Demystifying Spooky Action At A Distance, with Sean Hodgman

[00:00:00]Because photons travel at the speed of light,  if you just measure entanglement with that, you could perhaps come up with some sort of  explanation like that. But in our system, we measure it with atoms. Our atoms move very  slowly. What happens quantum mechanically is that when they do the collision, they go this  way and they go this way at the same time.

[00:00:15]Are you saying you're entangling atoms? Wow.  Yes. Exactly. So, so most of most entanglement so far has been done with things like photons.  God, how do you deal with this every day, man?

[00:00:39]This is Star Talk Cosmic Queries Edition. What  is the subject? Quantum entanglement. Chuck, are you ready for this? Never. I mean, let's  be I'm just going to be honest. Haven't you and I been quantum entangled for a while? Yes,  without a doubt. Um, anytime you feel pain, Neil, I feel it immediately. Oh, here you go. That's how  that works. You see? You see? Now, I have like a story book understanding of quantum entanglement.  So, to really get to the bottom of this, we combed the world to find somebody who actually  works in the field. And we found a physicist at the Australian National University, A&U. Oh, look  at that. Research school of physics there. And that would be Sean Hodman. Sean, welcome to Star  Talk. Thanks a lot for having me. Nobody doesn't like quantum entanglement. Everybody's into it.  And we have a million questions. Before we even get to co the queries part of this episode, we  have questions of our own. I have questions of my own. And so uh let's just uh let's just come  right out of the box and tell me uh what you publish papers on. What what is it you do? Yeah.  So I my my group works on uh a whole range of um experiments. Um our particular apparatus  that we work on involves making helium atoms uh really cold. So we take them and we cool them  down to almost absolute zero. So absolute zero is as cold as you can get when there's essentially  no motion in the system. Um again remembering that thermal temperature is basically just random  thermal motion. We take all the motion out of the system and we uh make it really cold. The  temperatures we get to are um a millionth of a degree above absolute zero. I'd say that's cold.  Okay. Yeah, it's it's super cold. Sean, listen, man. You're you're almost there. Okay. Keep at  it. Keep trying. Yeah. Keep keep at it, man. Keep at it. You're You're almost there, man. Uh helium,  we're familiar as a gas that you can inhale out of a balloon in a in a in a birthday party. Uh remind  me, it liquefies around 3°. Is that correct? Um so normally at normal pressure it would, but because  we do it in a vacuum system, we keep it at a in the gaseous phase. So it's still it's still a  gas at these really cold temperatures. Um just at really low density. Whoa. Cool. Okay. And so  why the hell do you do that? Yeah. Well, I mean we we ask ourselves that question too sometimes  though. But um yeah, so the uh the purpose of this at these cold temperatures, all the atoms will  form a single coherent quantum state um called a Bose Einstein condensate. So that's where um  at quantum mechanically at low temperatures, so really cold and when atoms are moving really  slowly, they don't uh they don't behave like these little billyard ball uh situations that we like  to think of. Um what they actually behave like is they become these fuzzy smeared out quantum  blobs and at these temperatures they all become essentially an identical quantum state which  is very similar to a laser where a laser is the same for photons. Is this the same thing  as as you cool it down its effective wavelength increases? Exactly. Yeah. Is that a fair way to  say that? And so that the wavelength is so long, they're all just sharing the same wavelength  and so they all they have a hive of mind at that point. Is that a fair way to characterize  this? Definitely. So, so the reason we don't see these quantum effects of particles behaving like  waves at normal temperatures is because their wavelength is too small to actually see. Once you  get to the temperatures that we cool them down to, then they form this single quantum state and  their their wavelengths are actually it's it's macroscopic. So it's inside the trap it's maybe  100 micrometers. So 0.1 of a millimeter. Um I'm not great on inches. So for your American,  I'm not quite sure. You don't know what you're talking about. Um but yeah, and and when we when  we drop the atoms from the trap and release them onto our detector, so they fall nearly a meter  and in that distance they expand. And so by the time they hit the detector, they're actually  sort of cime. And so we have a quantum object that is on the cime scale by the time it hits the  detector. That's amazing. And when you say blob, what what kind of structure? Because in a gas it's  almost random, like you know, they're just sliding around everywhere. But you know, in a structure  sometimes it's like a lattice or but so what does the quantum state look like? Yeah. How do they  look like compared to each other? Yeah. So because they're all identical, they're essentially an  identical particle. So it's basically just one one state that just looks a very smooth smooth sort  of blob essentially. Um there's no random motion, so they're not not really bouncing around off each  other. There's just essentially one smooth blob.

[00:05:41]I remember first reading about this many years  ago and was just totally impressed and it's got Einstein's name on it and Bose who is an Indian  physicist, right? And we it's we credit him for the word we use for Bzans the particles. Is that  right? Yeah exactly. So so the particles we cool down are bzons. Um we can also call firmians  and they do a whole completely different set of physics. But yeah um the there's the two types of  elementary particles are bzons and firmians. And for Bose Einstein condensates we use Bzons which  yeah were named after um the Indian physicist Bose who came up with the statistics to describe them  and then to describe this state of Bose Einstein condensation. No Einstein was not a fan of quantum  physics. So why did he get something named after him? What's up with that? Yeah I mean it's kind  of funny that that Einstein he essentially was one of the inventors of quantum physics. it was  his um his black body radiation paper that um the the that came up with a lot of the initial physics  stuff. What he had a problem with was some of the aspects of physics and kind of the interpretations  of quantum quantum physics were what he really struggled with a little bit. Some of the things  such as entanglement. So he didn't like the fact that when you have an entangled system, if you  have two particles, it essentially means that if you take two particles and you separate them, if  you measure one of them, you'll instantaneously know the state of the other. And this is what  Einstein didn't like because that implies that something travels faster than the speed of light  which famously violates one of his other famous um works on relativity. Um and so he he really  didn't like that and um uh yeah so he he worked hard to sort of say that well quantum mechanics  must be incomplete. There must be a way that there must be some information that we're missing  here. And it was only sort of um maybe 30 40 50 years after that that we're actually able to  prove that no that really is how the world seems to work. Yeah. So Einstein was wrong in his  assumption that it's in incomplete I guess or maybe it's still incomplete philosophically but  everything works. So no right he was just upset because it made him look it made his suppositions  look stupid. That's what was wrong. He was like, "Don't you know, Einstein? Do you know how smart I  am? This can't be the case because now everything that I figured out in my physical representation  of the universe can't be." So, guess what? No.

