Artificial Black Holes Emit Radiation, Mimicking Hawking’s Groundbreaking Prediction

Researchers are increasingly exploring condensed matter systems to simulate and understand phenomena associated with black holes, and a new study by Jaiswal, Shankaranarayanan, and colleagues from the Department of Physics, Indian Institute of Technology Bombay, details the emergence and detection of Hawking radiation within a quenched chiral spin chain. This work is significant because it moves beyond simply demonstrating analogous black hole conditions to analysing the characteristics of the emitted radiation and proposing methods for its unambiguous detection. By employing both field-theoretic calculations and modelling operational quantum sensors, the team reveal deviations from ideal blackbody spectra and establish a clear protocol for differentiating genuine analog Hawking radiation from background noise in experimental platforms.

Analogue Hawking radiation emerges from a chirally-driven spin chain quantum simulator through collective excitations of magnons and triplons

Researchers have demonstrated the emergence and detection of Hawking radiation within a one-dimensional chiral spin chain, offering a novel platform for investigating quantum gravity phenomena. This work simulates gravitational collapse using a sudden quantum quench, inducing a phase transition that mimics the formation of a black hole horizon.
By mapping the spin chain dynamics onto a Dirac fermion in a curved spacetime, the study meticulously analyzes the resulting radiation spectrum and its detectability through two distinct approaches: field-theoretic modes and operational quantum sensors. Initial findings reveal that the observed radiation spectrum deviates from the ideal Planckian form, exhibiting frequency-dependent characteristics analogous to greybody factors, yet maintains robust Poissonian statistics indicative of information loss at the formation scale.

To further probe this analogue Hawking radiation, a qubit was introduced as a stationary Unruh-DeWitt detector, coupled to the chiral spin chain. The research demonstrates that this qubit functions as a reliable sensor of the Hawking temperature only under weak-coupling conditions, where its population dynamics are governed solely by the spectral density of the surrounding bath.

Conversely, in the strong-coupling regime, the qubit thermalizes with the global environment, effectively obscuring the thermal signature originating from the horizon. These results establish a clear operational protocol for differentiating genuine analogue Hawking radiation from environmental noise within quantum simulation platforms, a crucial step towards validating theoretical predictions.

The study builds upon previous work establishing that the chiral spin chain Hamiltonian accurately mimics black hole formation conditions, even when the Hoop conjecture, a key criterion for black hole identification, appears to be violated. This current investigation focuses specifically on the stationary radiation spectrum and its detectability, moving beyond the initial demonstration of horizon formation.

Through the use of localized Gaussian wave packets as realistic detectors, researchers observed deviations from a purely Planckian spectrum, suggesting a more complex radiation profile than previously anticipated. The introduction of a qubit as a quantum sensor provides a unique method for characterizing the emergent thermal features of the horizon, offering insights into the fundamental properties of Hawking radiation and its potential detectability in analogue systems.

Simulating Hawking Radiation via Quenched Dynamics and Unruh-DeWitt Detection in a Chiral Spin Chain reveals emergent spacetime phenomena

A 72-qubit superconducting processor forms the foundation of this work, utilized to investigate the emergence and detection of Hawking radiation within a one-dimensional chiral spin chain model. The research simulates gravitational collapse through a sudden quench, inducing a horizon and subsequently analysing the resulting stationary radiation spectrum.

Localized Gaussian wave packets, functioning as realistic detectors, were employed to map the spin chain dynamics to a Dirac fermion in a curved (1 + 1)-dimensional spacetime. Analysis of the radiation spectrum revealed deviations from the ideal Planckian form, exhibiting frequency-dependent greybody factors while maintaining robust Poissonian statistics indicative of lost formation-scale information.

Complementary to the field-theoretic approach, a qubit was introduced, coupled to the spin chain to function as a stationary Unruh-DeWitt detector. This qubit’s population dynamics were examined to assess its ability to faithfully sense the Hawking temperature, demonstrating functionality only within the weak-coupling regime where the dynamics are governed by the bath spectral density.

In contrast, strong-coupling conditions caused the probe qubit to thermalize with the global environment, effectively obscuring the thermal signature induced by the horizon. This distinction is crucial for differentiating genuine analog Hawking radiation from background noise in simulation platforms. The study further refined the methodology by implementing a precise operational protocol for distinguishing analog Hawking radiation from environmental noise.

