Physicists from the University of Bonn have presented a method that may be suitable for the production of so-called quantum repeaters. These should improve the transmission of quantum information over long distances. The researchers used an effect with which light particles can be shot in a much more targeted manner. Their results appear in the Physical Review Letters.
Let's suppose you were allowed to blindfold German soccer star Timo Werner and turn him on his own axis several times. Then you'd ask him to take a shot blind. It would be extremely unlikely that this would hit the goal.
The four lenses surround the resonator and are used to focus the laser beams that hold the atom in the resonator and to observe the atom.
© Miguel Martinez-Dorantes / University of Bonn
With a trick, Bonn physicists nevertheless managed to achieve a 90-percent score rate in a similar situation. However, their player was almost 10 billion times smaller than the German star striker - and much less predictable.
It was a rubidium atom that the researchers had irradiated with laser light. The atom had absorbed radiation energy and had entered an excited state. This has a defined lifespan. The atom subsequently releases the absorbed energy by emitting a particle of light: a photon.
The direction in which this photon flies is purely coincidental. However, this changes when the rubidium is placed between two parallel mirrors, because then the atom prefers to shoot at one of the mirrors. In the example with Timo Werner, it would be as if the goal magically attracted the ball.
This phenomenon is called the Purcell effect. The existence of it was already proven several decades ago. “We have now used the Purcell effect for the targeted emission of photons by a neutral atom,” explains Dr. Wolfgang Alt from the Institute of Applied Physics at the University of Bonn.
There is great interest in the Purcell effect, partly because it makes the construction of so-called quantum repeaters possible. These are needed to transmit quantum information over long distances. Because, whilst it is possible to put a photon into a certain quantum state and send it through a light guide, this can only be done over limited distances; for greater distances, the signal has to be buffered.
Repeaters pass on quantum information
In the quantum repeater, the photon is for instance guided to an atom which swallows it and thereby changes into another state. In response to a reading pulse with a laser beam, the atom spits out the light particle again. The stored quantum information is retained.
The emitted photon must now be collected and fed back into a light guide. But that is difficult when the photon is released in a random direction. “We have succeeded in forcing the photons onto the path between the two mirrors using the Purcell effect,” explains Alt. “We have now made one of the mirrors partially transmissive and connected a glass fiber to it. This allowed us to introduce the photon relatively efficiently into this fiber.”
The Purcell effect also has another advantage: It shortens the time it takes the rubidium atom to store and release the quantum information. This gain in speed is extremely important: Only if the repeater works fast enough can it communicate with the transmitter of the information, a so-called quantum dot. Today, quantum dots are regarded as the best source for single photons for the transmission of quantum information, which is completely safe from being intercepted. “Our experiments are taking this important future technology one step further,” says Alt.
Prof. Dieter Meschede
Tel.: +49 (0)228 733477
Jose Gallego, Wolfgang Alt, Tobias Macha, Miguel Martinez-Dorantes, Deepak Pandey and Dieter Meschede: Strong Purcell effect on a neutral atom trapped in an open fiber cavity; Physical Review Letters; https://doi.org/10.1103/PhysRevLett.121.173603
Dr. Andreas Archut | idw - Informationsdienst Wissenschaft
Appreciating the classical elegance of time crystals
20.09.2019 | ETH Zurich Department of Physics
'Nanochains' could increase battery capacity, cut charging time
20.09.2019 | Purdue University
How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.
Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in...
To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
19.09.2019 | Event News
10.09.2019 | Event News
04.09.2019 | Event News
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences