Group Seminar via Zoom: Precise spinor matterwave control with nanosecond Raman pulses in a "biased-rotation” regime

Liyang Qiu, Fudan University
Group Meeting via video conference (Zoom)
Friday, July 8, 9.00 am (MEZ)

Abstract:

From inertial sensing to quantum computation, unlocking quantum advantages of ultracold atomic system requires ultra-precise single-body control of spinor matterwave. Such state-of-art controls are becoming closely achieved for quantum information processing with trapped ions. However, when applying these techniques to larger ensembles, severe difficulties associated with weak and inhomogeneous optical illumination emerge. We re-investigate Raman spinor wave control technique in an intermediate regime of single-photon detuning for achieving fast, precise and robust matterwave control in a power-efficient manner. In this regime, rotations of atomic spinors by the Raman coupling are biased by a significant Stark shift. Furthermore, for species with I>1, "coherent spin leakage" can be driven by tensorial shifts on a hyperfine manifold. We demonstrate numerically that high-fidelity universal qubit gates can nevertheless be achieved in this "biased-rotation" regime, within nanoseconds, to parallelly drive the weakly-coupled qubits within the hyperfine manifold. Experimentally, the directionality of the fast spin-dependent recoil-momentum transfer on a delay line is supported by spatially resolving the counter-propagating Raman pulses for the first time.  Equipped with a wideband optical arbitrary waveform generator, we demonstrate adiabatic spin-dependent kicks to accelerate mesoscopic Rb85 atomic samples within 40 nanoseconds, with 97.6(3)% of fidelity, with 20mW of laser power.

[1]  Liyang Qiu, Lingjing Ji, Yizun He, Jiangyong Hu, Yuzhuo Wang and Saijun Wu, "Precise spinor matterwave control with nanosecond adiabatic spin-dependent kicks," arXiv:2202.09709.