At 9:10 AM, the lab next door was blasting “Born to Be Wild.”
I was at Oxford, moonlighting as a visiting researcher during fall 2013. My hosts included quantum theorists in Townsend Laboratory, a craggy great-uncle of a building. Poke your head out of the theory office, and Experiment would flood your vision. Our neighbors included laser wielders, ion trappers, atom freezers, and yellow signs that warned, “DANGER OF DEATH.”
Hardly the neighborhood Mr. Rogers had in mind.
The lab that shared a wall with our office blasted music. To clear my head of calculations and of Steppenwolf, I would roam the halls. Some of the halls, that is. Other halls had hazmat warnings instead of welcome mats. I ran into “RADIATION,” “FIRE HAZARD,” “STRONG MAGNETIC FIELDS,” “HIGH VOLTAGE,” and “KEEP THIS TOILET NEAT AND TIDY.” Repelled from half a dozen doors, I would retreat to the office. Kelly Clarkson would be cooing through the wall.
“We can hear them,” a theorist observed about the experimentalists, “but they can’t hear us.”
Experiment should test, disprove, and motivate theories; and theory should galvanize and (according to some thinkers) explain experiments. But some theorists stray from experiment like North America from Pangaea.
The theoretical physics I’ve enjoyed is abstract. I rarely address platforms, particular physical systems in which theory might incarnate. Quantum-information platforms include electrons in magnetic fields, photons (particles of light), ion traps, quantum dots, and nuclei such as the ones that image internal organs in MRI machines.
Instead of addressing electrons and photons, I address mathematics and abstract physical concepts. Each of these concepts can incarnate in different forms in different platforms. Examples of such concepts include preparation procedures, evolutions, measurements, and memories. One preparation procedure defined by one piece of math can result from a constant magnetic field in one platform and from a laser in another. Abstractness has power, enabling one idea to describe diverse systems.
I’ve enjoyed wandering the hills and sampling the vistas of Theory Land. Yet the experimentalist next door cranked up the radio of reality in my mind. “We can hear them,” a theorist said. In Townsend Laboratory, I began listening.
My Oxford collaborators and I interwove two theoretical frameworks that describe heat transferred and work performed on small scales. One framework, one-shot statistical mechanics, has guest-starred on this blog. The other framework consists of fluctuation-dissipation relations. Fluctuation relations describe the loss of information stored in a system tarnished by its environment. Imagine storing information in a particle’s spin (basically, the particle’s orientation). If the spin points in one direction, it encodes one number; if the spin points in another direction, it encodes another number. If air molecules jostle your particle, or if a shot of energy causes your particle to bounce around, the memory’s reliability degrades. Fluctuation relations quantify the degradation.
My colleagues and I addressed “information,” “systems,” and “interactions.” We deployed abstract ideas, referencing platforms only when motivating our work. Then a collaborator challenged me to listen through the wall.
Experimentalists have tested fluctuation relations. Why not check whether their data supports our theory? At my friend’s urging, I contacted experimentalists who’d shown that DNA obeys a fluctuation relation. The experimentalists had unzipped and re-zipped single DNA molecules using optical tweezers, which resemble ordinary tweezers but involve lasers. Whenever the experimentalists pulled the DNA, they measured the force they applied. They concluded that their platform obeyed an abstract fluctuation theorem. The experimentalists generously shared their data, which supported our results.
My colleagues and I didn’t propose experiments. We didn’t explain why platforms had behaved in unexpected ways. We checked calculations with recycled data. But we ventured outside Theory Land. We learned that one-shot theory models systems modeled also by fluctuation relations, which govern experiments. This link from one-shot theory to experiment, like the forbidden corridors in Townsend Laboratory, invite exploration.
In Townsend, I didn’t suffer the electric shocks or the explosions advertised on the doors (though the hot water in the bathroom nearly burned me). I turned out not to need those shocks. Blasting rock music at 9:10 AM can wake even a theorist up to reality.