and then I get a 410 nanometer. For music producers who use keyboards, it's the jog wheel on the left is the same idea. When you jog the wheel up, it >> Yeah. The octave just goes up. This is just like it's going from, you know, a C to the uh the C. That's the dodo. Yeah. You know, it's just the octave is is now up. >> Yes. Makes sense. >> So now we've got a laser. >> Right. >> Now we've got to cool our hydrogen atoms down to 5 Kelvin. >> Trivial, you know,

1:27:28>> trivial. [laughter] Honestly, at this rate, this is this is pretty trivial. Okay, cooling them down to 5 Kelvin. But even at 5 Kelvin, these hydrogen atoms in your cloud of hydrogen atoms that you're trying to like probe, those hydrogen atoms are moving at hundreds of meters/s, >> which means there's going to be some moving towards you, some moving away from you. So there's going to be Doppler shifting, right? And so if you're trying to measure the frequency of light, >> well, the guys that are coming towards you, >> they're going to be sensitive to shorter wavelengths. the guys that are going over away from you are going to be sensitive to the longer wavelengths. And so you're going to have a Doppler broadening of your transition line. And the whole point is I really need to measure what frequency this transition

1:28:09line is at. >> Yes. >> Okay. So that's going to be a huge problem. >> We don't want a range. We want an explicit. >> Yeah. >> I want like this is the frequency. >> Yes. >> Right. And so here's what they very cool. What they did was Doppler-free one photon spectroscopy. Effectively, the idea is they custom built like these active fiberbased retroreflectors, okay? And what it's going to do is it's going to fire a laser at the atoms. The atoms are going to capture it >> and then it's going to and then the atoms come back. >> It's going to reflect that perfectly back into the atoms. Okay. >> The other thing that you want is you want this beam to be perfectly straight. >> Mhm. >> The beam of the lasers, it can't be like

1:28:52spreading out as it [clears throat] goes into my apparatus. And the usual optics that's built for 486 nanometer wavelengths, which is blue green, >> you can buy that like kind of off the shelf. Okay. There's like specialized science companies where you can buy that stuff. >> Sure. >> If it works for 486, it's not going to work for 410. >> Okay. At at that at that like frequency, like it's it's the opposite of diminishing returns. Like every nanometer is a headache. So, you need to build custom optics such that my beam is like completely straight. >> My new purple laser that we also had to custom make. >> Yes. >> We have to keep it in line. And so, we need these custom like literally like

1:29:33optics glass lenses >> that keep it in a line. >> Yeah. >> And because it's a frequency where most optics are not built for it, that purple laser, it's fully it has to be fully >> custom. Yeah. Yeah. So, the whole thing is like a custom apparatus, right? And then and then on top of that there's like the quantum hurdle which is you're you're you're putting in light in here, right? And the light is like bouncing back because of that earlier thing that I said. Well, if the light is going there and bouncing back, now you've created a standing wave. Same thing with the guitar. When you like pluck a string, it's fastened at both ends. So the wave is going to go back and forth. It's going to create a standing wave, right? There's going to be nodes and anti-nodes. Nodes are going to be where the light piles up.

1:30:15>> Anti-nodes are going to be where there's nothing. Yes. >> Now, usually you don't care, >> but when we're doing a precision measurement where we've put hydrogen into the 6p state, the electron orbital is a little bit like it's not spherical, right? And so, because it's got these nodes, that electron is going to start caring about where the anti-nodes and the nodes are because the electric field is going to be higher here, lower here, higher here. And so, the the hydrogen atom that you're trying to >> understand is now getting perturbed by the system itself. Right. >> And so they had to make so many like Monte Carlo supercomputer simulations to model what would the electron do. >> Right. >> In this space.

1:30:56>> Yes. >> And and then correct for that. >> Right. Right. Because because it [laughter] >> there's so much headache which is why this took like 10 years. >> That that makes sense. It it's it's effectively you have to remove the noise. >> Yeah. It's called the stark shift. >> Okay. Okay. Right. And in order to do that, you kind of have to you have to simulate first. Yeah. >> Because it's too expensive to do it experimentally all these times. >> No, but yeah, it's like Well, it's like the experiment has this artifact >> in it in it. So in itself, I got you. You need you need It's like um it's like when you have a Google photos and it's the feature where you take a photo of you and your loved one in a crowd and then they have the Google magic eraser

1:31:37and you just select someone's head behind your head and then and then it's gone >> and you shoot it up. That's exactly what they're doing, right? Yeah, but but they need to build it and like do the Monte Carlo simulation completely >> in order to then be able to even have the thingy that will remove the noise. So they they have to >> like [laughter] >> it's nuts, >> people. I love the I love the uh the just the drive to not be beaten. >> Yeah. >> By mother nature. >> No, [laughter] dude. No, it's like it's I will figure out what the size of the proton is. You are not going to stop me. [laughter] >> Okay, it might take me 10 years, but I want to know how big the proton is.

1:32:17[laughter] >> That's so good. Okay, that makes sense. >> Yeah, it's it's absolutely nuts. And finally, after all of this, they publish their measurement. >> They publish their measurement. >> Okay.