[00:08:08]No. The Chuck account of the of the history here.  So, so, so Sean, where does entanglement come in to this Bose Einstein condensate? the the bzar  condensate we essentially just use as a source for our experiments on entanglement. So what we do  is we take we take our condensate we split it in two and we collide the two parts of the condensate  together. So we basically give give one half of it a kick with a laser beam and then it collides with  the other half and in those collisions you get all these individual pairs of atoms from each of them  will collide off each other and they could go in all sorts of different directions. Let let's just  focus on two of the directions they could go. So, if you have two atoms, um I could probably do it  with I normally do this with um a couple of coins.

[00:08:55]So, if you have a couple of imagine these these  coins are the atoms, you bounce off each other.

[00:09:00]They could either go that way or they could go  that way. Okay? So, you either this way or that way. And classically, if if we think of them  as little billyard balls, they could either go this sort of up or down. It doesn't uh they  do either of those. and you do the experiment, they go this way, you measure it, or they go this  way and you measure it. Now, quantum mechanically, that's not what happens. What happens quantum  mechanically is that when they do the collision, they go this way and they go this way at the  same time. The atoms go both ways. However, when you measure it, there's only still two atoms  in the system. We're not we're not creating matter here. We're not creating anything. And so, when  you measure it, you'll only either get northwests or northeasts, southwest. But until you measure  it, the atoms have gone both paths. And that's that's what entanglement the entanglement. Oh  my god. Okay. So now I've only ever heard of entanglement with regard to uh particles. And  now you're describing an entire atom. At those temperatures, the hydrogen nucleus will have its  complement of electrons. So you've got a whole freaking atom here. And are you saying you're  entangling atoms? Wow. Yes. Exactly. So, so most of most entanglement so far has been done with  things like photons uh which is a very elementary particle. It's just a exitation of light. But like  you like you said Neil, I mean a helium atom is quite complicated. It's got a nucleus which has  two protons, two neutrons. It's got two electrons whizzing around that. And now we're taking two of  these and we're entangling them together. First of all, that's crazy. Um, based on everything  that you know so far, now you're starting to see where Einstein was coming from. Yeah, I am. I Oh,  you're in good company, Chuck. Okay. Yeah. Damn.

[00:10:47]That's I mean, that's that's kind of insane, you  know. So, now all right, here. How long How long do they stay entangled? Cuz that's a big contest  out there, right? I mean, I remember reading some papers about what they were doing in China where  they had two entangled particles. One was in orbit and one was in a lab. And so, it's like, how are  they doing this? And what are they after? Is it distance or is it time or do you have to make sure  nobody messes with one of the particles? So, you have to you have to make sure it stays isolated.  What what are the conditions to sustain this?

[00:11:24]Yeah, that's that's pretty much all correct. So um  you can for for so so in our case we're entangling our particles in momentum that or or in the  path that they travel. So the direction they go um and that's that's really hard to keep your  particles entangled because if they go slightly differently from that path. So instead of going  northeast they go slightly towards northnortheast say then you're no longer going to be entangled  because you've you've now gone on a different path and you'll you've broken this the symmetry  of it I guess. Yeah. Yeah. You might you might um you might collapse the entanglement  or degrade it to an extent. Um where so our particles don't stay entangled for long. It's  it's uh our whole experiments about a millisecond um that that we do this entanglement for. A  millisecond is not a millionth of a second even though it sounds like it should be. Millisecond  would be a thousandth of a second. Correct.

[00:12:17]Thousandth of a second. Exactly. Yes. Right. Like  a millimeter is a thousandth of a meter. So a millisecond is a thousandth of a second. Okay.  So these people eternity on a quantum scale.

[00:12:31]It all depends on your perspective. Yeah. Is  is there a long-term goal for this experiment or is it sort of an existence proof that you  can entangle atoms? Yes. So so this particular experiment that we did, it was um uh kind of  a a demonstration that we could do this. So So people have there's been a lot of entanglement  previously done with photons. Um there's been some entanglement done with atoms as well. Um but the  entanglement that's been done with atoms hasn't involved external degrees of freedom. Um uh by  external degrees of freedom I mean basically the fact that it moves in different paths. Um or so  things like momentum. Um previous experiments have just been things such as spin. So you might put it  in a superp position of being in different states um but they stay at the same place. And so ours  was the first experiment that showed momentum entanglement with atoms. And um the reason why  that's interesting is because uh one of the things you might want to look at atoms for over  photons is that atoms interact much more strongly with a gravitational field. And so potentially we  could look at effects such as how does um gravity interact with entanglement um down the track  we're talking about. And so that might open up uh avenues to explore things such as quantum  gravity theories. It's not that gravity doesn't interact with the photons. It would just be much  harder to measure, right? So with whereas a a tangible particle, you've got something whose  path you can track, I guess. Is that is that what's going on there? Yeah, exactly. It's a much  stronger interaction. Streaming on July 23rd, Star Trek Strange New Worlds returns with a brand new  season exclusively on Paramount Plus. Get ready to boldly go one step closer to where it all began  as Captain Christopher Pike and the crew of the USS Enterprise embark on thrilling new adventures  across the galaxy as they journey to strange new worlds. They battle inner demons and external  threats, encounter colorful new characters, and reunite with familiar faces. Don't miss the  brand new season of Star Trek Strange New World streaming on July 23rd exclusively on Paramount  Plus. Hey, Sean, can you help me out as as I'm trying to wrap my head around this um with the  undetermined state um and the path because you said I if it if it goes on a different path,  can you talk a little bit of more about that cuz I'm I'm not quite understanding the you know  the superp position before the actual measurement because if China has a particle in orbit and a  particle in the lab that sounds like they're on different paths, right? So, what what where does  the sensitivities come from for changing what one particle does relative to the other? Well,  thank you, Neil. That was my question, Sean.

