If an atomic physicist like Nathan Lundblad could slip the surly bonds of Earth鈥檚 gravitational pull, what kind of experiment would he dream up?
About a decade ago, that very question was posed to physicists around the country when NASA issued a call for proposals to do funded research using a new facility to be installed aboard the International Space Station.
Lundblad, a 乐播传媒 professor of physics, had a research proposal at the ready: He would attempt something never before done on Earth: create tiny bubbles of ultracold atoms.
In response its call, NASA announced in 2014 that it would fund seven research projects, including one headed by Lundblad, to conduct the first experiments aboard the Cold Atom Laboratory, which was launched to the International Space Station, about 250 miles above the Earth, in 2018.
This week, Lundblad and his coauthors published their first research findings, 鈥淥bservation of ultracold atomic bubbles in orbital microgravity,鈥� in the journal Nature, which is now attracting .
Before we explain the bubbles, we need to explain why they鈥檙e important, which has to do with exploring the wonders of quantum physics.
Lundblad鈥檚 research looks at what happens when a cloud of atoms become ultracold 鈥� near absolute zero, that is. This ultracold cloud of 10,000 or so atoms slow down 鈥� way, way down 鈥� until they come together 鈥渋n a blob, or clump,” explains Lundblad.
Large enough to be visible to the naked eye, this blob of atomic gas is known as a Bose-Einstein condensate. Named for Albert Einstein and fellow physicist Satyendra Nath Bose, who correctly predicted their existence in the 1920s, BEC鈥檚 are considered a different state of matter from a gas, liquid, solid, or plasma. They intrigue physicists for their quantum properties, such as acting like a wave rather than individual particles, a property called 鈥渨ave-particle duality.鈥�
Lundblad describes a BEC as a “very special gas, where atoms become blurred out such that we don’t know where the atoms are within the blob.鈥�
The singular achievement reported by Lundblad and his research team in their Nature article is that they’ve successfully made a bubble out of a BEC, 鈥渓ike inflating a bubble from a blob of soap,鈥� he explains. 鈥淲hen we blow it up, the bubble鈥檚 diameter can grow to a few tenths of a millimeter, larger than the diameter of a hair,鈥� and visible to the eye. The sphere is relatively large compared to its thickness, 鈥渙nly a few atoms thick.鈥�
Until now, it鈥檚 not been possible to create ultracold atomic bubbles because gravity squashes them. For Lundblad and other researchers, that was a big draw of doing cold atom research aboard the space station: It’s a gravity-free place.
Successfully creating ultracold bubbles didn’t surprise Lundblad, but it was nonetheless still gratifying. 鈥淭here was really no reason to expect that it wouldn’t work. But it was really nice to see it in action for the first time, and see how the bubble curled up around the sides.鈥�
This series of images shows an ultracold atom bubble being formed inside NASA鈥檚 Cold Atom Lab, as part of research led by 乐播传媒 Professor of Physics Nathan Lundblad.
The intrigue around creating and examining an ultracold bubble instead of a basic BEC is “similar to what’s special about doing physics on a curved earth instead of a flat earth,鈥� he says. 鈥淵ou can get interesting and counterintuitive effects.鈥�
For example, “some theoretical work suggests that if we work with one of these bubbles that is in the BEC state, we might be able to form vortices 鈥� basically, little whirlpools 鈥� in the quantum material,鈥� says Lundblad. 鈥淭hat鈥檚 one example of a physical configuration that could help us understand BEC properties better and gain more insight into the nature of quantum matter.鈥�
Currently, the ultracold bubbles created in the Cold Atom Lab are not themselves Bose-Einstein Condensates. The bubble becomes a bit too warm to remain a BEC. That鈥檚 the next step for Lundblad and researchers, to transition the ultracold gas composing the bubbles to the BEC state and see how it behaves.
Before now, Lundblad would create BECs in an apparatus on the ground floor of Carnegie Science Hall, so the new Cold Atom Lab research represents a sea change in how data is collected and shared in the field of ultracold atomic physics: It can now be done in space, on a shared user facility, 鈥渇ar from a scientist’s home institution,鈥� says Lundblad.
But in other areas of physics, 鈥測ou do your sample prepping at your home institution, then you travel to an X-ray or beamline user facility for a week, then you come back to your home institution. The science is done in a shared facility.鈥� For example, Lundblad points out that his colleague Aleks Diamond-Stanic 鈥渄oesn’t own the Hubble space telescope but he applies for time to use it. It’s a user facility.鈥�
鈥淚鈥檒l get text messages with screen shots of images when I鈥檓 putting the kids to bed,鈥� says Lundblad. 鈥淭hat鈥檚 cool.鈥�
鈥淧art of what’s neat about this project is that it started out with, 鈥榃hat if we could create an atomic physics user facility? And that’s what the Cold Atom Lab is doing here,鈥� he said.
Lundblad gets access to the Cold Atom Lab for several days every few weeks. He communicates with the Jet Propulsion Lab in California, which executes what Lundblad outlines. (The astronauts aboard the space station are not involved.)
The experiments are run during business hours at JPL, so the data starts coming in later in the day. 鈥淚鈥檒l get text messages with screen shots of images when I鈥檓 putting the kids to bed,鈥� says Lundblad. 鈥淭hat鈥檚 cool.鈥�
鈥淭he BEC machine in Carnegie has been running for five or six years. It鈥檚 like an extension of my senses. I just know everything about it.鈥�
Lundbland could tell when the Carnegie BEC wasn鈥檛 working right, and he鈥檇 mention it to a student, who鈥檇 ask, 鈥淗ow do you know that?鈥� And Lundblad would say, 鈥淚t just doesn’t sound right.鈥�
Now, working with the Cold Atom Lab, circling the Earth a couple hundred miles above the 乐播传媒 campus, 鈥測ou don’t have that direct experience, so that鈥檚 a bit stressful.
With this advance in science, Lundblad knows he鈥檚 said goodbye to a more hands-on era of his work. 鈥淚t’s just a new way of doing things.鈥�
