Quantum control of the hyperfine-coupled electron and nuclear spins in alkali atoms

TL;DR

This paper demonstrates quantum control of hyperfine states in alkali atoms using radio frequency and microwave fields, enabling arbitrary state manipulation with high fidelity in a decoherence-resistant manner.

Contribution

It establishes controllability conditions for hyperfine manifolds and designs control waveforms for alkali atoms, expanding quantum control techniques in atomic systems.

Findings

Achieved controllability of the hyperfine manifold in alkali atoms.

Designed control waveforms for arbitrary state preparation.

Identified practical operating points with high fidelity.

Abstract

We study quantum control of the full hyperfine manifold in the ground-electronic state of alkali atoms based on applied radio frequency and microwave fields. Such interactions should allow essentially decoherence-free dynamics and the application of techniques for robust control developed for NMR spectroscopy. We establish the conditions under which the system is controllable in the sense that one can generate an arbitrary unitary on the system. We apply this to the case of $^{133}$Cs with its $d=16$ dimensional Hilbert space of magnetic sublevels in the $6S_{1/2}$ state, and design control waveforms that generate an arbitrary target state from an initial fiducial state. We develop a generalized Wigner function representation for this space consisting of the direct sum of two irreducible representation of SU(2), allowing us to visualize these states. The performance of different control scenarios is evaluated based on the ability to generate high-fidelity operation in an allotted time with the available resources. We find good operating points commensurate with modest laboratory requirements.