Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Magic wavelengths

12.05.2015

Tuning up Rydberg atoms for quantum information applications

Rydberg atoms, atoms whose outermost electrons are highly excited but not ionized, might be just the thing for processing quantum information.


Rubidium atoms are held in place using a pair of laser beams at a wavelength of 1064 nm. Two other beams, promote the atoms from their ground state (5s) first to the 5p state and then to the still higher 18 s state. - See more at: http://jqi.umd.edu/news/magic-wavelengths#sthash.GGwhXrVu.dpuf

Credit: Kelley/JQI

These outsized atoms can be sustained for a long time in a quantum superposition condition -- a good thing for creating qubits -- and they can interact strongly with other such atoms, making them useful for devising the kind of logic gates needed to process information. Scientists at JQI (*) and at other labs are pursuing this promising research area.

One problem with Rydberg atoms is that in they are often difficult to handle. One approach is to search for special wavelengths -- "magic wavelengths" -- at which atoms can be trapped and excited into Rydberg states without disturbing them. A new JQI experiment bears out high-precision calculations made predicting the existence of specific magic wavelengths.

RYDBERG ATOMS

Named for Swedish physicist Johannes Rydberg, these ballooned-up atoms are made by exciting the outermost electron in certain elements. Alkali atoms are handy for this purpose since they are hydrogen-like. That is, all the inner electrons can lumped together and regarded, along with the atom's nucleus, as a unified core, with the lone remaining electron lying outside; it's as if the atom were a heavy version of hydrogen.

The main energy levels of atoms are rated according to their principle quantum number, denoted by the letter n. For rubidium atoms, the species used in this experiment, the outermost electron starts in an n=5 state. Then laser light was used here to promote the electron into an n=18 state. Unlike atoms in their ground state, atoms in the n=18 excited state see each other out to distances as large as 700 nm. Rydberg atoms with higher values of n can interact at even larger separations, up to many microns. For comparison, the size of an un-excited rubidium atom is less than 1 nm.

Actually the energy required to promote the atom to the 18s state directly would require a laser producing ultraviolet light, and the researchers decided it was more practical to boost the outer electron to its higher perch in two steps, using two more convenient lasers whose energy added to the total energy difference.

DIPOLE TRAP AND STARK EFFECT

Rb atoms are in the trap in the first place because they have been gathered into a cloud, cooled to temperatures only a few millionths of a degree above absolute zero, and then maintained in position by a special trapping laser beam system.

The trapping process exploits the Stark effect, a phenomenon in which the strong electric field of the confining laser beam alters the energy levels of the atom. By using a sort of hourglass-shaped beam, the light forms a potential-energy well in which atoms will be trapped. The atoms will congregate in a tidy bundle in the middle of this optical dipole trap. The trouble is that the Stark effect, and along with it the trapping influence of the laser beams, depends on the value of n. In other words, a laser beam good for trapping atoms at one n might not work for other values of n.

Fortunately, at just the right wavelengths, the "magic wavelengths," the trapping process will confine atoms in both the low-lying n=5 state and in the excited n=18 state. The theoretical calculations predicting where these wavelengths would be (with a particularly useful one around a value of 1064 nm) and the experimental findings bearing out the predictions were published recently in the journal Physical Review A.

The first author on the paper is Elizabeth Goldschmidt. "We made a compromise, using atoms in a relatively low-n Rydberg state, the 18s state. We work in this regime because we are interested in interaction lengths commensurate with our optical lattice and because the particular magic wavelength is at a convenient wavelength for our lasers, namely 1064 nm." She said that in a next round of experiments, in the lab run by Trey Porto and Steve Rolston, will aim for a higher Rydberg level of n greater than 50.

JQI fellow Marianna Safronova helped to produce the magic wavelength predictions. "To make a prediction," said Safronova, "you need to know the polarizability -- the amount by which the Stark effect will shift the energy level -- for the highly-excited n=18 level. The job for finding magic wavelengths beyond n=18 with our high-precision first-principles approach would be pretty hard. Agreement of theoretical prediction with experimental measurement gives a great benchmark for high-precision theory."

"The most important feature of our paper," said Porto, "is that the theorists have pushed the theoretical limits of calculations of magic wavelengths for highly excited Rydberg atoms, and then verified these calculations experimentally."

###

Reference publication: "Magic wavelengths for the 5s-18s transition in rubidium," E. A. Goldschmidt, D. G. Norris, S. B. Koller, R. Wyllie, R. C. Brown, and J. V. Porto, U. I. Safronova, M. S. Safronova, Physical Review A 91 032518 (2015); http://journals.aps.org/pra/pdf/10.1103/PhysRevA.91.032518

Research Contact: Elizabeth Goldschmidt, goldschm@umd.edu

Media Contact: Phillip F. Schewe, pschewe@umd.edu, (301) 405-0989

(*) The Joint Quantum Institute (JQI) is operated jointly by the National Institute of Standards and Technology in Gaithersburg, MD and the University of Maryland in College Park.

Media Contact

Phillip Schewe
pschewe@umd.edu
301-405-0989

http://jqi.umd.edu 

Phillip Schewe | EurekAlert!

Further reports about: QUANTUM Rydberg energy levels experimental highly laser beam lasers levels wavelength wavelengths

More articles from Physics and Astronomy:

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

nachricht The universe up close
15.01.2018 | Georg-August-Universität Göttingen

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

White graphene makes ceramics multifunctional

16.01.2018 | Materials Sciences

Breaking bad metals with neutrons

16.01.2018 | Materials Sciences

ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records

16.01.2018 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>