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 Transportable laser
23.01.2018 | Physikalisch-Technische Bundesanstalt (PTB)

nachricht New for three types of extreme-energy space particles: Theory shows unified origin
23.01.2018 | Penn State

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: Optical Nanoscope Allows Imaging of Quantum Dots

Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.

Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Rutgers scientists discover 'Legos of life'

23.01.2018 | Life Sciences

Seabed mining could destroy ecosystems

23.01.2018 | Earth Sciences

Transportable laser

23.01.2018 | Physics and Astronomy

VideoLinks Science & Research
Overview of more VideoLinks >>>