Single-Photon Emitter for Quantum Info-Processing

First known material capable of single-photon emission at room temperature and at telecommunications wavelengths, using chemically functionalized carbon nanotubes. (Source: LANL)

Los Alamos National Labora­tory has produced the first known material capable of single-photon emission at room tempera­ture and at tele­communications wave­lengths. These carbon nanotube quantum light emitters may be important for opti­cally-based quantum information processing and infor­mation security, while also being of significant interest for ultra­sensitive sensing, metrology and imaging needs and as photon sources for funda­mental advances in quantum optics studies.

“By chemically modifying the nanotube surface to control­lably introduce light-emitting defects, we have developed carbon nano­tubes as a single photon source, working toward implemen­ting defect-state quantum emitters operating at room tempera­ture and demonstrating their function in techno­logically useful wave­lengths,” said Stephen Doorn, leader of the project at Los Alamos and a member of the Center for Inte­grated Nano­technologies (CINT). “Ideally, a single photon emitter will provide both room-tempera­ture operation and emission at telecom wave­lengths, but this has remained an elusive goal. Up to now, materials that could act as single photon emitters in these wave­lengths had to be cooled to liquid helium tempera­tures, rendering them much less useful for ultimate appli­cations or scientific purposes,” he said.

A critical break­through in the CINT nanotube work was the ability of the team to force the nanotube to emit light from a single point along the tube, only at a defect site. The key was to limit defect levels to one per tube. One tube, one defect, one photon. By emitting light only one photon at a time, one can then control the photons’ quantum pro­perties for storage, mani­pulation and trans­mission of information. The CINT researchers were able to attain this degree of control using diazonium-based chemistry, a process they used to bind an organic molecule to the nanotube’s surface to serve as the defect. The diazonium reaction chemistry allowed a control­lable intro­duction of benzene-based defects with reduced sensi­tivity to natural fluc­tuations in the sur­rounding environ­ment. Impor­tantly, the versa­tility of the diazonium chemistry also permitted the researchers to access the inherent tunability of nanotube emission wave­lengths.

The wave­lengths of the photons produced in most other approaches had been too short for tele­communications appli­cations, where photons need to be effi­ciently mani­pulated and transported within optical circuits. The team found that by choosing a nanotube of appro­priate diameter, the single photon emission could be tuned to the essential telecom wave­length region. The func­tionalized carbon nanotubes have signi­ficant prospects for further develop­ment, Doorn noted, including advances in func­tionali­zation chemistry; integration into photonic, plasmonic and meta­materials structures for further control of quantum emission pro­perties; and implemen­tation into elec­trically driven devices and optical circuitry for diverse appli­cations. (Source: LANL)

Reference: X. He et al.: Tunable Room-Temperature Single-Photon Emission at Telecom Wavelengths from sp3 Defects in Carbon Nanotubes, Nat. Phot., online 31 July 2017; DOI: 10.1038/nphoton.2017.119

Link: Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, USA

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