add analogcircuit example

Author: refraction-ray

examples/analog_rydberg.py

@@ -0,0 +1,53 @@
+"""
+Analog circuit simulation for Rydberg array
+"""
+
+import numpy as np
+import tensorcircuit as tc
+
+K = tc.set_backend("jax")
+tc.set_dtype("complex128")
+
+# Define simulation parameters
+# a compatible set of units: mus, mum, MHz
+nqubits = 12
+omega = 2.0 * np.pi
+delta = 0.0
+c6 = 8e8
+evolution_time = 2.0
+
+# Define the 1D lattice
+chain = tc.templates.lattice.ChainLattice([nqubits], lattice_constant=10, pbc=False)
+
+# Instantiate the AnalogCircuit
+ac = tc.AnalogCircuit(nqubits)
+
+# 1. Create the sparsely excited state
+ac.x([i for i in range(nqubits) if i % 4 == 0])
+
+rydberg_hmatrix = tc.templates.hamiltonians.rydberg_hamiltonian(
+    chain, omega=omega, delta=delta, c6=c6
+)
+
+
+# 2. Define the time-dependent Rydberg Hamiltonian
+def rydberg_hamiltonian_func(t):
+    # In this example, the Hamiltonian is time-independent, but it could be a function of t
+    return rydberg_hmatrix
+
+
+# 3. Add the analog evolution block
+ac.add_analog_block(rydberg_hamiltonian_func, time=evolution_time)
+
+# 4. apply some digital gates if needed, say for random measurements
+
+# for i in range(nqubits):
+#     j = np.random.choice(3)
+#     if j == 1:
+#         ac.h(i)
+#     elif j == 2:
+#         ac.rx(i, theta=-np.pi/4)
+
+# 5. Sample from the final state in the computational basis
+sample = ac.sample(batch=1024, allow_state=True, format="count_dict_bin")
+print("\nSampled bitstrings:\n", sample)

tests/test_analogcircuit.py

@@ -146,6 +146,7 @@ def hamiltonian(t):
 
         ac.add_analog_block(hamiltonian, [1.0, 2.3])
         # jaxodeint somehow incompatible with h0 outside hamiltonian function
+        # https://github.com/jax-ml/jax/issues/31792
         ac.cx(1, 0)
         return tc.backend.real(ac.expectation_ps(z=[1]))