Senior RF Engineer (QRF)

Description 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. Position Summary Infleqtion is seeking a hands-on Senior RF Engineer to establish and own the RF and electromagnetics discipline within the QRF team. Reporting to the QRF Product Engineer, this engineer will lead the design, modeling, integration, calibration, and verification of broadband RF hardware and test environments. The work centers on calibrated electromagnetic field generation and delivery, sensor interfaces, low-noise signal chains, RF structures, and traceable measurement—not the modem, protocol, or network design typical of a conventional communications role. Prior quantum experience is not required, but the successful candidate must be able and motivated to learn the atomic physics and Rydberg sensing principles needed to make sound RF design decisions. Job Responsibilities 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 RF and electromagnetic requirements, architectures, interfaces, performance budgets, and verification methods for QRF sensor heads, test systems, and integrated hardware. • Design, simulate, build, and characterize RF structures such as electrodes, resonators, antennas, fixtures, interconnects, shielding, and field delivery hardware. • Develop RF signal generation, amplification, filtering, frequency conversion, local oscillator, distribution, and analog interface approaches that support broadband sensor operations • Build and improve controlled conducted and radiated RF test environments, including field generation, field mapping, and calibration configurations. • Define and execute measurements for field strength, frequency response, impedance, insertion and return loss, phase, coupling, shielding, noise, linearity, dynamic range, spurious response, and uncertainty. • Build and maintain RF performance budgets for gain, loss, noise, phase noise, leakage, coupling, compression, harmonics, spurious signals, and other limits that affect sensor performance. • Lead RF hardware bring-up, characterization, troubleshooting, and root-cause analysis across benchtop, subsystem, sensor head, and integrated system configurations. • Use electromagnetic and circuit simulation to guide hardware and test fixture design, component selection, design trades, and interpretation of measured results; reconcile models with laboratory data. • Develop Python or comparable automation for instrument control, parameter sweeps, calibration, regression testing, data analysis, and technical reporting. • Work with applied physicists to relate RF field delivery and signal-chain behavior to atomic response, sensitivity, bandwidth, stability, dynamic range, and repeatability. • Collaborate with optical-mechanical, electrical, embedded-systems, software, manufacturing, and technician personnel to define interfaces, resolve cross-domain problems, and transfer RF designs into repeatable builds and acceptance tests. • Document designs, models, interfaces, calibration methods, test procedures, configurations, results, trade studies, risks, and recommendations for technical reviews, verification, and future production. Requirements • Bachelor’s degree in electrical engineering, applied physics, electromagnetics, or a closely related technical field, or equivalent practical experience. • At least five years of relevant professional experience in RF, microwave, electromagnetics, antenna, advanced sensor, or related hardware development. • Demonstrated experience independently designing, building, integrating, characterizing, and troubleshooting RF or microwave hardware and test systems. • Hands-on laboratory experience with equipment such as vector network analyzers, spectrum or vector-signal analyzers, signal generators, oscilloscopes, power meters, and RF probes or sensors. • Practical knowledge of impedance matching, gain and loss, noise, dynamic range, linearity, phase noise, spurious response, leakage, coupling, shielding, grounding, and measurement uncertainty. • Experience developing RF requirements, signal-chain budgets, test methods, calibration approaches, and quantitative acceptance criteria. • Experience with at least one RF, circuit, or electromagnetic simulation environment such as Ansys HFSS, CST Studio Suite, Keysight ADS, Cadence AWR, COMSOL, FEKO, or an equivalent tool. • Experience using Python, MATLAB, LabVIEW, or a comparable environment for instrument control, test automation, modeling, or data analysis. • Ability to own the RF domain, document technical work clearly, collaborate across disciplines, and learn the atomic physics, spectroscopy, and Rydberg sensing concepts needed to connect RF design choices with quantum sensor performance. • Preferred Qualifications • Experience with Rydberg atoms, electromagnetically induced transparency, atomic RF electrometry, quantum sensing, atomic clocks, or related atomic physics instrumentation. • Experience with calibrated free-space or radiated RF measurement, field mapping, anechoic or controlled RF environments, TEM or GTEM cells, or measurement-uncertainty analysis. • Experience designing or characterizing electrodes, RF resonators, antennas, couplers, fixtures, shielding, enclosures, or other application-specific electromagnetic structures. • Experience with low-phase-noise oscillators, synthesizers, mixers, frequency-conversion architectures, distribution networks, or low-noise analog signal chains. • Experience with RF PCB design, controlled-impedance routing, grounding, shielding, signal integrity, or electromagnetic-interference and compatibility mitigation. • Experience with software-defined radio, RFSoC platforms, digital signal processing, RF data acquisition, or mixed hardware-software receiver systems. • Experience transferring complex RF hardware from prototype development into repeatable manufacturing, calibration, and acceptance testing. • Experience with configuration-controlled hardware and verification evidence for aerospace, defense, scientific instrumentation, or U.S. government programs; a current or previously held U.S. government security clearance is preferred but not required. Work is performed primarily on site in laboratory, office, production, and integration/test environments and involves work around RF and microwave equipment, laser systems, electronic test equipment, optical tables, tools, and precision instrumentation. Required personal protective equipment will be provided and must be used in accordance with company requirements. With or without reasonable accommodation, the role requires the ability to work at laboratory benches for extended periods, perform fine electronic and mechanical adjustment tasks, and occasionally lift and carry equipment or components weighing up to forty pounds. Up to 10% travel may be required. Benefits • Salary Range: per year 160000-185000 • 100% company-paid medical, dental, vision, short/long-term disability • Employer-funded Health Savings Account • Unlimited PTO • 401(k) match • Company-paid Life and AD&D Insurance • Flexible Savings Account • Paid FMLA, Maternity/Paternity Leave • Employee Assistance Program • Student Loan Repayment • Equit