Slow and fast single photons from a quantum dot interacting with the excited state hyperfine structure of the Cesium D1-line

Tim Kroh,Stephan Reitzenstein,Eugenio Zallo,Andreas Ahlrichs,Oliver Benson,Oliver G Schmidt,Johannes S Wildmann,Armando Rastelli,Janik Wolters,Andreas W Schell,Alexander Thoma,Rinaldo Trotta

doi:10.1038/s41598-019-50062-x

Abstract

Hybrid interfaces between distinct quantum systems play a major role in the implementation of quantum networks. Quantum states have to be stored in memories to synchronize the photon arrival times for entanglement swapping by projective measurements in quantum repeaters or for entanglement purification. Here, we analyze the distortion of a single-photon wave packet propagating through a dispersive and absorptive medium with high spectral resolution. Single photons are generated from a single In(Ga)As quantum dot with its excitonic transition precisely set relative to the Cesium D1 transition. The delay of spectral components of the single-photon wave packet with almost Fourier-limited width is investigated in detail with a 200 MHz narrow-band monolithic Fabry-Pérot resonator. Reflecting the excited state hyperfine structure of Cesium, “slow light” and “fast light” behavior is observed. As a step towards room-temperature alkali vapor memories, quantum dot photons are delayed for 5 ns by strong dispersion between the two 1.17 GHz hyperfine-split excited state transitions. Based on optical pumping on the hyperfine-split ground states, we propose a simple, all-optically controllable delay for synchronization of heralded narrow-band photons in a quantum network.

Highlights

Forthcoming quantum networks require various building blocks to perform tasks such as logical operations, or error correction on quantum bits, entanglement generation, distillation and distribution, as well as storage of quantum bits[1,2]
Electromagnetically induced transparency (EIT) type experiments remain unaffected by four-wave mixing[18] and yield an improved signal-to-noise ratio (SNR) compared to Raman type experiments[19]
This would allow for a flexible distribution of stand-alone, ambient-condition quantum repeater nodes consisting of memories as well as Si-based single-photon detection for entanglement swapping, and cold sources of single, entangled photon pairs such as semiconductor quantum dots (QDs)[20,21,22,23]

Summary

Introduction

Forthcoming quantum networks require various building blocks to perform tasks such as logical operations, or error correction on quantum bits, entanglement generation, distillation and distribution, as well as storage of quantum bits (or qubits)[1,2]. The latter two are important for future long distance quantum networks. Photonic qubits underlie non-zero absorption in communication channels like air or optical fiber, which lead to an exponential decrease of the transmission probability with distance This limitation can be overcome by integrating so-called quantum repeaters into the network[6]. This would allow for a flexible distribution of stand-alone, ambient-condition quantum repeater nodes consisting of memories as well as Si-based single-photon detection for entanglement swapping, and cold sources of single, entangled photon pairs such as semiconductor quantum dots (QDs)[20,21,22,23]

Methods

Results

Conclusion