Two physicists who developed techniques to study the interplay between light and matter on the smallest and most intimate imaginable scale won the Nobel Prize in Physics on Tuesday. They are Serge Haroche, of the Collège de France and the École Normale Supérieure, in Paris, and David Wineland, of the National Institute of Standards and Technology and the University of Colorado.
They will split 8 million Swedish krona, or about $1.2 million, and receive their award in Stockholm on Dec. 10.
Their work, the academy said, enables scientists to directly observe some of the most bizarre effects -- like the subatomic analogue of cats who are alive and dead at the same time -- predicted by the quantum laws that prevail in the microcosm, and could lead eventually to quantum computers and super accurate clocks.
Reached by the Nobel committee while walking with his wife this morning in Paris, Dr. Haroche said that when he saw the area code on his phone, he said he had to go sit down on a bench. "It was real," he said in a phone news conference.
Scientists have known for a hundred years now that atoms are not like you and me. On the smallest scales of nature the common sense laws of science had been overthrown by the strange house rules of quantum mechanics, in which physical systems were represented by mathematical formulations called wave functions that encapsulated all the possibilities of some event or object. Light or a subatomic particle like an electron could be a wave or a particle depending on how you wanted to look at it, and causes were not guaranteed to be linked to effects. An electron could be in two places at once, or everywhere until someone measured it, courtesy of Heisenberg's Uncertainty principle, which caused a cranky Einstein to grumble that God didn't play dice.
Erwin Schrödinger, one of the founders of the theory, as was Einstein for that matter, once complained that according to quantum principles a cat in box would be both alive and dead until somebody looked at it.
Until recent years this was all philosophy, and physicists could comfort themselves with the realization that quantum mechanics works so spectacularly well -- every time you turn on your computer, for example -- that for some of them the real problem is why the ordinary world does not work that way; why, for example, your sunglasses are not simultaneously in the car, back at the summer cabin or on the shelf when you want them.
Now scientists like Dr. Haroche and Dr. Wineland and their colleagues have been able to direct experiments and catch nature in the act of being quantum and thus explore the boundary between quantum reality and normal life. Their work involves isolating the individual nuggets of nature -- atoms and the particles that transmit light, known as photons -- and making them play with each other.
Dr. Wineland's work has focused on the matter partner in the light-matter dance. He and his colleagues trap charged beryllium atoms, or ions, in an electric field and cool them with specially tuned lasers so that they are barely moving, which is another way of saying they are very, very cold.
In one set of experiments they then tapped the beryllium ions with lasers with just enough energy to produce another kind of cat state. In this one, the outermost electrons in the ion are stuck between two of the permitted orbits around the beryllium nucleus; as a result they oscillate back and forth and the beryllium ion is in two different energy states at once.
Because cold atoms vibrate and emit light at very precise frequencies, Dr. Wineland and his colleagues have also used their trapped ions to make the world's most accurate clocks. Modern day atomic clocks are based on the cesium atoms, which vibrate in the microwave range of frequencies, but beryllium vibrates 100 times faster, in the visible range of frequencies. A good optical clock would only have lost 5 seconds over the whole course of cosmic time -- 13.7 billion years.
Dr. Haroche, conversely traps photons, the particles that transmit light, in a mirrored cavity whose walls are so finely polished that one photon will bounce back and forth for a tenth of a second -- an eternity in atomic physics -- before leaking out or being absorbed. Then he sends in a single atom, as a spy, to interact with the light.
Normally to detect light is to destroy it, photons are absorbed in our retinas or in the C.C.D. chips in our cameras. But in one case by observing subtle effects of the light on the atoms, he and his colleagues could count the photons "as one would do with marbles in a box," as he put it on his Web site without destroying them.
In another case in 1996, Dr. Haroche and his colleagues put Schrödinger out of his misery by putting their boxed photon into a "cat state," in which one photon is out of phase with itself, essentially oscillating in opposite directions at the same time. Then by sending in their spy atoms, they measure how long it took for the "cat state" to decay and the photon to oscillate in one direction or the other.
In more recent experiments, they have developed feedback techniques to keep the cat state going longer. Such techniques are crucial for the dream of quantum computers, which manipulate so-called qubits that are 1 and 0 simultaneously to solve some problems like factoring gigantic numbers to break codes beyond the capacity of ordinary computers. Such computers depend on the ability to keep their qubits isolated from the environment in order to preserve their magical computing powers and yet still have to be able to read out the answer.
In 1995 Dr. Wineland's group used trapped ions to carry out a 2-qubit operation. Recently researchers have done it with as many as 14 qubits, but a lot of work remains to be done, scientists say, before serious quantum computers are a reality.
This article originally appeared in The New York Times.