Emergent Hawking Radiation and Quantum Sensing in a Quenched Chiral Spin Chain

Abstract

We investigate the emergence and detection of Hawking radiation (HR) in a 1D chiral spin chain model, where the gravitational collapse is simulated by a sudden quantum quench that triggers a horizon-inducing phase transition. While our previous work Jaiswal [2025] established that this model mimics BH formation conditions even when the Hoop conjecture is seemingly violated, we here focus on the resulting stationary radiation spectrum and its detectability. By mapping the spin chain dynamics to a Dirac fermion in a curved (1 + 1)-dimensional spacetime, we analyze the radiation using two complementary approaches: field-theoretic modes and operational quantum sensors. First, using localized Gaussian wave packets to model realistic detectors, we find that the radiation spectrum exhibits deviations from the ideal Planckian form, analogous to frequency-dependent greybody factors, while retaining robust Poissonian statistics that signal the loss of formation-scale information. Second, we introduce a qubit coupled to the chain as a stationary Unruh-DeWitt detector. We demonstrate that the qubit functions as a faithful quantum sensor of the Hawking temperature only in the weak-coupling regime, where its population dynamics are governed solely by the bath spectral density. In the strong-coupling limit, the probe thermalizes with the global environment, obscuring the horizon-induced thermal signature. These results provide a clear operational protocol for distinguishing genuine analog HR from environmental noise in quantum simulation platforms.

Figures (7)

• Figure 1: Schematic diagram of the Qubit-Environment Coupling in Chiral Spin Chain.
• Figure 2: Penrose diagram of the gravitational collapse process where a single shock wave located at $w=w_0$ collapse to form a BH.
• Figure 3: $\log(|\alpha_{ff^\prime}^G|/|\beta_{ff^\prime}^G|)$ as a function of outgoing frequency $f$ for various fixed incoming frequencies $f^\prime$ (left), and particle number spectrum $n_f^G$ as a function of $f$ comparing the thermal prediction with the localized Gaussian wave-packet probe (right).
• Figure 4: Poissonian statistics of Hawking emission for the plane-wave (left) and Gaussian wave-packets (right).
• Figure 5: The dynamics of the decoherence factor (left) and the effective temperature (right) of the qubit for different values of $g_2$.