Cat's out of the box as we peer into quantum world

Physicists get to see particles in two states at once, just like the famous Schrodinger paradox, while chemists listen in on private lines to cells

PUBLISHED : Sunday, 14 October, 2012, 12:00am
UPDATED : Sunday, 14 October, 2012, 3:26am

Many people have heard of Schrodinger's cat. The winners of this year's Nobel Prize in physics have shown deep insights into this famous paradox of quantum mechanics.

In addition to the physics Nobel, this week also saw the announcement of the Nobel Prize in chemistry. Both science prizes went to work focusing on the transfer of information. While the prize-winning physics predictably involved brain-bending quantum mechanics, the chemistry prize focused not on test-tube reactions, but on cellular biology.

The Nobel Prize in physics was jointly awarded to Frenchman Serge Haroche, of the College de France and Ecole Normale Superieure, in Paris, and American David Wineland, of the National Institute of Standards and Technology and the University of Colorado Boulder, "for groundbreaking experimental methods that enable measuring and manipulation of individual quantum systems".

These experiments involve the sort of quantum weirdness described by physicist Erwin Schrodinger in 1935. By extrapolating quantum mechanics to the everyday world, he described a "ridiculous" situation in which a cat was placed in a box with a flask of poison and some radioactive material whose decay could shatter the flask.

According to quantum mechanics, the cat would be both alive and dead at the same time; but of course, if anyone opened the box, they could only find either a live cat or a dead one.

Until recently, it had been thought difficult or impossible to observe individual atoms and sub-atomic particles that might be in two quantum states at the same time: physicists usually studied many particles at once. But sophisticated new techniques, with pioneering work by teams led by Haroche and Wineland, are helping us peer into the quantum world.

Both teams have succeeded by finding ways to trap particles.

Haroche traps light particles - photons - in a cavity between mirrors of superconducting material so reflective that a photon can remain trapped for a tenth of a second without being absorbed - enough time for it to travel 40,000 kilometres bouncing about in a space roughly 3cm wide. He then fires in specially prepared atoms, each of which interacts with the photon, resulting in a tiny shift in the wave motion of the atom.

Using this shift, Haroche can detect photons without destroying them - unlike normal detectors that convert photon energy to electrical energy.

He has monitored photons in their "cat state", essentially oscillating both up and down at the same time, until they oscillated one way or the other.

Wineland, by contrast, keeps electrically charged atoms - ions - trapped within a vacuum in an electric field. Using a laser to encourage energy emission, his group members lower the temperatures of the ions to almost absolute zero, so they are near motionless. Here, too, he can create states like Schrodinger's cat, with laser pulses nudging an ion into two states simultaneously.

Wineland has used the ion traps to create the world's most accurate clocks, albeit they are short-lived and hardly the sort of timepieces you can buy in a store. These may help with applications such as navigation.

The Nobel Foundation also envisages that the work by Haroche and Wineland could pave the way towards creating quantum computers that could transform lives as radically as have the computers we use today.

The chemistry prize is for work that's more readily understood, but can also have far-reaching consequences. It was awarded to Americans Robert Lefkowitz, of the Howard Hughes Medical Institute and Duke University, both on the east coast of the United States, and Brian Kobilka, of the west coast Stanford University School of Medicine, "for studies of G-protein-coupled receptors".

The origins of their work can be traced to the late 19th century, when scientists found adrenaline raised the blood pressure and heart rate, but they could not discover how. Adrenaline did not enter cells, so how did information get through? A mechanism involving nerves was ruled out.

As a student, Lefkowitz was tasked with helping to finding the answer. It led to a position as head of a research team and Lefkowitz chose to focus on this question.

Using radioactive tagging, the team extracted receptors - molecular sensors - from living tissue. Other researchers had found what were called G-proteins within cells; a signal from a receptor can trigger these to cause a series of reactions altering a cell's metabolism.

Kobilka joined the team, and helped find the gene for the adrenaline receptor protein - which suggested the sensor probably winds through the cell wall seven times. In what he later described as a "real eureka moment", Lefkowitz realised this was the same number of spiral strings as in light receptors others had found, and concluded there must be a family of receptors that looked alike and functioned in the same manner.

In a new position at Stanford, Kobilka set himself the task of creating an image of the receptor. He needed to use X-ray crystallography, which had been successfully used for water-soluble proteins. Yet the receptors are not water soluble, and Kobilka took two decades before at last obtaining an image. This was published last year, and shows a receptor as it is passing a signal to a G-protein.

"This image is a molecular masterpiece - the result of decades of research," the Nobel Foundation notes.

Lefkowitz has likewise stayed at the forefront of the field, which has revealed almost 1,000 genes that code for receptors, roughly half of which receive odours, while a third are for hormones and other signalling substances like adrenaline, histamine and dopamine. Some capture light, and the functions of more than 100 are unknown.

As about half of all medications act through these receptors, they are of immense importance in creating more effective drugs.

That's all very well, you're probably thinking now. But how can I get myself a Nobel Prize? Perhaps surprisingly, an outstanding school performance is not essential: a school report on John Gurdon, joint winner of this year's Nobel Prize for Medicine, said his ideas about becoming a scientist were "quite ridiculous". You might have more luck if you're a man: only four women have ever won the chemistry prize. Plus: eat plenty of chocolate.

Yes, chocolate. For in more science news this week, the New England Journal of Medicine published findings that the higher a nation's per capita chocolate consumption, the more Nobel laureates it spawns.

Author Franz Messerli acknowledges this might be coincidence, but advises: "If you want a physics Nobel Prize, it pretty much has got to be dark chocolate."

Martin Williams is a Hong Kong-based writer, with a Cambridge University PhD in physical chemistry