Tag Archives: haroche

The 2012 Nobel Prize in Physics

This year’s Nobel has been awarded jointly to the French physicist Serge Haroche and American physicist David J. Wineland, for their independent usage of a special ultracool cavity and an ion trap respectively, to capture and study individual particles in their quantum states. This might sound extremely theoretical, but it could lead to the advancement of quantum computing, where computers can perform incredibly complicated algorithms in a fraction of the time they take to finish today.

All this is the result of the mind-bendingly odd physics that happens down at the atomic level, a quantum state that’s unlike anything we see in classical physics.

Quantum weirdness, to be honest, happens all the time: particles are naturally imbued with the ability to be both a, well, particle as well as a wave depending on how they’re measured and observed. But we don’t see cows, for instance, waving enthusiastically in fields because at the macro level these quirks of the quantum world cancel out. And they do so because of how the particles themselves interact with the external world.

In their natural, unobserved state — a sort of Platonic ideal, really — particles exist in a cloud of probable locations. They can’t really be pinned down, as Heisenberg discovered; they can be measured spatially or their velocities can be tracked, but never both simultaneously. This is said to be a superposition of states. This is where Schrodinger’s cat, poor creature, comes into the picture. The paradox, as the physicist put it, is that since every particle is in a state of flux, then so must the macro object be in flux. If you put a cat in a box, and place a dangerous radioactive isotope in it, then you essentially have three probable states once the radioactive isotope decays: the cat is dead; the cat is alive, or the cat is in a bizarre superposition of both dead and alive states. Yet when we open the box, the cat is either dead or alive, and can never be both simultaneously. Why is this so, and how did we resolve that strange paradox?

Much of the work that Wineland and Haroche have been doing centers on this very question. I don’t mean to say that they’ve solved the entire problem of what a quantum atomic particle is, or anything fundamentally philosophical* regarding the field of quantum physics, but I do know that their work has illuminated the stages by which an atom or photon resolves itself from a haze of probability into a classical particle, like a distant object comes into focus when we train a pair of binoculars onto it.

Their work is very different, yet very complementary. Here are quotes from Stockholm’s** press release package regarding the nature of Wineland’s research:

…electrically charged atoms or ions are kept inside a trap by surrounding them with electric fields. The particles are isolated from the heat and radiation in their environment by performing the experiments in vacuum at extremely low temperatures.

Actually those particles are created using a very interesting method outlined in the advanced background PDF from the Nobel website: they’re first energized by a laser, and then allowed to decay to a lower energy state — so low, in fact, that it’s close to absolute zero. Then, Wineland’s team further stimulates the atom with a laser so that it achieved something that’s halfway between two of the states that it could occupy. Left in a strange limbo between one state and another, the atom is now in a superposition of states, and its weird and wonderful properties can be studied.

In contrast, Haroche and his team created a cavity from extremely reflective superconducting glass, which contained a variable number of photons that bounced back and forth between the mirrors for an extremely long distance (a whopping 40,000 km, to be precise). To measure the presence of the photons, the team sends in very carefully prepared atoms that don’t absorb the photons but are changed by it; they undergo what’s known as a phase shift. As the press release package puts it,

…if you think of the atom’s quantum state as a wave, the peaks and the dips of the wave become shifted

Haroche’s team effectively built a nano-lab that could be used to chart the evolution of an atom as it went from a highly complex quantum state to one where it behaved essentially like a classical particle.

This could lead the way to those most magical of technologies that we’ve been dreaming about this century: a quantum computer.

*In fact, I’d be wholly unqualified to answer that.

** Only because I think saying “Stockholm” is so much cooler than saying “the Nobel committee”