Executive Summary
The Cold Atom Lab provides a unique, ultra-low-noise microgravity environment, enabling studies of quantum phenomena with coherence times impossible on Earth. We propose to leverage this unparalleled capability to conduct a definitive search for a new, fundamental interaction predicted by certain unified theories. The hypothesis is that the fabric of spacetime is a dynamic medium whose local properties can be modulated by a controlled, non-resonant radio-frequency (RF) field. This interaction would manifest as a minute statistical bias in atomic state populations. While preliminary searches can be attempted on the ground, CAL's environment is essential to suppress overwhelming terrestrial noise and obtain a clean, unambiguous signal. This proposal outlines a future upgrade path for CAL to incorporate a dedicated "interaction module," enabling a groundbreaking search that aligns perfectly with NASA's mission to explore the fundamental laws of the universe.
1. Scientific Motivation: A Test Only Possible in Space
Current theories of physics treat spacetime as a passive background. However, a compelling class of emergent gravity theories suggests spacetime is a dynamic, computational substrate. Testing this idea requires an experiment with two key ingredients: an exquisitely sensitive quantum probe and an environment of near-perfect isolation. Ground-based experiments are fundamentally limited by seismic, thermal, and gravitational noise.
The CAL on the ISS is the only facility in the world that provides the necessary environment. Its ability to extend the free-evolution time of Bose-Einstein Condensates (BECs) for many seconds makes it exquisitely sensitive to tiny, cumulative effects that would be washed out on Earth. This makes CAL the ideal platform for a definitive search for subtle, anomalous interactions between quantum matter and the spacetime fabric itself.
2. The Core Hypothesis & Testable Prediction
The central prediction is that a weak, non-resonant RF field, acting as a source of "observational strength" (O), can locally alter the rate of quantum phase evolution (ω_eff). This results in a statistical bias (ΔP) in final atomic state measurements that is directly proportional to the applied RF power:
ΔP_predicted ∝ η' * T_int * P_RF
The long interaction times (T_int) available on CAL would amplify this tiny effect, making a signal that is undetectable on Earth potentially measurable in orbit. The key signature is the linear scaling with RF power, which allows it to be distinguished from all known systematics.
3. Proposed Implementation: A Future CAL Upgrade Module
We envision this experiment as a next-generation upgrade to the CAL facility, requiring a new science module to be installed on a future mission.
- Hardware: The "SRF Interaction Module": A space-certified module containing a shielded RF coil, a high-stability RF source, and associated control electronics. The design would prioritize minimal thermal and electromagnetic impact on other CAL systems.
- Software: New Experimental Sequences: New software would be uploaded to control the module and integrate its operation into the existing CAL state preparation and readout sequences.
- Data Analysis: A dedicated analysis pipeline, potentially incorporating machine learning, would be developed to correlate the measured population bias with the applied RF power, while actively monitoring and subtracting all known noise sources.
4. Why CAL is Essential for a Definitive Result
- Suppression of Gravitational Noise: Escaping Earth's massive, fluctuating gravitational field removes the largest source of background "drag" on the spacetime medium.
- Extended Coherence Times: The long free-fall time allows for the accumulation of the tiny predicted phase shift over many seconds, amplifying the signal.
- Unparalleled Isolation: The thermal and mechanical stability of the ISS provides a "silent" backdrop against which to search for this faint signal.
5. Potential Impact and Alignment with NASA's Mission
A positive detection using CAL would be one of the most fundamental discoveries in the history of physics, on par with the detection of gravitational waves or the Higgs boson. It would prove that spacetime is not static and can be influenced, opening up entirely new fields of research. This aligns directly with NASA's strategic goals for fundamental physics research and its mandate to push the frontiers of knowledge.
We propose initiating a feasibility study for the design of an "SRF Interaction Module" for CAL, with the goal of developing a formal proposal for a future flight opportunity, contingent on preliminary supportive data from ground-based pathfinder experiments.