Time evolution realized by Trotter decomposition

Author: ls-iastu

examples/timeevolution_trotter.py

@@ -0,0 +1,47 @@
+"""
+Time evolution of Heisenberg model realized by Trotter decomposition
+"""
+
+import numpy as np
+import tensorcircuit as tc
+
+K = tc.set_backend("tensorflow")
+tc.set_dtype("complex128")
+
+xx = tc.gates._xx_matrix
+yy = tc.gates._yy_matrix
+zz = tc.gates._zz_matrix
+
+nqubit = 4
+t = 1.0
+tau = 0.1
+
+
+def Trotter_step_unitary(input_state, tau, nqubit):
+    c = tc.Circuit(nqubit, inputs=input_state)
+    for i in range(nqubit - 1):  ### U_zz
+        c.exp1(i, i + 1, theta=tau, unitary=zz)
+    for i in range(nqubit - 1):  ### U_yy
+        c.exp1(i, i + 1, theta=tau, unitary=yy)
+    for i in range(nqubit - 1):  ### U_xx
+        c.exp1(i, i + 1, theta=tau, unitary=xx)
+    TSUstate = c.state()  ### return state U(τ)|ψ_i>
+    z0 = c.expectation_ps(z=[0])
+    return TSUstate, z0
+
+
+TSU_vmap = tc.backend.jit(
+    tc.backend.vmap(
+        Trotter_step_unitary,
+        vectorized_argnums=0,
+    )
+)
+
+ninput = 2
+input_state = np.zeros((ninput, 2 ** nqubit))
+input_state[0, 0] = 1.0
+input_state[1, -1] = 1.0
+
+for _ in range(int(t / tau)):
+    input_state, z0 = TSU_vmap(input_state, tau, nqubit)
+    print("z: ", z0)