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Simulating the Unruh Effect on Real Quantum Hardware

Zuhair Ahmed

Published Jan 1, 2025• 0 citations
Publisher

Abstract

Abstract The Unruh effect, a cornerstone of quantum field theory, predicts that an accelerating observer perceives a thermal bath of particles in a vacuum, bridging quantum mechanics and relativity. This study presents the first successful simulation of the Unruh effect on real quantum hardware, conducted at the Centre of Excellence for Technology, Quantum, and AI Canada (CETQAC). Using a two-qubit quantum circuit executed on IBM’s su perconducting qubits via Qiskit Runtime Services, we encoded the effect’s key features: quantum superposition, Bogoliubov transformations, and thermodynamic signatures. Re sults demonstrate a strong concentration in the |11⟩ basis state, with metrics such as pu rity (0.5), entropy (1.0), entanglement entropy (1.0), fidelity (0.46), and expectation value (Z =0.0) aligning with theoretical predictions. Visualizations, including statevector plots and Q-sphere representations, confirm the simulation’s success. This work advances quan tum thermodynamics and relativistic quantum physics, establishing Canada as a leader in quantum computing applications.

DOI
10.21203/rs.3.rs-6911166/v1

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Abstract The Unruh effect, a cornerstone of quantum field theory, predicts that an accelerating observer perceives a thermal bath of particles in a vacuum, bridging quantum mechanics and relativity. This study presents the first successful simulation of the Unruh effect on real quantum hardware, conducted at the Centre of Excellence for Technology, Quantum, and AI Canada (CETQAC). Using a two-qubit quantum circuit executed on IBM’s su perconducting qubits via Qiskit Runtime Services, we encoded the effect’s key features: quantum superposition, Bogoliubov transformations, and thermodynamic signatures. Re sults demonstrate a strong concentration in the |11⟩ basis state, with metrics such as pu rity (0.5), entropy (1.0), entanglement entropy (1.0), fidelity (0.46), and expectation value (Z =0.0) aligning with theoretical predictions. Visualizations, including statevector plots and Q-sphere representations, confirm the simulation’s success. This work advances quan tum thermodynamics and relativistic quantum physics, establishing Canada as a leader in quantum computing applications.
The Unruh effect is a quantum relativistic effect where the accelerated observer perceives the vacuum as a thermal state. Here we propose the experimental realization of the Unruh effect for interacting ultracold fermions in optical lattices by a sudden quench resulting in vacuum acceleration with varying interactions strengths in the real temperature background. We observe the inversion of statistics for the low lying excitations in the Wightman function as a result of competition between the spacetime and BCS Bogoliubov transformations. This paper opens up new perspectives for simulators of quantum gravity.
The Unruh effect predicts that an accelerating observer perceives the Minkowski vacuum as a thermal bath, yet direct detection remains experimentally inaccessible. Its timelike counterpart, arising from the entanglement of massless fields between the future and past light cones, offers a more feasible route but requires a detector whose transition frequency follows a specific conformal-time scaling. We propose and analyze a practical implementation of such a detector using superconducting fluxonium circuits, which naturally provide two quasi-degenerate ground states and a tunable excited state, forming an effective ΛΛΛ-system. By modulating the excited-state transition frequency in Minkowski time, the detector accumulates a geometric phase associated with the timelike Unruh effect. Open-system simulations predict ∼10%\sim 10\%∼10% shift in the ground-state population within 530530530 ns, representing a three-order-of-magnitude sensitivity enhancement over two-level Unruh-DeWitt detectors. These results establish a realistic quantum-circuit platform for experimentally probing the timelike Unruh effect and, more broadly, for testing fundamental nature of quantum fields using engineered quantum systems.
The Unruh effect predicts that a uniformly accelerated observer perceives the vacuum seen by an inertial observer as a thermal bath at a temperature proportional to its proper acceleration. This phenomenon is often regarded as a flat spacetime ``cousin" of Hawking radiation. In this Letter, we first study the entanglement dynamics of a quantum system composed of two polarizable two-level subsystems undergoing centripetal acceleration in a vacuum. We demonstrate that the system's steady state can be entangled irrespective of the initial state, a distinct characteristic attributable to the circular manifestation of the Unruh effect. Through meticulous analysis, we then propose that this phenomenon can feasibly be detected using state-of-the-art optomechanical technologies, particularly with a quantum system of two molecules.
