As if building a computer out of rubidium atoms and laser beams weren’t difficult enough, scientists sometimes have to work as if blindfolded: The quirks of quantum physics can cause correlations between the atoms to fade from view at crucial times.
What to do? Focus on the noise patterns. Building on earlier work by other groups, physicists at the National Institute of Standards and Technology (NIST) have found that images of “noise” in clouds of ultracold atoms trapped by lasers reveal hidden structural patterns, including spacing between atoms and cloud size.
The technique, described in the Feb. 23 issue of Physical Review Letters,* was demonstrated in an experiment to partition about 170,000 atoms in an “optical lattice,” produced by intersecting laser beams that are seen by the atoms as an array of energy wells arranged like an egg carton. By loading just one atom into each well, for example, scientists can create the initial state of a hypothetical quantum computer using neutral atoms to store and process information.
The atoms first are cooled to form a Bose-Einstein condensate (BEC), a unique form of matter in which all the atoms are in the same quantum state and completely indistinguishable. The optical lattice lasers then are slowly turned on and the BEC undergoes a transformation in which the atoms space out evenly in the lattice. More intense light creates deeper wells until each atom settles into its own lattice well. But during this transition, scientists lose their capability to see and measure key quantum correlations among the atoms.
Key structures are visible, however, in composite images of the noise patterns, which reveal not only atom spacing but also cloud size and how much of the BEC has undergone the transition.
In the NIST experiments, the BEC was placed in an optical lattice at various laser intensities. The lattice was turned off, and scientists took pictures of the expanding cloud of atoms after 20 to 30 milliseconds. To identify and enhance the noise signal, scientists looked for identical bumps and wiggles in the images and made composites of about 60 images by identifying and overlaying matching patterns. Lead author Ian Spielman likens the technique to listening to a noisy ballroom: While it may be impossible to hear specific conversations, correlations in noise can show where people (or atoms) are located in relation to each other, and the volume of noise can indicate the size of the ballroom (or atomic cloud), Spielman says.
The authors are affiliated with the Joint Quantum Institute, a new collaborative venture of NIST and the University of Maryland. The work was partially supported by the Disruptive Technology Office, an agency of the U.S. intelligence community that funds unclassified research on information systems, and by the Office of Naval Research.
Observing Quantum Transactions In A Nanotube Excitons are "quasiparticles" created when a photon strikes a semiconductor and excites an electron to a higher energy level. The electron leaves behind a positively charged void called a "hole." That hole pairs with the electron to form the exciton, which takes on a life of its own that ends abruptly when it emits a photon or becomes quenched.
Quantum Bit (qubit) Circuit NEC Corporation, Japan Science and Technology Agency (JST) and the Institute of Physical and Chemical Research (RIKEN) have together successfully demonstrated the world's first quantum bit (qubit) circuit that can control the strength of coupling between qubits. Technology achieving control of the coupling strength between qubits is vital to the realization of a practical quantum computer, and has been long awaited in the scientific field.
Spintronics Technology In 1994, Bandyopadhyay and colleagues were the first group to propose the use of spin in classical computing. Then two years later, they were among the first researchers to propose the use of spin in quantum computing. The recent work goes a long way toward implementing some of these ideas.
Center for Extreme Quantum Information Theory (xQIT) The new center enables a major new push by MIT theorists in the international race to determine the ultimate capabilities of quantum information systems. Establishing these theoretical capabilities would be a step towards being able to exploit quantum effects for novel applications, including computers, communication networks and global positioning systems.
Quantum Computer Demonstrated Quantum computing offers the potential to create value in areas where problems or requirements exceed the capability of digital computing, the company said. But D-Wave explains that its new device is intended as a complement to conventional computers, to augment existing machines and their market, not as a replacement for them.
Quantum Computing Breakthrough "Our work represents a breakthrough in the search for a nanoscopic [atomic scale] mechanism that could be used for a data readout device," says Christoph Boehme, assistant professor of physics at the University of Utah. "We have demonstrated experimentally that the nuclear spin orientation of phosphorus atoms embedded in silicon can be measured by very subtle electric currents passing through the phosphorus atoms."
Research: Ion Trap Physicists at the National Institute of Standards and Technology (NIST) have designed and built a novel electromagnetic trap for ions that could be easily mass produced to potentially make quantum computers large enough for practical use. The new trap, described in the June 30 issue of Physical Review Letters,* may help scientists surmount what is currently the most significant barrier to building a working quantum computer—scaling up components and processes that have been successfully demonstrated individually.
Information Processing In the drive to understand and harness quantum effects as they relate to information processing, scientists in Waterloo and Massachusetts have benchmarked quantum control methods on a 12-Qubit system. Their research was performed on the largest quantum information processor to date.
A Quantum Computer, One Dot at a Time Quantum computers do not yet exist, but it is known that they can bypass all known encryption schemes used today on the Internet. Quantum computers also are capable of efficiently solving the most important equation in quantum physics: the Schrödinger equation, which describes the time-dependence of quantum mechanical systems. Hence, if quantum computers can be built, they likely will have as large an impact on technology as the transistor.
Better Memory with Quantum Computer Bits Physicists at the National Institute of Standards and Technology (NIST) have used charged atoms (ions) to demonstrate a quantum physics version of computer memory lasting longer than 10 seconds—more than 100,000 times longer than in previous experiments on the same ions. The advance improves prospects for making practical, reliable quantum computers (which make use of the properties of quantum systems rather than transistors for performing calculations or storing information). Quantum computers, if they can be built, could break today’s best encryption systems, accelerate database searching, develop novel products such as fraud-proof digital signatures or simulate complex biological systems to help design new drugs.
The chemical bond between carbon and fluorine is one of the strongest in nature, and has been both a blessing and a curse in the complex history of fluorocarbons. Now, in a powerful demonstration of the relatively new field of “computational chemistry,” researchers at the National Institute of Standards and Technology (NIST) and the Interdisciplinary Network of Emerging Science and Technology group (INEST, sponsored by Philip Morris USA) have designed—in a computer—a wholly theoretical molecule to pull the fluorine out of fluorocarbons.*