Axions and Black Holes Enable Detection of Squeezed Graviton States

The search for gravitons, the hypothetical particles mediating gravity, remains one of the greatest challenges in modern physics, and new theoretical work proposes a pathway to their detection through the interplay of axions, black holes, and subtle quantum effects. Nick E. Mavromatos, Panagiotis Dorlis, Sarben Sarkar, and colleagues investigate a scenario where rotating black holes surrounded by axionic clouds generate entangled, squeezed states of gravitons, potentially within reach of current detectors. This research demonstrates how both standard gravitational interactions and more exotic effects linked to the chiral nature of gravity could produce these detectable signals, offering a novel approach to both astrophysical observation and cosmological investigation. Importantly, the team’s calculations suggest that existing data from the LIGO/Virgo experiments already place limits on the properties of these axionic clouds, while also hinting at the possibility of observing primordial gravitational waves with unique signatures that could resolve long-standing cosmological puzzles.

Researchers investigate scenarios where rotating black holes surrounded by axionic clouds generate entangled, squeezed states of gravitons, potentially within reach of current detectors. This research demonstrates how both standard gravitational interactions and more exotic effects linked to the chiral nature of gravity could produce these detectable signals, offering a new approach to both astrophysical observation and cosmological investigation. Importantly, existing data from the LIGO/Virgo experiments already place limits on the properties of these axionic clouds, while also hinting at the possibility of observing primordial gravitational waves with unique signatures that could resolve long-standing cosmological puzzles.,.

Axion Clouds and Entangled Graviton Squeezing

Scientists have developed a methodology to investigate the potential emergence of entangled squeezed graviton states originating from superradiant axionic clouds surrounding rotating black holes. The study centers on analyzing both conventional General Relativity interactions and gravitational Chern-Simons anomalous terms coupled to axions, recognizing that these terms contribute differently to the symmetry of the resulting entangled states. Researchers estimated the squeezing parameter within a weak-field framework, establishing a crucial link between theoretical predictions and potential observational constraints. This approach enables the assessment of how effectively current and future interferometric detectors might identify these subtle quantum gravitational effects.

The team employed a sophisticated analysis of quantum noise in gravitational waves, drawing parallels with techniques used in quantum optics to generate and detect squeezed states of light. Modern gravitational wave detectors, such as LIGO and Virgo, utilize Michelson interferometers enhanced with Fabry-Perot cavities to increase the effective path length of laser light and amplify the interaction with gravitational waves. Scientists harnessed this configuration, modeling how a gravitational wave stretches one interferometer arm while compressing the other, inducing measurable phase shifts. The study pioneered a quantum treatment of this interaction, demonstrating how the coupling between laser light and gravitational waves depends on the quantum state of the gravitational wave itself.

Researchers reduced the complex multi-mode squeezed state to a single-mode graviton state coupled to a single Fabry-Perot cavity, providing a crucial step toward detecting quantum aspects of gravitational waves. This reduction allows for the calculation of induced noise within the interferometer, enabling scientists to place constraints on the lifetime of axionic clouds based on data from LIGO-Virgo-KAGRA. Furthermore, the team investigated the potential for detecting stochastic gravitational wave backgrounds, which arise from the superposition of signals from numerous astrophysical and cosmological sources, by analyzing correlated noise between multiple spatially separated detectors. This approach, which focuses on identifying correlations that cannot be explained by independent detector noise, offers a pathway to circumventing existing theoretical oppositions and potentially identifying squeezed graviton states in a detectable regime.,.

Squeezed Gravitons from Rotating Black Hole Clouds

Scientists have achieved a detailed understanding of how squeezed graviton states can emerge from superradiant axionic clouds surrounding rotating black holes, revealing a potential pathway for detecting quantum gravity effects. The research focuses on the production of entangled squeezed gravitons through both conventional General Relativity interactions and gravitational Chern-Simons anomalous terms, demonstrating that both mechanisms contribute to the entangled states with differing symmetry characteristics. The team estimated the squeezing parameter within a weak-field framework, paving the way for assessing detectability with current and future interferometric devices. Crucially, current data from the LIGO/Virgo experiments can impose upper-bound constraints on the lifetime of the axionic clouds themselves.

The analysis reveals that the number of gravitons in the squeezed vacuum state is significantly enhanced by the large number of axions within the cloud and the extended lifetime of the cloud, potentially reaching an average of 10 6 to 10 7 gravitons. Calculations demonstrate that the upper limit for the GR-related squeezing quantity is approximately 2.5x 10 -15 T μb , where T represents the lifetime of the axionic cloud. Furthermore, the team found that the lifetime of the axionic cloud, estimated to be as large as 10 7times the superradiance time scale, plays a critical role in amplifying the squeezing effect.

Specifically, the research establishes an upper bound on the squeezing parameter of approximately 60 to 75, suggesting a robust potential for exponential enhancement of the squeezed graviton signal. In contrast, the squeezing induced by the gravitational Chern-Simons anomaly remains highly suppressed compared to that induced by General Relativity, indicating that higher curvature interactions are less significant in this regime. These findings suggest that observing squeezed gravitons offers promising prospects for probing quantum gravity effects, particularly with enhancements from astrophysical distributions or cosmological origins like inflation.,.

Entangled Gravitons from Rotating Black Hole Clouds

This research demonstrates the emergence of quantum-entangled squeezed graviton states originating from superradiant axionic clouds surrounding rotating black holes. The team investigated how both conventional general relativity interactions and gravitational Chern-Simons terms contribute to the production of these entangled states, revealing differing symmetry contributions from each mechanism. Calculations estimate the squeezing parameter within a weak-gravity framework, opening possibilities for detection using current and future interferometric devices. Importantly, the findings suggest that existing data from LIGO and Virgo experiments can already constrain the lifetime of the axionic clouds by setting upper bounds on the squeezing parameter. Beyond direct detection, the research explores indirect detection pathways through cosmology, proposing that chiral gravitational waves in the early universe could indicate condensation of gravitational Chern-Simons terms, potentially leading to a novel inflationary model and alleviating current tensions in cosmological measurements.