Abstract This study presents a groundbreaking experimental demonstration of gravity induced decoherence in quantum systems, achieved through the development and execution of the Quantum Gravity-Induced Decoherence Circuit (QGIDC) on IBM quantum hardware. This research provides the first measurable evidence of how gravitational effects can influence quantum entanglement, building upon and ex tending theoretical frameworks proposed by prominent physicists such as Roger Penrose and Gerard ’t Hooft. The experiments were conducted using both Qiskit simulators and real IBM quantum computers, including the advanced IBM Bris bane backend, with multiple repetitions to ensure scientific reproducibility. A com prehensive set of metrics—fidelity, purity, entropy, trace distance, measurement counts, and Bloch vector dynamics—were meticulously analyzed to differentiate gravity-induced noise from standard environmental decoherence. Additionally, a mathematical model is introduced to quantify the decoherence rate, while Bloch sphere visualizations offer a visual representation of qubit state evolution under gravitational influence. This work, completed as of 06:12 PM on Monday, May 19, 2025, marks the first empirical validation of gravity-induced decoherence, estab lishing a significant milestone in the quest to reconcile quantum mechanics with general relativity.
Quantum effects in non-inertial frames and curved space-time have been studied for decades. One of the most intriguing discoveries is the existence of virtual particles in the quantum vacuum. One example in which such particles can be observed is through the Unruh effect, which predicts that a uniformly accelerated observer would see a thermal bath of (virtual) particles in the quantum vacuum. Initial doubts on the existence of these virtual particles were allayed by the Unruh De-Witt (UDW) detector, which promoted these virtual particles to real excitations of the detector. Ever since, semiclassical approaches to relativistic quantum field theory (QFT) in flat and curved space-time have been predominantly analysed through a two-level Unruh De-Witt detector utilizing perturbation theory. It is noted, however, that the change of relativistic frame preserves Gaussian properties (e.g. Gaussian distribution of the Wigner function) of the system. In this thesis, we specifically explore the effects of relativistic (non-inertial) reference frames on QFT by considering relativistic QFT in flat-space time. These systems are analysed from the perspective of Gaussian quantum information, via homodyne detection and UDW detectors with a harmonic oscillator degree of freedom.Our project starts by reviewing and developing bipartite/multi-partite entanglement measures (specifically, entanglement of formation), in the hope that we can utilize these measures to understand the entanglement properties of the quantum vacuum. In general, these measure have infinite degrees of freedom and are incomputable. In this project the multi-partite entanglement measure is applied to the Gaussian regime, which reduces the number of degrees of freedom to a finite one, hence making it a computable measure.In our next project, we attempt to understand how relativistic reference frames affect the communication between different observers. To obtain an intuition of its effect, a passive (time-delay) signal sent from a uniformly accelerated observer to a stationary observer was analysed. When we naively implemented the self-homodyne detection scheme, the signal appeared noisy. This effect was referred to as apparent decoherence, and its effect could be traced back to our naive assumption that all of the signal’s information would be stored in the time-delayed mode; the vacuum entanglement that pre-existed before the (time-delay) signal was created must be accounted for. We follow by analysing the effects that emerge due to communication between different relativistic reference frames. We then develop a communication technique referred to as ideal-homodyne which is a homodyne detection scheme robust to these effects. We used this detection scheme to analyse the correlation/entanglement properties of an accelerated signal (created via accelerated mirror, squeezer and phase shifter) sent to an inertial observer.In our last project, we utilize the knowledge that was gained through the prior projects to analyse (subcycle) electro-optic sampling. In the literature, there were doubts as to whether electro-optic sampling were truly detecting virtual particles in the quantum vacuum, or particle excitations that were created as a by-product of the detection mechanism. We were able to pin-point some similarities between electro-optic sampling and subcycle probe via the UDW detector. The regime in which the electro-optic sampling directly maps virtual particles from the vacuum into real excitations of the probe field was identified by establishing an equivalence to the UDW detector in certain parameter regimes.
A uniformly accelerated atom captures Pancharatnam-Berry phase in its quantum state and the phase factor depends on the vacuum fluctuation of the background quantum fields. We observe that the thermal nature of the fields further affects the induced phase. Interestingly the induced phase captures the exchange symmetry between the Unruh and real thermal baths. This observation further supports the claim that the Unruh thermal bath mimics a real thermal bath. Moreover for certain values of system parameters and at high temperature, the phase is enhanced compared to zero temperature situation. However the required temperature to observe the phase experimentally is so high that the detection of Unruh effect through this is not possible within the current technology.