Quantum nodes are the key functional elements for applications in quantum sensing, secure communication or quantum computing. In these nodes a QuBit can be stored as a stationary QuBit and transferred onto a flying QuBit, distributing the information. We want to implement such an interface, realized as a coupled emitter-cavity system, in a photonic crystal. A photonic crystal slab promises low losses for cavities and waveguides, allowing for multiple nodes on a single chip, which is important for scaling.
A coupled system of a cavity and a photon emitter, such as an atom, molecule or quantum dot with a suitable energy level structure can be used as a stationary QuBit. There, the quantum information is stored in the electron population. To send this information to another node it needs to be imprinted on a suitable property of a photon, where it is called a flying QuBit. The most famous candidate is the polarization of the photon, where two orthogonal polarizations (e.g. horizontal-vertical or left-right-circular) are used. As polarization insensitive optical systems are difficult to realize, a time bin encoding seems more promising. There, the orthogonal states are early and late emission of a photon, as indicated in Fig.1.
Figure 1
Studying this device includes several computational steps. First, a suitable cavity needs to be designed. This is done using a 3D vectorial finite element method [1]. Second, the coupling of emitter and cavity is calculated after solving a Jaynes-Cummings Hamiltonian for the coupling constant by hand [2]. In the final step the values obtained in the previous steps are fed into a full quantum mechanical simulation of the emitter and cavity dynamics. To operate the device appropriate electromagnetic pulses are calculated for ideal population transfer and photon emission.
The results for a Lanthanide molecule coupled to a semiconductor photonic crystal slab cavity will be presented at the NUSOD 2021 conference.
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