State selective detection of hyperfine qubits

TL;DR

This paper develops and demonstrates generalized state detection methods for hyperfine qubits, improving measurement fidelity by accounting for multiple possible state changes during detection.

Contribution

The paper introduces generalized time-resolved and π-pulse detection methods tailored for hyperfine qubits with multiple state changes, enhancing detection accuracy.

Findings

Numerical simulations show improved detection fidelity.

Experimental results confirm the effectiveness of the generalized methods.

Real-time state discrimination becomes feasible with the new techniques.

Abstract

In order to faithfully detect the state of an individual two-state quantum system (qubit) realized using, for example, a trapped ion or atom, state selective scattering of resonance fluorescence is well established. The simplest way to read out this measurement and assign a state is the threshold method. The detection error can be decreased by using more advanced detection methods like the time-resolved method or the $\pi$-pulse detection method. These methods were introduced to qubits with a single possible state change during the measurement process. However, there exist many qubits like the hyperfine qubit of $^{171}Yb^+$ where several state change are possible. To decrease the detection error for such qubits, we develope generalizations of the time-resolved method and the $\pi$-pulse detection method for such qubits. We show the advantages of these generalized detection methods in numerical simulations and experiments using the hyperfine qubit of $^{171}Yb^+$. The generalized detection methods developed here can be implemented in an efficient way such that experimental real time state discrimination with improved fidelity is possible.