PBG Cavity in NV-Diamond for Large Scale Type II Quantum Computing

摘要

The objective of this project was to investigating the feasibility of realizing a type II quantum computer (QC) on a large scale, using nitrogen- vacancy color centers in diamond (NV-Diamond). To see the basic mechanism behind this scheme, consider a small volume of this medium. A laser beam incident on this volume can interact with all the centers in this volume. However, each center has a transition frequency that is slightly different from that of the others, a feature known as inhomogeneous broadening. This implies that individual centers can be addressed distinctively by tuning the laser. . In order to perform two qubit operations, such as the controlled-NOT (CNOT), it is necessary to couple two centers that are spectrally adjacent. One mechanism for such a coupling is the dipole-dipole interaction. However, since the spectral neighbors are not necessarily close to each other spatially, it is necessary to enhance this interaction artificially. This can be achieved by embedding the centers in a high-Q optical cavity. A key challenge in realizing this scheme is the cavity. If one were to embed the NV-diamond crystal inside a bulk-mirror based cavity, the residual reflection from the crystal surfaces would degrade the Q to an unacceptable level. A photonic band gap (PBG) cavity holds the best promise to overcome this constraint. The small mode volume of the PBG cavities (on the order of lambda 3 ) implies that the coupling of cavity photons to atoms in the cavity will be enhanced by three or more orders of magnitude over conventional bulk-mirror based cavity couplings. Another key feature of this approach is that the whole substrate will contain many QC's that can be operated simultaneously. Such a structure is ideally suited for type II quantum computing on a large scale. Such a QC may enable efficient computation of complex fluid dynamics, for example.