The Operator Tensor Formulation of Quantum Theory

Understand

A typical quantum experiment has a bunch of apparatuses placed so that quantum systems can pass between them.

• We regard each use of an apparatus, along with some given outcome on the apparatus (a certain detector click or a certain meter reading for example), as an operation.
• An operation can have zero or more quantum systems inputted into it and zero or more quantum systems outputted from it.
• We can wire together operations to form circuits.