When I reached IBMâs Watson research center, Iâd barely seen Aaron in three weeks. Aaron is an experimentalist pursuing a physics PhD at Caltech. I eat dinner with him and other friends, most Fridays. The group would gather on a sidewalk in the November dusk, those three weeks. Light would spill from a lamppost, and weâd tuck our hands into our pockets against the chill. Aaronâs wife would shake her head.
âThe fridge is running,â sheâd explain.
Aaron cools down mechanical devices to near absolute zero. Absolute zero is the lowest temperature possible,1 lower than outer spaceâs temperature. Cold magnifies certain quantum behaviors. Researchers observe those behaviors in small systems, such as nanoscaleÂ devices (devices about 10-9Â meters long). Aaron studies few-centimeter-longÂ devices. Offsetting the devicesâ size with cold might coax them into exhibiting quantum behaviors.
The cooling sounds as effortlessÂ as teaching a cat to play fetch. Aaron lowers his fridgeâs temperature in steps. Each step involves checking for leaks: A mix of two fluidsâtwo types of heliumâcools the fridge. One type of helium costs about $800 per liter. Lose too much helium, and youâve lost your shot at graduating. Each leak requires Aaron to warm the fridge, then re-cool it. He hauled helium and pampered the fridge for ten days, before the temperature reachedÂ 10 milliKelvins (0.01 units above absolute zero). He then worked likeâ¦well, like a grad student to check for quantum behaviors.
Aaron came to mind at IBM.
âHow long does cooling your fridge take?â I asked Nick Bronn.
Nick works at Watson, IBMâs research center in Yorktown Heights, New York. Watson has sweeping architecture frosted with glass and stone. The building reminded me of Fred Astaire: decades-old, yet classy. I found Nick outside the cafeteria, nursing a coffee. He had sandy hair, more piercings than I, and a mandate to build a quantum computer.
âMight I look around your lab?â I asked.
âDefinitely!â Nick fished out an ID badge; grabbed his coffee cup; and whisked me down a wide, window-paneled hall.
Different researchers, across the world, are building quantum computers from different materials. IBMers use superconductors. Superconductors are tiny circuits.Â They function at low temperatures, so IBM has seven closet-sized fridges. Different teams use different fridges to tackle different challenges to computing.
Nick found a fridge that wasnât running. He climbed half-inside, pointed at metallic wires and canisters, and explained how they work. I wondered how his cooling process compared to Aaronâs.
âYou push a button.â Nick shrugged. âThe fridge cools in two days.â
IBM, I learned, has dry fridges. Aaron uses a wet fridge. Dry and wet fridges operate differently, though both require helium. Aaronâs wet fridge vibrates less, jiggling his experiment less. Jiggling relatesÂ to transferring heat. Heat suppressesÂ the quantum behaviors Aaron hopes to observe.
Heat and warmth manifest in many ways, in physics. Count Rumford, an 18th-century American-Brit, conjectured the relationship between heat and jiggling. He noticed that drillingÂ holes into canons immersed in water boils the water. The drill bits rotated–moved in circles–transferring energy of movement to the canons, which heated up.Â Heat enraptures me because it relates to entropy, a measure of disorderliness and ignorance. The flow of heat helps explain why time flows in just one direction.
A physicist friend of mine writes papers, he says, when catalyzed by âblinding rage.â He reads a paper by someone else, whose misunderstandings anger him. His wrath boils over into a research project.
Warmth manifests as the welcoming of a visitor into oneâs lab. Nick didnât know me from Fred Astaire, but he gave me the benefit of the doubt. He let me pepper him with questions and invited more questions.
Warmth manifests as a 500-word disquisition on fridges. I asked Aaron, via email, about how his cooling compares to IBMâs. I expected two sentences and a link to Wikipedia, since Aaron works 12-hour shifts. But he took pity on his theorist friend. He also warmed to his subject. Canât you sense the zealÂ in âHelium is the only substance in the world that will naturally isotopically separate (neat!)â? No knowledge of isotopic separation required.
Many quantum scientists like it cold. But understanding, curiosity, and teamwork fire us up. Anyone under the sway of those elements of scienceÂ likes it hot.
With thanks to Aaron and Nick. Thanks also to John Smolin and IBM Watsonâs quantum-computing-theory team for their hospitality.
1In many situations. Some systems, like small magnets, can access negative temperatures.