Quantum error-detecting codes offer a near-term path for improving the performance of quantum simulations on noisy hardware. Using IBM’s superconducting quantum computer ibm boston, we show that partially fault-tolerant encoded quantum simulations of the Ising model in 1+1D and 2+1D outperform their unencoded counterparts in estimating local observables. To represent 42 logical qubits on the heavy-hex quantum processor, 21 blocks of the [[4, 2, 2]] Iceberg code and up to 136 physical qubits are used. By pairing fault-tolerant syndrome extraction with non-fault-tolerant logical operations, this scheme preserves many of the benefits of error detection while avoiding the overhead typically required for a fully fault-tolerant logical gate set. The encoding’s square logical connectivity, together with the freedom to place logical qubits within each block, enables simulations of a 2D spatial lattice with lower circuit depth than an unencoded implementation would require. We introduce Observable-Ranked Postselection, a selective-filtering technique based on syndrome correlations that recovers reliable results without the prohibitive shot loss of full syndrome postselection. Under the cumulative effect of device errors, this encoding improves local-observable accuracy over the unencoded baseline by 2-6% at intermediate times in 1+1D simulations, growing with circuit depth to over 200% in 2+1D at the latest times studied.

We would like to thank John Preskill for helpful discussions. This work was supported, in part, by U.S. Department of Energy, Office of Science, Office of Nuclear Physics, InQubator for Quantum Simulation (IQuS) under Award Number DOE (NP) Award DE-SC0020970 via the program on Quantum Horizons: QIS Research and Innovation for Nuclear Science. Support is also acknowledged from the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator (Award No. DE-SCL0000121). This work was also supported, in part, by the Department of Physics and the College of Arts and Sciences at the University of Washington, and enabled, in part, by the use of advanced computational, storage and networking infrastructure provided by the Hyak supercomputer system at the University of Washington. We acknowledge the use of Claude for code development. We acknowledge the use of IBM Quantum Credits for this work. The views expressed are those of the authors, and do not reflect the official policy or position of IBM or the IBM Quantum team. The Quimb library was used for tensor network simulations, and QuSpin was used for exact diagonalization computations.

The applications for which quantum computers will clearly outperform classical computers remain surprisingly unclear and benchmarking such an advantage is challenging. We propose a scalable verification scheme for non-equilibrium quantum simulation based on stabilizer scars, a special class of quantum many-body scars, whose structure ensures both classical simulability and efficient direct fidelity estimation. Assuming a physically motivated error model, we show that the fidelity of quantum simulating these states bounds the fidelity of classically intractable simulations, providing a benchmark for quantum-advantage experiments in non-equilibrium dynamics.

We calculate the real-time symmetric correlation function of the stress-energy tensor for a non-integrable Ising field theory consisting of three stable scalar particles via lattice Hamiltonian simulation. Using classical exact diagonalization and the matrix product state tensor network methods, we find that in the scaling region of the lattice theory, Umklapp processes are suppressed and the sound modes of relativistic hydrodynamics emerge at long wavelength and late time. The extracted ratio of bulk viscosity to entropy density is $\zeta/s=14.19\pm 0.90$ and the speed of sound is $c_s/c=0.76 \pm 0.02$ at the temperature $T\approx 7.14$ in units of the lowest stable particle’s mass. Our study demonstrates the utility of real-time lattice Hamiltonian simulation for describing hydrodynamization and calculating transport coefficients nonperturbatively.

One of the goals of quantum simulation is to provide novel insights into quantum systems, such as the gauge theories that are relevant for high-energy and nuclear physics. Recent years have seen rapid improvements in both the hardware and software necessary for these simulations. A central consideration in the design of such simulations is the quantum complexity of a given quantum state. This work takes a step towards studying a specific kind of complexity, namely the non-stabilizerness, in a simple yet non-trivial system: SU(2) lattice gauge theory of two plaquettes. The non-stabilizerness of low-energy eigenstates is studied and the implications for quantum simulations are discussed. The real-time evolution of this system is simulated on ibm_marrakesh and the non-stabilizerness is measured using a random measurement protocol. New techniques enhancing the efficiency of this protocol are developed, including both a new way to calculate the estimator for non-stabilizerness and a flexible error mitigation technique called Bit String Decoherence Renormalization. This mitigation method is central to accurately resolving the experimental time dependence of non-stabilizerness, and is anticipated to have broad applicability in digital quantum simulations.

We report a quantum simulation of the nucleon-antinucleon interaction in large-N two-dimensional quantum chromodynamics (QCD2) on the IBM Quantum Nighthawk processor. In the large-N limit, QCD2 admits a bosonized description in which baryons emerge as topological solitons (kinks) of an effective mesonic field theory, providing a controlled, nonperturbative framework for baryon-antibaryon dynamics.  We formulate the problem by mapping the continuum bosonized Hamiltonian to a spin-chain representation equivalent to an XXZ model with anisotropy set by the QCD parameters. In this mapping, nucleon and antinucleon states correspond to kink and antikink excitations, respectively, while their interaction is encoded in the spin correlations of the chain. Using Jordan-Wigner encoding, we implement the resulting XXZ Hamiltonian on a finite set of qubits and realize it via a variational ground state ansatz and postselected nonunitary disorder operator insertions optimized for the Nighthawk architecture.  We then show the kink-antikink interaction potential built from the conditional energies of these nonunitary string operators can be robustly extracted from the quantum hardware due to structured error cancelation. The resulting potential exhibits the expected attractive behavior. The quantum simulation results are benchmarked against exact diagonalization, ideal statevector evaluation showing good agreement. To connect the device result to the continuum field theory, we extract the potential in the continuum limit using large-L matrix product state calculations.