[00:15:26]In our case, it's the fact that it's the momentum  states of the atom. So, it's the direction it's traveling that is the entanglement. So if if if  you imagine sort of north south sorry northeast southwest northwest southeast um uh pairs then  um you can imagine that uh it's it's it's the fact that the atoms are either going northwests  or they're going northeast southwest and they're going those two directions at the same time. Now  what's happened with previous atoms is you'll have an atom sitting somewhere and then you have  another atom sitting somewhere and you'll use photons to communicate between those two and to  flip the atom into a particular state. So it's still sitting there. It's doing whatever it's  doing. It yes it might be orbiting the earth.

[00:16:11]It might be uh sitting in a lab which is of course  rotating earth. So it is moving but it's not the motion that's entangled. That motion doesn't  change. So the im momentum is really the the key here. I got it. Okay. I got it. Right. And  the photon is your measurement of the state, right? Cuz you can't measure it unless you  interact with it in some way. For our atoms, it's actually slightly different. So, no, no, I meant  for the other case. Sorry. Yeah. Yeah. Okay. Got it. Got it. Got it. Okay. All right. So, this is  So, so I have in my notes here to inquire with you about the the Bell inequality theorem. Is that how  is that relevant to what's going on here? Yeah. So historically, if we're going back to um Einstein  and what he didn't like about entanglement, so he he didn't like the idea that you could be in  these two states at once and then measure um and that would collapse your superp position so that  you'd then know which state you're Was that or was that not his invocation of the phrase spooky  action at a distance? Yeah, that was exactly what he said. So he described it a spooky action  at a distance and he says you can't have this, you can't have this that you'll collapse to being  in this state. Um, but before you collapse it, you're in both states once. He didn't like that.  He he thought there must be something. Ed, am I correct in that? Because I've heard two different  answers, but you're the horse's mouth here. That the other particle knows of this not simply faster  than light, but instantaneously. Which of those is the right way to think about it? To the best  of our knowledge, it seems to be instantaneous, but it's very hard to prove that it's exactly  instantaneous. Wow. People have proven that it's faster than faster than uh speed of light, though.  So, tell me about the the inequality theorem.

[00:17:58]Yeah. So, um Einstein and his co-authors Bolski  and Rosen wrote this paper which was the famous spooky action at a distance paper saying that this  can't be how the world works and there must be something in quantum mechanics that's incomplete.  everyone for sort of decades kind of thought well you're never going to be able to test this so uh  it's just a philosophical debate to an extent and then fast forward sort of 30 years or so into  the 60s and John Bell um who was another famous theorist uh came up with a experiment where you  could actually measure this and because because the problem is with entanglement if you imagine  that you're in this super superp position of northeast southwest and northwest southeast um but  you only ever get one result out of the system so it's very hard to prove the difference between  being in that superp position and not being in that superp position. And so what John Bell said  is hang on, we'll take that superp position and we'll then interfere it back with itself. So  if you imagine if you have the particles going um northeast, southwest, northwest, southeast, you  then take those two parts of the superp position and you reflect them back on each other so that  you have particles go like this and particles that go like that and you end up there's a spot  where they overlap again. And because the halves of the superp position can overlap, you can then  get quantum interference at that point. And so Bell came up with this uh inequality called  the Bell inequality which he said that if they really are in this superp position, you'll get  this interference. And um he as far as we know thought that his inequality would always hold. Um  it would that i.e. that classical physics would um be correct and that um the quantum prediction  which predicts that his inequality is violated um wouldn't be correct and then yeah a couple  couple of decades later uh some physicists such as Alana Spay and uh co um meas measured it  and showed that it is is actually violated.

[00:19:51]So so that was a thought experiment not an  actual experiment that he conducted. Wow.

[00:19:56]Right. Right. Look at that. Let's go to our  fan base, our Patreon supporters, each paying $5 a month to gain access to our guests in the  form of a question. Yes. Let's start with John Mayer. And John Mayer says, "Dear doctors Tyson,  Hodsman, and Lord Nice. I've been reading about entanglement for decades, but I have never felt  I could understand its nature. So, thank you for this episode. My question is three parts. So,  one, how do you entangle a particle? And two, how do we know they are entangled with spooky  etchin and not just similarly related? So I love the show and bravo. And let me jump in the middle  and ask, can you just take two random particles and forcibly entangle them or must they be birthed  together to be entangled in the way you describe?

[00:20:52]Um, so you need to uh ju just just to  Neil's I'll go to Neil's point first. So um you just need some way that those particles  can be identical. So they don't in our case we used identical helium atoms. Um but you wouldn't  you wouldn't need to. For instance, if you had nonidentical particles, you could just collide  them off each other and one would go one way, the other would go the other way and they'd be  in a superp position of say let's let's again we'll go back to my coins. Say we have sort of  a red and a blue particle. You could collide.

[00:21:21]So red goes one way, blue goes the other way.  Or blue goes one way, red goes the other way.

[00:21:26]Um that would be fine as well. A red and a blue  particle. Yeah. Yep. Did not know that. I thought they had to be kind of sort of symmetrically  identical, you know, with just complimentary uh elements like spin or whatever. So I did.  That's interesting to me. Okay. So in practice, how are you entangling particles? That's the first  question, right, Chuck? Yeah. Yep. Yep. Yep. So in practice that's that's um we we take one one  particle and we give it a kick and we collide it with the other particle and they bounce off each  other and then you get in this superp position of um the particles going as we were talking about  northeast southwest or northwest southeast and um uh so you're in these these different momentum  states and that's your um initial entangled state.

[00:22:13]So the act of colliding them off each other one  another entangles them brings their wave functions into harmony so that what was two wave functions  becomes one. Yeah. Yeah. I think that's a really good way to describe it. It's it's there's two  separate wave functions that you can describe separately. Um and then after you collide them  there's no way that you can describe them with two different wave functions. You have to use a  single wave function. Wow. Gotcha. Uh and this and this is because the wave particle duality of  nature at those smallest scales. This is quantum physics at its finest, right? Okay. So the second  question was what Chuck? How do we know they are actually entangled with spooky action and not  just similarly related? That seems to be the uh the real question there. Uh yeah. Yeah. So  I think that that kind of goes back to again if they were classical particles you could put them  in this you could put them in kind of a superp position where they either go one way or the other  way but quantum mechanically they go one way and the other way at the same time. And so the reason  we can and the way we can prove that even though we only ever measure one outcome is that if we  then take the two halves of that superp position and we combine them back together and interfere  them then we can show that there will be different um outcomes and so the particle can essentially  interfere with itself and um uh we can show we'll get different outcomes to what you would get  classically. Okay. Wow man that's all right that is some freaky stuff. I love it. Freaky. It's  freaky Friday. Yeah. So, this is Hayden Goring.

[00:23:57]I think Goring. He says, "Hey, Dr. Tyson, Dr.  Hosman, Lord Nice. Hope you are all doing well.

[00:24:05]It's in the paper by Dr. Hodman at all. Uh,  that the helium atoms were momentum entangled and I hadn't heard of subtypes of entanglement  before. What other types of entanglement are there? And why did the team opt to use momentum  entanglement for the BEC uh made of helium atoms?

[00:24:31]Uh all the best Hayden from London, England. Pip  pip. What is the inventory of entanglements that you have? Yeah, so there's there's there's lots of  different types of entanglements. So if you have uh the original experiments with photons, it  would often be something such as polarization.

[00:24:48]So polarization is just if you imagine a photon  as a small particle of light, it's basically which way is the light vibrating. Is it vibrating this  way or is it vibrating this way? So vertical or horizontal. And you might entangle your photons  in that so that one of your photons has vertical polarization. One has horizontal. And so you could  be in a superp position of vertical going right, horizontal going left, or horizontal going  left, vertical going right. And then you could um measure that. And yeah. And so that was a  lot of the original experiments were u done with photons with things such as polarization. Um  atoms previous experiments have done things such as spin. So spin is just a it's a fundamental  property of um atoms or part charged particles that you can ei have sort of spin up or spin down  and you could be in a superp position of spin up and spin down and entangled with that. And in our  case we did momentum. Um, pretty much any quantum property can be entangled. Um, you you just have  to be able to put it into a superp position of those states. Well, let's get back to the spin.  So, in the two entangled spin particles, does one have to be spin up and the other has to be spin  down? No. No. Definitely not. Um as physicists we tend to use a shorthand that if there's if there's  any system that is uh a two spin system um you'll call that spin up and spin down because that's  how we tend to learn about it in uh undergraduate physics and we tend to just stick with that way  of writing it all the way through. Yeah. Yeah.

[00:26:15]So for instance in my lab we've done previous  experiments where we've used a spin one and a spin zero state of helium and we've entangled them. Um  and uh but we still call it spin up and spin down because it's just this shorthand that physicists  understand easily because when I think of quantum particles I think they have complimentary quantum  states but that's not the case. They can have any quantum state. You just have to be able to  couple between those quantum states. If you can't couple between the quantum states then  you can't uh interfere them. So if you can't change the state coupling just means changing. So  if I I can't change controllably from spin one to spin zero or spin up to spin down or horizontal to  vertical polarization. Whatever your entanglement parameters are in our experiment it's momentum.  Um and so if as long as you can change coherently between those states you can uh get entanglement  and show that you've uh show of bell inequality violation. Okay. Wow. Look at that. That is  mindbending stuff. I did not know that. I did not know that. Okay, bring bring on some more.  He says, "Hello, Dr. Tyson, Dr. Hosman. This is uh Jonas Williams uh from New York City." Uh  my question for you, has the study of quantum entanglement and subatomic particles changed or  influenced how you understand reality? I like that. Oh, I like that. If you're not purposely  entangling particles, is that something that could happen to them by natural causes? Oh, definitely.  Yeah. Yeah. Entanglement can happen um all the time. It's just that it's because it happens  on such a small scale um we normally don't see the effects of it. Um and so yeah. Yeah. and and  and I think that's so back to the question for me um it's kind of it's really weird and I think  a lot of us who have studied quantum mechanics when you first encounter it whether it's in an  undergrad or high school or um through a podcast like this when you first hear about these quantum  features you might think yeah that that that sounds sounds really weird that can't be how the  world works. It's not how our brains have evolved.

[00:28:28]our brains have kind of evolved to um uh be used  to sort of I don't know throwing throwing things at animals I guess um which is a very classical  way of looking at the world and if if I throw a a cricket ball or what do you have baseball  in America if I throw a baseball let's say um and uh it's it's not going to be in two places  at once it's not going to go two directions at the same time so when we read about quantum  mechanically that a small particle which we like to think of as just a smaller smaller ball  um when we read that can go both directions at once uh we just sort of think oh well it must be  some mathematical trick and the fact that we can actually do these experiments to show no no at the  very small scale or very cold um this is how the universe works it's yeah it's a bit mindbending  right yeah without a doubt to summarize uh because it happens on these microscopic scales there's  no macroscopic manifestation of entanglement that we experience yeah that's correct because we're  just trying to not get eaten by a lion and that doesn't require quantum physics to accomplish.  Are they forever forever separated the quantum and the macrophysical or is there a possibility  that there is a point of crossover? Yeah, that's that that that's a really good question and  that's that's a really active area of research at the moment that because clearly at the small scale  quantum works, at the large scale quantum doesn't, but there's got to be somewhere in between.  There's either must be a hard point where they stop working or maybe it's a fuzzy boundary. A  lot of the research we're kind of seeing these days is there might be a fuzzy boundary where  you just kind of get less and less quantum and more and more classical. Wow. All right.  God, how do you deal with this every day, man?

[00:30:18]All right. Here we go. This is Do Do you arrive at  home at the end of the day depressed or jubilant?

[00:30:24]jubilant like what what is normally depends on  how much university bureaucracy I've had to deal with in a particular day as they depressed your  quantum physics is the easy part of the job some days as they say the administration is a new  kind of subatomic particle called the morons damn okay this is Mike Parker and Mike  Parker says Dr. Hodsman Dr. Tyson, Lord Nice, Mike Parker from Virginia. It seems entanglement  is observed in larger and larger particles. Is there an uppercase limit to entanglement? Could  there ever be a way to use particle entanglement for instant long distance communication  or other practical purposes? This is the question that every sci-fi fan wants to know,  man. Can we have faster than light communication like on Star Trek where Captain there's a  subspace communication waiting for you in your quarters? Or can you entangle molecules?  I mean, yeah, we're impressed with the atoms, but what have you done with us lately? Can you can  you entangle molecules, be they simple or complex on on the uh entangling larger particles? That's  that's another really active area of research.

[00:31:42]People keep pushing it further and further. There  have been people that have entangled collections of atoms and molecules and they're sort of push I  believe I believe it's of order a thousand atoms, but don't quote me on that because I could be um I  could be wrong on that is one is all I care about.

[00:31:57]It's well more than way more than one. Yep. Yep.  And so yeah in trying to push this entanglement on the bigger scale and work out where it breaks  down at some level it clearly doesn't uh it doesn't work anymore. And so yeah, where that  transition is is a really active area of research.

[00:32:13]So maybe you were familiar with George Gammo's Mr.  Tommpkins and Wonderland. I don't know if you I'm a little older than you, so I don't know if this  was around in your day, but George Gammo uh Mr. Wonderland was a place where the laws of physics  were different simply by the physical constants being different. So in one of them, the speed of  light is like 60 miles hour, right? And so you're driving down the street and then you see these  these relativistic effects just by approaching the speed of light as your speed limit on the  road. One of them was they changed the value of the planks constant so that macroscopic objects  would feel uh quantum phenomena that you'd walk through the door and you'd like defract as you  went through the door. It just it's fun to think about what how that if you have a knob that could  tune it what different things would happen to you or we just simply develop a new sense of of what  the world is, right? Like you said, we throw the ball and it follows one arc. But if quantum rules  were all around us at all times and you threw the ball and it split into two states, you would  say, "Oh, it's just splitting into two states."

[00:33:30]It wouldn't even be odd to watch that because it  would happen so frequently. Is that a fair way to think about this? Yeah, I think so. Our brains  are great at adapting and I'm pretty sure that if if we'd had to evolve to live in a quantum world,  I'm sure we'd just think it was normal and Yeah, just normal. That's right. That's cool. That's  right. And what about the communication uh portion of Mike's question? Oh yeah. Would it ever be a  viable use for long-distance communication? Is there a future in this? Yeah. So this is this  is what everyone thinks as soon as you hear entanglement. You think there's instant measuring  one instantly changes the other. We could use that to communicate faster than the speed of light. Um  unfortunately that doesn't seem to be the case.

[00:34:12]And essentially it's because the way you measure  it um contains information. So if you make a measurement on that particle um yes you'll you  will know what the other one is but you won't be able to communicate that in a useful way unless  you communicate it classically because you'll let you'll then the other person would then have to  uh make a particular measurement to get anything useful out of that. And so um yeah you wouldn't  you you can't actually use it to uh for faster than light communication. There's there's a  theorem called the no communication theorem um which basically says that yeah you can't um  you can't use entangle states to communicate faster than the speed of light. Really that's the  name of the theorem? The no communication theorem.

[00:34:54]That's the best name they can come up with. Yeah  that I believe that's what many women call their husbands the communication the no communication  theorem. Uh but yeah, so so basically what you're saying is the collapse of the superp position and  once that information is set, you you can't know it unless you're making the same measurement that  the other person is making on the other side. And you wouldn't be able to know which position it is  unless you were to call them and say, "Here's the position." Yeah. Exactly. Because because quantum  measurement perturbs the stake. Um if you I if if you make your measurement in a way that uh could  exploit that information, it will change the state of it. And so then that will change the state and  then when they make their measurement, they'll get a different result out of it. A different result  unless you've called ahead and told them, hey, you need to make this particular measurement,  which by the way is how you know that it's entangled. That's how you know it's entangled.  Exactly. It's kind of frustrating. You're like, we should be able to do this, but yeah, we  we can't. So we can't use it for um encrypted message sending. Uh now that's that's a completely  different question. You can use entanglement for encrypted message sending. So that's that's where  you exploit the fact that if you measure one half of that, you will change the other half. And  so if you encrypt your message on two uh photon pairs and you send one of them to the person that  you want to and you keep the other one yourself, then if you make measurements on that and compare  the results with the person you've sent it to, you'll know if anyone's messed with your system  because you'll get different results. And so you'll know if it has been eavesdropping on  your uh messaging. And so there's there's mathematically provably secure encryption  protocols uh using quantum communication which can be shown that uh you you you just can't break  them because if you interfered with it if you you interfere with the state if you listen to it you  interfere with the state and people wouldn't know your eavesdropping and um you could just abort the  communication. So this is a pipe dream then it's a pipe dream that people have for it. These things  have been demonstrated um at at at various scales and um yeah they're they're essentially um it's  it's almost an engineering problem at this stage to get it to work better. Okay, look at that. All  right, this is William Warren and William says, "Hi, Dr. Tyson and Dr. Hodman." This is  William Warren from Abington, Maryland. If quantum entanglement is a fundamental feature of  nature, could space-time itself emerge from a vast network of entangled particles? In other words,  is it possible that distance isn't fundamental, but rather a consequence of how information is  connected at the quantum level. Thank you so much.

[00:38:02]We've heard on another installment of Star Talk  from one of our physicist friends, Brian Green, that it might be that the virtual particles in the  vacuum of space that are connected to each other by entanglement. They're entangled. That that  entangled gap between them may be a wormhole. And a wormhole would have the same property because  you just step through and it's you're just there, right? You're not moving faster than light. The  the hole enabled that and it's not cuz you had special rockets. So So what what is the latest  thinking other than what I just shared with you about what the entangled pathway actually is?  Yeah. Wow. This is um you got to remember I'm only a dumb experimentalist. Um I basically make  measurements and what the world the world does.

