swap test added

Author: mrtkp9993

README.md

@@ -74,6 +74,12 @@ Scheme for find the period `r` for `f(x) = 2^x mod 15`:
 
 ![Shor's Algorithm](./circuit_diagrams/07_shors_algorithm.png)
 
+### Swap Test
+
+> Task. For given two unknown quantum states, determine how much them differs.
+
+![Swap test](./circuit_diagrams/c1_swap_test.png)
+
 ## References
 
 - [Jonahtan Hui, Quantum Computing Series, Medium](https://medium.com/@jonathan_hui/qc-quantum-computing-series-10ddd7977abd)

c1_Swap_test.py

@@ -0,0 +1,41 @@
+'''
+    Swap Test
+
+    Task. For given two unknown quantum states, determine how much them differs.
+
+'''
+from qiskit import IBMQ, BasicAer
+from qiskit import QuantumCircuit, ClassicalRegister, QuantumRegister, execute
+
+qr = QuantumRegister(3)  # Initialize qubits
+cr = ClassicalRegister(1)  # Initialize bits for record measurements
+circuit = QuantumCircuit(qr, cr)
+
+# Our 'unknown' states
+circuit.x(qr[1])
+
+circuit.barrier()
+
+# Swap test
+circuit.h(qr[2])
+circuit.cswap(qr[2], qr[0], qr[1])
+circuit.h(qr[2])
+
+circuit.barrier()
+
+# Measure
+circuit.measure(qr[2], cr[0])
+''' If unknown states are: 
+    * Orthogonal, then 0 is measured with probability 50%;
+    * Equal, then 0 is measured with probability 100%.
+'''
+
+# Run our circuit with local simulator
+backend = BasicAer.get_backend('qasm_simulator')
+shots = 1024
+results = execute(circuit, backend=backend, shots=shots).result()
+answer = results.get_counts()
+print(answer)
+# Since our states are orthogonal (qr[0] = |0>, qr[1] = |1>)
+# 0 is observed with probability approx. 50%  and
+# 1 is observed with probability approx. 50%.