laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminar, 6th February 2017 (13h30 L363-365)

Natalia Ares (University of Oxford)
Sensitive radio-frequency probing of quantum devices

Radio-frequency circuits are a powerful tool to perform fast and sensitive measurements on quantum devices [1]. In the first part of this talk, I will focus on how we optimize this tool for readout of some of the most promising qubits in the solid-state. Sensitive measurements of these quantum devices are essential for high-fidelity single-shot qubit readout, but are hindered by poor impedance matching to the device. I will show how we achieved controllable perfect matching with a high device impedance; a gate-defined GaAs quantum dot [2]. Voltage-controlled capacitors allow in situ tuning of the matching condition, even accounting for parasitics, and enable an absolute calibration of the capacitance sensitivity. I will benchmark the results against the requirements for single-shot qubit readout using quantum capacitance. I will also show how radio-frequency circuits provides a new insight on the tunnelling processes occurring in a quantum dot.

In the second part of the talk, I will focus on measurements of motion. A radio frequency circuit allowed us to probe the vibrations of a suspended carbon nanotube [3]. By using a gate voltage to tune the carbon nanotube into resonance with the radio-frequency signal, the mechanical signal is transduced efficiently to an electrical signal. I will evaluate the suitability of this readout scheme for monitoring mechanical motion at the level of uncertainty necessitated by the Heisenberg uncertainty principle.

/References /

[1] “The radio-frequency single-electron transistor (rf-set): A fast and ultrasensitive electrometer”, R. J. Schoelkopf et al., Science *280*, 1238 (1998).

[2] “Sensitive radio-frequency measurements of a quantum dot by tuning to perfect impedance matching”, N. Ares et al., Phys. Rev. Applied *5*, 34011 (2016).

[3] “Resonant optomechanics with a vibrating carbon nanotube and a radio-frequency cavity”, N. Ares et al., Phys. Rev. Lett. *117*, 170801 (2016).