Implement clock model (#13)

* clock_model

* format and remove notebook junk

---------

Co-authored-by: dartsushi <[email protected]>

src/models/ising.jl

@@ -56,3 +56,21 @@ function classical_Potts(q::Int64, β::Float64)
     end
     return A_potts
 end
+
+function classical_Clock(q::Int64, β::Float64)
+    V = ℂ^q
+    A_clock = TensorMap(zeros, V ⊗ V ← V ⊗ V)
+    clock(i, j) = -cos(2π / q * (i - j))
+
+    for i in 1:q
+        for j in 1:q
+            for k in 1:q
+                for l in 1:q
+                    E = clock(i, j) + clock(j, k) + clock(k, l) + clock(l, i)
+                    A_clock[i, j, k, l] = exp(-β * E)
+                end
+            end
+        end
+    end
+    return A_clock
+end