Applied Physicist - Quantum RF Sensing; QSS

Infleqtion is a global quantum technology company solving some of the world’s most challenging problems. We build and integrate quantum computers, sensors, and networks. From fundamental physics to leading-edge commercial products, Infleqtion enables “quantum everywhere” through an ecosystem of devices and platforms.

Quantum Spectrum, also known as QRF, develops fieldable radio-frequency sensing systems based on Rydberg atoms. The team combines atomic physics, lasers and photonics, RF electronics, embedded controls, software, and precision hardware to turn laboratory prototypes into repeatable, integrated sensing systems.

Infleqtion is seeking an Applied Physicist to build, operate, and improve experimental platforms for Rydberg-atom radio-frequency sensing. Reporting to the Director of R&D, Quantum RF, this physicist will independently own defined experiments and testbeds under senior technical direction, translate atomic, optical, and RF behavior into measurable sensor improvements, and carry validated improvements into integrated QRF systems. The role is centered on hands‑on laboratory work;

modeling supports experiment design and interpretation rather than serving as the principal output.

The duties and responsibilities below describe the essential functions of the role. Depending on business needs, the position may perform some or all these duties. Duties, responsibilities, and activities may change, or new ones may be assigned at any time with or without notice.

• Own defined experimental campaigns addressing QRF sensitivity, noise, stability, bandwidth, dynamic range, and repeatability.

• Build, align, commission, operate, maintain, and troubleshoot persistent testbeds that integrate lasers and optics, atomic‑sensing hardware, RF and electronic instrumentation, controls, and data acquisition.

• Design and execute controlled experiments that isolate performance limitations and convert results into specific hardware, operating‑point, calibration, or control‑system improvements.

• Integrate validated experimental improvements into sensor heads, subsystems, and complete QRF systems; verify performance against quantitative requirements and documented test methods.

• Characterize vapor cells and RF resonators, including thermal, optical, geometric, material, field‑delivery, and repeatability effects that influence sensor performance.

• Establish and maintain laser‑frequency locks, optical‑power stability, photodetection, and associated noise‑characterization methods.

• Calibrate and characterize RF delivery through electrodes, resonators, antennas, TEM or GTEM cells, and related test configurations using appropriate RF and microwave instrumentation.

• Develop automated instrument‑control, parameter‑sweep, optimization, calibration, and data‑analysis workflows using Python or comparable scientific tools.

• Analyze experimental data with appropriate uncertainty, noise, and repeatability treatment; use atomic, optical, or electromagnetic models to guide experiments, interpret results, and investigate discrepancies among predicted, benchtop, subsystem, and integrated‑system performance.

• Translate findings into design recommendations, configuration records, test procedures, technical reports, and verification evidence that engineers and technicians can reproduce.

• Work with RF, optical‑mechanical, electrical, embedded‑software, systems, and technician personnel to make experimental configurations stable, maintainable, and transferable.

• Provide occasional support for laboratory or field demonstrations and customer‑program testing as assigned, following applicable safety, export‑control, configuration‑control, and documentation requirements.

• Bachelor’s degree in physics, applied physics, optical engineering, electrical engineering, or a closely related field plus at least four years of relevant hands‑on experimental experience; a master’s degree plus at least two years; or a PhD with directly relevant experimental research. Equivalent combinations of education and experience will be considered.

• Demonstrated hands‑on experience personally building, aligning, operating, and troubleshooting…