Yksifotonilähteet

Yksifotonilähteet, or single-photon sources, are devices designed to emit precisely one photon at a time. This capability is crucial for a variety of advanced quantum technologies, including quantum communication, quantum computing, and quantum metrology. The ability to control the emission of individual photons allows for the manipulation and transfer of quantum information.

There are several physical systems that can act as single-photon sources. Among the most promising are semiconductor quantum dots, which are tiny semiconductor nanocrystals that exhibit quantum mechanical properties. When excited by a laser pulse, a quantum dot can emit a single photon. Another important class of single-photon sources utilizes single atoms or ions, often trapped in electromagnetic fields. These systems can also be stimulated to emit single photons. Other approaches involve defects in solid-state materials, such as the nitrogen-vacancy center in diamond, and molecules.

The performance of a single-photon source is typically evaluated by several key metrics. Photon indistinguishability, which refers to how similar photons are to each other in terms of properties like wavelength and polarization, is vital for interference-based quantum protocols. High purity, meaning the source rarely emits more than one photon at a time, is also essential. Furthermore, efficient coupling of the emitted photons to optical interfaces, such as optical fibers or waveguides, is necessary for practical applications. Research in this field continues to focus on improving these parameters to enable more robust and scalable quantum technologies.