Jul 19, 2017

Two-Dimensional Materials Combined to Produce “Quantum LED”

One of the many scientific and engineering challenges to realizing the prospects of quantum computing—which involves the use of quantum phenomena, like entanglement, to perform complex calculations—is  creating a device that can electrically generate a single photon to be used for carrying data in a quantum network. One method for producing these single photons is the use of complex multiple laser arrangements that have been precisely set up with optical components to produce these single photons. Lately, layered materials that serve as quantum emitters have begun to show a way forward. But even these layered materials require some kind of light source to trigger the emission of a single photon.

Now researchers at the University of Cambridge in England have constructed devices made from thin layers of graphene, boron nitride, and transition metal dichalcogenides (TMDs) that generate a single photon entirely electrically.  The combination of these three types of two-dimensional (2D) materials produces devices that are essentially all-electrical ultrathin quantum light-emitting diodes (LEDs).

In research described in the journal Nature Communications, the U.K.-based researchers demonstrated that the TMDs of tungsten diselenide and tungsten disulfide, which are both known for being optically active semiconductors, can serve as a platform for producing quantum-light generating devices.

The TMD layers provide a tightly confined area in two dimensions where electrons fill in holes. When an electron moves into one of these holes that reside at a lower energy, the difference in energy produces a photon. In the quantum LEDs produced by the U.K. researchers, a voltage pushes electrons through the device and fill holes, producing single photons when they do.

The researchers believe that this ultrathin platform run entirely electrically will bring on-chip single-photon emission for quantum communication closer to reality.

“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, in a press release. “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.”

This research demonstrated that tungsten diselenide can operate electrically as a quantum emitter. But the researchers also showed that tungsten disulfide is an entirely new class of quantum emitter and offers all-electrical single-photon generation in the visible spectrum.

Atatüre added: “We chose tungsten disulfide because we wanted to see if different materials offered different parts of the spectra for single photon emission. With this, we have shown that the quantum emission is not a unique feature of tungsten disulfide, which suggests that many other layered materials might be able to host quantum dot-like features as well.”

Keywords:quantum communications,tungsten dislenide,quantum computing,lasers,tungsten disulfide,LEDs, graphere, transition metal dichalcogenides, quantum emitters


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