Resonant optomechanics with carbon nanotubes

In an optomechanical setup, the coupling between cavity and resonator can be increased by tuning them
to the same frequency. We study this interaction between a carbon nanotube resonator and a radio- frequency tank circuit acting as a cavity. In this resonant regime, the vacuum optomechanical coupling is enhanced by the dc voltage coupling the cavity and the mechanical resonator. Using the cavity to detect the nanotube’s motion, we measure the nanotube's mechanical ring down. Further improvements to the system could enable the measurement of mechanical motion at the quantum limit.

Capabilities

Machine learning for quantum device control

As the race to scale up reliable quantum computing accelerates, fault-tolerant error correction requires each logical qubit to be encoded in many physical qubits. Fault-tolerant factorization using a surface code will require ~10^8 physical qubits. An approach inspired by integrated circuits is to use electron spins in semiconducting devices. 

A crucial challenge of scaling semiconductor spin qubits is that electron spins do not experience identical electrostatic confinement potentials. The variability must be compensated by adjusting gate voltages. Each qubit occupies a multi-dimensional parameter space, and the problem will escalate in complexity as the number of qubits increases for scalable quantum computing. The goal is to optimise not simply the performance of each qubit, but the readout accuracy and crucially the fidelity of entangling operations between qubits.

Single quantum dot in AlGaAs/GaAs

Low temperature measurement setups

Triton 200.

Nanofabrication

Our cleanroom has ebeam lithography, metal deposition,  reactive ion etching.

CVD furnace

We have a chemical vapor deposition furnace for carbon nanotube growth.