then had wreaked havoc on the original salt compound, instructing the lab to rip out a number of the atoms of holmium, bit by bit, and replace them with yttrium, a silvery metal without such natural magnetic attraction, until he was left with a strange hybrid of a compound: a salt called lithium holmium yttrium tetrafluoride.
By virtually eliminating the magnetic properties of the compound, Rosenbaum eventually had created spin-glass anarchy – the atoms of this Frankenstein monstrosity pointing any way they liked. Being able to manipulate the essential property of elements like holmium by creating weird new compounds so cavalierly was a little like having ultimate control over matter itself. With these new spin-glass compounds, Rosenbaum could virtually change the properties of the compound at will; he could make the atoms orientate in a particular direction, or freeze them in some random pattern.
Nevertheless, his omnipotence had a limit. Rosenbaum’s holmium compounds behaved themselves in some regards, but not in others. One thing he could not do was to get them to obey the laws of temperature. No matter how cold Rosenbaum made his refrigerator, the atoms inside them resisted any sort of ordered orientation, like an army refusing to march in step. If Rosenbaum was playing God with his spin glasses, the crystal was Adam, stubbornly refusing to obey His most fundamental law.
Sharing Rosenbaum’s curiosity about the strange property of the crystal compound was a young student called Sayantani Ghosh, one of his star PhD candidates. Sai, as her friends called her, a native of India, had graduated with a first-class honours degree from Cambridge, after which she had chosen Tom’s lab for her doctoral programme in 1999. Almost immediately, she had distinguished herself by winning the Gregor Wentzel Prize, given each year by the University of Chicago’s physics department to the best first-year graduate student teaching assistant. The slight 23-year-old, who at first glance appeared abashed, hiding behind her copious dark hair, had soon impressed her peers and teachers alike with her bold authority, a rarity among science students, and her ability to translate complex ideas to the level an undergraduate could comprehend. Sai shared the distinction of winning the coveted prize with only one other woman since its inception 25 years before.
According to the laws of classical physics, applying a magnetic field will disrupt the magnetic alignment of a substance’s atoms. The degree to which this happens is the salt’s ‘magnetic susceptibility’. The usual pattern with a disordered substance is that it will respond to the magnetic field for a time and then plateau and tail off, as the temperature drops or the magnetic field reaches a point of magnetic saturation. The atoms will no longer be able to flip in the same direction as that of the magnetic field and so will begin to slow down.
In Sai’s first experiments, the atoms in the lithium holmium yttrium salt, as predicted, grew wildly excited with the application of the magnetic field. But then, as Sai increased the field, something strange began to happen. The more she turned up the frequency, the faster the atoms continued to flip over. What is more, all the atoms, which had been in a state of disarray, began pointing in the same direction and operating as a collective whole. Then, small clusters of about 260 atoms aligned, forming ‘oscillators’, spinning collectively in one direction or another. No matter how strong the magnetic field that Sai applied, the atoms remained stubbornly aligned with each other, acting in concert. This self-organization persisted for 10 seconds.
At first, Sai and Rosenbaum thought these effects might have something to do with the strange effects of the remaining atoms of holmium, known to be one of the very few substances in the world with such long-range internal forces that in some quarters it was described and worked out mathematically as something existing in another dimension.2 Although they didn’t understand the phenomenon they had observed, they wrote up their results, which were published in the journal Science in 2002.3
Rosenbaum decided to carry out another experiment to attempt to isolate the property in the crystal’s essential nature that had enabled it to override such strong outside influences. He left the study’s design to his bright young graduate student, suggesting only that she create a computerized three-dimensional mathematical simulation of the experiment she had intended to carry out. In experiments of this nature on such tiny matter, physicists must rely on a computerized simulation to confirm mathematically the reactions they are witnessing experimentally.
Sai spent months developing the computer code and building her simulation. The plan was to find out a bit more about the salt’s magnetic capability, by applying two systems of disorder to the crystal chip: higher temperatures and a stronger magnetic field.
She prepared the sample by placing it in a little 2.4 x 4.8 cm copper holder, then wrapped two coils around the tiny crystal: one a gradiometer, to measure its magnetic susceptibility and the direction of spin of the individual atoms, and the other to cancel out any random flux affecting the atoms inside.
A connection attached to her PC would enable her to change the voltage, the magnetic field or the temperature, and would record any changes whenever she altered one of the variables by the tiniest degree.
She began lowering the temperature, a fraction of a kelvin (K) at a time, and then began applying a stronger magnetic field. To her amazement, the atoms kept aligning progressively. Then she tried applying heat, and discovered they again aligned. No matter what she did, in every instance the atoms ignored the outside interference. Although she and Tom had flushed out most of the compound’s magnetic component, of its own volition, as it were, it was turning into a larger and larger magnet.
That’s weird, she thought. Perhaps she should take more data, just to ensure they had encountered nothing strange in the system.
She repeated her experiment over six months until the early spring of 2002, when her computer simulation was finally complete. One evening, she mapped the results of the simulation on a graph, and then she superimposed the results from her actual experiment. It was as though she had drawn a single line. There on the computer screen was a perfect duplicate: the diagonal line formed from the computer simulation lay exactly over the diagonal line created from the results of the experiment itself. What she had witnessed in the little crystal was not an artefact, but something real that she had now reproduced in her computer simulation. She had even mapped out where the atoms should have been on the graph, had they been obeying the usual laws of physics. But there they were in a line: a law completely unto themselves.
She wrote Rosenbaum a guarded email late that evening: ‘I’ve got something interesting to show you in the morning.’ The following day, they examined her graph. There was no other possibility, they both realized; the atoms had been ignoring her and instead were controlled by the activity of their neighbours. No matter whether she blasted the crystal with a strong magnetic field or an increase in temperature, the atoms overrode this outside disturbance.
The only explanation was that the atoms in the sample crystal were internally organizing and behaving like one single giant atom. All the atoms, they realized with some alarm, must be entangled.
One of the strangest aspects of quantum physics is a feature called ‘non-locality’, also poetically referred to as ‘quantum entanglement’. The Danish physicist Niels Bohr discovered that once subatomic particles such as electrons or photons are in contact, they remain cognizant of and influenced by each other instantaneously over any distance forever, despite the absence of the usual things that physicists understand are responsible for influence, such as an exchange of force or energy. When entangled, the actions – for instance, the magnetic orientation – of one will always influence the other in the same or the opposite direction, no matter how far they are separated. Erwin Schrödinger, another one of the original architects of quantum theory, believed that the discovery of non-locality represented no less than quantum theory’s defining moment – its central property and premise.
The activity of entangled particles is analogous to a set of twins being separated at birth, but retaining identical interests and a telepathic connection forever. One lives in Colorado, and the other in London. Although they never meet again, both like the colour blue. Both take a job in engineering. Both like to ski; in fact when one falls