Electronic circuits are based on electrons, but one of the most promising technologies for future quantum circuits are photonic circuits, i.e. circuits based on light (photons) instead of electrons.
First, it is necessary to be able to create a stream of single photons and control their direction. Researchers around the world have made all sorts of attempts to achieve this control, but now scientists at the Niels Bohr Institute have succeeded in creating a steady stream of photons emitted one at a time and in a particular direction. The breakthrough has been published in the scientific journal Physical Review Letters.
This is an illustration of the single-photon cannon. A quantum dot (illustrated with the yellow symbol) emits one photon (red wave packet) at a time. The quantum dot is embedded in a photonic-crystal structure, which is obtained by etching holes (black circles) in a semiconducting material (light grey). Due to the holes, the photons are not emitted in all directions, but only along the channel where there are no holes. Only 1.6 percent of the emitted photons will be emitted in other directions (illustrated by the upward moving photon) and is thus lost, while 98.4 percent are emitted in the desired direction.
Credit: Illustration: Marta Arcari, Niels Bohr Institute
Photons and electrons behave very differently at the quantum level. A quantum is the smallest unit in the atomic world and photons are the basic units of light and electrons of electrical current. Electrons are so-called fermions and can easily flow individually, while photons are bosons that prefer to clump together. But because information for quantum communication based on photonics lies in the individual photon, it is necessary to be able to send them one at a time.
"So you need to emit the photons from a fermionic system and we do this by creating an extremely strong interaction between light and matter," explains Peter Lodahl, Professor and head of the research group Quantum Photonics at the Niels Bohr Institute at the University of Copenhagen.
The researchers have developed a kind of single-photon cannon integrated on an optical chip. The optical chip consists of an extremely small photonic crystal that is 10 microns wide (1 micron is a thousandth of a millimeter) and 160 nanometers thick (1 nanometer is a thousandth of micron.) Embedded in the centre of the chip is a light source, a so-called quantum dot.
"What we then do is shine laser light on the quantum dot, where there are atoms with electrons in orbit around the nucleus. The laser light excites the electrons, which then jump from one orbit to another and thereby emit one photon at a time. Normally, light is scattered in all directions, but we have designed the photonic chip so that all of the photons are sent through only one channel," explains Søren Stobbe, Associate Professor of the Quantum Photonic research group at the Niels Bohr Institute.
Peter Lodahl and Søren Stobbe explain that it not only works, but also that it is extremely effective. "We can control the photons and send them in the direction we want with a 98.4 percent success rate. This is ultimate control over the interaction between matter and light and has amazing potential. Such a single-photon cannon has long been sought after in the research field and opens up fascinating new opportunities for fundamental experiments and new technologies," they explain.
The two researchers are in the process of patenting several parts of their work, with a specific goal of developing a prototype high-efficiency single-photon source, which could be used for encryption or for calculations of complex quantum mechanical problems and in general, is an essential building block for future quantum technologies. It is expected that the future's quantum technology will lead to new ways to code unbreakable information and to carry out complex parallel calculations.
For more information contact:
Peter Lodahl, Professor and head of the Quantum Photonic research group at the Niels Bohr Institute at the University of Copenhagen. Tel: +45 2056-5303, firstname.lastname@example.org
Søren Stobbe, Associate Professor in the Quantum Photonic research group at the Niels Bohr Institute at the University of Copenhagen. Tel: +45 6065-6769, email@example.com
Gertie Skaarup | Eurek Alert!
Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State
What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy