Featured Research

from universities, journals, and other organizations

Undisturbed excitation with pulsed light

Date:
November 22, 2012
Source:
Physikalisch-Technische Bundesanstalt (PTB)
Summary:
The best method to obtain the most precise information on the inner structure of atoms and molecules is to excite them by means of resonant laser light. Unfortunately, just this laser light (above a certain intensity) can lead to measurable modifications within the atom's electron shell. Scientists have now shown experimentally how to prevent such "light shifts." This confirms the advantages of "hyper" Ramsey excitation that had already been predicted theoretically.

Stylized representation of the excitation of a single ion in a trap by means of a "hyper" Ramsey pulse sequence.
Credit: Image: PTB

The best method to obtain the most precise information on the inner structure of atoms and molecules is to excite them by means of resonant laser light. Unfortunately, just this laser light (above a certain intensity) can lead to measurable modifications within the atom's electron shell. Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have now shown experimentally how to prevent such "light shifts." This confirms the advantages of "hyper" Ramsey excitation that had already been predicted theoretically.

This method can make their optical ytterbium atomic clocks even more accurate. Furthermore, "hyper" Ramsey excitation can be helpful in numerous applications where the focus lies on a precise, controlled interaction between atoms and laser light. The results have been published in the current issue of the scientific journal Physical Review Letters.

"Light shift" means that intense laser light modifies the position of the atomic energy levels; the shift depends on the intensity and the wavelength of the laser used. If one is seeking the properties of the atom as an undisturbed quantum object, this shift must be either prevented or corrected. With the new procedure, which has been applied experimentally for the first time at PTB, a sequence of judiciously selected laser pulses used to excite the atom eliminates the disturbing light shift effect.

The basic idea of using pulsed radiation to perform precise measurements goes back to Norman Ramsey, who was awarded the Nobel Prize in physics in 1989 for this finding. With this method, a first laser pulse is shot at the atom, where it starts a resonant excitation. Then the pulsation excited in the electron shell of the atom continues undisturbed "in the dark" until eventually a second laser pulse completes the comparison between the resonance frequency of the atom and the laser frequency. A similar approach is also usual in clock comparisons: two clocks are set to the same time, they are then left to run on and are eventually compared again. The result shows which clock was faster or slower than the other.

The signal of the Ramsey excitation contains, due to the dark phase between the laser pulses, an averaging over the positions of the states of the atom with and without a light shift. In principle, it would be possible to compensate for the light shift by modifying the laser frequency by exactly this quantity (exclusively) during the pulses. This, however, would not bring great improvement from a practical point of view as the precise information concerning the disturbance of the atom should be known to begin with. In 2010, a group of scientists (also with PTB's participation) suggested a method they called "hyper" Ramsey excitation in order to solve this problem. This theoretical consideration has now been confirmed experimentally for the first time. In the case of "hyper" Ramsey excitation, a third laser pulse of the same intensity and the same frequency, but with an inverted phase, is inserted into the dark phase. This third laser pulse automatically compensates for possible errors which could occur due to misjudgment as regards the size of the light shift and due to small variations in the laser intensity during the light pulses.

Realizing "hyper" Ramsey excitation experimentally succeeded in an atomic transition which allows very slight frequency variations to be detected and, at the same time, exhibits a large light shift, since a high laser intensity is necessary for its excitation. It is an electrical octupole transition in the Yb+ ion which is being investigated as a basis for an optical clock. The experiment confirmed the theoretical predictions concerning the advantages of "hyper" Ramsey excitation and attained a 10,000-fold suppression of the light shift. This opens up the possibility for the optical Yb+ clock to achieve even greater accuracy. This method could also be interesting for other researchers trying to obtain a precisely controlled interaction between atoms and laser light, for instance in the field of quantum information processing.


Story Source:

The above story is based on materials provided by Physikalisch-Technische Bundesanstalt (PTB). Note: Materials may be edited for content and length.


Journal Reference:

  1. N. Huntemann, B. Lipphardt, M. Okhapkin, Chr. Tamm, E. Peik, A. Taichenachev, V. Yudin. Generalized Ramsey Excitation Scheme with Suppressed Light Shift. Physical Review Letters, 2012; 109 (21) DOI: 10.1103/PhysRevLett.109.213002

Cite This Page:

Physikalisch-Technische Bundesanstalt (PTB). "Undisturbed excitation with pulsed light." ScienceDaily. ScienceDaily, 22 November 2012. <www.sciencedaily.com/releases/2012/11/121122095413.htm>.
Physikalisch-Technische Bundesanstalt (PTB). (2012, November 22). Undisturbed excitation with pulsed light. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2012/11/121122095413.htm
Physikalisch-Technische Bundesanstalt (PTB). "Undisturbed excitation with pulsed light." ScienceDaily. www.sciencedaily.com/releases/2012/11/121122095413.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins