Abstract: Gauge theories describe a wide range of phenomena, from elementary particles and early-universe cosmology to condensed matter systems. However, solving gauge theories with classical computers faces significant challenges. Recently, we performed quantum simulation of a 1+1D U(1) lattice gauge theory using a microscopically engineered quantum device [1-3]. We are now developing a new...
We review some recent results on the development of efficient tree tensor network algorithms and their applications to high-dimensional many-body quantum systems. In particular, we present recent results on two and three-dimensional lattice gauge theories in presence of fermionic matter at finite densities. Moreover, we show how to compute the entanglement of formation in critical many-body...
Tensor Network States suggest an efficient, entanglement-based approach, for dealing with strongly correlated many-body physics. Gauged gaussian PEPS (GGPEPS) form a class of such states, suitable for studying lattice gauge theories. Using GGPEPS, one can construct tensor network states describing fermionic matter coupled to dynamical gauge fields, with full gauge invariance, as well as...
The ground and meta-stable clock state pair in ytterbium (Yb) provides an excellent resource for applications in quantum metrology, simulation and computation. Being capable of individually addressing the two optical clock qubit states in a state- selective manner enhances the controllability of such systems, allowing for novel methods for state preparation, read-out or Hamiltonian...
Ab initio simulations of the Standard Model will require thousands of qubits and millions of gates. Developing efficient quantum simulation algorithms for such settings, which will only be feasible in the era of fault-tolerant quantum computing, demands entirely new principles, distinct from those applicable in the near term. A valuable guiding principle for developing new algorithms is to...
Trapped atomic ions serve as powerful digital, analog, and hybrid quantum simulators for many-body quantum systems using their spin and motional degrees of freedom. Our experiment is based on a chain of 171Yb+ ions with individual laser beam addressing, creating a fully connected device capable of executing any sequence of single- and two-qubit gates, as well as continuous evolution involving...
Tensor Networks are among the most promising methods to study quantum many-body systems out-of-equilibrium. This can be particularly interesting for dynamical lattice gauge theories scenarios, which escape the traditional methods. However, entanglement growth severely limits the simulation of out-of-equilibrium dynamics with standard MPS algorithms. Yet, they allow us to explore physically...
One of the most challenging problems in the computational study of localization in quantum many-body systems is to capture the effects of rare events, which requires sampling over exponentially many disorder realizations. We implement an efficient procedure on a quantum processor, leveraging quantum parallelism, to efficiently sample over all disorder realizations. We observe localization...
In confining theories, separating two charges results in the generation of new charges that screen the original ones. This process, known as “string breaking”, prevents isolation of individual charges and is one of the fundamental phenomena in gauge theories such as quantum chromodynamics, as well as in simpler models exhibiting confinement. The rapid development of analog and digital quantum...
Hamiltonian simulation of lattice gauge theories (LGTs) is a non-perturbative method of numerically solving gauge theories that offers novel avenues for studying scattering processes in gauge theories. With the advent of quantum computers, Hamiltonian simulation of LGTs has become a reality. Simulating scattering on quantum computers requires the preparation of initial scattering states in the...
Lattice QCD has enabled the non-perturbative calculation of many static quantities such as hadron masses and form factors. Quantum computers are expected to enable lattice calculations to directly probe the real time dynamics of quantum field theories. Recent developments in quantum computers have enabled the first simulations of gauge theories on large lattices. In this talk, I will review...
In this talk we explore numerical simulations, including Tensor Networks (TNs) methods, to study Hamiltonian Lattice Gauge Theories (LGTs), a numerical framework for investigating non-perturbative properties of Quantum Field Theories. We develop a model-independent approach for constructing Matrix Product Operators (MPOs) representations of one-dimensional quasiparticles with definite momenta,...
Confinement is a paradigmatic phenomenon of gauge theories, and its understanding lies at the forefront of high-energy physics. Here, we study confinement in a simple one-dimensional Z2 lattice gauge theory at finite temperature and filling, which is within the reach of current cold-atom and superconducting-qubit platforms. By employing matrix product states (MPS) calculations, we investigate...
We explore the first-order phase transition in the lattice Schwinger model in the presence of a topological θ-term by means of the variational quantum eigensolver (VQE). Using two different fermion discretizations, Wilson and staggered fermions, we develop parametric ansatz circuits suit- able for both discretizations, and compare their performance by simulating classically an ideal VQE...
