���Ҵ�ý�ƽ������

We all know what a tenth of a second feels like. It’s a jiffy, a snap of the fingers, or a camera shutter click. But what does 14 billion years–the age of the universe–feel like? JILA’s atomic clock has the precision to measure the age of the universe to within a tenth of a second. That sort of precision is difficult to intuit. Yet, JILA’s atomic clock, which is the most precise clock in the world, continues to improve its precision. The latest jump in precision, of nearly 50 percent, came about from a new perspective.

Why are we here? This is an age-old philosophical question. However, physicists like Will Cairncross, Dan Gresh and their advisors Eric Cornell and Jun Ye actually want to figure out out why people like us exist at all. If there had been the same amount of matter and antimatter created in the Big Bang, the future of stars, galaxies, our Solar System, and life would have disappeared in a flash of light as matter and antimatter recombined.

Imagine A Future . . . The International Moon Station team is busy on the Moon’s surface using sensitive detectors of gravity and magnetic and electric fields looking for underground water-rich materials, iron-containing ores, and other raw materials required for building a year-round Moon station. The station’s mission: launching colonists and supplies to Mars for colonization. Meanwhile, back on Earth, Americans are under simultaneous assault by three Category 5 hurricanes, one in the Gulf of Mexico and two others threatening the Caribbean islands. Hundreds of people are stranded in the rising waters, but thanks precision cell-phone location services and robust cell-tower connections in high wind, their rescuers are able to accurately pinpoint their locations and send help immediately.

The Regal group recently met the challenge of measurements in an extreme situation with a device called an interferometer. The researchers succeeded by using creative alterations to the device itself and quantum correlations. Quantum correlations are unique, and often counterintuitive, quantum mechanical interactions that occur among quantum objects such as photons and atoms. The group exploited these interactions in the way they set up their interferometer, and improved its ability to measure tiny motions using photons (particles of light).

In the Ye group’s new quantum simulation experiment, cold strontium atoms, which are analogs of electrons, are allowed to tunnel between the pancakes that confine the atoms with laser light. Because the atoms moving in an array of pancakes are analogs of electrons moving in solids, such studies are expected to shed light on the complex physics of metals and other solids.

Bob Peterson and his colleagues in the Lehnert-Regal lab recently set out to try something that had never been done before: use laser cooling to systematically reduce the temperature of a tiny drum made of silicon nitride as low as allowed by the laws of quantum mechanics. Although laser cooling has become commonplace for atoms, researchers have only recently used lasers to cool tiny silicon nitride drums, stretched over a silicon frame, to their quantum ground state. Peterson and his team decided to see just how cold their drum could get via laser cooling.

The Ye and Rey groups have discovered the strange rules of quantum baseball in which strontium (Sr) atoms are the players, and photons of light are the balls. The balls control the players by not only getting the atoms excited, but also working together. The players coordinate throwing and catching the balls. While this is going on, the balls can change the state of the players! Sometimes the balls even escape the quantum baseball game altogether and land on detectors in the laboratory.

Graduate student Adam Kaufman and his colleagues in the Regal and Rey groups have demonstrated a key first step in assembling quantum matter one atom at a time. Kaufman accomplished this feat by laser-cooling two atoms of rubidium (87Rb) trapped in separate laser beam traps called optical tweezers. Then, while maintaining complete control over the atoms to be sure they were identical in every way, he moved the optical tweezers closer and closer until they were about 600 nm apart. At this distance, the trapped atoms were close enough to “tunnel” their way over to the other laser beam trap if they were so inclined.

Our work in collaboration with the Garrett Cole and the Aspelmeyer group in Vienna has been published in APL. We have demonstrated single-crystal high-stress membranes with a mechanical Q similar to SiN membranes.

Research associate Tom Purdy and his colleagues in the Regal group have just built an even better miniature light-powered machine that can now strip away noise from a laser beam. Their secret: a creative workaround of a quantum limit imposed by the Heisenberg Uncertainty Principle. This limit makes it impossible to simultaneously reduce the noise on both the amplitude and phase of light inside interferometers and other high-tech instruments that detect miniscule position changes.