Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A transistor-like amplifier for single photons

28.07.2014

A team of scientists at MPQ achieves a twentyfold amplification of single-photon signals with the help of an ultracold quantum gas.

Data transmission over long distances usually utilizes optical techniques via glass fibres – this ensures high speed transmission combined with low power dissipation of the signal. For quite some years possibilities have been explored how to go one step further and perform all-optical data processing, with optical transistors and optical logic gates.


By exciting one atom into a Rydberg state a single photon (red wave packet) reduces the transmission of a laser pulse through a cloud of ultracold rubidium atoms by 20 light quanta. (Graphic: MPQ, Quantum Dynamics Division)

In particular in the case of quantum information this option would be highly recommendable as the information is often stored in faint light pulses which – at the ultimate limit – contain a single photon only. A team around Professor Gerhard Rempe, Leader of the Quantum Dynamics Division and Director at the Max Planck Institute of Quantum Optics, has now made a kind of optical transistor using a cloud of ultracold rubidium atoms.

With this new device they observed a twentyfold amplification of signal variations at the one-photon level (PRL, 28 July 2014).

The gain of a transistor describes what effect a small change of the input signal has on the output signal. A significant amount of gain is the precondition for distributing the output signal to the input ports of several transistors without signal attenuation, setting the ground for building complex digital switching circuits.

In the case of an optical transistor the input signal is a weak light pulse, called gate pulse, which modifies the transparency of a “medium” for a second pulse, called target pulse. In the experiment described here the medium consists of a cloud of about 150 000 rubidium atoms, kept in an optical dipole trap which is generated by two crossed laser beams. At temperatures of about 0.30 micro-Kelvin (this is just above absolute zero, zero Kelvin correspond to minus 273 degrees Celsius) the cloud can be held in place for several seconds.

The effect of “electromagnetically induced transparency” (EIT), in which a control laser modifies the interaction of a faint light pulse with the medium, makes the atomic cloud transparent for light pulses of certain frequencies.

The atomic cloud is irradiated with two light pulses of the same colour (795 nm), separated in time by two microseconds. The first gate pulse is extremely weak, containing less than one photon on average. In combination with the applied control laser it brings one atom in the cloud into a highly excited Rydberg state.

As in this state one of the outer electrons orbits at a large distance from the nucleus, this single excitation has a long-range effect: by the mere presence of the Rydberg atom the corresponding energy levels of all other atoms in the cloud are slightly shifted. When the second target pulse hits the cloud, its colour does not match the EIT conditions anymore. That is why the target pulse is blocked by the atoms.

A couple of months ago the team of Prof. Rempe has demonstrated that it is possible to switch the transmission properties of a cloud of rubidium atoms with single photons (PRL, Feb. 18th, 2014). However, this effect was achieved under severe limitations concerning duration as well as intensity of the target pulses.

“In the present experiment we have changed a few things, most importantly, we use control lasers with different wavelengths for gate and target pulses.”, Dr. Stephan Dürr, leading scientist at the experiment, points out. “That way we avoid that the target pulse couples to the Rydberg excitation and retrieves the gate pulse, even for long durations of the target pulse.”

Furthermore, different Rydberg states were chosen that give rise to a Förster resonance at which the Rydberg atoms interact with each other even more strongly than they usually would. “The Förster-resonance enhances the effect of the Rydberg blockade which is the true mechanism that prevents the target pulse from traversing the atomic cloud”, Daniel Tiarks, doctoral candidate at the experiment, explains.

“Furthermore, with the principle quantum numbers of the chosen Rydberg states we get a smaller effect of self-blockade of the photons in the target pulse, another obstruction that we had to deal with in our previous experiment. With all these measures we were able to increase the duration of the target pulse by two orders of magnitude, up to 200 microseconds.”

By comparing the intensities of the outgoing target pulses with and without a preceding gate pulse (a single photon), the reduction of the target signal was determined. “Right at the Förster-resonance we observe a reduction of 20 photons.”, Stephan Dürr says.

“This effect should make it possible – at least in principle – to cascade such transistors in order to solve complex computational tasks. In addition, the present experiment demonstrates a new and non-destructive method for the detection of Rydberg excitations. Because of the high amplification we can reveal whether a single Rydberg excitation has been created in the atomic cloud in a single shot.” Olivia Meyer-Streng

Original publication:
Daniel Tiarks, Simon Baur, Katharina Schneider, Stephan Dürr and Gerhard Rempe
Single-Photon Transistor using a Förster-Resonance
Physical Review Letters, 28 July 2014

Contact:

Prof. Dr. Gerhard Rempe
Director at Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -701 /Fax: -311
E-mail: gerhard.rempe@mpq.mpg.de

Dipl. Phys. Daniel Tiarks
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -397
E-mail: daniel.tiarks@mpq.mpg.de

Dr. Stephan Dürr
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -291 /Fax: -311
E-mail: stephan.duerr@mpq.mpg.de

Dr. Olivia Meyer-Streng
Press & Public Relations
MPQ Garching, Germany
Phone: +49 (0)89 / 32 905 -213
E-mail: olivia.meyer-streng@mpq.mpg.de

Dr. Olivia Meyer-Streng | Max-Planck-Institut

Further reports about: Max-Planck-Institut Phone Quantenoptik Quantum Rydberg microseconds photons reduction transistors

More articles from Physics and Astronomy:

nachricht Distant planet's interior chemistry may differ from our own
01.09.2015 | Carnegie Institution

nachricht Interstellar seeds could create oases of life
28.08.2015 | Harvard-Smithsonian Center for Astrophysics

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: An engineered surface unsticks sticky water droplets

The leaves of the lotus flower, and other natural surfaces that repel water and dirt, have been the model for many types of engineered liquid-repelling surfaces. As slippery as these surfaces are, however, tiny water droplets still stick to them. Now, Penn State researchers have developed nano/micro-textured, highly slippery surfaces able to outperform these naturally inspired coatings, particularly when the water is a vapor or tiny droplets.

Enhancing the mobility of liquid droplets on rough surfaces could improve condensation heat transfer for power-plant heat exchangers, create more efficient...

Im Focus: Increasingly severe disturbances weaken world's temperate forests

Longer, more severe, and hotter droughts and a myriad of other threats, including diseases and more extensive and severe wildfires, are threatening to transform some of the world's temperate forests, a new study published in Science has found. Without informed management, some forests could convert to shrublands or grasslands within the coming decades.

"While we have been trying to manage for resilience of 20th century conditions, we realize now that we must prepare for transformations and attempt to ease...

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Siemens sells 18 industrial gas turbines to Thailand

01.09.2015 | Press release

An engineered surface unsticks sticky water droplets

01.09.2015 | Materials Sciences

New material science research may advance tech tools

01.09.2015 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>