Advancing Quantum Information Science
Unlocking Secrets

NIST Fellow David Wineland leads the ion-trap research that inspired the creation of the Quantum Information Program. © Geoffrey Wheeler

Few people realize that America’s future prosperity and security may rely in part on the exotic properties of some of the smallest particles in nature. Research in quantum information (QI) seeks to control and exploit these properties for scientific and societal benefit. The field combines physics, information science, and mathematics in an effort to design nanotechnologies that may accomplish feats that are impossible with today’s technology. QI has the potential to expand and strengthen the U.S. economy and security in the 21st century just as transistors and lasers did in the 20th century.

Today’s digital information systems use tiny electrical switches, magnets, or light signals to represent information, or bits. In quantum information processing, various “quantum states” of particles or systems are used as quantum bits (qubits). The unusual properties of the quantum world—especially the ability to exist in two states at once, and to perform what Albert Einstein called “spooky action at a distance”—can provide unprecedented power.

Quantum Information Applications

Ultra-secure Encryption. Early versions of quantum communications systems are already generating “unbreakable” codes for encrypting information, and a few systems have been commercialized.

Code Breaking. Quantum computers—if they can be built at all—could quickly break today’s best conventional encryption codes. Researchers often point out that, for specific classes of problems, a quantum computer with 300 qubits potentially has more processing power than a conventional computer containing as many bits as there are particles in the universe.

Powerful Problem Solving. Quantum computers might be used to optimize complex systems such as airline schedules, accelerate database searching, develop novel products such as fraud-proof digital signatures, or simulate complex biological systems for use in drug design.

New Scientific Tools. Techniques developed in QI research may improve measurement science, perhaps leading to improved atomic clocks and navigation instruments. QI research also supports advances in nanotechnology, a field that has become a national priority.

The history of science suggests that important applications will arise that cannot be imagined today. In 1947 when the transistor was invented, no one envisioned the $600 billion U.S. electronics and related industries it would create.

Many technical challenges need to be overcome before the full potential of QI can be demonstrated and exploited. But nations around the world are investing heavily in QI research in recognition of the potential economic and security implications. A significant part of the U.S. effort is based at the National Institute of Standards and Technology (NIST), which has the largest internal QI research program of any federal agency.

Link to Measurement Science

NIST laboratories routinely develop the measurement and standards infrastructure needed to promote innovation in emerging fields that may transform the future. Few fields need this support as much as QI, which involves entirely new concepts of information processing as well as complex hardware for precision control of individual atoms, very small quantities of light, and electrical currents billions of times weaker than those in light bulbs. As the nation’s measurement experts, NIST researchers have long had world-class capabilities in precision measurement and control of atoms, light, and other quantum systems. NIST is using its expertise and facilities to advance the QI field by demonstrating new technology, developing new methods and tests for evaluating QI system components, and developing new knowledge of quantum phenomena.

An interdisciplinary Quantum Information Program, featuring strong collaborations among physicists, electrical engineers, mathematicians, and computer scientists, has established NIST as one of the premier QI programs in the world. Participants include physicist David Wineland, a NIST Fellow and Presidential Rank Award winner; physicist William D. Phillips, 1997 Nobel Prize winner in physics; mathematician Emanuel Knill, a leading QI theorist; and physicist Sae Woo Nam, winner of a Presidential Early Career Award for Scientists and Engineers.

Strong synergy exists between NIST’s core mission work on measurement and standards and the QI research program. For instance, NIST scientists gained much of their expertise in quantum systems from decades of work developing atomic clocks. NIST’s ultra-precise atomic fountain clock—the world’s most accurate device for measuring time—is based on the precise manipulation and measurement of two quantum energy levels in the cesium atom. This clock would neither gain nor lose one second in about 60 million years (as of March 2005), an accuracy level that is continually being improved. NIST quantum computing research is producing new techniques that may lead to even more accurate atomic clocks.

