Remote Entanglement of a Trapped Ytterbium Ion and a Zinc Oxide Defect

We aim to create a novel hybrid entanglement system between a trapped ytterbium ion qubit and a zinc oxide defect donor qubit. Entanglement will be achieved through single-photon which-path erasure. To do this, it’s necessary to make the photons emitted from each qubit as identical as possible in all aspects, including frequency, temporal profile, phase, polarization and arrival time. Yb+ and the ZnO donor were chosen as the hybrid pair because both exhibit transitions near 369 nm. However, their excited-state lifetimes differ significantly, causing a mismatch in their photons’ temporal profiles. To correct this difference, we are developing a machine learning algorithm for a process called pulse shaping, where the excitation pulse is modified by an acousto-optic modulator (AMO) before interacting with the ion. The goal of the algorithm is to determine the optimal pulse shape for the excitation and adjust the AMO accordingly. This leaves phase, polarization and arrival time. We anticipate addressing phase by phase-locking the two excitation pulses via a transfer cavity. Polarization will further be addressed with the unique geometry of our trap. The trap utilizes a parabolic mirror, which improves photon collection efficiency. The ytterbium ion can decay along three pathways from its excited state; two produce σ± Raman photons, which have elliptical polarizations once reflected off the parabolic mirror, and the third produces a π Rayleigh photon, which has linear polarization when reflected off the parabolic mirror. When focused into a single-mode optical fiber, the linearly polarized photons perfectly destructively interfere, leaving only the elliptically polarized. Finally, as all photons will travel through optical fibers before entanglement, we can control the lengths of these fibers to ensure no delay between arrivals. To verify indistinguishability, the photons emitted from each qubit will interact in a Hong-Ou-Mandel interferometer. We will then move to the weak excitation regime to produce single-photon entanglement between the two matter qubits.