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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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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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