First Step Towards Photonic Quantum Network
January 26, 2017 | Niels Bohr Institute at the University of CopenhagenEstimated reading time: 3 minutes
QUANTUM TECHNOLOGY: Advanced photonic nanostructures are well on their way to revolutionising quantum technology for quantum networks based on light. Researchers from the Niels Bohr Institute have now developed the first building blocks needed to construct complex quantum photonic circuits for quantum networks.
Illustration of a photon gun. A quantum dot (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 semiconductor material. Due to the holes, the photons cannot be emitted in all directions, but only along the waveguide, which is formed by omitting a number of holes. (Illustration: Søren Stobbe, NBI)
Quantum technology based on light (photons) is called quantum photonics, while electronics is based on electrons. Photons (light particles) and electrons behave differently at the quantum level. A quantum entity is the smallest unit in the microscopic world. For example, photons are the fundamental constituent of light and electrons of electric current. Electrons are so-called fermions and can easily be isolated to conduct current one electron at a time. In contrast photons are bosons, which prefer to bunch together. But since information for quantum communication based on photonics is encoded in a single photon, it is necessary to emit and send them one at a time.
Increased information capacity
Information based on photons has great advantages; photons interact only very weakly with the environment – unlike electrons, so photons do not lose much energy along the way and can therefore be sent over long distances. Photons are therefore very well suited for carrying and distributing information and a quantum network based on photons will be able to encode much more information than is possible with current computer technology and the information could not be intercepted en route.
Many research groups around the world are working intensively in this research field, which is developing rapidly and in fact the first commercial quantum photonics products are starting to be manufactured.
Control of the photons
A prerequisite for quantum networks is the ability to create a stream of single photons on demand and the researchers at the Niels Bohr Institute succeeded in doing exactly that.
“We have developed a photonic chip, which acts as a photon gun. The photonic chip consists of an extremely small crystal that is 10 microns wide (one micron is a thousandth of a millimetre) and is 160 nanometres thick (1 nanometre is a thousandth of a micron). Embedded in the middle of the chip is a light source, which is a so-called quantum dot. Illuminating the quantum dot with laser light excites an electron, which can then jump from one orbit to another and thereby emit a single photon at a time. Photons are usually emitted in all directions, but the photonic chip is designed so that all the photons are sent out through a photonic waveguide,” explains Peter Lodahl, professor and head of the Quantum Photonics research group at the Niels Bohr Institute, University of Copenhagen.
Directional emission of photons. The figure shows the calculations of the photon emission in the new directional single-photon source. If the spin of the quantum dot’s electron points up, the photon will be emitted in the one direction (blue). If the spin of the quantum dot’s electron points down, the photon will be emitted in the opposite direction (red). (Illustration: Sahand Mahmoodian and Søren Stobbe, NBI)
In a long, laborious process, the research group further developed and tested the photonic chip until it achieved extreme efficiency and Peter Lodahl explains that it was particularly surprising that they could get the photon emission to occur in a way that was not previously thought possible. Normally, the photons are transmitted in both directions in the photonic waveguide, but in their custom-made photonic chip they could break this symmetry and get the quantum dot to differentiate between emitting a photon right or left, that means emit directional photons. This means full control over the photons and the researchers are beginning to explore how to construct complete quantum network systems based on the new discovery.
“The photons can be sent over long distances via optical fibres, where they whiz through the fibres with very little loss. You could potentially build a network where the photons connect small quantum systems, which are then linked together into a quantum network – a quantum internet,” explains Peter Lodahl.
He adds that while the first basic functionalities are already a reality, the great challenge is now to expand them to large, complex quantum networks.
Suggested Items
Stan Rak: Elevating the Ideas and Insights of IPC's Thought Leaders Program
04/25/2024 | Stanton Rak, SF Rak CompanyAs a member of the IPC Thought Leaders Program (TLP), I am responsible for identifying knowledge-sharing opportunities that can generate ideas and insights that strengthen the IPC community as well as create a sustainable and lasting future for its members. I am delighted to highlight some of my recent contributions as a member of the TLP.
indie Semiconductor Launches Advanced Smart Connectivity Solutions for In-Cabin Applications
04/23/2024 | indie Semiconductorindie Semiconductor, Inc., an Autotech solutions innovator, has introduced a family of new high-performance video converters and retimers to enable in-cabin connectivity applications, including audio and video transport and device interfacing.
The Need for a Holistic Global Sustainability Standard
04/10/2024 | Michael Ford, Aegis SoftwareNo one can deny that the resources of our fragile planet are finite. The environment seems like a third party, subject to constant degradation. We’re acutely aware of the effects of pollution on our climate, and despite our “throw-away” culture, recycling and recovery of materials has remained relatively expensive, even as we use more energy just to survive.
Technica Leads the Way Into Automation and Machine Learning at IPC APEX EXPO 2024
03/28/2024 | Marcy LaRont, PCB007 MagazineAs a significant partner to PCB fabricators since almost the beginning of multilayer boards, Technica USA brings a lot of expertise to the industry. This year’s IPC APEX EXPO show will showcase their biggest booth yet, and a whole lot of information, discussion and demonstration around automation and AI machine learning. In this interview, Jason Perry discusses Technica's plans for the show, and why attendees should stop by.
Airbus to Acquire INFODAS and Strengthen its Cybersecurity Portfolio
03/25/2024 | AirbusAirbus Defence and Space has entered into an agreement to acquire INFODAS, a Cologne-based, German company that provides cybersecurity and IT solutions in the public sector including for defence and critical infrastructures.