The Top 6 Physics Stories of 2006

Invisibility cloak invented, teleportation works (but not for you), Einstein the swinger, and more.

Monday, January 8, 2007

16. Quantum Teleportation Leaps Toward Reality

It's not exactly "Beam me up, Scotty," but for the first time scientists have teleported information between light and atoms, hastening the long-awaited advent of ultrafast quantum computers and unbreakable encryption schemes. Quantum teleportation is the process of making a subatomic particle's physical state vanish from one place and appear in another, a little like Captain Kirk's transporter. What makes this possible is a bizarre phenomenon known as entanglement, in which a pair of particles have complementary characteristics, such as two electrons spinning in opposite directions. The irreducible uncertainty of quantum mechanics makes it impossible to predict the state of a given electron, but because the two particles are entangled, measuring the state of one automatically determines the state of the other, regardless of how far apart they are.

In order to teleport a state between light and atoms, Eugene Polzik and his colleagues at the Niels Bohr Institute in Copenhagen, in collaboration with Ignacio Cirac of the Max Planck Institute for Quantum Optics in Germany, entangled a light beam with a magnetized gas of cesium atoms. The researchers then encoded the state they wanted to teleport into the light beam with laser pulses. By separating the entangled quantum information from the light beam and uncovering the laser message, the team was able to teleport the complementary state to the atoms at a distance of half a yard. "For the first time," Polzik says, quantum teleportation "has been achieved between light—the carrier of information—and atoms." This was also the first time that it was done with a macroscopic atomic object acting as the target. Scientists had previously teleported states only between pairs of photons or pairs of atoms. But a practical quantum computer, Polzik notes, requires the transfer of information between a data stream, such as light, and a stored quantum state, such as the atoms in a hard drive.

Curt Suplee

32. Invisibility Cloak Invented!

When a tabloid best known for topless pinups breaks a Science journal embargo to publish news of a major physics finding, you know the world has gone a little gaga. "Boffin invents invisibility cloak," blared British newspaper The Sun on October 19, reporting that physicists from Duke University and Imperial College London had designed radical new materials that can bend microwaves around an object so that they are neither absorbed nor scattered. This achievement is the "first practical realization" of a cloak of invisibility, says lead scientist David Smith. The researchers succeeded in cloaking a two-inch-wide foam-filled copper cylinder from microwaves. If they could guide shorter-wavelength visible light waves around the same object, "it would appear as though they came through free space, as if nothing was there," Smith says. Despite the screaming headlines—and the entreaties of both government intelligence agencies and Harry Potter fans—Smith admits "it may be a while" before he makes anyone vanish.

Josie Glausiusz


The invisibility device

50. New Letters Explore Einstein's Family Life

Albert Einstein has long been revered as a scientist, but in recent years he's been judged harshly as a neglectful husband and father. A cache of 1,300 personal letters made public in July by the Albert Einstein Archives at the Hebrew University of Jerusalem reveal a far more complicated picture.

When away from home, Einstein wrote almost daily to his second wife, Elsa, and stepdaughter, Margot, who bequeathed these letters to the archives upon her death in 1986 — stipulating that they be sealed for 20 years. The honesty with which Albert confided in both women is startling. According to archivist Barbara Wolff, he names six mistresses. His airy dismissals of these women, intended to reassure his family, sound hollow. From Oxford he wrote to Margot, at home in Berlin, "Out of all the dames, I am in fact only attached to Mrs. L[enbach] who is absolutely harmless and decent, and even with this there is no danger to divine world order."

However, in a letter to a friend, Einstein revealed a layer of guilt beneath his bravado: "What I admire in your father is that, for his whole life, he stayed with only one woman. This is a project in which I grossly failed, twice." He was also well aware of his shortcomings as a parent, writing of Margot that he loved her as a daughter, "perhaps even more so. Who knows what kind of brat she would have become [had I fathered her]."

The newly released letters also bear witness to Einstein's attempts to foster relationships with his sons, Hans Albert and Eduard, who lived in Zurich with his ex-wife, Mileva. Some biographers have suggested that Einstein wrote off Eduard due to his mental illness, but the correspondence reveals a father grieving as his child descends into schizophrenia. What the writing doesn't tell much about is Einstein's life as a scientist, as he seems to have kept work and family largely separate.

Anne Casselman

71. Anti-Repulsion Discovered

Normally, atoms that repel each other will fly apart, just as the like poles of two magnets facing each other will. But this year physicists forced atoms to be bound by their mutual repulsion. Andrew Daley, a physicist at the University of Innsbruck in Austria, and his colleagues provoked this bond by pumping an ultracool, high-density collection of rubidium atoms — known as a Bose-Einstein condensate — into a 3-D "cage" of laser light, known as an optical lattice. The lattice confines atoms in discrete energy bands, much the way atoms are trapped in a crystal. Because of how quantum mechanics works, gaps between the bands are forbidden zones, requiring energy values that no atom in the lattice can attain. By calibrating the frequency of the laser light, Daley and his crew created conditions such that the energy a pair of repelling atoms would gain by separating would land them within the verboten region. With nowhere to go, the atoms must stay together. "It's like two people who hate each other, but hate each other so much that they can't separate," says coresearcher Adrian Kantian. These love-hate configurations of atoms could be used to test quantum computers and model high-temperature superconductors, materials that transmit electricity with near-perfect efficiency.

Alex Stone

87. Light Moves in Reverse

Physicists at the University of Rochester have coaxed light into traveling backward — and, weirdly enough, to do so faster than light itself. In a clever tabletop experiment, the researchers sent a pulse of light through a single optical fiber doped with erbium, a metal that alters the speed at which light waves move through the fiber. Just as one light pulse enters, a second pulse appears at the opposite end, as if by magic. This second pulse then splits in two, with half propagating backward and the other half exiting the fiber. The overall effect is that "the pulse appears to leave before it enters," says physicist Robert Boyd, who designed the experiment. No physical laws are violated because the information in the pulse never breaks the light-speed barrier. In recent years physicists have also learned to slow light or to ramp it up past the usual speed of 186,282 miles per second. Confused? This animated Web site may help. Replacing electrical switches with optical buffers that control the speed of light could lead to more efficient high-speed telecommunication networks.

Alex Stone

99. Element 118 Debuts On the Periodic Table

Chemists will soon have to make room on the periodic table for a new element discovered in October. Element 118, tentatively called ununoctium, is the heftiest to date — it has 118 protons and 176 neutrons, compared with 82 protons and 126 neutrons in lead — but it is also one of the shortest-lived, decaying in less than a millisecond. To whip up a batch of ununoctium, a team of Russian and American nuclear physicists shot calcium atoms (element 20) at a target of radioactive californium (element 98) in a particle accelerator at the Joint Institute for Nuclear Research in Dubna, Russia. Every so often, the nuclei of the two atoms would hit head on and stick, overcoming the repulsive force between positively charged protons. It wasn't easy: After two months and 30,000,000,000,000,­000,000 collisions, the group managed to create only three atoms of the new species. Starting in 2007, they will search for even heavier elements, some of which are predicted to live for several hours. 

Alex Stone

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