We show how one can reproduce the state evolution known from interacting QFT from an ontological deterministic theory. This is an important step in finding the reality that underlies QFT.In previous work ontic theories behind free QFTs were found, for all QFTs that occur in the Standard Model (spin-0, spin-1/2 & spin-1). In this paper we extend the ontological theory behind QFT to the case with interactions. We do this by starting out from the ontic theories found for free QFTs and see what happens if we try to include interactions (known from QFT). This will lead us to the conjecture that the ontic theory behind any QFT with interaction is, at the basis, the corresponding classical field theory. We study such a classical field theory for the case of a real scalar field with φn-interaction. We determine the evolution of the probability density of the ontic fields and cast it into a formalism known from QFT. We will focus on the simplest case of self-interaction, to illustrate our procedure. We find that we can reproduce the probability evolution from real scalar QFT with (self-)interaction, for this simplest case.We show how one can reproduce the state evolution known from interacting QFT from an ontological deterministic theory. This is an important step in finding the reality that underlies QFT.In previous work ontic theories behind free QFTs were found, for all QFTs that occur in the Standard Model (spin-0, spin-1/2 & spin-1). In this paper we extend the ontological theory behind QFT to the case with interactions. We do this by starting out from the ontic theories found for free QFTs and see what happens if we try to include interactions (known from QFT). This will lead us to the conjecture that the ontic theory behind any QFT with interaction is, at the basis, the corresponding classical field theory. We study such a classical field theory for the case of a real scalar field with φn-interaction. We determine the evolution of the probability density of the ontic fields and cast it into a formalism known from QFT. We will focus on the simplest case of self-interaction, to illustrate our procedure. We find that we can reproduce the probability evolution from real scalar QFT with (self-)interaction, for this simplest case.

Apr 26, 20260 citations

Simulating Quantum Field Theories with Boundaries in Curved Spacetimes Using Open Spin Systems

Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto +1 more

We develop a framework to simulate quantum field theories (QFTs) with boundaries in $(1+1)$ -dimenmsional curved spacetimes by employing open spin systems. Building upon our previous work that established a mapping from spin systems to QFTs in periodic geometries, we extend the correspondence to systems with boundaries, where boundary conditions play a crucial role in shaping the dynamics. Focusing on Majorana fermions, we derive the allowed boundary conditions from the requirement of inner product conservation and formulate their realization in spin systems. The corresponding spin model is shown to reproduce boundary conditions of QFT accurately when a free function in the spin model is appropriately chosen. As an explicit demonstration, we analyze a flat spacetime example, comparing spectra, mode functions, and linear responses between the continuum and lattice descriptions. Our findings confirm that open spin systems can successfully replicate QFT dynamics with boundaries.We develop a framework to simulate quantum field theories (QFTs) with boundaries in $(1+1)$-dimenmsional curved spacetimes by employing open spin systems. Building upon our previous work that established a mapping from spin systems to QFTs in periodic geometries, we extend the correspondence to systems with boundaries, where boundary conditions play a crucial role in shaping the dynamics. Focusing on Majorana fermions, we derive the allowed boundary conditions from the requirement of inner product conservation and formulate their realization in spin systems. The corresponding spin model is shown to reproduce boundary conditions of QFT accurately when a free function in the spin model is appropriately chosen. As an explicit demonstration, we analyze a flat spacetime example, comparing spectra, mode functions, and linear responses between the continuum and lattice descriptions. Our findings confirm that open spin systems can successfully replicate QFT dynamics with boundaries.

hep-thCross-listedarXiv:2602.17935Feb 23, 20260 citations

SPIN IN RELATIVISTIC QUANTUM MECHANICS

B. Kuchowicz

Jan 1, 19620 citations

Spin systems as quantum simulators of quantum field theories in curved spacetimes

Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto +1 more

We demonstrate that a quantum field theory (QFT) in general two-dimensional curved spacetimes can be realized by a system of quantum spins or qubits. We consider a spin-1/2 model on a one-dimensional ring with spatially and temporally varying exchange couplings and magnetic fields. This model reduces to a QFT of Majorana fermions in the continuum limit. From this correspondence, we establish a dictionary for translating between the spacetime-dependent parameters of the spin model and the general metric on which the QFT is defined. After addressing the general case, we consider the Friedmann-Lemaître-Robertson-Walker (FLRW) metric as a simple example. According to the dictionary, the QFT of Majorana fermions on the FLRW metric corresponds to the Ising model with a time-dependent transverse magnetic field. We demonstrate that the production of Majorana particles in the expanding universe can be simulated with the transverse-field Ising model by increasing the strength of the magnetic field. Furthermore, we examine the Unruh effect through the spin system by using our prescription and show the direct relation between the entanglement (or modular) Hamiltonian in the spin system and the Rindler Hamiltonian. This approach provides an experimentally viable system for probing various phenomena in QFT within curved spacetime, while also opening the door to uncovering nontrivial phenomena in spin systems inspired by curved spacetime physics. It offers fresh perspectives on both QFT in curved spacetimes and quantum many-body spin systems, revealing profound connections between these fields.We demonstrate that a quantum field theory (QFT) in general two-dimensional curved spacetimes can be realized by a system of quantum spins or qubits. We consider a spin-1/2 model on a one-dimensional ring with spatially and temporally varying exchange couplings and magnetic fields. This model reduces to a QFT of Majorana fermions in the continuum limit. From this correspondence, we establish a dictionary for translating between the spacetime-dependent parameters of the spin model and the general metric on which the QFT is defined. After addressing the general case, we consider the Friedmann-Lemaître-Robertson-Walker (FLRW) metric as a simple example. According to the dictionary, the QFT of Majorana fermions on the FLRW metric corresponds to the Ising model with a time-dependent transverse magnetic field. We demonstrate that the production of Majorana particles in the expanding universe can be simulated with the transverse-field Ising model by increasing the strength of the magnetic field. Furthermore, we examine the Unruh effect through the spin system by using our prescription and show the direct relation between the entanglement (or modular) Hamiltonian in the spin system and the Rindler Hamiltonian. This approach provides an experimentally viable system for probing various phenomena in QFT within curved spacetime, while also opening the door to uncovering nontrivial phenomena in spin systems inspired by curved spacetime physics. It offers fresh perspectives on both QFT in curved spacetimes and quantum many-body spin systems, revealing profound connections between these fields.

arXiv:2410.07587Physical Review ResearchMay 29, 20255 citations

We develop a framework to simulate quantum field theories (QFTs) with boundaries in

(1+1)

-dimenmsional curved spacetimes by employing open spin systems. Building upon our previous work that established a mapping from spin systems to QFTs in periodic geometries, we extend the correspondence to systems with boundaries, where boundary conditions play a crucial role in shaping the dynamics. Focusing on Majorana fermions, we derive the allowed boundary conditions from the requirement of inner product conservation and formulate their realization in spin systems. The corresponding spin model is shown to reproduce boundary conditions of QFT accurately when a free function in the spin model is appropriately chosen. As an explicit demonstration, we analyze a flat spacetime example, comparing spectra, mode functions, and linear responses between the continuum and lattice descriptions. Our findings confirm that open spin systems can successfully replicate QFT dynamics with boundaries.