Superfast light source made from artificial atom

April 26, 2016, University of Copenhagen
In a quantum dot, there are both negatively charged particles and positively charged particles that are missing electrons (also referred to as holes). The attraction between the electron and hole creates a new quantum state with a very strong light-matter interaction and a corresponding quick release of light.

All light sources work by absorbing energy – for example, from an electric current – and emit energy as light. But the energy can also be lost as heat and it is therefore important that the light sources emit the light as quickly as possible, before the energy is lost as heat. Superfast light sources can be used, for example, in laser lights, LED lights and in single-photon light sources for quantum technology. New research results from the Niels Bohr Institute show that light sources can be made much faster by using a principle that was predicted theoretically in 1954. The results are published in the scientific journal, Physical Review Letters.

Researchers at the Niels Bohr Institute are working with quantum dots, which are a kind of artificial atom that can be incorporated into optical chips. In a quantum dot, an electron can be excited (i.e. jump up), for example, by shining a light on it with a laser and the electron leaves a 'hole'. The stronger the interaction between light and matter, the faster the electron decays back into the hole and the faster the light is emitted.

But the interaction between light and matter is naturally very weak and it makes the light sources very slow to emit light and this can reduce energy efficiency. Already in 1954, the physicist Robert Dicke predicted that the interaction between light and matter could be increased by having a number of atoms that 'share' the excited state in a quantum superposition.

Quantum speed up

Demonstrating this effect has been challinging so far because the atoms either come so close together that they bump into each other or they are so far apart that the quantum speed up does not work. Researchers at the Niels Bohr Institute have now finally demonstrated the effect experimentally, but in an entirely different physical system than Dicke had in mind. They have shown this so-called superradiance for photons emitted from a single quantum dot.

Søren Stobbe and Petru Tighineanu in the group’s laboratories at the Niels Bohr Institute in Copenhagen
"We have developed a quantum dot so that it behaves as if it was comprised of five quantum dots, which means that the light is five times stronger. This is due to the attraction between the electron and the hole. But what is special is that the quantum dot still only emits a single photon at a time. It is an outstanding single-photon source," says Søren Stobbe, who is an associate professor in the Quantum Photonic research group at the Niels Bohr Institute at the University of Copenhagen and led the project. The experiment was carried out in collaboration with Professor David Ritchie's research group at the University of Cambridge, who have made the quantum dots.

Petru Tighineanu, a postdoc in the Quantum Photonics research group at the Niels Bohr Institute, has carried out the experiments and he explains the effect as such, that the atoms are very small and light is very 'big' because of its long wavelength, so the light almost cannot 'see' the atoms – like a lorry that is driving on a road and does not notice a small pebble. But if many pebbles become a larger stone, the lorry will be able to register it and then the interaction becomes much more dramatic. In the same way, light interacts much more strongly with the quantum dot if the quantum dot contains the special superradiant quantum state, which makes it look much bigger.

Increasing the light-matter interaction

The experiments were carried out in the group’s laboratories on Blegdamsvej in Copenhagen.
"The increased light-matter interaction makes the quantum dots more robust in regards to the disturbances that are found in all materials, for example, acoustic oscillations. It helps to make the photons more uniform and is important for how large you can build future quantum computers," says Søren Stobbe.

He adds that it is actually the temperature, which is only a few degrees above absolute zero, that limits how fast the light emissions can remain in their current experiments. In the long term, they will study the at even lower temperatures, where the effects could be very dramatic.

Explore further: Photons open the gateway for quantum networks

More information: Petru Tighineanu et al. Single-Photon Superradiance from a Quantum Dot, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.163604

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antialias_physorg
4.6 / 5 (10) Apr 26, 2016
laser lights, LED lights

Pet peeve: The acronyms 'laser' and 'LED' already contain the words 'light'.

can be excited (i.e. jump up)

Higher energy level is not 'up'.
Benni
1.8 / 5 (15) Apr 26, 2016
laser lights, LED lights

Pet peeve: The acronyms 'laser' and 'LED' already contain the words 'light'.

can be excited (i.e. jump up) Higher energy level is not 'up'.


