Quantum Communication

Quantum Communication: Photon each account

Ultrafast, efficient and reliable single photon detectors are among the most sought after components of photonics and quantum communication, which have not yet reached maturity for practical application. Physicist Dr. Wolfram Pernice, the Karlsruhe Institute of Technology (KIT), in collaboration with colleagues from Yale University, Boston University, and Moscow State Pedagogical University, achieved the breakthrough in the integration of a single photon detectors with nano-photonic chips. The detector combines near-unit detection efficiency with high time resolution and has a very low error rate.
Without reliable detection of individual photons, it is impossible to make real use of the latest advances in optical data transmission and quantum computing, is like having no analog-digital converter in a conventional computer to determine if the applied voltage is 0 or 1. Although a number of different models of single photon detector have been developed in recent years, to date, none has provided satisfactory performance.
Several new ideas and advanced developments entered the prototype developed in the "Integrated Quantum Photonics" project at the Center for Functional Nano-structures DFG (CFN). The new single-photon detector, tested in the wavelength range of telecommunications achieves detection efficiency previously achieved 91%.
The detector was made by fabricating superconducting nano-wires directly on top of one nanophotonic wave-guide  This geometry can be compared with a tube that conducts electricity, around which a wire is wound a superconducting state and, as such, has no electrical resistivity. The nano-scale wire of niobium nit ride absorbs photons propagating along the wave-guide  When a photon is absorbed, the superconductivity is lost, which is detected as an electrical signal. The longer the tube, the greater the probability of detection. The lengths involved are in the micrometer range.
A special feature of the installation detector is directly over the chip, allowing it to replicate randomly. Single photon detectors ever built were independent units, which were connected to chips with optical fibers.
Provisions of this kind suffer from photons lost in the fiber connection or an absorption of other ways. These channels do not exist in the loss detector is now fully integrated into a silicon photonic circuit. In addition to high detection efficiency, this leads to a markedly low rate of dark count. Dark counts arise when a photon is detected erroneously, eg due to a spontaneous emission, an alpha particle or a spurious field. The new design also offers jitter ultrashort picosecond timing of 18, which is 18 times 10 to 12 seconds.
The new solution also enables the integration of several hundred of these detectors on a single chip. This is a fundamental condition for future use in optical quantum computers.
The detector is shown in this study was designed to operate at wavelengths in the range of Telecom  The architecture same detector can also be used for wavelengths in the visible light range. This would allow the top to be used in the analysis of all the light emitting structures bit, ie photons, such as individual molecules or bacteria.