Purpose of the role
In a context where magnetic flux noise directly limits the coherence of superconducting quantum circuits, Alice & Bob uses flux-tunable resonator chips as local probes of the electromagnetic environment seen by its quantum processors. The current measurement relies on a Pound-Drever-Hall (PDH) lock whose feedback loop bandwidth restricts the sensing to a narrow frequency band.
Responsibilities:
- Develop and set up the flux noise measurement experiment - Design and assemble the cryogenic and RF measurement chain (wiring, filtering, amplification, instrumentation) - Implement and document the measurement and control software in Python
- Characterise flux noise measurement chips - Calibrate the flux-tunable resonators (frequency vs. flux, operating point, PDH lock parameters) - Measure the flux noise power spectral density and extract the relevant metrics
- Analyse the limitations to broadband operation - Model and measure the feedback loop bandwidth, latencies and noise contributions of the readout chain - Identify the dominant physical and instrumental limits across the frequency band
- Propose and test solutions to extend the measurement bandwidth - Evaluate alternative locking, readout or analysis schemes - Implement and validate the most promising approaches experimentally
- Report and share results - Document experiments, analyses and conclusions in the team's internal tools - Present progress and findings to the HERMES team
Requirements:
- LANGUAGES: Proficient in English
- EXPERIENCE: Prior lab or project experience in RF/microwave measurements or low-temperature physics; experience with cryostats or superconducting quantum circuits is a plus
- Solid understanding of magnetic fields, flux and electromagnetic coupling
- Knowledge of microwave engineering: waveguides, resonators, transmission lines, S-parameters
- Proficiency in Python for instrument control, data acquisition and analysis
- Understanding of feedback and control loops (gain, bandwidth, latency, stability)
- Familiarity with noise characterisation and spectral analysis (power spectral density)
- Hands-on experimental skills: assembling and debugging measurement setups
- Rigour in documenting experiments and analysing results
- Autonomy, curiosity and a problem-solving mindset