Introduction
Interested in learning how to program quantum computers? Then check out our Qiskit textbook Introduction to Quantum Computing with Qiskit.
In this tutorial we will explore the effects of T2 dephasing on IBM quantum computers in Qiskit.
What is T2 dephasing time?
Also known as T2 dephasing time this is where a qubits state dephases from either |+〉or |-〉to a mixture of phases such that the phase cannot be accurately predicted. For example if our initial state is |+〉then the state may decay to a mixture of |+〉and |-〉due to T2 dephasing.
The effects of T2 dephasing can be seen very easily with the following steps:
Put the qubit in to superposition using a Hadamard gate
Add a delay to the circuit
Bring the qubit out of superposition using another Hadamard gate
Measure the qubits state
The longer the delay the more measurements there will be for |1〉 due to dephasing.
Implementation
In Qiskit T2 dephasing can be observed very easily by with the following steps:
Step 1: Initialise the quantum and classical registers
The first step is to initialise the registers. Our circuit will consist of two registers. A quantum register that holds our qubit and a classical register that holds the bit used to hold the qubits state.
In Qiskit the registers can be initialized using the following code: