Getting Entangled with Sean Hodgman

**SPEAKER_1** (0:00)
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**Chuck Nice** (0:32)
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**Neil deGrasse Tyson** (1:27)
Chuck, love me some quantum physics, and apparently so does everybody else, especially when we're talking about quantum entanglement.

**Chuck Nice** (1:34)
I'll say some of the best questions we received on quantum entanglement, yeah.

**Neil deGrasse Tyson** (1:38)
One of the world's experts we went down under to Canberra. Australia's Sean Hodgman coming right up, a physicist on top of the situation.
Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.
This is StarTalk, Cosmic Queries edition. What is the subject? Quantum entanglement. Chuck, are you ready for this?

**Chuck Nice** (2:16)
Never. I mean, I'm just going to be honest.

**Neil deGrasse Tyson** (2:21)
Haven't you and I been quantum entangled for a while?

**Chuck Nice** (2:24)
Yes, without a doubt. Anytime you feel pain, Neil, I feel it immediately.

**Neil deGrasse Tyson** (2:29)
Here you go. That's how that works, you see?
You see? Now, I have like a storybook, 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, ANU, Research School of Physics there. That would be Sean Hodgman. Sean, welcome to StarTalk.

**Sean Hodgman** (2:58)
Thanks a lot for having me.

**Neil deGrasse Tyson** (2:59)
Yeah. Nobody doesn't like Quantum Entanglement. Everybody's into it. We have a million questions before we even get to, because the queries part of this episode, we have questions of our own. I have questions of my own.
Let's just come right out of the box and tell me what you publish papers on. What is it you do? Yeah.

**Sean Hodgman** (3:30)
My group works on a whole range of experiments.
Our particular apparatus that we work on involves making helium atoms really cold. We take them and we cool them down to almost absolute zero. Absolute zero is as cold as you can get when there's essentially no motion in the system. Again, remembering that thermal temperature is basically just random thermal motion. We take all the motion out of the system and we make it really cold. The temperatures we get to are a millionth of a degree above absolute zero.

**Neil deGrasse Tyson** (4:01)
I'd say that's cold.

**Chuck Nice** (4:03)
Okay.

**SPEAKER_1** (4:04)
Yeah.

**Sean Hodgman** (4:05)
It's super cold.

**Chuck Nice** (4:06)
Sean, listen, man. You're almost there. Okay?

**Neil deGrasse Tyson** (4:10)
Keep at it.

**Sean Hodgman** (4:11)
Keep trying.

**Chuck Nice** (4:11)
Yeah, keep at it, man. Keep at it. You're almost there, man.

**Neil deGrasse Tyson** (4:15)
Helium, we're familiar as a gas that you can inhale out of a balloon in a birthday party. Remind me, it liquefies around 3 degrees, is that correct?

**Sean Hodgman** (4:27)
So normally, at normal pressure it would, but because we do it in a vacuum system, we keep it in the gaseous phase. So it's still a gas at these really cold temperatures, just at really low density.

**Chuck Nice** (4:39)
Whoa, cool.

**Neil deGrasse Tyson** (4:41)
Okay, and so why the hell do you do this?

**Sean Hodgman** (4:45)
Yeah, we ask ourselves that question too sometimes.
Yeah, so the purpose of this, at these cold temperatures, all the atoms will form a single coherent quantum state, called a Bose-Einstein condensate. So that's where quantum mechanically at low temperatures, so really cold and when atoms are moving really slowly, they don't behave like these little billiard ball situations that we like to think of. What they actually behave like is they become these fuzzy smear out quantum blobs. 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.