01 / PROBLEM
What is unresolved?
We know that quantum matter responds to gravity. We also know that matter and energy shape spacetime.
What remains unresolved is the nature of the transition between two quantum systems interacting only through gravity.
QUANTUM SYSTEM A → GRAVITY → QUANTUM SYSTEM B
General relativity describes gravity classically, as spacetime geometry. Quantum mechanics describes matter through
quantum states, superposition, uncertainty and entanglement.
The key question is therefore not simply whether gravity affects a quantum system, but whether gravity can transmit
genuinely quantum information — or only classical information about mass, position and energy.
02 / CONSIDERATION
What follows from it?
The obvious first test is to ask whether gravity alone can generate entanglement between two quantum systems.
But entanglement by itself may not be decisive: some theoretical frameworks allow classically described gravity
to coexist with quantum matter in ways that can still produce entanglement.
The stronger question is:
What properties must the mediator possess for the observed transfer of information to be possible?
A genuinely quantum mediator should reveal more than a final correlation. It should constrain the structure of
possible transformations — for example through non-commuting observables, measurement disturbance, preservation of
quantum coherence, or a channel that cannot be reduced to purely classical communication.
Instead of trying to observe the mediator directly, we reconstruct its properties from what it is capable of doing
to two controlled systems.
03 / EXPERIMENT
How could we test it?
A / SYSTEM
Prepare two highly isolated quantum systems, A and B — for example two atom interferometers or two optomechanical systems.
Place them close enough for their mutual gravitational interaction to become measurable, while suppressing electromagnetic
coupling, vibration, thermal radiation, Casimir forces, external fields and shared environmental noise.
The intended remaining interaction channel: gravity.
B / INPUT
Prepare system A in a sequence of precisely known quantum states. Keep system B in a controlled reference state.
Let them interact for a defined time while systematically varying distance, interaction time, mass, state preparation
and degree of spatial superposition.
C / MEASUREMENT
After each run, measure both systems. Do not look for a single effect only. Record phase shift, output distributions,
correlations, decoherence, coherence preservation and any generated quantum correlations.
INPUT → UNKNOWN GRAVITATIONAL CHANNEL → OUTPUT
Repeat this for many controlled inputs to reconstruct the transformation produced by the gravitational interaction.
D / QUANTUM-INFORMATION TEST
Test whether the reconstructed channel behaves like a channel capable only of classical communication, or whether it
preserves and transfers features that require a non-classical mediator.
The strongest result would not merely be “entanglement appeared,” but evidence that the observed transformation cannot
be reproduced by the allowed class of classical mediator models.
CONTROL
Repeat the experiment across different separations, masses and interaction times. A genuine gravitational effect must
scale consistently with gravitational predictions. Deliberately vary possible non-gravitational channels to identify
their signatures and exclude them as explanations.
POSSIBLE OUTCOMES
A — No detectable effect: inconclusive. The interaction may be too weak for the apparatus.
B — Gravitational but classically explainable effect: gravity affects the quantum system, but no quantum structure of the mediator is demonstrated.
C — Entanglement: highly significant, but not automatically a final proof of quantum gravity.
D — Information transfer requiring a non-classical mediator: the gravitational interaction reveals measurable non-classical structure.
WHAT THIS ACTUALLY TESTS
This experiment does not ask “What is gravity?” in one step. It asks a narrower and testable question:
What kind of information transformation can gravity produce between two quantum systems?
With enough controlled inputs and sufficiently precise output measurements, we begin to infer the structure of the
layer between them — not by guessing what the mediator is, but by forcing it to reveal what transformations it permits.