[00:39:04]You're a huge mass experimentalist. Okay.  Yeah. I I I probably I would certainly defer um yeah thinking on that to things such to the  experts like Brian and um and co cuz um yeah that's that's kind of a bit a bit beyond um what  what we're working on. It it certainly sounds like a um a interesting take. Uh, but I'm Yeah, I'm  not not really sure, unfortunately. Sorry. Okay.

[00:39:31]N that Listen, we we like that answer. Uh, you  know, nowadays it's hard to get somebody to say, "Hey, I'm not that sure. Sorry." You know what I  mean? Yeah. I It's a really good point. I think it's a it's a big part of being a scientist  is you've got to learn to know what don't you know. And it's one of those things that the more  you know, the less you know you know. It's kind of the reverse Dunn and Krueger effect. you know,  the Dun and Krueger effect, but the less you know, the more you think you know. Um, it's  kind of the reverse. The more you know, the more you realize that, wow, there's heaps  of stuff that I just don't know at all. And um, yeah, Dunning Krueger, we get along very  well. Very well. Dunning and Krueger, I know them. We have a great relationship. They told  me I do the best Dunning and the best Krueger.

[00:40:19]All right. I think there's a I think there's  a value in uh saying I don't know and allowing people to understand that that science is  sometimes the answer is well we don't know you know that's different from him not knowing they're  two different there's science doesn't know and there's this I don't know those are two different  things right and they're both the same for me whether physics itself knows I think the answer's  still out on that as well I think there's still um some open theories in that because again  you can come up with a theory but you have to be able to prove it experimentally and I think to  prove something like that experimentally it it would be extremely hard. So there's there's some  really interesting theories and the trick is going to be a bit like with Einstein spooky action at  a distance claim coming up with an experiment to test it. That's that's what we'll be yeah  that that would be a big Nobel Prize you know discovery. Cool. These days, we're used to getting  things delivered on demand. Groceries, a new gadget, or the latest book, expanding your view  of the universe. And now, you can add T-Mobile 5G home internet to that list. Just order from  T-Mobile and enjoy same day delivery with Door Dash. And you can set it up yourself in about 15  minutes. No advanced engineering degree required.

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[00:41:59]So, if you're moving into a new place or just  ready to upgrade your connection to something a little more advanced, visit t-mobile.com/home  internet to check availability and get your home internet delivered today. Same day delivery for  most internet eligible customers. See if it's an option during checkout. Fastest according to UCLA  speed test intelligence data second half 2025. All rights reserved. All right, let's go to Alejandro  Guardo. And he says, he's from Hackinack, New Jersey. No, where's he from? Where's he from? Uh,  I don't think Alejandro says where he's from. Uh, oh, okay. He says, he's from Montre Washington  State. I'm sorry. He Washington State. Washington state speaks that way. I just want you to know  that. Okay. All right. That's that's my fantasy of Alejandro in Washington in Washington State.  Um he says, "Hey, Dr. Tyson and Dr. Hosman. Lord, nice Alejandro here from Washington State. My  question is, what stabilizes quantum fluctuations when particles fuse or collide? How does this  increasing proximity affect entanglement? More extremely, how would this work for particles in  the singularity of a black hole? Thank you. Yeah.

[00:43:37]So, I'm going to reshape that just a little bit.  So, if I have two particles, we know that quantum physics says there's everything is always in  motion. There's always some energy to the state.

[00:43:49]is does that disrupt any attempt to entangle two  particles? So in other words, can two particles natively break apart simply because of quantum  fluctuations that are inherent in all particles in all systems? Quantum fluctuations  um at some level will probably have an effect on entanglement but it's normally at such  a small scale that uh it won't stop entanglement happening I think. And in fact, when you cool  down your helium atoms, you're reducing the quantum fluctuations by dropping the temperature.  Correct. Uh we're kind of reducing the classical fluctuations. So temp temperature is temperature  is really a classical a classical uh phenomenon.

[00:44:33]Um it's just random motion of particles. We're  reducing the classical fluctuations to get to the scale where you can in principle see quantum  fluctuations. However, for our entanglement, um the quantum flu for our particular system, the  quantum fluctuations don't really come into it.

[00:44:48]It's that there's there's much larger things  that cause the entanglement to deco things such as classical uh so magnetic stray magnetic  fields and um uh yeah, the like your microscopic disruptions to it. Yeah. Okay. Yeah, definitely.  We're not really at a level where we're sensitive to the microscopic quantum fluctuations.  This is Mikael Boycever who says, "Hello, Guardians of the Geeks." Mikael here from Canada.  I like that. Guardians of the Geeks, right? How would the universe change if the programmer behind  would suddenly toggle particle entanglement off?

[00:45:32]Would we notice a change in our everyday life?  Wow. By the way, in the same spirit of that, I heard someone suggest that evidence we're in in  an in a simulation is that the programmer already put a limit to how fast things can go because  they can't simulate it faster than that. So, the speed of light is the programmer's limit that  we've bumped up against. And it took a long time to get there, but we finally got there. So it's  like in the Truman show he finally gets to the the outer uh edge of of the set of the television  set of the of the set of the set. So yeah so what hap turn off quantum entanglement what's  different about the world. Yeah. So at at the macroscopic level I think um pro probably not  not a huge amount like the entanglement's only at the very small scale. Um, however, well, yeah,  however, there are a range of processes that we're starting to have hints at that may be really  entanglement may be really important. There's some biological processes such as um people are  postulating the stability of DNA maybe due to um entanglement within the molecules itself. Um,  navigation of birds. Some birds use magnetic uh sensors and there's hints that um there's quantum  elements of that that rely on entanglement.

