Quantum Dots Generate 1260nm Photons for Secure Networks

Researchers at the Niels Bohr Institute have achieved an advance in quantum communication by generating single photons around 1300nm wavelengths, overcoming a major obstacle to utilizing existing optical fiber networks. Previously, quantum dots, tiny collections of around 30,000 atoms behaving as artificial atoms, were limited to functioning around 930nm, necessitating new infrastructure for long-distance quantum data transmission. The newly created quantum dots, measuring 5.2nm tall and 20nm wide, emit one photon when excited, a characteristic essential for secure communication as information encoded in a single photon cannot be copied. Leonardo Midolo explains that this breakthrough addresses a long-standing problem: “Noisy in this context means that you couldn’t generate one photon after another with the same properties.” This development allows linking quantum technologies to current fiber-optic networks, promising secure quantum information transfer.

Telecom-Band Quantum Dots Overcome Noise & Coherence Limits

Single photons, inherently uncopyable due to the laws of quantum mechanics, are now being reliably generated around 1300nm, a wavelength crucial for compatibility with existing optical fiber networks. This achievement bypasses the need for costly and disruptive infrastructure overhauls previously required for quantum communication. A researcher emphasized the fundamental security advantage, stating, “Not two or a decimal amount but exactly one photon.” Previously, attempts to create telecom-band photons suffered from excessive noise, rendering them unusable for practical applications. The team successfully produced photons that are both coherent and identical, a combination long considered unattainable at these wavelengths. This breakthrough challenges a long-held assumption within the research community. Midolo notes, “For years, a belief circulated…yes, you can make photons in the telecom band, but they will be noisy and incoherent – which meant ‘useless’ for quantum applications.”

Collaboration in Bochum, Germany was instrumental in optimizing the growth of these low-noise emitters, while advanced nanofabrication techniques at the Niels Bohr Institute integrated the materials into quantum photonic circuits. Midolo concludes that this development opens up many possibilities previously considered out of reach, signaling a significant step toward a functional quantum internet.

2nm Quantum Dot Emitters Enable Single Photon Generation

This advancement, originating from the Niels Bohr Institute, leverages quantum dots, nanoscale semiconductors, to produce these secure, uncopyable particles of light, enabling practical quantum networks. The core innovation addresses a long-standing challenge: achieving both coherence and identical properties in telecom-band photons. The team’s quantum dots are designed to emit one photon when stimulated by a laser, a crucial feature for quantum key distribution and computation. This single-photon emission is achieved through the quantum dot’s internal structure, where discrete energy levels allow for controlled excitation and decay. This technology overcomes a material science hurdle; silicon photonic chips, commonly used for miniaturizing optical circuits, absorb light below 1100nm, limiting integration with near-infrared emitters. By operating around 1300nm, these quantum dots, which are about 5.2nm tall and 20nm wide, can be directly embedded within silicon chips, streamlining the construction of quantum devices and networks. Marcus Albrechtsen notes that at the Niels Bohr Institute, they “fabricate nanochips and probe them with lasers at low temperatures to confirm they emit highly coherent single photons.” This progress dismantles a previously held belief within the field, that telecom-band photons would inevitably be noisy and incoherent, and opens the door to a functional quantum internet.

1300nm Wavelength Compatibility Integrates with Fiber Networks

Previously, quantum dot technology, while promising for secure data transmission, was largely limited to wavelengths around 930nm, a significant disadvantage given that standard telecommunication relies on wavelengths starting at 1260nm. This limitation necessitated costly and complex infrastructure upgrades to accommodate quantum signals, hindering widespread adoption. Now, the team has engineered quantum dots capable of emitting photons around 1300nm, directly aligning with the wavelengths already in use for conventional fiber optic communication. This advancement bypasses the need for entirely new cabling or conversion technologies, dramatically simplifying the path toward a functional quantum internet. The newly developed quantum dots, each 5.2nm tall and 20nm wide, achieve this feat by locally forming discrete energy levels, mimicking the behavior of atoms. Leonardo Midolo explains that for years, the research community operated under the assumption that generating coherent photons in the telecom band would inevitably result in excessive noise.

The team’s success in producing both coherent and identical photons at 1300nm directly challenges this long-held belief. Compatibility with silicon photonic chips, the standard material for miniaturizing optical circuits, allows for direct integration of quantum light sources, paving the way for scalable quantum networks built upon existing infrastructure.