# Ryo Sakai's scientific contributions

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## Publications (11)

We discuss the use of quantum simulation to study an $N$ flavor theory of interacting relativistic fermions in(1+1) dimensions on NISQ era machines. The case of two flavors is particularly interesting as it can be mapped to the Hubbard model. We derive the appropriate qubit Hamiltonians and associated quantum circuits. We compare classical simulati...

Tensor network methods are becoming increasingly important for high-energy physics, condensed matter physics and quantum information science (QIS). We discuss the impact of tensor network methods on lattice field theory, quantum gravity and QIS in the context of High Energy Physics (HEP). These tools will target calculations for strongly interactin...

We discuss recent progress in Tensor Lattice Field Theory and economical, symmetry preserving, truncations suitable for quantum computations or simulations. We focus on spin and gauge models with continuous Abelian symmetries such as the Abelian Higgs model and emphasize noise-robust implementations of Gauss's law. We discuss recent progress concer...

The $q$-state clock model is a classical spin model that corresponds to the Ising model when $q=2$ and to the $XY$ model when $q\to\infty$. The integer-$q$ clock model has been studied extensively and has been shown to have a single phase transition when $q=2$,$3$,$4$ and two phase transitions when $q>4$.We define an extended $q$-state clock model...

Motivated by recent attempts to quantum simulate lattice models with continuous Abelian symmetries using discrete approximations, we define an extended-O(2) model by adding a γcos(qφ) term to the ordinary O(2) model with angular values restricted to a 2π interval. In the γ→∞ limit, the model becomes an extended q-state clock model that reduces to t...

We define an extended-O(2) model by adding a $\gamma \cos(q\varphi)$ term to the ordinary O(2) model with angular values restricted to a $2\pi$ interval. In the $\gamma \rightarrow \infty$ limit, the model becomes an extended $q$-state clock model that reduces to the ordinary $q$-state clock model when $q$ is an integer and otherwise is a continuat...

We discuss the successes and limitations of statistical sampling for a sequence of models studied in the context of lattice QCD and emphasize the need for new methods to deal with finite-density and real-time evolution. We show that these lattice models can be reformulated using tensorial methods where the field integrations in the path-integral fo...

We construct a tensor network representation of the partition function for the massless Schwinger model on a two-dimensional lattice using staggered fermions. The tensor network representation allows us to include a topological term. Using a particular implementation of the tensor renormalization group we calculate the average plaquette and topolog...

## Citations

... In recent years, Hamiltonian-simulation methods based on tensor networks have significantly advanced [352][353][354], targeting generally low-dimensional theories and systems without volume-law entanglement. The progress in the applications of tensor networks to lattice gauge theories in both the Hamiltonian and path-integral formulations will continue over the next decade, as discussed in a Snowmass whitepaper [355] and recent reviews [356,357]. Nonetheless, more general Hamiltonian-simulation methods are needed, particularly pertinent to QCD and for real-time situations that exhibit an entanglement growth. ...

... While the perturbation considered here had an explicit Z N symmetry, which may have had a dominant effect on the resulting phase structure, it would also be interesting to explore the effect of perturbations with less symmetry to see how the results are modified. For example, N could be extended away from integer values as was considered in the limit of a large perturbation here [47,48]. Determining the effect of small perturbations with varying degrees of symmetry could be important to understanding the errors inherent in simulations on resource limited and noisy near-term quantum simulators. ...

... The Schwinger model, that is, 2D QED, shares some features with QCD [33,34] and is often used as a testbed for new algorithms for lattice gauge theories [21,[35][36][37][38][39][40][41][42][43][44]. In the context of flow-based sampling and related approaches, this theory has already been investigated in Refs. ...