Seminar "Towards quantum frequency conversion and microwave memories with Erbium dopants in YSO" by Prof. Jevon Longdell, University of Otago

Speaker: Associate Professor, Jevon Longdell

Affiliation: Univerisy of Otago, New Zealand

Date: July 27, Friday 2018

Venue: C016, Lab1

Abstract

The ability to transfer quantum states encoded in microwave frequency excitations to light would greatly enrich superconducting qubits as a platform for quantum information processing. Superconducting qubits operate in the microwave frequency regime and can interact strongly with microwave photons. However quantum states encoded in microwave photons are swamped by thermal noise at room temperature. This and the relatively high loss of room temperature microwave transmission lines means that microwave photons can’t be used for long distance quantum communication.

We have demonstrated microwave to optical-telecommunications-band signal conversion with a number efficiency of $\eta = 1.26\times 10^{-5}$ by means of an Er$^{3+}$:Y$_2$SiO$_5$ crystal embedded in both a microwave cavity and an optical cavity at 4.6\,K. The introduction of the optical cavity in the system has provided an enhancement in the conversion efficiency of $6\times10^3$ compared to its counterpart without an optical cavity. The dependencies on input microwave power and optical pump power give more information about the conversion process. By analysing the experimental data with a theoretical model we propose that matching the impedances of both cavities and lowering the temperature to mK will bring our system to a near unit conversion efficiency. These results suggest there is great potential for cavity enhanced upconversion in rare earth ions to act as a bridge between microwaves and light for hybrid quantum computing systems.