Visualizing the Invisible Qubit Phase
Explore the concept of qubit phase and how it influences quantum states. Understand how to visualize phases using simulators and mathematical descriptions on the Bloch sphere. This lesson helps you grasp the significance of positive and negative amplitudes, rotation gates, and how phase differences impact measurement probabilities in quantum computing.
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The phase of a qubit is the decisive factor when we work with amplitudes. Even though we can’t measure the phase directly, it’s not invisible. We can use our simulator to visualize it. We can also use math to describe it precisely.
States with positive amplitudes
When we look at the Bloch sphere, states with a positive amplitude reside at the front-side of the X-axes and Z-axes.
States with negative amplitudes
By contrast, states with a negative amplitude reside at the back-side of the Bloch sphere.
States spanned by theta
Let’s consider some simple states first. If we rotate the qubit state vector around the Y-axis by the angle ...