Quantum Dots Now Emit Secure Photons at 1260 nm Wavelength

Researchers at the Niels Bohr Institute have achieved an advance in quantum communication by successfully emitting secure, single photons around 1300nm, a frequency compatible with existing fiber optic networks. This breakthrough overcomes a longstanding barrier that previously restricted quantum information transfer to less practical platforms. The newly developed quantum dots, measuring 5.2nm tall and 20nm wide, are comprised of approximately 30,000 atoms and function as remarkably stable artificial atoms capable of generating these coherent photons. “Noisy in this context means that you couldn’t generate one photon after another with the same properties,” explains Leonardo Midolo, highlighting the challenge of achieving identical, quantum-coherent photons at telecom wavelengths; his team has now demonstrably overcome this hurdle, allowing for integration with current communication infrastructure.

Telecom-Band Quantum Dots Overcome Noise & Coherence Limits

A newly engineered quantum dot, measuring 5.2nm by 20nm, is now capable of emitting single photons around 1300nm, a wavelength critical for compatibility with existing telecommunication fiber optic networks. These nanoscale artificial atoms, comprised of approximately 30,000 atoms, function as remarkably efficient single-photon emitters, a feat previously hampered by the inability to produce coherent signals at telecom wavelengths. For years, researchers assumed that generating coherent, identical photons in the telecom band was impossible; however, Leonardo Midolo and his team have challenged this notion. The team successfully created a quantum dot that delivers both quantum coherence and emission directly within the 1300nm range, the standard wavelength for fiber-optic communication. This eliminates the need for complex and inefficient workarounds like nonlinear frequency conversion, streamlining the integration of quantum technologies with current infrastructure.

Marcus Albrechtsen elaborates on the fabrication process, noting that advanced nanofabrication techniques within the institute’s cleanroom are used to pattern the materials into quantum photonic circuits. The ability to operate at 1300nm is particularly advantageous because it allows for direct integration with silicon photonic chips, the most common and cost-effective material for controlling light on a chip. Midolo states that this development opens possibilities that were long considered out of reach, emphasizing the potential for building quantum chips, repeaters, and long-distance communication networks on existing fiber infrastructure.

2nm Quantum Dot Emitters Enable Single Photon Generation

Researchers have surmounted a critical obstacle in quantum communication by demonstrating single photon emission at wavelengths compatible with existing telecommunication networks; previously, viable quantum dots operated at significantly shorter wavelengths, limiting their practical application. Despite its diminutive size, each emitter comprises approximately 30,000 atoms, demonstrating the complexity achieved within this artificial atom. This innovation addresses the longstanding issue of signal loss in optical fibers, a major impediment to long-distance quantum information transfer. Leonardo Midolo explains that prior attempts to generate photons in this telecom band resulted in “noisy” signals, meaning the photons lacked the necessary uniformity for reliable quantum applications. “We fabricate nanochips and probe them with lasers at low temperatures to confirm they emit highly coherent single photons,” he adds.

1300nm Wavelength Compatibility Integrates with Silicon Photonics

This development circumvents the previous limitation of quantum dots functioning optimally around 930nm, a range unsuitable for long-distance data transmission; only these longer wavelengths allow for efficient distribution of information-carrying photons. This compatibility with silicon photonics is particularly significant, as silicon is the dominant material used in miniaturized optical circuits for controlling light on a chip. Previously, silicon’s absorption of light below 1100 nanometers prevented the integration of near-infrared emitters like these quantum dots; now, quantum-grade light sources can be directly embedded within commercial silicon photonic chips.