Pet Peeve: a Biologist like you, one who imagines he's qualified to critique anyone who professionally engages in any discipline such as the topic under discussion.
HeloMenelo
3.2 / 5 (9) Apr 26, 2016
laser lights, LED lights

Pet peeve: The acronyms 'laser' and 'LED' already contain the words 'light'.

can be excited (i.e. jump up) Higher energy level is not 'up'.


Pet Peeve: a Biologist like you, one who imagines he's qualified to critique anyone who professionally engages in any discipline such as the topic under discussion.

Antigoracle ala obama socks, a monkey like you who admitted he created many sockpuppets including benni :

more on antisciencgorilla monkey's lies, and then he tries to cover it up by telling another lie LOL:

http://phys.org/n...ate.html

monkey wants bananas :D
antialias_physorg
4.4 / 5 (7) Apr 26, 2016

Pet Peeve: a Biologist like you, one who imagines he's qualified to critique anyone who professionally engages in any discipline such as the topic under discussion.

1) Human biology ..not biologist
2) I have a masters degree in EE and have studied lasers and LEDs, so I know what I'm talking about here from a practical and theoretical level

So...yeah. I do criticize the science journalists who write about science sometimes. Deal with it.
Hyperfuzzy
1 / 5 (3) Apr 26, 2016
OK, i get the quantum dot "thang"; however, why not simply define every point in the field generated by all the particles in that space. Try just two types and the different possibilities. Which are calculable for whatever field. So I'm thinking your super fast light source has a simpler description. The field is updated and superposition using only two particles that may also be reduced as equal to two particles. Infinity down to infinitesimal. juz say'n simple the field is caused by the motion and the motion is caused by the field. better view in 4D, causality!
Whydening Gyre
3 / 5 (6) Apr 26, 2016
Pet Peeve - Benni blah-blah...
obama_socks
1.7 / 5 (6) Apr 26, 2016
Pet Peeve - being accused of being someone's sock puppet by a science wannabe who can't do the science - HeloManolo needs to stick a banana in its ear.
Hey, maybe I'm antialias_physorg's sock puppet too. We both have degrees in EE.
Whydening Gyre
3.4 / 5 (5) Apr 26, 2016
Pet Peeve - being accused of being someone's sock puppet by a science wannabe who can't do the science - HeloManolo needs to stick a banana in its ear.
Hey, maybe I'm antialias_physorg's sock puppet too. We both have degrees in EE.

Only if you opted out of human biology prior to your EE.
I had equivalent back when I first started computers in the early 70's. All the intervening 1's and 0's and software, networking, yada, yada kind drove the actual EE part out of me, I guess... (Altho I can still read a schematic fairly well)
Whydening Gyre
4 / 5 (4) Apr 27, 2016
Why on earth would computers drive EE out of you? You must not have been doing anything significant. And you could have been there at the roots of BSD, System V, etc.

Really wasn't all that significant. Fixed things. Replaced parts, etc. Didn't design anything. Didn't require EE theories or application thereof.

Sad lot you have cast for yourself mate. But I suppose you are above petty organizations like IEEE. What do they possibly have to do with advanced meta-EE things you know like networking?

You make unsupported supposition. Usually, that's driven by overactive ego of the supposer...
Most modern computer problems are software error, not electrical hardware.
Was a career field I left 15 years ago...
HeloMenelo
3.7 / 5 (6) Apr 27, 2016
Pet Peeve - being accused of being someone's sock puppet by a science wannabe who can't do the science - HeloManolo needs to stick a banana in its ear.
Hey, maybe I'm antialias_physorg's sock puppet too. We both have degrees in EE.


Can't be, Antialias_physorg has got a brain, and that has been proven, can't say the same for you and your clan of puppets though ;)
Obama socks got a degree in swinging trees, he was introduced by one of his socks forestgnome who revealed to him the art of tree swinging... from there om monkey obama/antigoracle went bannanas ! :D
Hyperfuzzy
1 / 5 (2) Apr 27, 2016
WTF juz make up s#it!
Da Schneib
5 / 5 (3) Apr 30, 2016
The whole article has a rather ESL Northern European flavor about it.

That aside, this is an interesting development. Now, if we can get the quantum dots to be designed so they can operate in a shirtsleeve environment, and figure out a fabrication method, we've got a lead on a highly efficient light source. And as the first paragraph rather impenetrably implies, a source of photons for quantum computing and quantum experimentation.

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