Quantum tomography of entangled spin-multi-photon states

TL;DR

This paper introduces a new quantum tomography technique for multi-qubit states, specifically applied to spin-multi-photon states generated via periodic excitation of a quantum dot, enabling detailed characterization and robustness assessment of entangled photon clusters.

Contribution

The paper presents a novel quantum tomography method tailored for spin-multi-photon states produced by a quantum dot, improving entanglement robustness and generation rate.

Findings

Demonstrated deterministic generation of entangled photon strings in a cluster state.

Quantified entanglement robustness using the process map.

Achieved a threefold increase in generation rate compared to previous methods.

Abstract

We present a novel method for quantum tomography of multi-qubit states. We apply the method to spin-multi-photon states, which we produce by periodic excitation of a semiconductor quantum-dot- confined spin every 1/4 of its coherent precession period. These timed excitations lead to the deterministic generation of strings of entangled photons in a cluster state. We show that our method can be used for characterizing the periodic process map, which produces the photonic cluster. From the measured process map, we quantify the robustness of the entanglement in the cluster. The 3-fold enhanced generation rate over previous demonstrations reduces the spin decoherence between the pulses and thereby increases the entanglement.