Position Title:
Postdoctoral Research Associate - Ames National Laboratory
Appointment Type:
Post Doc/Trainee
Job Description:
Summary of Duties and Responsibilities:
The Division of Materials Science and Engineering at Ames National Laboratory seeks a Postdoctoral Research Associate to conduct experimental research on measurements and understanding the microscopic origins of low-frequency (1/f) magnetic and electric noise in superconducting quantum circuits, with particular focus on transmon qubits. The primary experimental tool will be quantum sensing with nitrogen-vacancy (NV) centers in diamond, used as local, magnetically selective passive probes of the noise environment at the surfaces, interfaces, and thin films from which superconducting devices are built.
The central research goal is to identify which physical mechanisms – surface and interface spins, magnetic defects, two-level systems, trapped flux and vortex motion, and nonequilibrium quasiparticles – generate the 1/f flux and charge noise that limits qubit coherence, and to determine what fraction of a qubit’s decoherence is magnetic in origin. This will be achieved by combining NV-based noise spectroscopy (spin relaxometry and dynamical-decoupling measurements of T1 and T2) and static-field ODMR magnetometry with standard transmon characterization and qubit-intrinsic noise spectroscopy (CPMG and spin-locking sequences) on the same devices, in the same cryostat and cooldown.
The postdoctoral researcher will play a key role in commissioning a new cryogen-free dilution-refrigerator platform that integrates confocal optical access and NV positioning with filtered microwave wiring for qubit control and dispersive readout. Specific tasks include optimizing diamond sensor geometry, NV depth and NV-to-device standoff; developing pulse sequences, measurement protocols and analysis pipelines; and devising strategies that isolate the qubit from the optical and microwave excitation used for NV readout, including systematic characterization of light-induced quasiparticle effects. The work will complement the group’s established tunnel-diode resonator quasiparticle spectroscopy.
The work will include planning and conducting experiments, critically analyzing measured noise spectra and modeling them in terms of microscopic fluctuator ensembles, and performing numerical calculations or simulations where appropriate. The researcher must be able to work both independently and collaboratively and to communicate effectively across condensed-matter physics, materials science, quantum sensing, and quantum information science.
Required Minimum Qualifications (for temps/postdocs only, delete for all other positions):
Ph.D. in experimental condensed-matter physics, applied physics, quantum science and engineering, atomic, molecular and optical physics, materials science and engineering, or a closely related field.
Preferred Qualifications:
Hands-on experience with NV centers in diamond or other optically addressable spin defects, including optically detected magnetic resonance (ODMR), pulsed microwave spin control, confocal microscopy, and single-photon detection. Experience with shallow NV ensembles, near-surface sensing, T1 relaxometry or dynamical-decoupling noise spectroscopy is highly desirable, as is NV magnetometry of superconducting or magnetic materials.
Solid understanding of noise physics and quantum noise spectroscopy: power spectral densities, filter-function analysis of pulse sequences, the fluctuation–dissipation relation, and microscopic models of 1/f flux and charge noise (surface spins, two-level systems, trapped vortices).
Experience with superconducting qubits or high-Q superconducting resonators, including packaging, cryogenic microwave wiring, attenuation and filtering, dispersive readout, and coherence measurements (T1, Ramsey, echo, CPMG). Direct experience with both NV centers and qubits is rare; strong expertise in one area and a clear commitment to mastering the…