[00:46:57]Migration migration of birds. Migration of birds.  Yeah. Navigation during migration is kind of what I mean. Like like when when they migrate, how  do they know to go north? Yeah. How do they know which way to go? And so there's there's there's  there's thoughts of that. And even things such as I think photosynthesis is the latest one that  they're looking at that may have um elements. Now, I think the jury is still out on all of these.  Again, it's not quite my area of expertise, but I believe the jury is still out on all of  these as to whether it's um definitely quantum entanglement enhanced, but there's definitely  some evidence that's starting to point towards some of these biological processes, quantum  physics is really important and entanglement in particular. And so yeah, while while at first  glance you might think that if the programmer of the universe turned off entanglement,  we wouldn't see anything any difference, uh it may actually be uh really important. Okay,  very cool. I love the idea of photosynthesis and quantum entanglement. That sounds so cool.  All right, this is Bruce Leie and Bruce says, "Dr. Tyson's and Hodsman." This is Bruce Leie from  [ __ ] Creek, Virginia. My question is related to entanglement and spooky action at a distance as  Einstein phrased it. If spacetime for a photo traveling at the speed uh he said photo but I  think he means photon uh traveling at the speed of light represents zero time experienced by the  photon because at the speed of a light distance is non-existent. Why did Einstein have a problem with  instantaneous communications between entangled particles? Nothing is at a distance for particles  that travel at the speed of light. Yeah. So I' I'd say that's one of the reasons why it's really  important to measure entanglement for things not just that aren't photons. So yeah, like like  because photons travel at the speed of light, if you just measure entanglement with that, you could  perhaps come up with some sort of explanation like that. But in our system, we measure it with  atoms. Our atoms move very slowly. Um we give them a kick and they move at several centimeters  per second. Let's call it an inch per second for you Americans with your freedom units. Um, so  who centimeters per second? Oh my god. Freedom units. That's exactly what we used to measure the  octagon on the White House lawn. Freedom units.

[00:49:25]So yeah. So back back to the Adams. So it cuz cuz  they're moving relatively slowly. You can't come up with that sort of an explanation to explain  it. Um it really uh and simultaneous and yeah instantaneous communication suddenly becomes  a problem again. Wow. That's really cool man because yeah they have mass and um yeah they're  entangled at much much much slower speeds. So yeah that's really that's what a well it's still  a good question. Oh it's a great question. Great question. Yeah, really good question, Bruce.  Thanks. All right, this is David Barlo. And David Barlo says, "Uh, greetings, Dr. Hosman,  Dr. Tyson Lord Nice." David Barlo from Chicago, Illinois here, a newly signed up Patreon  supporter. Kudos to you, my friend. Um, he says, "I was wondering if as an experimental physicist  and an observer within the quantum field, you and your associates knew for a certain for  certain that you were not affecting the results of your experiments in the Bell's theorem. What  loophole prevention precautions were taken to negate your field collapse of the wave function  when taking measurements? Love your fantastic science broadcast, guy. Uh so so yeah, how how  you know this that's you not messing it up like it it could well be. That's that you always have  a big doubt that yeah, did we just do something wrong and measure something? That's why we have to  do sort of rigorous and multiple tests and um uh and and for the scientific method in general. It's  part of the reason why you have to publish these papers that other scientists can then go, "Hang  on, did you think about this? Did you try turning this off? Did you try turning that on?" And yeah,  um it's it's yeah, it's an important part of the process. Um for our particular experiment, so  maybe I should just briefly cover what loopholes are that are referred to there. So with with Bell  with Bell experiments, um there's these things called loopholes, which are basically ways that  people come up to say, well, maybe to to still preserve locality, to still preserve the fact that  um you don't have instantaneous communication.

[00:51:37]And so it can be things such as well maybe uh  maybe the experiment is conspiring in a way such that it only lets certain results through  or maybe your um uh maybe the observer is is uh doing something is communicating a way maybe  like like if you if you set the interference on the two halves of the system and the measurement.  um if you don't set them after you've I if you set them in a way that they could communicate with  each other, maybe there would be some really weird um uh theory that could explain that. Um and so  uh a lot of these all these loopholes have been closed with the um experiments on photons. For our  particular experiment um we didn't close all these loopholes. So our experiment isn't loophole  free. In principle um you could make some of these criticisms about our experiment. However,  the fact that they've been closed with photons means that we'd probably expect that they should  also be closed for atoms as well. Um, and so yeah, um, and and part of the reason why we didn't  close them was because a couple of them are technically extremely challenging to close with  atoms, just because atoms move a lot slower than photons and they move over much smaller distances.  And so, yeah, it's an ongoing area of work, but it would be a good area of future work for groups  like us. That's a damn good question. Chuck, we have time for a couple more. Cleo Fox, he says,  "Hello, Dr. Tyson. My name is Cleo from Denver, Colorado." Modern quantum physics has  achieved extraordinary predictive accuracy, but many of its foundational interpretations  remain experimentally indistinguishable. Given recent advances in quantum information theory,  weak measurements, quantum computing, and tests of non-locality. Do you think the next major  breakthrough in quantum physics is more likely to come from developing new mathematical frameworks  or from entirely new experimental methodologies capable of probing quantum phenomena in ways  we cannot currently access? Put another way, are are we currently limited by our theories or  by the tools we use to test them? Yeah. So I was going to say something similar to that in summary  of that question. So Sean, there's, you know, philosophers like believing they have access  to emerging truths uh in science in general, but especially in quantum physics where there's  so much that makes no freaking sense. So is there room for philosophers to guide the physicists  through this and or out of it? or are we just stuck just as they say shut up and calculate?  And so that's that's a that's a nuanced way of saying is it was the final question there. Are we  currently limited by our theories and the tools we use to test them on on the shut up and calculate  versus phil philosophy debate? I'm a big believer as an experimentalist. I'm a big fan of shut up  and calculate. Experiments are hard enough as is.

