Simple Quantum Circuits to Understand Multiple Qubit States
Quantum Circuits and Bloch Sphere
Previously I have described about building simple quantum circuits and thinking quantum gates as matrix operators. Also using superposition of qubits, we learnt to how to create entangled states. If you suddenly find yourself here in this post without reading the previous two posts, it may be little difficult to follow along. Before diving deep into an important concept known as ‘Phase Kickback’, in this post I will describe various quantum circuits and how to build intuition to get started with multiple qubits and quantum gates. Since Bloch Sphere is often used to visualize quantum states, we will also learn how to visualize and understand the quantum states. Let’s get in !!
1st Circuit:
In the last post I have described how to create entangled state using one Hadamard gate and one CNOT (CX) gate. First we create a superposition state by applying the Hadamard gate, then we apply the CX gate. Instead of using one Hadamard gate what happens if we apply 2 Hadamard gates? Let’s first build the circuit —
import qiskit as q
import matplotlib.pyplot as pltqr = q.QuantumRegister(2)
cr = q.ClassicalRegister(2)circuit = q.QuantumCircuit(qr, cr)
