Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum Odyssey in an Ion Trap

31.08.2009
MPQ scientists demonstrate quantum walks with single trapped ions.

Many classical algorithms in computer science include so called "random walks", where possible ways to solve a problem are chosen at random. Algorithms of that kind are found in fields like physics, biology, economics, and even psychology.


In a quantum labyrinth all possible paths are in a state of superposition and can be taken simultaneously. This gives rise to interferences that lead to strange phenomena such as the self-encounter of the quantum walker. Due to these \"tricks\" the exit out of the maze, e.g. die solution of an algorithm or the most efficient way of energy transfer in plants, can be found dramatically faster than with classical methods. MPQ / Tobias Schätz

In quantum systems these decisions become obsolete because all possible paths are in a state of superposition and can be followed at the same time. As a consequence interferences occur that give rise to new phenomena.

E.g., at crossings a quantum walker can encounter himself. Quantum walks could substantially speed up algorithms used for quantum systems. But they can also lead to new insight into the behavior of mesoscopic systems that mark the border between the classical and the quantum mechanical world. In a "proof-of-principle"-experiment, using an ion trap, Dr. Tobias Schätz, leader of the Junior Research Group "Quantum Simulations" at Max Planck Institute of Quantum Optics in Garching near Munich, and his collaborators were now able to unambiguously demonstrate the difference between the classical and the quantum mechanical "Odyssey" of an ion (Physical Review Letters, 28. August 2009).

Every time we arrive at a crossroad, we have to choose - perhaps by flipping a coin - the route to tackle. After several crossings and choices we will have followed a few out of many possible paths, maybe some of them more frequently than others.

A quantum walker in contrast does not have to decide - indeed there is no choice. At each coin toss a superposition of head and tail is generated, allowing the walker to follow all the possible paths simultaneously. As a consequence strange phenomena may show up. E.g., if paths recombine again at subsequent crossings, the walker can meet himself - and due to interference - increase his probability to be at this crossing or even disappear.

In the experiment described here a single magnesium ion stored in an electromagnetic trap plays the role of the quantum walker. Its motional ground state represents the initial state of the walk. By irradiation of radiofrequency pulses a superposition of electronic states gets excited. This simulation of the coin toss results in a superposition of "left" and "right" decision. Now ultraviolet light of a well chosen frequency gives the ion the necessary "push" to get moving. Depending on its particular electronic state the ion gets pushed to the left or to the right, whereby a superposition of the two permitted motions is generated. Therefore, quantum walks are connected with a high degree of entanglement between the two values of the coin and the two motion possibilities of the ion.

Three times the actions "coin toss" and "change of position" are repeated; this is the least requirement for the observation of quantum effects. Once this quantum evolution is completed the state of the coin and the particular end position of the ion gets detected. This procedure exploits the fact that only one of the coin states allows the ion to fluoresce. From the statistics of about a thousand measurements the physicists infer how often the ion has moved to the right or to the left. The experimental data clearly confirm the theoretical prediction of an unbalance between the two directions, in contrast of what would be expected for a classical system.

In this experiment the group of Dr. Schätz has clearly revealed the difference of a quantum system to its classical counterpart by allowing the walker/ion to take all classical paths simultaneously: Quantum interferences enforce asymmetric, non-classical distributions in the highly entangled coin and position states. Yet the number of repetition steps is limited by non-linear effects. To overcome these restrictions the scientists now propose an altered protocol that would make it possible to scale the quantum walk to many, in principle to several hundreds of steps.

Quantum walks are predicted to be of fundamental interest for many "applications". Searching for the right path might get dramatically boosted in efficiency if one does not have to try out randomly each individual one but all of them simultaneously. This mind puzzling behaviour could, for example, help to enhance the power of search algorithms in computational science. But it is, for example, also suspected to be responsible for the high efficiency of energy transfer on multiple paths in plants, far beyond what human beings reach with their yet classical approach.

[Tobias Schätz/Olivia Meyer-Streng]

Original publication:
H. Schmitz, R. Matjeschk, C. Schneider, J. Glückert, M. Enderlein, T. Huber and T. Schätz
"Quantum walk of a trapped ion in phase space"
Physical Review Letters, 28. August 2009
Contact:
Dr. Tobias Schätz
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching
Phone: +49 - 89 / 32905 - 199
Fax: +49 - 89 / 32905 - 311
E-mail: tobias.schaetz@mpq.mpg.de
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics
Phone: +49 - 89 / 32905 - 213
Fax: +49 - 89 / 32905 - 200
E-mail: olivia.meyer-streng@mpq.mpg.de

Dr. Olivia Meyer-Streng | Max-Planck-Institut
Further information:
http://www.mpq.mpg.de

More articles from Physics and Astronomy:

nachricht NASA's SDO sees partial eclipse in space
29.05.2017 | NASA/Goddard Space Flight Center

nachricht Strathclyde-led research develops world's highest gain high-power laser amplifier
29.05.2017 | University of Strathclyde

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: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

New photocatalyst speeds up the conversion of carbon dioxide into chemical resources

29.05.2017 | Life Sciences

NASA's SDO sees partial eclipse in space

29.05.2017 | Physics and Astronomy

New drug reduces transplant and mortality rates significantly in patients with hepatitis C

29.05.2017 | Statistics

VideoLinks
B2B-VideoLinks
More VideoLinks >>>