Ramsey Interference in a Multi-level Quantum System

TL;DR

This paper demonstrates Ramsey interference in a negatively charged quantum dot, revealing coherence properties and multi-level system behavior under magnetic fields, with implications for quantum control.

Contribution

It introduces the observation of Ramsey interference in a multi-level quantum dot system and explores phase-sensitive control of population and spin qubits.

Findings

Ramsey interference decay limited by spectral width

Magnetic field induces Zeeman splitting revealing multi-level behavior

Single-laser pulses can prepare both population and spin qubits

Abstract

We report Ramsey interference in the excitonic population of a negatively charged quantum dot revealing the coherence of the state in the limit where radiative decay is dominant. Our experiments show that the decay time of the Ramsey interference is limited by the spectral width of the transition. Applying a vertical magnetic field induces Zeeman split transitions that can be addressed by changing the laser detuning to reveal 2, 3 and 4 level system behaviour. We show that under finite field the phase-sensitive control of two optical pulses from a single laser can be used to prepare both population and spin qubits simultaneously.