This protocol leverages the qubit’s sensitivity to coupling strength, providing a clear threshold for reliable detection. By meticulously controlling the interaction between the qubit and the spin chain, researchers established a robust method for characterizing the horizon-induced thermal signature, advancing the field of analog gravity and quantum simulation. The combination of field-theoretic modelling and quantum sensing techniques provides a comprehensive framework for exploring Hawking radiation in condensed matter systems.

Spectral deviations from Hawking radiation detected using localized Unruh-DeWitt detectors suggest novel quantum effects

Radiation spectrum analysis reveals deviations from a strictly Planckian form, exhibiting characteristics analogous to frequency-dependent greybody factors while maintaining robust Poissonian statistics that indicate a loss of formation-scale information. Localized Gaussian wave packets, used to model realistic detectors, demonstrate these spectral deviations, challenging the assumption of information-free Hawking radiation.

Initial investigations focused on the radiation spectrum, employing both idealized plane waves and physically realistic Gaussian wave packets to characterize the emitted particles. The qubit, when functioning as a stationary Unruh-DeWitt detector, accurately senses the Hawking temperature only within the weak-coupling regime, where its population dynamics are governed exclusively by the bath spectral density.

In the strong-coupling limit, the qubit thermalizes with the global environment, effectively obscuring the thermal signature induced by the horizon. This thermalization prevents accurate temperature measurement, highlighting the importance of weak coupling for reliable sensing. The research establishes a clear operational protocol for distinguishing genuine analog Hawking radiation from environmental noise within quantum simulation platforms.

Analysis of the system’s dynamics following a sudden quantum quench demonstrates a quantum phase transition driven by the competition between nearest-neighbor hopping and chiral interaction, occurring at a critical point where the absolute value of the effective chiral coupling equals the absolute value of the hopping strength. The study models gravitational collapse using a time-dependent Hamiltonian, transitioning from a pre-horizon state governed by the XX spin chain to a horizon-inducing Hamiltonian activated at time t0.

The pre-horizon regime is described by the XX spin chain, defined by a Hamiltonian with nearest-neighbor coupling strength U and periodic boundary conditions. A conserved quantity, Q, associated with the qubit, allows decomposition of the dynamics into independent sectors labeled by eigenstates, facilitating the diagonalization of the total Hamiltonian in momentum space. Effective chiral coupling is modified by the probe interaction, resulting in a dispersion relation dependent on the momentum and the coupling parameters.

Detecting non-thermal signatures from analogue horizon interactions is crucial for validating theoretical models

Researchers have demonstrated a robust analogue of Hawking radiation within a chiral spin chain model initiated by a sudden quantum quench. This simulation of gravitational collapse reveals key insights into horizon formation, thermality, and the detectability of emitted radiation. Analysis of both theoretical field modes and quantum sensor probes clarifies how these phenomena interact within the model.

The investigation distinguishes between purely mathematical thermal spectra and physically detectable radiation. While idealized models predict a strictly thermal spectrum, realistic detectors, represented as localized Gaussian wave packets, exhibit deviations from the Planckian distribution, similar to greybody factors observed in gravitational systems.

This suggests that measurement processes naturally introduce non-thermal features, potentially revealing information about the interaction between the detector and the horizon. Furthermore, the resulting radiation statistics remain consistently Poissonian, indicating a loss of information regarding the initial conditions of horizon formation and supporting the concept of Hawking radiation as a late-time attractor independent of microscopic details.

The model operates within a continuous limit, reproducing the continuous Hawking spectrum expected from semiclassical gravity but excluding discrete effects like the Bekenstein-Mukhanov spectrum. A limitation acknowledged by the researchers is the model’s inability to capture these discrete lattice effects without retaining the chain’s discrete structure or employing alternative probes.

Future research could explore these discrete effects or investigate the model’s behaviour with different probe types. Crucially, the study establishes a clear protocol for distinguishing genuine analogue Hawking radiation from environmental noise, identifying that a qubit functions as a reliable thermometer only in the weak-coupling regime, probing the spectral density of the surrounding environment. Strong coupling, however, leads to thermalization with the broader environment, obscuring the specific thermal signature of the horizon.