Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists Show Quantum Entanglement in Mechanical System

05.06.2009
NIST physicists have demonstrated entanglement—a phenomenon peculiar to the atomic-scale quantum world—in a mechanical system similar to those in the macroscopic world. The work extends the boundaries of the arena where quantum behavior can be observed and shows how laboratory technology might be used to build a functional quantum computer.

Physicists at the National Institute of Standards and Technology (NIST) have demonstrated entanglement—a phenomenon peculiar to the atomic-scale quantum world—in a mechanical system similar to those in the macroscopic everyday world. The work extends the boundaries of the arena where quantum behavior can be observed and shows how laboratory technology might be scaled up to build a functional quantum computer.

The research, described in the June 4 issue of Nature,* involves a bizarre intertwining between two pairs of vibrating ions (charged atoms) such that the pairs vibrate in unison, even when separated in space. Each pair of ions behaves like two balls connected by a spring (see figure), vibrating back and forth in opposite directions. Familiar objects that vibrate this way include pendulums and violin strings.

The NIST achievement provides insights into where and how "classical" objects may exhibit unusual quantum behavior. The demonstration also showcased techniques that will help scale up trapped-ion technology to potentially build ultra-powerful computers relying on the rules of quantum physics. If they can be built, quantum computers may be able to solve certain problems, such as code breaking, exponentially faster than today’s computers. (For further details, see: www.nist.gov/public_affairs/quantum/quantum_info_index.html.)

"Where the boundary is between the quantum and classical worlds, no one really knows," says NIST guest researcher John Jost, a graduate student at the University of Colorado at Boulder and first author of the paper. "Maybe we can help answer the question by finding out what types of things can—and cannot be—entangled. We've entangled something that has never been entangled before, and it's the kind of physical, oscillating system you see in the classical world, just much smaller."

Mechanical oscillators like two pendulum-based clocks have previously been synchronized, but their vibrations can still be independent, so that changes in one have no effect on the other. Quantum entanglement—"spooky action at a distance," in Einstein’s words—is a far more counterintuitive process: If two objects are entangled, then manipulating one instantaneously affects the other, no matter how far away it is. Entangled objects do not necessarily have identical properties, just properties that are linked in predictable ways.

Jost and colleagues entangled the vibrational motions of two separated mechanical oscillators, each consisting of one beryllium and one magnesium ion. Each pair behaves like two objects connected by a spring 4 micrometers (millionths of a meter) long, with the beryllium and magnesium moving back and forth in opposite directions, first toward each other, then away, then back again. The two pairs perform this motion in unison, even though they are 240 micrometers apart and are located in different zones of an ion trap. The scientists created the desired entangled state at least 57 percent of the time they tried, and have identified ways to improve the success rate.

The NIST experiments suggest that mechanical oscillators can take part in both the quantum and classical worlds, possessing some features of each, depending in part on the energy and other properties of the vibrations. The experiments also achieved the first combined demonstration of arranging different ions into a desired order, separating and re-cooling them while preserving entanglement, and then performing subsequent quantum operations on the ions. These techniques could help scientists build large-scale quantum computers that use hundreds of ions to store data and perform many computational steps. The same NIST group has previously demonstrated the basic building blocks of a quantum computer using ion traps, as well as rudimentary logic operations.

To entangle the motion of the two oscillators, the NIST group first placed four ions together in one trap zone in a particular linear order (Be-Mg-Mg-Be), and entangled the internal energy states of the two beryllium ions. The team then separated the four ions into two pairs, with each pair containing one of the entangled ions. Finally, the scientists transferred the entanglement from the beryllium ions’ internal states to the oscillating motions of the separated ion pairs.

The research was funded in part by the Intelligence Advanced Research Projects Activity. The authors include former NIST post-doctoral scholars who are currently at the Weizmann Institute of Science in Israel and Lockheed Martin of Littleton, Colo.

*J.D. Jost, J.P. Home, J.M. Amini, D. Hanneke, R. Ozeri, C. Langer, J.J. Bollinger, D. Leibfried & D.J. Wineland. 2009. Entangled Mechanical Oscillators. Nature. June 4, 2009.

SIDEBAR: How NIST Entangled Two Mechanical Oscillators

NIST physicists entangled two vibrating mechanical systems each consisting of one beryllium and one magnesium ion, in an experiment that required 14 milliseconds, including verification of results, and involved about 600 laser pulses. The steps below expand on information provided in the figure.

Step 1—Initially, all four ions are placed in the same zone of an ion trap and cooled with lasers to very low temperatures. By tuning the voltages of the trap electrodes scientists arrange the ions in a particular order, with both heavier magnesium ions between the beryllium ions. Using a technique developed for quantum computing several years ago, scientists entangle the two beryllium ions' internal "spin states," which are analogous to tiny bar magnets pointing up or down. Two ultraviolet laser beams, positioned at right angles, cause the ions to oscillate. The lasers are tuned so the difference between their frequencies is very close to the frequency of one of the ions’ natural vibrations, the rate at which it likes to oscillate back and forth. Based on differences in their spins, the ions "feel" a differing laser force that causes the ions to oscillate in a particular way. This coupling of the spin states to motion has the global effect of entangling the spins of the beryllium ions in a controlled way.

Step 2—Voltages are then applied to electrode X to separate the ions into two pairs, which are distributed to different trap zones located adjacent to electrodes A and B. The separation and transport boost the energy of motion in the oscillating ions.

Step 3—The magnesium ions are cooled with lasers to remove excess motional energy from the beryllium ions, a process called sympathetic cooling because one type of ion cools the other. This is the first time entangled ions have been re-cooled prior to further operations, a technique expected to be useful in computing.

Step 4—By manipulating laser beam colors and orientations in a sequence of pulses of specific intensity and duration, scientists transfer the entanglement from the beryllium spins to the motion. The two mechanical oscillators are now entangled. Under ideal conditions, the beryllium and magnesium ions are oscillating back and forth in opposite directions, toward each other and then away. The two pairs perform this motion in unison, even though they are 240 micrometers apart and are located in different zones of the trap.

Scientists are not able to measure the entangled motions directly. Instead, to verify the results, they conduct a cleanup procedure partway through the experiment to ensure the entanglement has been transferred successfully from the ions' spin to their mechanical motion. Then, at the end of the experiment, they essentially reverse the entire process to transfer the entanglement from the ion motion back to the spins, to reproduce the initial beryllium spin states, which they can measure through the light scattered by the beryllium ions (spin up scatters laser light, whereas spin down does not).

Laura Ost | Newswise Science News
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

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: 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...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

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

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>