Coupling distant quantum dots using a photonic crystal fano structure

Building a quantum computer by taking the advantage of quantum entanglement can lead to a significant increase in our ability to solve certain types of problems. Quantum computer has run on various forms in which photon has been recognized as a highly desirable one due to the robustness of photonic states against decoherence. In particular, it is promising to use a semiconductor on-chip nanophotonic system where photons can be manipulated via combinations of cavities and waveguides (WGs) [1] because of its multi-functionalities, robustness and scalability towards highly integrated chips. Photonic nanocavities combined with semiconductor quantum dots (QDs) constitute one of the best candidates [2]. To achieve QD-QD coupling, it is usually proposed to place the nanocavities, embedded with QDs, in close proximity with their physical distance on the order of a few wavelengths because the cavity mode is usually tightly confined in space, resulting in limited penetration depth of the evanescent fields. However, going beyond short-distant coupling to long-distant coupling is essential because of the requirement of producing and maintaining entanglement between spatially separated qubits on-chip, both for measurement purposes and to permit individual control of separated qubits.