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Two-Dimensional Materials Combined to Produce “Quantum LED”

An all-electrical quantum emitter brings quantum computing one step closer

2 min read
Microscope image of a quantum LED device shows bright quantum emitter generating a stream of single photons.
Image: Mete Atatüre

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.”

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Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.

Avicena

If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

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