Experimental Demonstration of Arbitrary Temporal Waveform Control of Single Photons Produced by Quantum Emitters Towards Hybrid Remote Entanglement between a Trapped Ytterbium Ion and a Zinc Oxide Semiconductor Defect

While many qubit types have been proposed and implemented, each has its own strengths and weaknesses in regards to creating a scalable system for quantum computing. Rather than attempting to perfect a single species, we propose a novel hybrid remote entanglement system between a trapped ytterbium ion and a zinc oxide defect donor, which would allow each qubit type to perform actions for which it is naturally better suited. Trapped ions exhibit long coherence times, making them ideal for memory, while semiconductor defects have efficient initialization and gate speeds, making them better for operations. Demonstrating entanglement between the two would open up pathways for hybrid quantum computers with different species registers optimized for different tasks. 

To entangle the qubits using the single-photon protocol via which-path erasure, we must ensure that an emitted photon from one qubit is indistinguishable from one emitted by the other, in wavelength, phase, polarization and temporal profile. Yb+ and the ZnO donor were chosen as the hybrid pair because both exhibit transitions near 369 nm, addressing the wavelength. Polarization and phase will be controlled through standard optical manipulation techniques. However, the excited-state lifetimes of the different emitters differ significantly, causing a mismatch in their photons’ temporal profiles and presenting a novel experimental challenge. To correct this, we have developed optimization techniques to generate ideal excitation pulse shapes to control the temporal waveform of a photon generated via spontaneous emission. 

Here, we show the first experimental steps taken towards implementing this optimization. With our current hardware, we achieve  photon temporal profile fidelities greater than 0.99 for a number of pulse shapes. We discuss experimental challenges in improving fidelities and current progress towards addressing these challenges and approaching our estimated achievable process fidelity of >0.996. Finally, we explore the use of phase control as a means of producing photons shorter than the excited state lifetime, and highlight the broader applicability of this technique.