We construct a toy model of a nucleon, in which three static quarks interact via a SU(3) gauge field on a planar honeycomb lattice. The dynamics of the gauge field is described by the Kogut-Susskind Hamiltonian, truncated to the lowest three SU(3) irreducible representations. We show that the internal structure of the toy nucleon reflects salient features of the physical nucleon state. We then find the entanglement entropy of the gauge field within the nucleon state and compute its time evolution after a quench, in which all three valence quarks are suddenly removed. We show that the entanglement entropy in the final state is dominated by the dynamically generated contribution rather than that in the initial state.

We analyze the emergence of nonlocal magic in Schwinger pair creation in strong non-Abelian (chromo)electric fields using holography. The produced quark–antiquark pair is entangled into a color singlet, yet accelerates into causally disconnected Rindler wedges. Using the Casini–Huerta–Myers conformal mapping and the probe-brane framework, we compute the refined Renyi entropy and its derivative, which captures the antiflatness of the entanglement spectrum for a spherical bipartition. We find that for boundary spacetime dimension d>2, the entanglement spectrum is non-flat, implying the dynamical generation of nonlocal magic in the pair creation process. Interestingly, the nonlocal magic in the holographic dual can be obtained from the free energy of the probe action.

Advances in quantum information science (QIS) are providing transformative insights into the complexity of quantum many-body systems, potentially defining new frontiers in nuclear and high-energy physics. This review explores how QIS-derived techniques are fostering new analytic frameworks and algorithms—both classical and quantum—to tackle (some of the) present barriers to discovery in fundamental physics, with applicability to other science domains. We highlight how these techniques are shedding new light on the structure and dynamics of hadrons, nuclei, matter in extreme conditions, and beyond. Importantly, they are expected to play an essential role in the development of large-scale quantum simulations of such systems, particularly in setting the balance among quantum and classical computational resources.

We would like to thank our colleagues, and the community more generally, for creating and discovering much of the work we have reviewed, and providing a stimulating environment in which we are able to make our contributions to this exciting field of research. We are grateful to the organizers and participants of workshops that brought together many of the ideas and themes in this area, including the 2024 IQuS workshops on Pulses, Qudits and Quantum Simulations and Entanglement in Many-Body Systems: From Nuclei to Quantum Computers and Back, as well as the First and Second International Workshops on Many-Body Quantum Magic. This work was supported, in part, by Universitat Bielefeld, by GSI Helmholtzzentrum fur Schwerionenforschung, by the Ministerium fur Kultur und Wissenschaft des Landes Nordrhein Westfalen (MKW NRW) under the funding code NW21-024-A, and by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the CRC-TR 211 ‘Strong interaction matter under extreme conditions’– project number 315477589 – TRR 211 (Caroline). This work is also supported by U.S. Department of Energy, Office of Science, Office of Nuclear Physics, InQubator for Quantum Simulation (IQuS) under Award Number DOE (NP) Award DE-SC0020970 via the program on Quantum Horizons: QIS Research and Innovation for Nuclear Science, and, in part, through the Department of Physics and the College of Arts and Sciences at the University of Washington (Martin).

We compute the entanglement entropy and the entanglement spectrum of the vacuum state in the massive Schwinger model at a finite theta angle. The theta term is implemented through a chirally rotated lattice Hamiltonian that preserves the periodicity in theta already at the operator level and maintains the correct massless limit without theta-dependent lattice artifacts. The physical origin of entanglement entropy enhancement at theta=pi is clarified by relating it to the competition between distinct electric-flux vacuum branches. We show that the peak near theta=pi persists across the range of masses studied and corresponds to the point of maximal competition between distinct vacuum branches with opposite electric-field orientation, where quantum fluctuations due to fermion pair creation are maximized. While this entropy enhancement is generic, a pronounced narrowing of the entanglement gap occurs only near the critical mass ratio m/g ~ 0.33. Using the Bisognano–Wichmann (BW) theorem, we construct a lattice BW entanglement Hamiltonian and compare it with the exact modular Hamiltonian obtained from the reduced density matrix. We observe agreement between these Hamiltonians in the infrared sector, indicating that the entanglement Hamiltonian is well approximated by a spatially weighted microscopic Hamiltonian. These results establish entanglement observables as sensitive probes of the theta-dependent vacuum structure and highlight the chirally-rotated formulation as a natural framework for open boundary conditions. Additionally, we discuss possible applications to entanglement in topological insulators and quantum wires.

We simulate the thermalization dynamics for minimally truncated SU(2) pure gauge theory on linear plaquette chains with up to 151 plaquettes using IBM quantum computers. We study the time dependence of the entanglement spectrum, Renyi-2 entropy and anti-flatness on small subsystems. The quantum hardware results obtained after error mitigation agree with extrapolated classical simulator results for chains consisting of up to 101 plaquettes. Our results demonstrate the feasibility of local thermalization studies for chaotic quantum systems, such as non-Abelian lattice gauge theories, on current noisy quantum computing platforms.