Quantum light source offers new possibilities for communications and computing

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Pictured is an atomically-thin MoTe2 layer (blue and yellow lattice) on strain-inducing nanopillars as site-controlled telecom-wavelength quantum emitters for coupling to optical fibers with minimal loss. Single photons (red) are generated upon optical excitation (green).

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A quantum light source recently developed by researchers at the Center for Integrated Nanotechnologies (CINT) presents new capabilities for quantum communication and computing. As described recently in Nature Communications, the technological advancement enables the integration of two-dimensional material-based quantum light sources into existing fiber optic communication networks for practical implementation of quantum cryptography and metrology applications. Light sources may also play a role in quantum computing networks.

Conventional light sources emit many photons simultaneously. Lasers also emit photons simultaneously, though they do so in a single color (wavelength) and in one direction. In today’s fiber optic communication networks, laser light pulses, each containing millions of photons, are used to encode the information being transmitted. As a result, information can easily be stolen by splitting some photons of the light pulses.  

In quantum communication, however, information is encoded in the phase of a single photon, making information impossible to steal. This new communication scheme requires light sources capable of emitting a stream of single photons at regular intervals. A “quantum” light source cannot be created by simply dimming the conventional light sources and lasers – no matter how much one dims such light sources, the probability of two photons emitted at the same time is always finite. Quantum light sources should also produce photons at the wavelength compatible with existing fiber communication networks (i.e., 1.35 or 1.55 microns). 

The CINT research team recently realized a quantum light source with operating wavelength tunable across O and C telecommunication bands by placing atomically thin molybdenum ditelluride (MoTe₂) semiconductor layers on top of an array of strain-inducing nanometer-sized pillars. Hanbury Brown and Twiss experiments conducted at 10 K reveal clear photon antibunching with 90% single-photon purity. The photon antibunching can be observed up to liquid nitrogen temperature (77 K). Because the pillars can be fabricated via electron beam lithography, the quantum light sources can be placed to a desired location with nanometer precision. 

In addition to quantum communication applications, facile layer-by-layer device fabrication allowed by the two-dimensional nature of the MoTe₂ provides an opportunity to integrate these light sources into emerging quantum computers as a key element for forming a quantum network. Because a stream of single photons can have intensity fluctuations smaller than the fundamental fluctuation limit possible for a laser light (i.e., shot-noise limit), fiber-coupled quantum light sources can also enable ultra-sensitive absorption/reflection measurements for chemo/bio sensing applications. 

Mission and Funding

This work was supported by the U.S. Department of Energy (DOE) Office of Science, the Office of Science Basic Energy Sciences program, the Laboratory Directed Research and Development program, the Quantum Science Center, and from a Laboratory Director’s Postdoc Fellow Award. The work supports the Global Security mission area and the Materials for the Future capability pillar.

Reference

“Site-Controlled Telecom-Wavelength Single-Photon Emitters in Atomically-thin MoTe2,” Nature Communications, 12, 6753 (2021); DOI: https://doi.org/10.1038/s41467-021-27033-w. Authors: Huan Zhao, Michael T. Pettes, Yu Zheng and Han Htoon.

Technical Contact: Han Htoon