SINGLE-PHOTON SOURCES: Quantum dots may hold the key to secure quantum cryptography

摘要

Quantum-dot-based single-photon sources are fast and efficient and remain at the forefront of candidates for use in quantum information schemes. Much as the laser dramatically changed the telecommunications industry and led to rapid scientific progress in many fields, a single-photon source (SPS) would push photonics to its fundamental limit--control of single quanta--and lead to major advances. While many of those advances are not immediately obvious, there are even now three uses for an SPS. First among these uses is in quantum cryptography, which promises unconditionally secure communications (see www.laserfocusworld.com/articles/346705). Second, an SPS could also be applied to quantum computation following the ingenious scheme of Knill, Laflamme, and Milburn, which requires only a source of indistinguishable single photons, high-efficiency photon detectors, and linear optical elements to carry out such tasks as Shor's algorithm for factoring large numbers in finite time and Grover's algorithm for searching an unordered database (see www.laserfocusworld.com/articles/355975). These algorithms promise to speed up difficult computational problems. Third, an emerging application of an SPS is to drive a different system such as an atom or even a mechanical oscillator.