Ph.D Thesis

Ph.D StudentBayn Igal
SubjectDiamond Photonic Crystals: Possible Implementation of Room
Temperature Atom-Photon Interaction Experiments
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Yosef Salzman
Full Thesis textFull thesis text - English Version


Quantum Information Technology (QIT), and in particular Quantum Computation (QC), show great potential for revolutionizing the methods by which one can collect and distribute data in diverse engineering contexts. Due to the highly demanding requirements and a high degree of coherence needed for QC, very few systems have demonstrated operating quantum bits (qubits). In this context, solid-state physics can be regarded as a very attractive avenue that will eventually provide the large scale QC integration solution.

 A novel solid state platform for QIT is a single crystal diamond. In fact, color centers in diamond are the only single-photon sources at room temperature reported so far. In particular, the negatively charged nitrogen-vacancy color center (NV) has an optical transition between states that display spin selectivity with extremely long coherence. This center satisfies all DiVincenzo criteria for a qubit, except scalability. Scalability can be achieved by a controllable interaction between distant NVs carried out by photons. This can be implemented by a diamond nanophotonic architecture where each NV is registered into a high-Q cavity, while the cavities are interconnected by waveguides. This research focuses on developing the basic photonic elements for this large-scale QC.

Here we present two possible implementations of this architecture via photonic crystals (PCs) and triangular nanobeams. For both, the numerical design of ultra-high-Q cavities with a small mode volume (Vm) is explored. Specifically, for the slab PCs a record high Q≈1.3?106 and Vm=1.77?(λ/n)3 is obtained theoretically. A novel triangular nanobeam displaying preferential vertical emission is introduced. For this optimized nanobeam, Q≈2.51?106 and Vm=1.06?(λ/n)3 is predicted.

The extreme chemical inertness of single crystal diamond and the lack of a nanofabrication technology has prevented, until recently, the implementation of nanophotonics. Here, several fabrication approaches such as formation of a free standing membrane with ion implantation or beams with Focused-Ion-Beam (FIB), high-precision nano-sized patterning of PCs and nanobeam gratings by FIB, are presented.

These advancements in nanofabrication and modeling allowed the first realization of single crystal diamond PC nanocavities. Their optical characterization revealed that ion implantation formed membranes exhibiting high optical losses and neutralized NV. Based on these results, a novel strategy towards the membrane formation has been proposed and an alternative triangular nanobeam approach has been demonstrated using FIB. The application of hydrogen plasma based surface treatment demonstrated gentle tuning of the cavity modes and presented the highest Q~700 with Vm~3.6?(λ/n)3. These results open new horizons for diamond based QIT.