Picture of the single atom trap. In the ultra-high vacuum glass cell a single Rubidium atom is captured, which later will be entangled with a photon. Photo: C. Olesinski/LMU
Physicists at LMU, together with colleagues at Saarland University, have successfully demonstrated the transport of an entangled state between an atom and a photon via an optic fiber over a distance of up to 20 km – thus setting a new record.
‘Entanglement’ describes a very particular type of quantum state which is not attributed to a single particle alone, but which is shared between two different particles. It irrevocably links their subsequent fates together – no matter how far apart they are – which famously led Albert Einstein to call the phenomenon as “spooky action at a distance”. Entanglement has become a cornerstone of new technologies based on effects at the quantum level and is distribution over long distances a central goal in quantum communication. Now LMU researchers led by physicist Harald Weinfurter, in collaboration with a team at the University of the Saarland in Saarbrücken, have shown that the entangled state of an atom and a photon can be transmitted via an optic fiber (like those used in telecommunications networks) over a distance of up to 20 km. The previous record was 700 meters. “The experiment represents a milestone, insofar as the distance covered confirms that quantum information can be distributed on a large scale with little loss,” says Weinfurter. “Our work therefore constitutes a crucial step toward the future realization of quantum networks.”
Quantum networks essentially consist of quantum memories (made up of one or more atoms, for example) that act as nodes, and communication channels in which photons (light quanta) can propagate to link the nodes together. In their experiment, the researchers entangled a rubidium atom with a photon, and were able to detect the entangled state – which now shares the quantum properties of both particles – after its passage through a 20-km coil of optic fiber.
The biggest problem the experimenters faced start with the properties of the rubidium atom. Following targeted excitation, these atoms emit photons with a wavelength of 780 nanometers, in the near-infrared region of the spectrum. “In an optic fiber made of glass, light at this wavelength is rapidly absorbed,” Weinfurter explains. Conventional telecommunications networks therefore make use of wavelengths around 1550 nanometers, which markedly reduces losses in transit.
Obviously, this wavelength would also improve the experimenters’ chances of success. So Matthias Bock, a member of the group in Saarbrücken, built what is called a quantum frequency converter that was specifically designed to increase the wavelength of the emitted photons from 780 to 1520 nanometers. This task itself posed a number of extremely demanding technical challenges. For it was imperative to ensure that conversion from only a single photon to only one other photon happens and that none of the other properties of the entangled state, especially the polarization of the photon, were altered during the conversion process. Otherwise, the entangled state would be lost. “Thanks to the use of this highly efficient converter, we were able to maintain the entangled state over a much longer range at telecommunications wavelengths, and therefore to transport the quantum information that it carries over long distances,” says Weinfurter.
In the next step, the researchers plan to frequency convert the light emitted by a second atom, which should enable them to generate entanglement between the two atoms over long telecommunications fibers. The properties of glass-fiber cables vary depending on factors such as the temperature and strain to which they are exposed. For this reason, the team intends to first carry out this experiment under controlled conditions in the laboratory. In the event of success, field experiments will be undertaken also adding new nodes to a growing network. After all, even long journeys can be successfully completely by taking one step at a time.
Physical Review Letters, 2020
The Latest Updates from Bing News & Google News
Go deeper with Bing News on:
Quantum networks
- IBM adds 10 historically Black colleges and universities to quantum computing centeron February 22, 2021 at 5:02 am
The IBM-HBCU Quantum Center announced on Monday that it is adding 10 historically Black colleges and universities to the center's 13 founding institutions. The center was launched last fall with the ...
- Encrypted Quantum Computing: When Ignorance Is Wantedon February 21, 2021 at 3:58 pm
Quantum technologies for computers open up new concepts of preserving the privacy of input and output data of a computation. Scientists from the University of Vienna, the Singapore University of Techn ...
- IBM Reveals Five Year Quantum Development Roadmapon February 18, 2021 at 7:47 pm
Every year we get closer to mainstream use of quantum computers. IBM's Quantum roadmap shows how the company plans to make quantum accessible to more developers.
- Quantum network is step towards ultrasecure interneton February 17, 2021 at 8:29 pm
Physicists have taken a major step towards a future quantum version of the Internet by linking three quantum devices in a network. A quantum internet would enable ultrasecure communications and unlock ...
- BP Joins IBM Quantum Networkon February 17, 2021 at 3:58 am
BP (NYSE: BP) has announced that it has joined the IBM Quantum Network to advance the use of quantum computing in the energy industry. ...
Go deeper with Google Headlines on:
Quantum networks
Go deeper with Bing News on:
Quantum communication
- China launches cloud-based quantum computing operating system software to challenge U.S. in technologyon February 22, 2021 at 11:31 pm
Quantum computers achieve their immense power by replacing traditional bits with qubits, which can function as both a '1' and a '0' at the same time.
- Researchers create 'beautiful marriage' of quantum enemieson February 22, 2021 at 1:45 pm
Cornell University scientists have identified a new contender when it comes to quantum materials for computing and low-temperature electronics.
- Planet Earth Report –“The Quantum Century to Events That Could Have Ended Humanity”on February 22, 2021 at 6:57 am
Planet Earth Report” provides descriptive links to headline news by leading science journalists about the extraordinary discoveries, technology, people, and events changing our knowledge of Planet ...
- B’luru institute takes big leap in quantum communicationon February 22, 2021 at 4:38 am
Researchers team headed by Urbasi Sinha at the Raman Research Institute (RRI) successfully demonstrated free space quantum distribution key between two ...
- Scientists create ‘beautiful marriage’ of quantum enemieson February 22, 2021 at 3:17 am
Cornell scientists have identified a new contender when it comes to quantum materials for computing and low-temperature electronics. Using nitride-based materials, the researchers created a material ...