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arXiv:2602.04593 · Physics Letters B

Emergent Hawking radiation and quantum sensing in a quenched chiral spin chain

Nitesh Jaiswal, S. Shankaranarayanan

Published Apr 17, 2026• 0 citations
arXivHTMLPDF

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 [33] established that this model mimics black hole (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, while retaining robust Poissonian statistics that signal the loss of formation-scale information. Second, we introduce a qubit coupled globally to the chiral spin chain. Rather than acting as a localized point detector (which would break translational invariance), the qubit couples to the collective chiral excitations of the analogue spacetime, functioning as a global quantum sensor. We demonstrate that the decoherence dynamics of this macroscopic probe faithfully encode the thermal nature of the HR in the weak-coupling limit, while strong-coupling dynamics reveal non-Markovian memory effects driven by the horizon. These results provide a clear operational protocol for distinguishing genuine analog HR from environmental noise in quantum simulation platforms.

DOI
10.1016/j.physletb.2026.140455

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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 [33] established that this model mimics black hole (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, while retaining robust Poissonian statistics that signal the loss of formation-scale information. Second, we introduce a qubit coupled globally to the chiral spin chain. Rather than acting as a localized point detector (which would break translational invariance), the qubit couples to the collective chiral excitations of the analogue spacetime, functioning as a global quantum sensor. We demonstrate that the decoherence dynamics of this macroscopic probe faithfully encode the thermal nature of the HR in the weak-coupling limit, while strong-coupling dynamics reveal non-Markovian memory effects driven by the horizon. These results provide a clear operational protocol for distinguishing genuine analog HR from environmental noise in quantum simulation platforms.
Abstract Hawking radiation is one of the quantum features of a black hole that can be understood as a quantum tunneling across the event horizon of the black hole, but it is quite difficult to directly observe the Hawking radiation of an astrophysical black hole. Remarkable experiments of analogue black holes on various platforms have been performed. However, due to the experimental difficulty of accurately constructing curved spacetime and precisely measuring the thermal spectrum, Hawking radiation and its quantum nature, such as entanglement, have not been adequately investigated. Based on the recent architecture breakthrough of tunable couplers for superconducting processors, we experimentally realize an analogue black hole using our newly developed chip with a chain of 10 superconducting transmon qubits with interactions mediated by 9 transmon-type tunable couplers. By developing efficient techniques to engineer the couplings between qubits via tuning couplers, we achieve both flat and curved spacetime backgrounds. The quantum walks of quasi-particle in the curved spacetime reflect the gravitational effect near the black hole, resulting in the behavior of Hawking radiation. By virtue of the state tomography measurement of all 7 qubits outside the analogue event horizon, we show that Hawking radiation can be verified. In addition, an entangled pair is prepared inside the horizon and the dynamics of entanglement in the curved spacetime is directly measured. Our results would stimulate more interests to explore the related features of black holes using the programmable superconducting processor with tunable couplers.
We investigate the apparent thermality of Hawking radiation in the semi-classical limit of quantum black holes using the mean-field limit of a chiral spin-chain simulator, which models fermions propagating on a black hole space-time in the continuum. In this free-theory regime, no genuine thermalisation occurs. Nevertheless, we show that a bipartition across the event horizon yields a reduced density matrix whose mode occupations follow an apparent thermal Fermi-Dirac distribution. In contrast, partitions away from the horizon do not exhibit such thermal distributions, reflecting the absence of thermal behaviour. Our results demonstrate that Hawking radiation appears thermal only with respect to horizon bipartitions in free theories, with genuine thermal behaviour expected to emerge only in the presence of strong interactions deep in the black hole interior, a study of which we leave for future work.
The complete evaporation of black holes, as a natural endpoint of Hawking radiation, gives rise to the black hole information paradox, which fundamentally challenges the principles of unitarity and information conservation in quantum mechanics. Although the AdS/CFT correspondence indicates that information is preserved during black hole evaporation, the precise mechanism by which it is recovered from the Hawking radiation remains an open question. To explore a potential resolution, we investigate information transfer in a spin-chain model featuring an effective horizon realized via position-dependent couplings within an XY spin chain. We derive and demonstrate Page curve-like behavior, and analyze the transmission of quantum resources, such as entanglement and coherence, across the effective horizon. Our results show that quantum resources initially localized within an interior subsystem can be transferred to the exterior via particle radiation through the horizon. This study provides a novel perspective from quantum simulation on how information may escape from black holes, thereby contributing to the further understanding of the black hole information paradox.
We construct two free fermion lattice models exhibiting Hawking pair creation. Specifically, we consider the simplest case of a d=1+1d=1+1d=1+1 massless Dirac fermion, for which the Hawking effect can be understood in terms of a quench of the uniform vacuum state with a nonuniform Hamiltonian that interfaces modes with opposite chirality. For both our models, we find that additional modes arising from the lattice discretization play a crucial role, as they provide the bulk reservoir for the Hawking radiation: the Hawking pairs emerge from fermions deep inside the Fermi sea scattering off the effective black hole horizon. Our first model combines local hopping dynamics with a translation over one lattice site, and we find the resulting Floquet dynamics to realize a causal horizon, with fermions scattering from the region outside the horizon. For our second model, which relies on a purely local hopping Hamiltonian, we find the fermions to scatter from the inside. In both cases, for Hawking temperatures up to the inverse lattice spacing, we numerically find the resulting Hawking spectrum to be in perfect agreement with the Fermi-Dirac quantum field theory prediction.
Non-Hermitian systems have recently emerged as a convenient platform to realize black-hole physics. Here, we propose a microscopic open quantum system, namely a fermionic tight-binding chain coupled to Markovian reservoirs, which emulates black-hole properties. The resulting quadratic Lindbladian admits an effective non-Hermitian limit that produces a gain and loss lattice model with a non-reciprocal next-nearest-neighbor hopping. The rapidity spectrum of the full Lindbladian forms tilted exceptional cones that define an effective Painlevé-Gullstrand geometry and separates into black-hole and white-hole sectors, while steady-state particle densities and currents retain clear signatures at the horizon positions. We then analyze the effective non-Hermitian Hamiltonian that arise from the microscopic quantum system. The biorthogonal flux identifies the outgoing exterior and interior channels. Finally, we introduce a fermionic Gaussian Nambu extension and formulate Hawking-pair witnesses through frequency-resolved scattering, nonlocal density-density correlations, and anomalous Hawking-partner amplitudes. The resulting correlations display analogue Hawking radiation signatures, while the frequency-resolved Hawking-partner correlations satisfy the fermionic covariance-positivity constraint. These results establish a connection between microscopic open-system dynamics, emergent non-Hermitian geometry, and fermionic many-body probes of analogue Hawking radiation.
We show that Hawking radiation spontaneously generated by dynamical black-hole formation can be realized in a local quantum spin model. Starting from the ground state corresponding to the early-time vacuum, with no initially prepared excitations, we follow the dynamics induced by the evolving geometry. In the corresponding continuum quantum field theory, Hawking particle creation is associated with nontrivial Bogoliubov mixing between the in- and out-mode decompositions. We derive the resulting renormalized local energy density in the continuum quantum field theory, which corresponds to an energy-weighted integral of the Hawking spectrum, and identify its counterpart as a local spin observable whose expectation value quantitatively reproduces the continuum prediction, including its dependence on the surface gravity. The agreement persists over a finite time window whose duration grows logarithmically with system size, revealing the crossover from universal continuum Hawking physics to lattice-cutoff dynamics. These results establish a microscopic route to quantum simulation of quantum field theory in curved spacetime, connecting field-theoretic particle creation directly to experimentally accessible many-body observables.