2000—NIST scientists demonstrate a technique enabling optical frequency combs—precision tools for measuring high frequencies, or colors, of light—to directly link optical and radio frequencies. This achievement contributed to the 2005 Nobel Prize in Physics shared by NIST physicist Jan Hall, who was cited for helping to transform lasers into precision measurement tools, including optical frequency combs. Frequency combs, made possible by the development of ultrafast lasers, have diverse applications and are essential to next-generation atomic clocks, functioning as the "gears" that link clock operations to lower frequencies that can be measured.
2001—Timekeeping took a leap forward when NIST physicist Jim Bergquist used a very stable laser and a frequency comb specially modified by NIST colleague Scott Diddams and NIST guest researcher Thomas Udem to make what became the world's best optical atomic clock, based on a single ion of mercury. Optical atomic clocks operate at much higher frequencies than microwave clocks such as NIST-F1. As of 2009, NIST's experimental mercury clock is the most precise clock in the world: If it could be operated for that long, the clock would neither gain nor lose 1 second in more than 1 billion years. Even so, it remains to be seen which atom and optical clock design are chosen the next international standard for time and frequency.
2003—NIST physicist Deborah Jin and colleagues at JILA created the first molecular condensate, or "super molecule," using laser cooling techniques. This advance may lead to a better understanding of superconductivity, the flow of electrons with no resistance. Jin has been recognized with numerous honors, including a MacArthur Fellowship (or "genius grant").
2004—NIST scientists, led by David Wineland, used lasers to demonstrate, concurrently with another research group in Austria, the first quantum "teleportation" of information stored in atoms, a technique that may be useful in quantum computers. Wineland helped launch the field of experimental quantum computing beginning in the mid-1990s.
Through many pioneering experiments, this group was the first to successfully demonstrate the building blocks of a practical quantum computer—which, if one can be built, could solve certain problems that are intractable using today's technology.
2004—NIST physicist John Kitching and colleagues used miniature lasers to demonstrate the first chip-scale atomic clock and first chip-scale atomic magnetometer, bringing atomic precision to a wide range of compact applications. The heart of these mini devices is about the size of a grain of rice. Several commercial versions of mini atomic clocks are in the works, and Kitching is now developing mini magnetometers for biomedical and security applications.
2004—NIST researchers Jack Stone and Alois Stejskal demonstrated a new instrument for measuring the refractive index of air. Using helium to self-calibrate a refractometer, the team was able to calculate the maximum uncertainty in length measurements introduced by the instrument itself. Uncertainty in the air refractive index is the limiting factor for realization of the meter using interferometry outside of a vacuum environment. (Length measurements in air require corrections based on precise knowledge of the air refractive index, and this sets the fundamental limitation for practical measurements.) The ability to correct for these errors provided a path toward future improvements in practical length measurements based on laser interferometry.
2006—NIST researcher John Lehman and collaborators turned lasers into tools for cleaning carbon nanotubes—tiny cylinders made of carbon atoms—which hold promise for diverse applications such as ultrastrong fibers, electrical wires in molecular devices, and hydrogen storage components for fuel cells. The team demonstrated a simple method of cleaning nanotubes using carefully calibrated laser pulses. The method greatly reduces the amount of carbon impurities in a sample of bulk carbon single-walled nanotubes. The method is simpler and less costly than conventional "wet chemistry" processes. NIST researchers also have used carbon nanotubes in custom coatings for devices that measure laser power.
2007—NIST researcher Kris Helmerson and colleagues from NIST and the University of Maryland made the first observation of a "persistent" current—a frictionless flow of particles—in an ultracold gas known as a Bose-Einstein condensate (BEC). To stir the gas, the researchers used a pair of laser beams that had been specially prepared to induce a kind of corkscrew motion, known as orbital angular momentum, to its constituent light particles (photons) and impart that motion to the atoms in the gas, causing them to swirl like a tornado. The technique could lead to the development of ultraprecise gyroscopes for navigation.
2008—NIST scientists demonstrated two different leading designs for experimental optical atomic clocks, which may one day supersede today's time and frequency standards. Till Rosenband and colleagues published the first evaluation of a prototype "quantum logic clock" based on aluminum ion (electrically charged atom). This clock uses the logical reasoning process of quantum computers and is competitive with NIST's world-leading experimental mercury ion clock. Meanwhile, Jun Ye and colleagues demonstrated a clock based on strontium atoms held in an optical lattice made of laser beams. This is the world's most precise clock based on neutral atoms.
2008—Researchers at NIST and the University of Maryland created the first quantum-entangled multi-pixel images using a simple yet powerful method known as "four-wave mixing," a technique in which light waves enter a gas and interact to produce outgoing light waves in a different form. This technique enabled lead author Vincent Boyer and his team to reduce the noise associated with quantum fluctuations in laser light by rearranging it in a way that improved desired image features. In addition to improving the detection of faint objects and the amplification and positioning of light beams, the researchers' technique—unprecedented in its simplicity, versatility, and efficiency—may someday be useful for storing patterns of data in quantum computers and transmitting large amounts of highly secure encrypted information.
For additional information about lasers and the 50th anniversary, see www.laserfest.org.