Quantum simulations of the dynamics of QCD have been limited by the complexities of mapping the continuous gauge fields onto quantum computers. By parametrizing the gauge invariant Hilbert space in terms of plaquette degrees of freedom, we show how the Hilbert space and interactions can be expanded in inverse powers of N_c. At leading order in this expansion, the Hamiltonian simplifies...
Due to rapidly improving quantum computing hardware, Hamiltonian simulations of relativistic lattice field theories, particularly lattice gauge theories, have seen a resurgence of attention. Unfortunately, implementing these theories onto digital quantum computers poses a number of difficulties, both theoretical and practical. Part of the difficulty is that gauge theories naturally result in...
Hamiltonian simulation of non-Abelian gauge theories remain nontrivial due to the local constraint structure governing the principle of gauge invariance. Recently developed Loop-string-hadron framework provides a solution to this problem by solving the local non-Abelian constraints analytically - yielding a complete theory that describes dynamics of manifestly gauge invariant variables, such...
Quantum fields in curved spacetimes have many tantalizing theoretical properties, for example particles are being produced by the time-dependence of the geometry. I will describe how quantum fields in geometries with spacetime curvature and different cosmologies can be quantum-simulated with Bose-Einstein condensates in specifically designed trapping potentials and with time-dependent...
Kogut-Susskind Hamiltonian is complicated because of the use of unitary variables. On the other hand, theories such as scalar field theories and matrix models are much simpler because of the use of noncompact variable. We show that we can use the idea of orbifold lattice to describe QCD in terms of noncompact variables. The Hamiltonian is much simpler, and it is almost trivial to write down...
Elucidating the microscopic mechanisms leading to thermalization of gauge theories is often advocated as an especially promising future application of quantum computing. What is usually not appreciated, however, is that many other approaches, e.g. lattice QCD, AdS/CFT duality, hydrodynamics, tensor networks, eigenstate thermalization (ETH) have already provided many complementary partial...
Classical methods for simulating lattice gauge theories generally encounter a sign problem when studying theories at finite chemical potential, theories with a topological θ-term, or their real-time dynamics. Quantum simulations of gauge theories offer a way to overcome some of these challenges by mapping the classically inaccessible real-time dynamics onto quantum devices. In this talk, I...
Quantum state tomography (QST) is the art of reconstructing an unknown quantum state through measurements. It is a key primitive for developing quantum technologies. Neural network quantum state tomography (NNQST), which aims to reconstruct the quantum state via a neural network ansatz, is often implemented via a basis-dependent cross-entropy loss function. State-of-the-art implementations of...
Particle physics underpins our understanding of the world at a fundamental level by describing the interplay of matter and forces through gauge theories. Yet, despite their unmatched success, the intrinsic quantum mechanical nature of gauge theories makes important problem classes notoriously difficult to address with classical computational techniques. A promising way to overcome these...
While exciting recent progress in the quantum simulation of lattice gauge theories has been achieved, their scaling remains highly challenging. In this talk, I will present some of our recent progress on exploiting qudit systems, such as recently demonstrated in a universal trapped-ions device. I will discuss a recent proposal to use qudits to simulate lattice gauge theories in 2+1 dimensions....
The extraordinary advances in quantum control of matter and light have been transformative for atomic and molecular precision measurements enabling probes of the most basic laws of Nature to gain a fundamental understanding of the physical Universe. Exceptional versatility, inventiveness, and rapid development of precision experiments supported by continuous technological advances and improved...
Quantum simulation of HEP has seen remarkable growth in recent years. Nevertheless, there is a continuous need for advancements in the overall simulation framework. I will discuss a specific foundational element - digitization, a crucial method for encoding field variables into qubits. This is particularly relevant for gauge theories with local symmetry and field variables of infinite...
Topologically ordered quantum matter exhibits intriguing long-range patterns of entanglement, which reveal themselves in subsystem entropies. However, measuring such entropies, which can be used to certify topological order, on large partitions is challenging and becomes practically unfeasible for large systems. We propose a protocol based on local adiabatic deformations of the Hamiltonian...
A central requirement for the faithful implementation of large-scale lattice gauge theories (LGTs) on quantum simulators is the protection of the underlying gauge symmetry. Recent advancements in the experimental realizations of large-scale LGTs have been impressive, albeit mostly restricted to Abelian gauge groups. Guided by this requirement for gauge protection, we propose an experimentally...
