Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists Find Way to Control Individual Bits in Quantum Computers

08.07.2009
Physicists at the National Institute of Standards and Technology (NIST) have overcome a hurdle in quantum computer development, having devised* a viable way to manipulate a single “bit” in a quantum processor without disturbing the information stored in its neighbors.

The approach, which makes novel use of polarized light to create “effective” magnetic fields, could bring the long-sought computers a step closer to reality.

A great challenge in creating a working quantum computer is maintaining control over the carriers of information, the “switches” in a quantum processor while isolating them from the environment. These quantum bits, or “qubits,” have the uncanny ability to exist in both “on” and “off” positions simultaneously, giving quantum computers the power to solve problems conventional computers find intractable – such as breaking complex cryptographic codes.

One approach to quantum computer development aims to use a single isolated rubidium atom as a qubit. Each such rubidium atom can take on any of eight different energy states, so the design goal is to choose two of these energy states to represent the on and off positions. Ideally, these two states should be completely insensitive to stray magnetic fields that can destroy the qubit’s ability to be simultaneously on and off, ruining calculations. However, choosing such “field-insensitive” states also makes the qubits less sensitive to those magnetic fields used intentionally to select and manipulate them. “It’s a bit of a catch-22,” says NIST’s Nathan Lundblad. “The more sensitive to individual control you make the qubits, the more difficult it becomes to make them work properly.”

To solve the problem of using magnetic fields to control the individual atoms while keeping stray fields at bay, the NIST team used two pairs of energy states within the same atom. Each pair is best suited to a different task: One pair is used as a “memory” qubit for storing information, while the second “working” pair comprises a qubit to be used for computation. While each pair of states is field- insensitive, transitions between the memory and working states are sensitive, and amenable to field control. When a memory qubit needs to perform a computation, a magnetic field can make it change hats. And it can do this without disturbing nearby memory qubits.

The NIST team demonstrated this approach in an array of atoms grouped into pairs, using the technique to address one member of each pair individually. Grouping the atoms into pairs, Lundblad says, allows the team to simplify the problem from selecting one qubit out of many to selecting one out of two – which, as they show in their paper, can be done by creating an effective magnetic field, not with electric current as is ordinarily done, but with a beam of polarized light. The polarized-light technique, which the NIST team developed, can be extended to select specific qubits out of a large group, making it useful for addressing individual qubits in a quantum processor without affecting those nearby. “If a working quantum computer is ever to be built,” Lundblad says, “these problems need to be addressed, and we think we’ve made a good case for how to do it.” But, he adds, the long-term challenge to quantum computing remains: integrating all of the required ingredients into a single apparatus with many qubits.

*N. Lundblad, J.M. Obrecht, I.B. Spielman, and J.V. Porto. Field-sensitive addressing and control of field-insensitive neutral-atom qubits. Nature Physics, July 5, 2009.

N. Lundblad | Newswise Science News
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>