Quantum optical networks will enable distribution of quantum entanglement at long distances, with applications including interconnects between future quantum computers and secure quantum communications. I will present our recent work on developing quantum networking components based on rare-earth ions such as single optically addressable quantum bits based on ytterbium 171 in yttrium orthovanadate, microwave to optical transducers based on erbium doped crystals coupled to microwave and optical resonators, and on-chip telecom optical quantum memories.Quantum optical networks will enable distribution of quantum entanglement at long distances, with applications including interconnects between future quantum computers and secure quantum communications. I will present our recent work on developing quantum networking components based on rare-earth ions such as single optically addressable quantum bits based on ytterbium 171 in yttrium orthovanadate, microwave to optical transducers based on erbium doped crystals coupled to microwave and optical resonators, and on-chip telecom optical quantum memories.

Photonic and Phononic Properties of Engineered NanostructuresMar 4, 20220 citations

Triply Resonant Microwave to Optical Conversion in Erbium-170 Doped Yttrium Orthosilicate

Gavin G. G. King, Luke S. Trainor, Jevon J. Longdell

We report microwave to optical upconversion in isotopically purified erbium-doped yttrium orthosilicate in a Fabry-Pérot resonator at millikelvin temperatures. This follows on from investigations made at higher temperatures and with natural isotopic ratios for the erbium dopants. In these previous investigations the highest efficiency was seen only for moderately strong microwave powers. The removal of the unwanted erbium-167 which has hyperfine structure and provides unwanted background optical absorption, and the lower temperatures has removed this problem. We now see efficiencies still increasing as the microwave power is decreased when we reach the smallest input powers for which we could measure an output. Efficiencies of $2\times10^{-6}$ were observed and we discuss potential improvements, including better optical cavity frequency stability and better thermalisation of the erbium spins.We report microwave to optical upconversion in isotopically purified erbium-doped yttrium orthosilicate in a Fabry-Pérot resonator at millikelvin temperatures. This follows on from investigations made at higher temperatures and with natural isotopic ratios for the erbium dopants. In these previous investigations the highest efficiency was seen only for moderately strong microwave powers. The removal of the unwanted erbium-167 which has hyperfine structure and provides unwanted background optical absorption, and the lower temperatures has removed this problem. We now see efficiencies still increasing as the microwave power is decreased when we reach the smallest input powers for which we could measure an output. Efficiencies of $2\times10^{-6}$ were observed and we discuss potential improvements, including better optical cavity frequency stability and better thermalisation of the erbium spins.

arXiv:2409.14612Sep 22, 20240 citations

Optical Spectroscopy of an Erbium-Doped Crystal

Optische Spektroskopie

Jan 1, 20130 citations

Theory of Microwave to Optical Photon Upconversion Using Erbium Doped Crystals

Peter S. Barnett

The subject of this thesis is coherent conversion from microwave photons to optical photons. This has applications for quantum computing, and would allow interfacing between superconducting qubits and optical fibres. Specifically, we will focus on photon conversion via erbium ions in a doped crystal. \n\nWe model a device which has an erbium doped crystal inside overlapping microwave and optical cavities. Input microwave photons are combined with photons from an optical pump laser via interactions with the erbium ions. This will produce optical output photons carrying the same quantum information as the input microwave photons. We develop a description of the interaction between the atoms and the light fields, accounting for both loss effects in the single atoms, and inhomogeneous broadening of the ensemble. Our theory is compared with experimental data, and shows good agreement. \n \nWe explore various phenomena which arise in this system, including the effects of temperature and microwave power. \n\nIt is shown that the description of this device from earlier work is not valid in the regime where the conversion efficiency is greatest. Hence, this work is necessary to be able to predict the maximum conversion efficiency. \n\nWe develop a linearised model which is accurate in the regime where the microwave and optical fields are small, such as the regime used for quantum information. This model is used to maximise the photon number conversion efficiency of the device. We predict conversion efficiencies above 20%, far higher than has been achieved experimentally with using rare earth ions. Modifying our device should further increase the conversion efficiency to above 80%.The subject of this thesis is coherent conversion from microwave photons to optical photons. This has applications for quantum computing, and would allow interfacing between superconducting qubits and optical fibres. Specifically, we will focus on photon conversion via erbium ions in a doped crystal. \n\nWe model a device which has an erbium doped crystal inside overlapping microwave and optical cavities. Input microwave photons are combined with photons from an optical pump laser via interactions with the erbium ions. This will produce optical output photons carrying the same quantum information as the input microwave photons. We develop a description of the interaction between the atoms and the light fields, accounting for both loss effects in the single atoms, and inhomogeneous broadening of the ensemble. Our theory is compared with experimental data, and shows good agreement. \n \nWe explore various phenomena which arise in this system, including the effects of temperature and microwave power. \n\nIt is shown that the description of this device from earlier work is not valid in the regime where the conversion efficiency is greatest. Hence, this work is necessary to be able to predict the maximum conversion efficiency. \n\nWe develop a linearised model which is accurate in the regime where the microwave and optical fields are small, such as the regime used for quantum information. This model is used to maximise the photon number conversion efficiency of the device. We predict conversion efficiencies above 20%, far higher than has been achieved experimentally with using rare earth ions. Modifying our device should further increase the conversion efficiency to above 80%.

Jan 1, 20201 citation

2\times10^{-6}

were observed and we discuss potential improvements, including better optical cavity frequency stability and better thermalisation of the erbium spins.