Abstract: A method for polarization alignment, preferably for and/or in the case of optical communication, quantum cryptography and/or quantum computing, comprising a source (2) for generating polarization-entangled photon pairs and two detection modules (3, 4), wherein the source (2) for transmitting the photons is connected via in each case one quantum channel (5) to the two detection modules, and wherein each detection module measures the polarization of the photons in two non-orthogonal bases, and including a polarization compensation unit (6) for polarization alignment of the polarization change during the transmission of the photons via the quantum channels, wherein the polarization compensation unit (6) has several optical components. The polarization alignment is effected by a downhill simplex algorithm and/or by a deterministic algorithm.

Abstract: A method for quantum communication between at least three receivers includes: i) generating an entangled photon pair in a source (2) with a signal photon in a signal wavelength range and an idler photon in an idler wavelength range, ii) assigning the signal and idler photons to the quantum channels (4) on the basis of their wavelength; iii) transmitting the photon pair to the receivers (3) via the quantum channels (4); iv) detecting the photon pair at the receivers (3).

Abstract: The invention relates to a method for producing an optical fiber coupler, having the following method steps: combining two or more light-guiding fibers (1, 2, 3) to form a fiber bundle; introducing the fiber bundle into a capillary (4); collapsing the capillary (4) onto the fiber bundle surrounded by the capillary. It is the object of the invention to provide an improved method for producing an optical fiber coupler. The method is intended to enable the positioning of the fibers within the capillary to be as precise as possible. At the same time, it should be possible to implement the method with comparatively little effort. To this end, the invention proposes that at least one of the fibers (1, 2, 3) is connected at the end to a guide body (5, 5?) whereof the diameter in the direction transversely to the longitudinal extent of the fiber (1, 2, 3) is larger than the diameter of the fiber (1, 2, 3) and smaller than the internal diameter of the capillary (4).

Abstract: A method for generating a laser pulse train is provided, including at least the following method steps: generating a laser pulse train at a pulse repetition frequency; coupling the laser pulse train into an acousto-optical modulator, and selecting individual laser pulses of the laser pulse train. A system for generating a laser pulse train is also provided, including at least a pulsed laser and an acousto-optical modulator, and an associated control device.

Abstract: The invention relates to a method for producing an optical fiber coupler, having the following method steps: combining two or more light-guiding fibers (1, 2, 3) to form a fiber bundle; introducing the fiber bundle into a capillary (4); collapsing the capillary (4) onto the fiber bundle surrounded by the capillary. It is the object of the invention to provide an improved method for producing an optical fiber coupler. The method is intended to enable the positioning of the fibers within the capillary to be as precise as possible. At the same time, it should be possible to implement the method with comparatively little effort. To this end, the invention proposes that at least one of the fibers (1, 2, 3) is connected at the end to a guide body (5, 5?) whereof the diameter in the direction transversely to the longitudinal extent of the fiber (1, 2, 3) is larger than the diameter of the fiber (1, 2, 3) and smaller than the internal diameter of the capillary (4).

Abstract: The invention relates to a method for generating a laser pulse train, comprising the following method steps: generating the laser pulse train (4a) at a pulse repetition frequency; coupling the laser pulse train (4a) into an acousto-optical modulator, and selecting individual laser pulses of the laser pulse train (4a) by driving the acousto-optical modulator with high-frequency pulses (4h), wherein the high-frequency pulses (4h) are generated by modulating a high-frequency carrier signal (4f) with a periodic switching signal (4e). In addition, the invention relates to a system for generating a laser pulse train, comprising a pulsed laser (1), which generates the laser pulse train at a pulse repetition frequency, and an acousto-optical modulator (2), in which the laser pulses propagate, and comprising a control device (7), which drives the acousto-optical modulator (2) with high-frequency pulses for the purpose of selecting individual laser pulses.