In a recent proposal on the experimental tests of quantum gravity creation of non-Gaussianity in a Bose-Einstein condensate (BEC) has been suggested as a decisive confirmation of quantum gravity. In a related proposal, a gas of ultracold Rb or Cs atoms has previously been suggested as a possible platform for tests of quantum gravity. Since a practical demonstration of above proposals is a very challenging and costly affair, exploring cost-effective alternatives to these technologically demanding experimental protocols becomes very important. We here show that the phenomenon of Bicoid (Bcd) gradient formation in the early fruit fly embryo, considered basically here as a multipartite quantum system with an ensemble of initial states and a unitary evolution U that implements a quantum Newtonian Hamiltonian over this gravitationally interacting system, naturally combines the essential features of above proposals in a single system giving a viable signature of quantum gravity through the creation of non-Gaussianity. We conclude that although the phenomenon of Bcd gradient formation in the early Drosophila embryo is accompanied by quantum gravitational effects, it might need further experiments to verify such a noval claim.
In a recent proposal on the experimental tests of quantum gravity creation of non-Gaussianity in a Bose-Einstein condensate (BEC) has been suggested as a decisive confirmation of quantum gravity. In a related proposal, a gas of ultracold Rb or Cs atoms has previously been suggested as a possible platform for tests of quantum gravity. Since a practical demonstration of above proposals is a very challenging and costly affair, exploring cost-effective alternatives to these technologically demanding experimental protocols becomes very important. We here show that the phenomenon of Bicoid (Bcd) gradient formation in the early fruit fly embryo, considered basically here as a multipartite quantum system with an ensemble of initial states and a unitary evolution U that implements a quantum Newtonian Hamiltonian over this gravitationally interacting system, naturally combines the essential features of above proposals in a single system giving a viable signature of quantum gravity through the creation of non-Gaussianity. We conclude that although the phenomenon of Bcd gradient formation in the early Drosophila embryo is accompanied by quantum gravitational effects, it might need further experiments to verify such a noval claim.
Abstract Despite almost a century’s worth of study, it is still unclear how general relativity (GR) and quantum theory (QT) should be unified into a consistent theory. The conventional approach is to retain the foundational principles of QT, such as the superposition principle, and modify GR. This is referred to as ‘quantizing gravity’, resulting in a theory of ‘quantum gravity’. The opposite approach is ‘gravitizing QT’ where we attempt to keep the principles of GR, such as the equivalence principle, and consider how this leads to modifications of QT. What we are most lacking in understanding which route to take, if either, is experimental guidance. Here we consider using a Bose–Einstein condensate (BEC) to search for clues. In particular, we study how a single BEC in a superposition of two locations could test a gravitizing QT proposal where wavefunction collapse emerges from a unified theory as an objective process, resolving the measurement problem of QT. Such a modification to QT due to general relativistic principles is testable near the Planck mass scale, which is much closer to experiments than the Planck length scale where quantum, general relativistic effects are traditionally anticipated in quantum gravity theories. Furthermore, experimental tests of this proposal should be simpler to perform than recently suggested experiments that would test the quantizing gravity approach in the Newtonian gravity limit by searching for entanglement between two massive systems that are both in a superposition of two locations.
Abstract We explore the possibility of testing the quantum nature of the gravitational field with an ensemble of ultra-cold atoms. The use of many microscopic particles may circumvent some of the experimental obstacles encountered in recent proposals involving a pair of particles with mesoscopic mass. We employ multi-parameter estimation techniques, including the quantum and classical Fisher information to provide a criteria for the observability of the quantum effects, and compare to other recently proposed schemes. Crucially, we find that by preparing the appropriate initial state, interactions mediated via a quantum-valued gravitational field provide a signature that is distinct from classical gravitational interactions. We find that a definitive demonstration of the quantum gravitational interaction is not possible with current experimental capabilities, due to uncertainty in the residual electromagnetic interactions between the atoms. However, it may be possible with significant improvements to current experimental techniques.
