SPS Device: Innovation, Other Competitors and the Market

The development of a Single Photon Source (SPS) prototype is discussed here which has the ability to efficiently produce polarized single photons on demand. The SPS prototype is to be of a relatively moderate size in order to be mass produced industrially and marketed as a ”Single Photon Gun” (SPG). The size and reliability of the SPG is of critical importance in meeting the needs of the current market for quantum cryptographic systems, whose current drawback is the lack of an efficient source of single photons. Even the recent deployment of a 67 km quantum communication channel under Lake Geneva by the swiss company id Quantique used heavily attenuated laser pulses as their source of single photons. Such sources are very unreliable when it comes to producing single photons on demand. While their low reliability is sufficient to meet the basic needs of cryptographic schemes, the speed and scalability of future systems will depend on the production of a much more reliable and efficient source of single photons. To that end, I have laid out the basic design of the SPG as envisioned at a very fundamental level. It is based on the use of semi-conductor nanocrystals, or quantum dots, as a fluorescent emitter of single-photons on demand. The quantum dots used here are made of PbSe and are immersed in a cholesteric liquid crystal host which increases their fluorescence intensity and decreases their fluorescence lifetime. The creation of the liquid crystal solution is carried out in a device that operates on the principle of a spin-coater for slides. In this case, the device will use a fast rotating tapered cylinder (see figure 1) that evenly distributes the quantum dots in the CLC solution using centrifugal forces. The liquid crystal solution is then run through a microfluidic channel that is of a size such that only one quantum dot is likely to flow through a certain area at a time. The optics of the system consist of a pulsed solid state diode laser operating at 532 nm which can be triggered on demand and is focused onto the microfluidic channel, whose flow can be correlated to the pulse rate of the laser in order to obtain optimum excitation of the quantum dots. The fluorescence photons from the quantum dots are detected using a confocal imaging lens set that is controlled by a piezo-