QBC Seminar Series – Paul Haljan

Seminar Title: Realizing a Structural Phase Transition of Trapped Ions in the Quantum Regime by Paul C Haljan, Department of Physics, Simon Fraser University

Abstract: Arrays of trapped ions are a versatile technological platform with exquisite control over experimental parameters at the single-atom level. This allows both manipulation of the internal quantum state of the ions and control of their quantum collective vibrational motion – phonons – in the trap. A focus of my research group is advancing the technology of phononic coherent control in trapped ions. As part of this, we are aiming to demonstrate precise manipulation of a single vibrational mode of trapped ions in order to control a quantum structural phase transition in a string of trapped ions – the 1D linear to 2D zigzag transition. This system would provide an intrinsic source of novel entangled states of ion crystal structures, which can be manipulated through trapped ion double-well interferometry. In this talk I will describe how we experimentally control and characterize the linear-zigzag structural transition for arrays of ions confined in a linear Paul trap and cooled to near their ground state of motion. I will show how Raman sideband spectroscopy can be used as a probe to reveal both the energy level structure and the motional population distribution of the ion crystal near the critical point of the transition. I will look at what our results reveal about the nature of the transition in practice, and finally I will consider prospects for coherence assessment near the critical point as well as potential applications in in-situ sensing of electric field noise.