2026 ARCS ANNUAL SCHOLAR CELEBRATION AND SYMPOSIUM

“ARCS Supernova: The Minds of TODAY Creating Solutions for TOMORROW.”

2026 ARCS ANNUAL SCHOLAR CELEBRATION AND SYMPOSIUM

“ARCS Supernova: The Minds of TODAY Creating Solutions for TOMORROW.”
Christina Bell

Stanford

“Radio-frequency Quantum Upconverters for Dark Matter Search”

A leading candidate for dark matter is the axion, a hypothetical particle expected to generate extremely weak, low-frequency electromagnetic signals that require highly sensitive detection techniques. I design and characterize a Radio-Frequency Quantum Upconverter, a device that transduces these signals into the microwave regime, where they can be measured with extreme sensitivity beyond traditional quantum limits.

ABSTRACT

Axion dark matter detection requires measuring extremely weak electromagnetic signals at low frequencies (≲300 MHz), where conventional readout schemes are fundamentally limited by quantum noise at the Standard Quantum Limit (SQL). In contrast, quantum-limited amplification and measurement techniques are highly developed in the microwave regime (4–8 GHz), motivating approaches that translate low-frequency signals into a frequency range where superior sensitivity is achievable.

We present the Radio-Frequency Quantum Upconverter (RQU), a superconducting circuit designed to transduce weak low-frequency signals into the microwave domain. The RQU employs tunable inductive elements, realized with Josephson junctions, embedded within a microwave resonator. A DC flux bias activates a nonlinear parametric interaction that enables coherent coupling between a low-frequency (MHz) mode and a high-frequency (GHz) resonator mode. This interaction upconverts the input signal into microwave sidebands, allowing detection with near-quantum-limited amplifiers. Beyond dark matter detection, this platform can advance NMR imaging, circuit quantum electrodynamics at MHz frequencies, and nuclear spin detection in quantum materials and devices.

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