Single Photon Carbon Nanotubes Quantum Technology

RIKEN Scientists Create Precision Carbon Nanotubes for Single-Photon Quantum Technologies

Carbon Nanotubes Emerge as Key Building Blocks for Quantum Communication

RIKEN researchers have developed a method to precisely create carbon nanotubes that emit single photon from a specific point along their length. These tiny carbon structures could become a cornerstone of future light-based quantum technologies.

Light already carries vast amounts of data across the globe through optical fibers. Harnessing it quantum properties, however, could deliver major advantages, including ultra-secure communication in which any attempted interception is immediately detectable.

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Such quantum communication systems depend on light sources that release photons one at a time. While several platforms can achieve this, carbon nanotubes are emerging as one of the most promising candidates.

Advantages and Challenges of Carbon Nanotubes

"Carbon nanotubes are unique quantum emitters, capable of releasing single photons at room temperature and at wavelengths compatible with telecommunications," said Yuichiro Kato of the RIKEN Centre for Advanced Photonics, noting their strong appeal for practical technologies.

Until now, however, scientists have struggled to control how many points along a nanotube emit light, as well as to pinpoint the exact location of those emission sites.

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Kato and his colleagues have now resolved both challenges, successfully engineering nanotubes that emit single photons from one precisely controllable location. Their findings have been published in Nano Letters.

Breakthroughs in Fabrication and Atomic-Level Control

Kato describes the work as a leap beyond conventional nanofabrication. "We are already moving beyond nanotechnology," he said. "This is the realm of atomically defined engineering, and that is tremendously exciting."

The researchers achieved this by suspending a carbon nanotube across a trench only a few micrometers wide and exposing it to iodobenzene vapour. An ultraviolet laser was then focused on a single point along the nanotube.

Together, the UV light and iodobenzene created precise defects known as colour centers.

To ensure only one colour center formed, the team continuously tracked the emitted light and halted the process the moment a tell-tale change signalled that the defect had appeared.

By precisely positioning the focused laser, the researchers were able to fix the location of the colour center along the carbon nanotube with micrometer-level accuracy.

Toward Practical Quantum Photonic Devices

Kato's long-term ambition is to build devices based on nanotubes that emit single photons.

"Our aim is to integrate them directly into on-chip photonic circuits," he said. "Once that milestone is reached, we can begin serious discussions with photonics manufacturers about practical applications."

The wider implications of quantum communication, secure data transmission and emerging technologies — including their relevance to healthcare, data protection and future human system — are examined at Human Health Issues.

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