Superconducting quantum devices

Abstract:

A novel reconfigurable equal to unequal Wilkinson power divider is presented. The proposed power divider adopts coupled microstrip line technique to implement a high impedance section to have unequal output power ratio. A varactor diode is placed between the coupled lines to achieve reconfigurability by changing the reverse biasing voltage on the varactor diode. This enables equal to 8 dB power division ratios between the output ports. A wide range of biasing voltage is used to achieve the smooth power division ratio. A prototype hardware is designed, fabricated and measured to validate the proposed approach. In the equal power division ratio scenario, the measured performance shows a bandwidth of 600 MHz at 5.4 GHz centre frequency. A higher bandwidth of 750 MHz is obtained in the case of unequal power division ratios.

Abstract:

The experimental investigation of quantum devices incorporating mechanical resonators has opened up new frontiers in the study of quantum mechanics at a macroscopic level. It has recently been shown that surface acoustic waves (SAWs) can be piezoelectrically coupled to superconducting qubits, and confined in high-quality Fabry-Perot cavities in the quantum regime. Here we present measurements of a device in which a superconducting qubit is coupled to a SAW cavity, realising a surface acoustic version of cavity quantum electrodynamics. We use measurements of the AC Stark shift between the two systems to determine the coupling strength, which is in agreement with a theoretical model. This quantum acoustodynamics architecture may be used to develop new quantum acoustic devices in which quantum information is stored in trapped on-chip acoustic wavepackets, and manipulated in ways that are impossible with purely electromagnetic signals, due to the 105 times slower mechanical waves.In this work, Manenti et al. present measurements of a device in which a tuneable transmon qubit is piezoelectrically coupled to a surface acoustic wave cavity, realising circuit quantum acoustodynamic architecture. This may be used to develop new quantum acoustic devices.