Scientists Test the Hawking Effect in Laboratory Black Holes
Physics has been fascinated by the Hawking effect for over 50 years, sometimes frustratingly. Stephen Hawking suggested this phenomenon in 1974, connecting quantum physics and general relativity. Modern theoretical research relies on it, although it has never been found in a black hole's event horizon.
Pioneering research is moving the hunt from orbit to the lab. Quantum fluids form “sonic black holes,” allowing scientists to capture the illusive “hiss” of the horizon using momentum-space correlation analysis.
Temperature and Scale Challenges the Universe
Looking for Hawking radiation in space is difficult due of its size and noise. Hawking believed quantum instabilities at a black hole's event horizon would cause spontaneous radiation emission. This creates pairs of virtual particles, one of which radiates and the other falls into the abyss.
The signal is faint for experimenters. A black hole the size of the sun has a "Hawking temperature" of 60 nanokelvins. Due to its colder temperature than the cosmic microwave background radiation, existing technology cannot detect such a faint trace against the galactic background noise.
Analogue Gravity: Sonic Horizon Creation
Physicists use laboratory devices to replicate black hole physics in “analogue gravity” to overcome this cosmic obstacle. They replace gravitational horizons with auditory (or acoustic) horizons in fluids like polaritonic light or Bose-Einstein Condensates (BECs).
These experiments manipulate fluid flow at subsonic and supersonic speeds. The fluid velocity passes the speed of sound at a sound wave event boundary, or phonon. As light cannot escape a black hole's gravitational pull, sound waves in these fluids cannot move “upstream” against supersonic velocity. Researchers can observe how lab-grown horizons spontaneously produce quanta.
A Momentum-Space Analysis Breakthrough
Previously, scientists analysed real-space correlations to uncover the Hawking effect in these fluids. This involved searching for density changes that formed a “moustache” pattern. This provided preliminary evidence of the effect, but its tendency to integrate over numerous frequencies sometimes obscured the liberated particles' quantum entanglement and finer spectrum features.
The recent work, coordinated by Marcos Gil de Olivera, Malo Joly, Antonio Z. Khoury, Alberto Bramati, and Maxime J. Jacquet, uses a complicated numerical algorithm that goes beyond “moustache” patterns. The team obtained more reliable signatures via momentum-space analysis. Their findings show a clear anti-correlation between emitted phonon pair momenta. This study helps diagnose the “Hawking” signal by separating it from fluid noise and background radiation.
Entanglement's "Smoking Gun"
The move to momentum-space improves quantum horizon knowledge for several reasons. First, one of the most advanced experimental methods can directly measure momentum signatures. This means researchers can rethink their data without building new facilities.
Second, and probably most importantly, these correlations directly indicate entanglement between the escaping Hawking effect and its companion going into the “hole.” The "smoking gun" for the radiation's quantum nature is its entanglement, proving that it is not classical noise. These connections were found by focussing on the angular distribution of emitted pairs, supporting the assumption that quantum mechanics caused the radiation.
Numerical Stability, Programmable Spacetimes
The team's findings are supported by polariton fluid dynamics simulations. With periodic boundary conditions, fluid stability in the face of numerical reflections and instabilities is one of the hardest jobs in these simulations. The researchers designed a sophisticated strategy that included an initial amplitude boost to swiftly establish the fluid configuration, a modified “pump” to generate the requisite potential, and spatially dependent loss to stop reflections.
This method considers quantum fluids “programmable spacetimes”. The researchers have created a repeatable setting to study quantum field theory in curved spacetime by providing specific parameters including cavity length, grid spacing, polariton mass, detuning, and nonlinear coupling constants.
Researchers can study how horizon thickness and curvature affect radiation. It also allows the study of "quasi-normal modes," the vibrations a black hole makes after a disturbance.
A Path to Experimental Verification
The researchers reduced background noise by building up computational “windows” around the acoustic horizon, revealing Hawking effect patterns. Their results confirm the frequency and momentum of these connections and corroborate the theoretical explanation.
As research nears major milestones like CES 2026, the relationship between fluid dynamics and quantum gravity is fascinating. To fully experimentally validate Hawking's 50-year-old idea, this multinational team's study is crucial. While humanity may not be able to create a real black hole soon, their hushed, supercooled labs are whispering the horizon's secrets.