[00:54:37]Count me on that vote as well. Okay. Yeah. Yeah.  It's basically the maths tells us the results that give us predictions of our experiments and  it works. Yeah. And it works and and and so at that level, yeah, I'm I'm happy with that. I'm  happy to leave the questions to the essentially to the realm of philosophy to an extent. If  if you if you're um if you can't actually make predictions of what an experiment will give  you, I think that's basically philosophy. And um I I think there's definitely a role for that. I  mean, we've we've seen that how brainbending some of these quantum effects are, and I think it's  really interesting to probe that. I think it's really interesting to have uh philosophers and the  like uh guide that and and theorists and interact with uh quantum theorists. But I think it's also  equally really important for experimentalists to actually test these results. And if you can if  you can't test these results, then uh you probably need to work harder on your theory. I think I I  spent some time at Princeton where they they're very theory based although they do quite a bit of  experiments there in the they have a a tokamac and and fusion reactor but there there's a strong  theoretical legacy in the department and there there's a sign up somewhere or some someone's  door it says never trust an observation unless it's backed up by a good theory. So yeah. Yeah.  So I think I think coming back to the question it really is it's both. There's there's a lot of  work on theory but there's also a lot of work on experiments to uh cover that. Do do they do they  inform one another? I think is kind of also the the the spirit of the question. Ideally there you  go. That's that's the correct way to think about that. Absolutely. There's there's plenty of times  like like our experiment on entanglement that was originally proposed by some theorists. uh we  tried to do it the way they proposed and it didn't work. So then we came up with a slightly  different way and then we came back to them and then they helped analyze our results and it yeah  it's really there's a lot of back and forth that okay goes on in science. Cool. Chuck, one  more question we got time for. All right, let's close it out with Melanie Stickler. And  Melanie says, "Hello, Dr. Tyson. I'm Melanie, originally from Austria, now in the Bay Area of  California. My question is about Dr. Hodsman's helium experiment. I understand massless photons  have wave particle duality. But how does a massive particle like a helium atom which is subject to  gravity function as a wave cloud? Furthermore, if measuring a quantum system collapses the wave  function, how did the team measure the atoms in simultaneous momentum states without instantly  destroying the superp position? I'm sure the paper covers this, but I'm having a hard time  wrapping my head around it. So, thank you. Yeah, helium is a massive particle compared to stuff  we're used to. And so, there's a wave function associated with such a massive particle. Yeah,  definitely. And um I should say great question.

[00:57:39]And um uh yeah, the there's a wave function  associated with helium atoms and that's why we need to cool them down to make it work. uh because  otherwise at room temperature the wave function is so small that you can't see it. But at these  temperatures the wave function is macroscopic.

[00:57:53]It's sort of in the order of tens to hundreds of  micrometers. So that's a 0.1 of a millimeter and um yeah it's it's quite uh large at that scale.  Um, the other part of the question, if I remember, if I'm getting it correctly, was how do you  measure that they're in two different states at once when they're only ever going to be in how do  you prove they're in two different states at once when you can only ever measure one result? And  again, that really comes down to John Bell's work for how you can measure this Bell inequality where  if you interfere those states, you can measure the results of that in the outcomes you get. You  can in interfere those states and you can get more probability of being in one than the other in  your output due to the fact that you were in this superp position of two states at the same time.  Is there a quantum entanglement arms race in the world? Like who's leading the quantum entanglement  experiments? Because I don't think it's us, is it?

[00:58:44]Well, us Americans, you're in Australia. Who's  who's ahead? Who's ahead and who's behind? Um, it it kind of depends what you're talking about. I  mean our our experiments probing the fundamentals of entanglement um uh there's there's there's  still work going on in that but a lot of what current uh quantum uh research is going into is  how we do something useful with entanglement.

[00:59:06]So how you can use it? So things such as quantum  computing. So quantum computing um is a computer that rather than using bits to encode information,  so bits have to be one or zero, you use cubits which can be in a superp position of one and zero  at the same time. And then if you have multiples of these together, you can end up with you can  entangle the different cubits. And by the fact that you can have cubits in many states at once  for certain types of problems, you can probe uh many answers at once even though you only ever  get one result when you get out and so when you do your final measurement and so there's a large so  in principle it seems really promising that you should be able to do uh much faster calculations  much uh higher level computation with this. Um, but the problem is that finding it only there's  only particular problems that we know of that this is true. That's so there's there's a lot of  work going into that. Then the other problem is that quantum systems are really hard to get to  work on a large scale. So have lots of cubits and so there's a lot of work going into building  these processes. Um, and so yeah, there really is, if you want to call it an arms race, there's a lot  of uh government and and private um investment in this at the moment. There's a lot of quantum  computing startups all around the world. on the assumption that whoever gets advances in it  first might have a leg up either economically or with regard to security or computing. And so  even if at the end of the day it's just a pipe dream because it's like it's just a fun physics  exercise but it doesn't have any practical use.

[01:00:43]No one knows that yet. Is that a correct way  to think about that? Absolutely. It it's still it's still really an open question as to what  the impact of quantum computing will be. Um quantum comput it could be anything from um like  you say h have massive economic implications, massive security implications um it could be  used for things such as medical implications like drug development um uh data processing all  all these massive things. or it could just be on a much smaller level and that it's kind of a toy  physics system that helps us advance physics but may not have quite such a wide um uh economic uh  implication and I I think it's a really really exciting time. I bet people said the same thing  about quantum physics a century ago. This is just a curiosity on the fringes of physics. We'll  never have any use for this but it's still fun anyway. And now it's the foundation of our IT  revolution. Everything and everything. Yeah.

[01:01:40]It's one of the reasons it's really important to  invest in basic research. I mean the the the work the work my group does is we're know what that  is anymore. The United States we don't know what that is anymore. Exactly. We don't we don't  do research here anymore. Okay. Will you hire hire hire you hiring? We Australia is not much  better. Unfortunately, we run on vibes. vibes.

[01:02:04]No, right now it's on physics fumes. That's  all that's left. Oh, yeah. Unfortunately, we'll find out. Yeah. Well, Sean, that that's  all the time we have. I'm saddened by this because this this topic has no end of curious  people out there thinking about it. They've read about it. And it's not every day you get  to bump into someone who gets paid for thinking about it. Congratulations on your Bose Iceland  condoset as a source of entanglement. Okay, we're we will look for our invitation to Stockholm  in the mail. Really good and thanks thanks a lot for the questions and yeah, thanks for having  me on your show. I am Neil Degrass Tyson, your personal astrophysicist finishing up  a very special edition of Cosmic Queries specializing in quantum entanglement.  Until next time, keep looking up.