Reducing Motional Decoherence in Ion Traps with Surface Science Methods

Dustin A. Hite, Yves Colombe, A. C. Wilson +4 more

Jonathon A. Sedlacek, Jules Stuart, Colin Bruzewicz +3 more

Philipp Schindler, Dylan J Gorman, Nikos Daniilidis +1 more

Electric-field noise in proximity to metallic surfaces is a poorly understood phenomenon that appears in different areas of physics. Trapped ion quantum information processors are particularly susceptible to this noise, leading to motional decoherence, which ultimately limits the fidelity of quantum operations. On the other hand, trapped ions present an ideal tool to study this effect, opening new possibilities in surface science. In this work we analyze and measure the polarization of the noise field in a microfabricated ion trap for various noise sources. We find that technical noise sources and noise emanating directly from the surface give rise to different degrees of polarization, which allows us to differentiate between the two noise sources. Based on this we demonstrate a method to infer the magnitude of surface noise in the presence of technical noise.

Alto Osada, Atsushi Noguchi

Abstract Trapped-ion quantum technologies have been developed for decades toward applications such as precision measurement, quantum communication and quantum computation. Coherent manipulation of ions’ oscillatory motions in an ion trap is important for quantum information processing by ions, however, unwanted decoherence caused by fluctuating electric-field environment often hinders stable and high-fidelity operations. One way to avoid this is to adopt pulsed laser ablation for ion loading, a loading method with significantly reduced pollution and heat production. Despite the usefulness of the ablation loading such as the compatibility with cryogenic environment, randomness of the number of loaded ions is still problematic in realistic applications where definite number of ions are preferably loaded with high probability. In this paper, we demonstrate an efficient loading of a single strontium ion into a surface electrode trap generated by laser ablation and successive photoionization. The probability of single-ion loading into a surface electrode trap is measured to be 82%, and such a deterministic single-ion loading allows for loading ions into the trap one-by-one. Our results open up a way to develop more functional ion-trap quantum devices by the clean, stable, and deterministic ion loading.

Marcelo Terra Cunha, Maria Carolina Nemes

E. Kim, Arghavan Safavi-Naini, Dustin A. Hite +4 more

The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamen-tal science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. We have investigated the origin of this noise by focusing on the diffusion of carbon-containing adsorbates on the Au(110) surface. We show how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, predicts a noise spectrum, in accord with the measured values.