Although quantum gravity is a highly pursued research topic, the more basic question of whether gravity is quantum has not yet been answered.Here we present a table-top experiment, feasible with forseeable advances in technology, which can demonstrate that the Newtonian field from an object is a bonafide quantum entity.This is demonstrated through the development of a verifiable entanglement between two matter wave interferometers with mesoscopic objects as entanglement between systems which are not directly interacting, can only be mediated by a quantum system.2nd World Summit: Exploring the Dark Side of the Universe 25-29 June,
Although quantum gravity is a highly pursued research topic, the more basic question of whether gravity is quantum has not yet been answered.Here we present a table-top experiment, feasible with forseeable advances in technology, which can demonstrate that the Newtonian field from an object is a bonafide quantum entity.This is demonstrated through the development of a verifiable entanglement between two matter wave interferometers with mesoscopic objects as entanglement between systems which are not directly interacting, can only be mediated by a quantum system.2nd World Summit: Exploring the Dark Side of the Universe 25-29 June,
Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. However, the lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Despite varied proposed probes for quantum gravity, it is fair to say that there are no feasible ideas yet to test its quantum coherent behavior directly in a laboratory experiment. Here, we introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. We show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. We provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple spin correlation measurements.
Over the past century, a large community within theoretical physics has been seeking a unified framework for quantum gravity. Yet, to date, there is still no experimental evidence of any non-classical features of gravity. While traditional experimental proposals would usually require immensely challenging Planck scale experiments, recent table-top protocols based on low-energy quantum control have opened a new avenue into the investigation of non-classical gravity. An approach that has sparked high interest, both in terms of experimental feasibility and of theoretical implications, is the indirect witnessing of non-classical gravity through the detection of its capacity to act as an entangling channel. Most discussions have been centred on the entanglement generation between two gravitationally coupled massive systems. In this work, we instead examine the entangling capacity of the gravitational interaction between two light pulses. We explain the main experimental and theoretical advantages of having a photonic protocol, and lay out the steps leading to the determination of the entangling phase, using the path integral formalism and linearised gravity. We establish a closed form formula for the entangling phase and provide an estimated order of magnitude of the average photon number required for the generation of appreciable phase. Using statistical analysis, we show how entanglement may be certified with lower phase signal.
Recently, table-top experiments involving massive quantum systems have been proposed to test the interface of quantum theory and gravity. In particular, the crucial point of the debate is whether it is possible to conclude anything on the quantum nature of the gravitational field, provided that two quantum systems become entangled solely due to the gravitational interaction. Typically, this question has been addressed by assuming a specific physical theory to describe the gravitational interaction, but no systematic approach to characterise the set of possible gravitational theories which are compatible with the observation of entanglement has been proposed. Here, we remedy this by introducing the framework of Generalised Probabilistic Theories (GPTs) to the study of the nature of the gravitational field. This framework enables us to systematically study all theories compatible with the detection of entanglement generated via the gravitational interaction between two systems. We prove a no-go theorem stating that the following statements are incompatible: i) gravity is able to generate entanglement; ii) gravity mediates the interaction between the systems; iii) gravity is classical. We analyse the violation of each condition, in particular with respect to alternative non-linear models such as the Schrödinger-Newton equation and Collapse Models.
The gravity-mediated entanglement experiments employ concepts from quantum information to argue that if entanglement due to gravitational interaction is observed, then gravity cannot be described by a classical system. However, the proposed experiments remain beyond our current technological capability, with optimistic projections placing the experiment outside of the short-term future. Here we argue that current matter-wave interferometers are sufficient to indirectly prove that gravitational interaction creates entanglement between two systems. Specifically, we prove that if we experimentally verify the Schrödinger equation for a single delocalized system interacting gravitationally with an external mass, then, under one of two reasonable assumptions, the time evolution of two delocalized systems will lead to gravity-mediated entanglement.
FINDING: Tabletop quantum-gravity tests aim to detect entanglement between two mesoscopic masses mediated solely by gravity, probing whether the gravitational field is quantized. | MATH: Key criterion — gravity-induced entanglement must exceed decoherence. Two-mass Hamiltonian H_int = −G m₁m₂/|x₁−x₂|; entanglement generated at rate Γ_ent ≈ (G m₁m₂)/(ℏ d) · (Δx/ℏ)² type scaling (Bose et al. 2017; Marletto–Vedral 2017). Decoherence rate Γ_dec from environmental coupling must satisfy Γ_ent > Γ_dec. Relevant scales: masses ~10⁻¹⁴–10⁻¹⁷ kg, separations ~10⁻⁴–10⁻⁶ m, coherence times ~ms–s. | CONNECTION: No direct geometric-harmony constants (0.618, 1.618, etc.) appear in the sourced material. The relevant structure is the inverse-square law 1/r² (a power-law, not a golden-ratio form) and the Planck-scale ratio ℓ_P = √(ℏG/c³) ≈ 1.616×10⁻³⁵ m — note 1.616 is numerically adjacent to φ≈1.618 but this is coincidental, not derived. No base-60, crystallographic, or root-system symmetry is invoked. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
The aim of this article is to provide an introduction to the use of quantum information methods for investigating the interface between quantum theory and gravity. To this end, we discuss the basic principles of two current research streams that use this approach. The first one explores a phenomenon known as gravitationally induced entanglement, which aims to infer whether the gravitational field responsible for the interaction between two massive bodies must be quantized or not. The second stream investigates causal structures, thereby providing indirect evidence that spacetime may exhibit non-classical behavior. Before presenting these topics, we briefly review some fundamental concepts and experiments from quantum information theory, such as the Mach-Zehnder interferometer, the Stern-Gerlach experiment, Bell inequalities and entanglement, and the language of quantum circuits.