Xiao Tang of NIST’s Information Technology Laboratory and colleagues conduct research on quantum communications over optical fiber channels. © Robert Rathe

Ultimately, NIST measurements, tests, and technologies for quantum information science are helping U.S. industry develop new information technologies, in an effort to ensure U.S. technological leadership and strengthen national security. The United States may have the lead in this field for now—based in part on NIST’s contributions—but competition from Europe, Japan, Australia, and developing countries such as China is strong and growing.

NIST’s QI research is supported in part by the Defense Advanced Research Projects Agency, Advanced Research and Development Activity/National Security Agency, and Director of Central Intelligence postdoctoral program.

NIST Quantum Computing Activities

NIST is pursuing three approaches to making qubits for quantum computing. NIST researchers believe these approaches provide the best near-term possibilities for breakthroughs while also having potential applications to other NIST mission activities. Related QI activities include essential theoretical research in quantum computer design.

Joshua Bienfang of NIST’s Physics Laboratory leads research on optical wireless quantum communications. Credit: Gail Porter/NIST

Ion Qubits. NIST’s work in ion-trap quantum computing is widely recognized as one of themost advanced QI efforts in the world. This group has achieved many firsts, including demonstrations of the first quantum “logic gate” and “teleportation” of information between ions (charged atoms). They have demonstrated all of the building blocks for a quantum computer based on ion traps.

Neutral Atom Qubits. Another NIST group is using large numbers of atoms confined in optical lattices, arrays of egg-carton-shaped traps created by intersecting laser beams. The group has taken a number of steps toward controlling arrays of neutral atom qubits for use in logic operations.

Superconducting Qubits. A third group is using “artificial atoms” made of superconducting electrical circuits. This group has made significant advances, including correlating the behavior of two qubits so they mimic the “spooky” properties observed in real atoms.

Quantum Architectures and Error Correction. NIST is developing designs for quantum computers and optimizing strategies for correcting inevitable errors in delicate quantum states. NIST recently developed a new error correction approach that conceivably could lead to reliable computing even with prototype hardware performance levels already achieved in NIST laboratories.

NIST Quantum Communications Activities

Quantum communications uses single photons, the smallest quantities of light, to transmit information. (By contrast, today’s fiber-optic systems require bits made of tens of thousands of photons.) The idea is straightforward but the implementation is markedly less so. In particular, it is difficult to build fast, reliable, long-distance quantum channels, process the information generated at high speeds, and connect quantum links to networks. It is also difficult to produce and count single photons efficiently.

Sae Woo Nam of NIST’s Electronics and Electrical Engineering Laboratory is developing single photon detectors. © Geoffrey Wheeler

Quantum Communications Testbed. NIST has built a quantum communications testbed for research, testing, and technology development in a high-speed Ethernet environment. Very weak laser pulses are created containing individual photons, which are sent and received by telescopes over a wireless optical channel between two buildings. NIST scientists set a record in 2004 for the fastest system for distributing quantum cryptographic “keys,” codes for encrypting messages. Due to the peculiarities of quantum physics, such messages cannot be intercepted without detection. A second, NIST fiber-based system uses similar technology.

Single-Photon Sources and Detectors. NIST has demonstrated both a single-photon “turnstile” and a certified single-photon source that ultimately will lead to improvements in the NIST high-speed quantum communications testbed. NIST also recently demonstrated devices that can detect and count single photons with 88 percent efficiency. These are worldleading efforts.

Device and System Metrology. NIST is developing calibration and characterization facilities for singlephoton sources and detectors. Additionally, NIST is working on the protocols and error correction software necessary to support high-speed quantum communications. This effort is essential to the development of a certification framework for these systems.

The Quantum Information Program is an interdisciplinary, collaborative effort of the NIST Physics Laboratory, Electronics and Electrical Engineering Laboratory, and Information Technology Laboratory.

Coordinator: Carl Williams
carl.williams@nist.gov, (301) 975-3531

For further information visit:

http://qubit.nist.gov
http://math.nist.gov/quantum
http://tf.nist.gov/ion/qucomp/intro.htm
http://emtech.boulder.nist.gov/div817b/whatwedo/qcomputing/qcomputing.htm
http://www.nist.gov

Date created: 10/3/05
Last updated: 10/3/05
Contact: inquiries@nist.gov