A detailed analysis of the constant quantum Yang–Baxter equation Rk1k2j1j2 Rl1k3k1j3Rl2l3k2k3= Rk2k3j2j3 Rk1l3j1k3Rl1l2k1k2 in two dimensions is presented, leading to an exhaustive list of its solutions. The set of 64 equations for 16 unknowns was first reduced by hand to several subcases which were then solved by computer using the Gröbner-basis methods. Each solution was then transformed into a canonical form (based on the various trace matrices of R) for final elimination of duplicates and subcases. If we use homogeneous parametrization the solutions can be combined into 23 distinct cases, modulo the well-known C, P, and T reflections, and rotations and scalings R̃=κ(Q⊗Q)R(Q⊗Q)−1.
A detailed analysis of the constant quantum Yang–Baxter equation Rk1k2j1j2 Rl1k3k1j3Rl2l3k2k3= Rk2k3j2j3 Rk1l3j1k3Rl1l2k1k2 in two dimensions is presented, leading to an exhaustive list of its solutions. The set of 64 equations for 16 unknowns was first reduced by hand to several subcases which were then solved by computer using the Gröbner-basis methods. Each solution was then transformed into a canonical form (based on the various trace matrices of R) for final elimination of duplicates and subcases. If we use homogeneous parametrization the solutions can be combined into 23 distinct cases, modulo the well-known C, P, and T reflections, and rotations and scalings R̃=κ(Q⊗Q)R(Q⊗Q)−1.
In this article we present all nonsingular upper triangular solutions to the constant quantum Yang-Baxter equation R j1j2 k1k2 R k1j3 l1k3 R k2k3 l2l3 = R j2j3 k2k3 R j1k3 k1l3 R k1k2 l1l2 in the three-state case. The upper triangular ansatz implies 729 equations for 45 variables. Fortunately, many of the equations turned out to be simple, allowing us to start breaking the problem into smaller ones. In the end we had a total of 552 solutions, but many of them were either inherited from two-state solutions or subcases of others. The final list contains 35 nontrivial solutions, most of them new.
The Yang-Baxter Equation (YBE) plays a crucial role for studying integrable many-body quantum systems. Many known YBE solutions provide various examples ranging from quantum spin chains to superconducting systems. Models of solvable statistical mechanics and their avatars are also based on YBE. Therefore, new solutions of the YBE could be used to construct new interesting 1D quantum or 2D classical systems with many other far-reaching applications. In this work, we attempt to find (almost) exhaustive set of solutions for the YBE in the lowest dimensions corresponding to a two-qubit case. We develop an algorithm, which can potentially be used for generating new higher-dimensional solutions of the YBE.
Abstract The formal derivatives of the Yang-Baxter equation with respect to its spectral parameters, evaluated at some fixed point of these parameters, provide us with two systems of differential equations. The derivatives of the R matrix elements, however, can be regarded as independent variables and eliminated from the systems, after which two systems of polynomial equations are obtained in place. In general, these polynomial systems have a non-zero Hilbert dimension, which means that not all elements of the R matrix can be fixed through them. Nonetheless, the remaining unknowns can be found by solving a few number of simple differential equations that arise as consistency conditions of the method. The branches of the solutions can also be easily analyzed by this method, which ensures the uniqueness and generality of the solutions. In this work we considered the Yang-Baxter equation for two-state systems, up to the eight-vertex model. This differential approach allowed us to solve the Yang-Baxter equation in a systematic way and also to completely classify its regular solutions.
We will present solutions to the constant Yang-Baxter equation, in any dimension n. More precisely, for any n, we will create an infinite family of n2 by n2 matrices which are solutions to the constant Yang-Baxter equation. The total number of non-vanishing entries of such a matrix is 4n2 for n even, and 4(n−1)(n)+1 for n odd. We will also present the unitary conditions for those matrices. Moreover, we discuss the entangling property of those matrices.
Multiple equations in math, physics, quantum information, and elsewhere are referred to as "the" Yang-Baxter equation, in spite of being a broad family of equations. Most of the equations are nonlinear matrix equations, where the unknown variable is a matrix. This is the case for the so called braided, algebraic, and generalized forms of "the" equation, which are the primary focus of this dissertation. Finding solutions to the various forms of these equations has been the subject of much research. The equations in all their forms are largely considered intractable in high dimensions, and only in dimension 2 have the solutions been fully classified. We begin with an introduction to quantum computation, with a focus on the topological model and its connection to the braid group. Next, we introduce the braided, algebraic, and generalized forms of "the" Yang-Baxter equation. We provide a full classification of diagonal solutions to each form. In particular, we show that any diagonal matrix is a solution to the algebraic form in any dimension, and each instance of the braided and generalized forms only have diagonal solutions that are scalar multiples of the identity. We exploit the relationship between the algebraic and braided forms to construct a solution in any dimension that is applicable to topological quantum computation as a universal gate. The generalized form of the equation is parameterized by three natural numbers, (d,m,l), and we show that the only invertible solutions when l ≥ m are scalar multiples of the identity. We completely classify all solutions arising from an X-shaped ansatz for five different choices of (d,m,l), and provide a complete classification of X-shaped solutions to every odd dimensional braided equation, where there are no X-shaped solutions in any dimension. We fully classify permutation solutions to each instance of the braided and algebraic equations that can be written as a product of 3 or fewer transpositions. We show that the problem of classifying all invertible upper triangular solutions to the 4-dimensional algebraic Yang-Baxter equation can be split into 48 cases, and fully classify one of the cases.
Trace Reductions of RLLL=LLLR
From this chapter onwards, we turn to applications of the 3D structures. The tetrahedron equation RLLL=LLLR can be composed n times in various directions. By tracing out a part of the spaces appropriately, it reduces to the Yang–Baxter equation among the remaining objects. The prescription, which we call the trace reduction, generates infinitely many solutions to the Yang–Baxter equation labeled with n in a matrix product form. In this chapter we demonstrate the method using the 3D R and 3D L in Sect. 3.5.2 . The resulting solutions to the Yang–Baxter equation are trigonometric. They are identified with the quantum R matrices for the symmetric and the anti-symmetric tensor representations of U±q−1(An−1(1)) . The cyclicity of the trace is reflected in the Dynkin diagram of the affine Lie algebra An−1(1) . The matrix product formula of the quantum R matrices naturally leads to an interpretation of the commuting transfer matrix of m×n layer either as the one for a Uq−1(An−1(1)) vertex model with size m or a Uq−1(Am−1(1)) vertex model with size n.