Black hole on a superconducting chip: temperature and chaos from a single model ✛
Context
Analog experiments have already reproduced Hawking radiation in Bose condensates and optical systems, and superconducting qubits have been used to simulate curved spacetime and measure OTOCs. However, these ingredients existed separately. This work joins attempts to unify semiclassical horizon physics and strongly interacting scrambling in a single microscopic model. Neighboring works explore quantum teleportation between simulated black holes, entanglement and apparent thermalization in simulations, and gravitational waves at the horizon. The distinction of this paper is the use of a single chiral chain, from which observable-specific circuits are derived for different probes, allowing one to test geometry, thermality, and scrambling on the same hardware.
Methods
On the ibm_boston processor, Trotterized quantum circuits were implemented for three variants of the chiral spin chain. The mean-field circuit $U_{MF}$ preserves single-particle dynamics and is used to extract the dispersion via single-excitation spectroscopy. The coordinate-equivalent XY circuit $U_{XY}$ has lower depth and is used to extract the Hawking temperature: a single excitation is localized just behind the horizon, then the population of the outer site is measured over time. For scrambling, a reduced interacting circuit $U_{int}$ is used, where the phase angle φ continuously tunes the interaction strength from free fermions to the strongly interacting limit. All measurements were performed with 10000 shots per point, with Pauli twirling, readout twirling, and zero-noise extrapolation.
Results
The dispersion measured on 24 qubits reproduces the theoretical formula ω(k)=v sin(2k)±2u cos(k) for three regimes: exterior (θ(v)=0), horizon (θ(v)=π/8), and interior (θ(v)=π/4). In the horizon regime, one branch flattens near the Fermi point, and in the interior regime additional Fermi points appear—a direct observation of the super-tilted light cone. For the Hawking temperature on 32 qubits, the population peak at the outer site j=16 was measured; the inverse peak time depends linearly on the parameter α, yielding a calibration constant γ≈0.197±0.008, consistent with the numerical value 0.186. In scrambling experiments on 18 and 24 qubits, the OTOC in the strongly interacting regime (φ=π) shows exponential decay with $λ_{fit}$/v≈0.88±0.02 for N=24, close to the benchmark $λ_L$/v≈0.78 for N=12. In the free limit (φ=0), the decay is non-exponential, and a formal fit gives only an effective decay scale $λ_{fit}$/v≈0.47±0.02.
Implications
The work shows that the same chiral model can serve as a platform for studying horizon geometry, Hawking thermality, and quantum scrambling. Unlike neighboring works where these aspects were considered separately, here they are unified through observable-specific reductions of the parent circuit. This opens the way to studying information protocols (Page, Hayden-Preskill) on quantum hardware and to testing interacting corrections to semiclassical radiation. The calibrated dynamical thermometer offers a hardware-efficient way to extract temperature without density matrix reconstruction.
Future development
Improving coherence, qubit connectivity, and error suppression methods will allow implementing the full parent circuit $U_C$ and simultaneously studying thermality and scrambling in a spatially inhomogeneous chain. Extending the model to two dimensions would give access to more complex horizons and possibly rotating black holes. Increasing the number of qubits and gate fidelities will bring simulations closer to regimes where classical computations become impractical.
Impact
The results are useful for quantum gravity, many-body physics, and quantum computing: they connect analog black hole models with chaos diagnostics and open new protocols for testing thermality on noisy processors.
Next steps
The next step is to implement the full interacting circuit U_C for simultaneous measurement of temperature and OTOC in a single chain. It is also important to increase the number of random initial states for accurate approximation of the infinite-temperature trace and to extend the thermometer calibration to other metric profiles.
Key open problems
In quantum gravity, the fate of information during black hole evaporation remains an open question. This work directly leads to experimental tests of information recovery scenarios: measuring OTOC and thermality in the same system is a step toward testing Page and Hayden-Preskill protocols. Also unresolved is the problem of precisely describing interacting corrections to Hawking radiation, for which the proposed platform can serve as a testbed.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The work implements a black hole simulator based on a chiral spin chain on a superconducting quantum processor. The quasiparticle dispersion was measured in three regimes (outside, at the horizon, and inside), the Hawking temperature was obtained from the arrival time of the population peak at the boundary site, and the OTOC was measured to assess scrambling. The results agree with theory: the dispersion reproduces the formula, the temperature follows the linear dependence of the inverse peak time on the parameter α, and the OTOC in the strongly interacting regime shows exponential decay with an exponent close to the reference value.
Where its strength is
Using a single chiral chain from which observable-specific circuits are derived for different probes allows one to test the horizon geometry, thermality, and scrambling on the same hardware. This unifies semiclassical horizon physics and quantum information mixing in one microscopic model.
Where it could go next
- It might be interesting to look at the connection with the work on a quantum chain hosting a black hole: there, perhaps, a different microscopic mechanism for horizon emergence is proposed, which could be compared with the chiral chain.based on: A Quantum Chain That Mimics a Black Hole arXiv:2603.07639
- Closely related is the tabletop Hawking radiation study—an analog experiment that may suggest which other observables (beyond temperature and OTOC) are worth measuring in your digital implementation.based on: Hawking Radiation on a Tabletop arXiv:2602.04593
- Since the work demonstrates scrambling in the strongly interacting regime, it may be useful to compare with results on quantum particles that remember their past: there, the connection between memory of the initial state and the rate of information mixing is likely discussed.based on: Quantum Particles Remember Their Past arXiv:2603.12675
Worth trying
- Test OTOC measurements for other operators or at other chain sites to check the universality of Lyapunov growth.
- Use shallower circuits (e.g., UXY) for longer chains to approach the thermodynamic limit when studying the Hawking temperature.
- Apply quantum process tomography methods for a more detailed analysis of scrambling, possibly using ideas from the work on quantum memory.
Why this may matter
Unifying horizon geometry, thermality, and scrambling on a single programmable platform paves the way for systematic studies of the connection between quantum chaos and gravitational physics in controlled experiments. This could help clarify the microscopic nature of Hawking radiation and the information paradox.
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Original abstract
as written by the authors arXiv:2608.19318v1
We implement a chiral spin-chain black hole simulator on IBM superconducting quantum hardware and probe, within a common microscopic framework, both semiclassical horizon physics and interacting quantum scrambling. We first measure the dispersion relation across the exterior, horizon and over-tilted interior regimes, reproducing the predicted evolution of the effective light-cone structure. To probe Hawking thermality, we prepare a localised excitation inside the horizon and monitor its density response at an exterior site, observing the predicted inverse relation between the peak arrival time and the surface gravity, thereby establishing a calibrated dynamical estimator of the Hawking temperature. Beyond the semiclassical regime, we continuously tune the interactions and distinguish non-exponential operator spreading in the free-fermion limit from Lyapunov-like OTOC decay in the strongly interacting chiral regime. These measurements use observable-specific Floquet circuits derived from the same parent chiral model, including its mean-field and coordinate-equivalent XY descriptions, to reduce circuit depth while preserving the physics relevant to each probe. Our results provide a unified programmable platform for studying horizon geometry, Hawking thermality and interacting scrambling on quantum hardware.
To extract the dispersion on 24 qubits, 4099 two-qubit CZ gates were needed after translation — a record depth for such simulations on superconducting hardware. In scrambling experiments, the number of CZ gates reached 5028 for intermediate values of φ.
The idea of simulating a black hole on a quantum computer echoes Greg Egan's novel 'Schild's Ladder', where physicists create artificial universes with tunable laws. Here, not the entire universe is tuned, but only a tiny part, the horizon and interior of a black hole.
Key numbers
- number of qubits for dispersion: 24
- number of qubits for Hawking temperature: 32
- calibration constant γ (experiment): 0.197 ± 0.008
- Lyapunov exponent λ_fit/v at φ=π, N=24: 0.88 ± 0.02
- effective decay scale λ_fit/v at φ=0: 0.47 ± 0.02