Researchers have developed all-electrical ultra-thin quantum LEDs, which
have potential as on-chip photon sources in quantum information applications,
including quantum networks for quantum computers.
Ultra-thin quantum light emitting diodes (LEDs) – made of layered
materials just a few atoms thick – have been developed by researchers at the
University of Cambridge. Constructed of layers of different ultra-thin
materials, the devices could be used in the development of new computing and
sensing technologies. The ability to produce single photons using only
electrical current is an important step towards building quantum networks on
compact chips.
The devices are constructed of thin layers of different materials
stacked together: graphene, boron nitride and transition metal dichalcogenides
(TMDs). The TMD layer contains regions where electrons and electron vacancies,
or holes, are tightly confined. When an electron fills an electron vacancy that
sits at a lower energy than the electron, the energy difference is released as
a photon, a particle of light. In the LED devices, a voltage pushes electrons
through the device, where they fill the holes and emit single photons.
A computer built on the principles of quantum mechanics would be both
far more powerful and more secure than current technologies, and would be
capable of performing calculations that cannot be performed otherwise. However,
in order to make such a device possible, researchers need to develop reliable
methods of electrically generating single, indistinguishable photons as
carriers of information across quantum networks.
The ultra-thin platform developed by the Cambridge researchers offers
high levels of tunability, design freedom, and integration capabilities.
Typically, single photon generation requires large-scale optical set-ups with
several lasers and precise alignment of optical components. This new research
brings on-chip single photon emission for quantum communication a step closer.
The results are reported in the journal Nature Communications.
“Ultimately, we need fully integrated devices that we can control by
electrical impulses, instead of a laser that focuses on different segments of
an integrated circuit,” said Professor Mete Atatüre of Cambridge’s Cavendish
Laboratory, one of the paper’s senior authors. “For quantum communication with
single photons, and quantum networks between different nodes, we want to be
able to just drive current and get light out. There are many emitters that are
optically excitable, but only a handful are electrically driven.”
The layered nature of TMDs makes them ideal for use in ultra-thin
structures on chips. They also offer an advantage over some other single-photon
emitters for feasible and effective integration into nanophotonic circuits.
With this research, quantum emitters are now seen in another TMD
material, namely tungsten disulphide (WS2). “We chose WS2 because we wanted to
see if different materials offered different parts of the spectra for single
photon emission,” said Atatüre, who is a Fellow of St John's College. “With
this, we have shown that the quantum emission is not a unique feature of WS2,
which suggests that many other layered materials might be able to host quantum
dot-like features as well.”
“We are just scratching the surface of the many possible applications of
devices prepared by combining graphene with other materials,” said senior
co-author Professor Andrea Ferrari, Director of the Cambridge Graphene. “In
this case, not only have we demonstrated controllable photon sources, but we
have also shown that the field of quantum technologies can greatly benefit from
layered materials. Many more exciting results and applications will surely
follow.”
Reference:
C. Palacios-Berraquero et al. ‘Atomically thin
quantum light emitting diodes.’ Nature Communications (2016). DOI:
10.1038/ncomms12978
Source Link: https://www.cam.ac.uk/research/news/ultra-thin-quantum-leds-could-accelerate-development-of-quantum-networks
