So far you learned how to express a single qubit state in the braket notation and its representation on the Bloch sphere. In this video, David will explain how these concepts extend to two and multiple qubit systems.

• A two-qubit state can be represented in a four dimensional basis, i.e. with a set of four complex numbers.
• Only six real parameters are needed to uniquely specify a two-qubit
• One can construct a basis for the two-qubit space by combining an orthonormal basis from each single qubit space
• An n qubit register can be in a linear superposition of  2ⁿ states