Hello, today we're going to be talking about the Bose Einstein codenstate. Now for those of you who really know what you're doing already, here's the short version. Once upon a time, wave fucked its anti-Semitic country exchange then Furbyans and went very cold, Pauli Exclusion principle. However, if Symmetric then Boseons and Bose Einstein codenstate the end. Kevin, you can't do that! I'm sorry about that. In case you're not quite up to Kevin's theme, we'll elaborate a bit. So what is the Bose Einstein codenstate? When we cool a substance down until it's really really cold, a Bose Einstein codenstate is one of the possible outcomes. This means that to understand a Bose Einstein codenstate, we need to examine exactly how matter cools. So what exactly happens when we cool stuff? When particles are cold, they lose heat, which means that they vibrate more and more slowly as they lose thermal energy. As they cool, the atoms cluster closer and closer together. Imagine a waddle of penguins or a bumper car ride. The more slowly the individual particles move, the less space there will be between them. In our case, the question is, how close together can they move? Can they all pile into the exact same spot or is there some minimum distance that will always separate them? Oddly, both are correct, but they apply to two different types of particles. The easiest way to identify these types is by looking at whether they obey the Pauli Exclusion Principle, which says that no particles in the same state can occupy the same point in space. The first type of particle, known as a fermion, obeys the Pauli Exclusion Principle. This means that only a small number of them can be in the same place simultaneously. The other type, which does not obey this principle, is called a boson, and an infinite number of them can therefore all pile into the exact same place at once. The electrons are much more interesting for us, because these are what form the bosieinstein condensate. Some examples of bosons are the element isotopes helium-4 and ribidium-89, and non-atomic particles such as photon. Therefore, if we cool any of these particles down to low enough temperatures, we should observe the formation of a bosieinstein condensate. The resulting problem is how one goes about cooling particles down to several billions of Kelvin, because no traditional method of cooling will do the trick. So one asks, how do you cool something down to the point of forming a bosieinstein condensate? The solution here is using the laser. The sample is loaded onto a so-called laser trap that has lasers pointing at the sample from each of the six coordinate axis. The lasers are tuned so that the wavelength of the beams are slightly longer than the electronic transitions of the atom. So as the atom moves towards the beam, the Doppler effect takes into effect by causing the beam to appear slightly more viewed to the atom, causing the wavelength of the beam to appear shortened, and will be at the exact energy level necessary of an electronic transition. Hey, can anyone explain to me why I just woke up stuffed into a closet down the hall? Don't worry about that right now. Now that you're in a way… No, no, no. Now that you're here, he means… Oh, yeah. Now that you're here, why didn't you just help us in explaining laser cooling? So now we have an atom that's sitting in a laser trap with laser beam pointing at it from all sides. How exactly does this cost the atom to cool down? Well, let's imagine that we're on the atom itself looking outwards. If the atom moves in any direction, the beam will look a little bluer because of the Doppler shift, and the atom will be able to absorb a photon. The atoms have momentum, and so in order to preserve momentum, the atom has to recoil in the other direction, kind of like a feed shot a little gun at it. Pwup, pwup, pwup! Now eventually, this absorbed photon has to be re-emitted, but it's emitted in a random direction. And so, if the atom is absorbing many photons from one direction and re-emitting them all in random directions, the net effect is to slow down its motion in that direction. By using this technique, we can actually cool atoms down to very, very cold temperatures, sometimes within a few micro-calvin of absolute zero. Unfortunately, the photon re-emission after the absorption defines a limit on how cold we can get the atom. Once the atom's motion is caused only by these random photon re-emissions, it is no longer possible to cool the atoms via this so-called Doppler cooling. So Doppler cooling is incredibly useful and incredibly fast. We can actually cool things from room temperature to a couple of micro-calvin on the order of seconds. Unfortunately, it's still not quite good enough to get us to the temperatures needed for a Bose-Einstein condancy. So what do we do from here? We use the exact same mechanism that you've probably used to cool yourself on a hot day, evaporation. In our collection of ultra-cold atoms, some atoms will still have more thermal energy than others. By allowing the high energy atoms to escape, we can lower the energy of the remaining atoms even further. Eventually, the energy of the leftover atoms becomes so low that they all coalesce to form a giant ball of wiggling, jiggling stuff. This blob of stuff, which contains hundreds of thousands of atoms, piled on top of each other, is what we call the Bose-Einstein condensate. This method of cooling that Kevin has just described so, elegantly, was employed by researchers in 1995 to produce the first ever Bose-Einstein condensate, 71 years after Bose and Einstein first predicted their existence. The first Bose-Einstein condensate of photons was made less than two years ago, which reminds us just how recently we've been able to observe this phenomenon. In the future, these types of breakthroughs may have practical outcomes and lead to a much deeper understanding of the quantum effects that govern our world. Currently however, they mostly serve as a time-consuming pursuit for the intellectually curious. For those who see the Bose-Einstein condensates, as exactly the type of classical rule-breaking anomaly that makes exploration into the world of quantum mechanics so freaking cool. The first Bose-Einstein condensate of photons was made less than two years ago, which reminds us just how recently we've been able to observe this phenomenon. In the future, these types of experiments may have practical outcomes and lead to a much deeper understanding of the quantum effects that govern our world of quantum mechanics.