Physics (Internal)

Improving the performance of solid-state qubits near surfaces

This event is part of the Biophysics/Condensed Matter Seminar Series.

Solid-state qubits, which act as artificial atoms, have many advantages over real atoms or ions, such as engineerability, scalability, and the lack of need for complex trapping or cooling schemes. However, their quantum coherence is generally limited due to the environment in which they reside. In particular, while high-quality, nearly flawless bulk materials can be used in these qubits, the presence of surfaces inevitably introduces imperfections. I will give two examples of improving of qubit performance by mitigating the effect of imperfect surfaces. The first example is the nitrogen-vacancy (NV) center in diamond, where efforts toward implementing nanophotonic structures for quantum communications demand high quality qubits close to the surface. We show that, with the proper treatment of materials, it is possible to achieve lifetime limited optical coherence in near-surface NV centers. The second example involves superconducting qubits on silicon, where micromachining techniques are used to replace lossy substrate material with a perfect dielectric – vacuum.