Abstract Experimental tests of quantum gravity have long been limited by the extreme energy scale of the Planck regime. In recent years, theoretical proposals for testing gravitational non-Gaussianity using tabletop quantum systems have made significant progress, but existing schemes face severe challenges in experimental feasibility: the BEC+Feshbach scheme of Howl et al. relies solely on the square of the atom number for sensitivity, yielding a weak signal; the recently proposed squeezing-enhanced dual-platform scheme by Li [2] amplifies the signal to but suffers from system complexity and cross-correlation difficulties. This paper simultaneously proposes two complementary experimental frameworks: Scheme A (Theoretical Benchmark) establishes a “gold standard” paradigm for quantum gravity tests within a rigorous theoretical framework (number-squeezing, precise Feshbach cancellation, exponential scaling law); Scheme B (Exploratory Precursor) is based on a set of engineering-friendly alternative assumptions (bidirectional quantum interface, gradient field spatial averaging, differential measurement), aiming for a near-term proof-of-principle exploration of the core phenomenon of “squeezing-enhanced non-Gaussian signals.” The two schemes share the same physical core: squeezing-enhanced non-Gaussian signals serve as a potential discriminative signature of quantum gravity. This paper details the theoretical foundations, experimental designs, feasibility assessments, and application scenarios of both schemes, providing alternative pathways for research groups with different experimental capabilities. Scheme B significantly lowers the environmental and technical barriers, making it possible to conduct proof-of-principle experiments in standard cold-atom laboratories; Scheme A provides a complete theoretical framework for future high-precision verification. The two schemes are proposed in parallel and complement each other, jointly forming a complete research roadmap from “preliminary detection” to “rigorous testing.” Keywords: quantum gravity; non-Gaussianity; BEC; squeezed states; tabletop experiments; theoretical benchmark; exploratory precursor 摘要 量子引力的实验检验长期受限于普朗克能标的极端能量尺度。近年来,利用桌面量子系统检验引力非高斯性的理论方案取得了重要进展,但现有方案在实验可行性上面临严峻挑战:Howl等人的BEC+Feshbach方案灵敏度仅依赖原子数平方 ,信号微弱;李政达 [2] 近期提出的压缩增强双平台方案虽将信号放大至 ,但系统复杂、互相关困难。本文同时提出两种互补的实验框架:A方案(理论基准型) 在严格的理论框架内(数模压缩、Feshbach精确调零、指数标度律判决)建立量子引力检验的“黄金标准”范式;B方案(先导探索型) 基于一组可工程化的替代性假设(双向量子接口、梯度空间平均、差分测量),旨在近期内对“压缩增强的非高斯信号”这一核心现象进行原理性探索。两种方案共享同一物理内核:压缩增强的非高斯信号是量子引力的潜在判决性特征。本文详细阐述两种方案的理论基础、实验设计、可行性评估和适用场景,为不同实验条件的团队提供可选择的路径。B方案显著降低了实验的环境和技术门槛,使其可能在常规冷原子实验室内进行原理探索;A方案则为未来精密验证提供了完整的理论框架。两种方案并行提出,互为补充,共同构成从“初步探测”到“严格检验”的完整研究路线。 关键词:量子引力;非高斯性;BEC;压缩态;桌面实验;理论基准;先导探索
The effect of noise induced by gravitons on a Bose-Einstein condensate has been explored in Sen and Gangopadhyay [Probing the quantum nature of gravity using a Bose-Einstein condensate, ]. In the previous paper, we investigated the effects of graviton while detecting a gravitational wave using a Bose-Einstein condensate. In this work, we shall explicitly calculate the decoherence due to the noise of gravitons for maximally entangled momentum states of the Bose-Einstein condensate. This decoherence happens due to bremsstrahlung from the Bose-Einstein condensates due to the effect of the noise induced by gravitons. It is observed that the maximally entangled state becomes entangled with the graviton state and it decays over time as a result of this gravitational bremsstrahlung. This new entangled state is termed as a Bose-Einstein supercondensate. Using this property of the Bose-Einstein condensate in a quantum gravity background, we propose an experimental test via the use of atom lasers (generated from the condensate) which would, in principle, help to detect gravitons in future generations of very advanced ultracold temperature experiments.
The capability to reach ultracold atomic temperatures in compact instruments has recently been extended into space. Ultracold temperatures amplify quantum effects, while free-fall allows further cooling and longer interactions time with gravity - the final force without a quantum description. On Earth, these devices have produced macroscopic quantum phenomena such as Bose-Einstein condensation (BECs), superfluidity, and strongly interacting quantum gases. Quantum sensors interfering the superposition of two ultracold atomic isotopes have tested the Universality of Free Fall (UFF), a core tenet of Einstein's classical gravitational theory, at the 10−12 level. In space, cooling the elements needed to explore the rich physics of strong interactions and preparing the multiple species required for quantum tests of the UFF has remained elusive. Here, utilizing upgraded capabilities of the multi-user Cold Atom Lab (CAL) instrument within the International Space Station (ISS), we report the first simultaneous production of a dual species Bose-Einstein condensate in space (formed from 87Rb and 41K), observation of interspecies interactions, as well as the production of 39K ultracold gases. We have further achieved the first space-borne demonstration of simultaneous atom interferometry with two atomic species (87Rb and 41K). These results are an important step towards quantum tests of UFF in space, and will allow scientists to investigate aspects of few-body physics, quantum chemistry, and fundamental physics in novel regimes without the perturbing asymmetry of gravity.
The quantum nature of gravity is one of physics' greatest unsolved problems, with existing experimental proposals facing formidable challenges in maintaining spatial superpositions of massive objects against decoherence. We propose a fundamentally different approach that bypasses these difficulties. The central insight is that a quantum gravitational field can imprint a gauge-invariant phase on a particle's wavefunction even along an open trajectory, arising from the quantum backreaction of the source. This phase, which manifests prior to the final recombination stage of an interferometer and cannot be generated by a classical gravitational field, provides an operationally direct witness to the quantumness of gravity. Our experimental design uses a single photon whose accumulated gravitational phase due to the Earth is transferred via absorption to auxiliary atoms near the end of the interferometer sequence, preserving the open-path character essential for the test. We scale the interferometer to yield a detectable phase of order 10−3 rad and show how non-local correlation measurements on the atoms can access this gauge-invariant signature. Leveraging established quantum optical and atomic techniques, this proposal offers a feasible path to distinguish quantum from classical gravity. A positive result would provide the first experimental evidence for the quantum nature of gravitational fields, with profound implications for quantum gravity theories.