Yesterday everything was normal until about 3:30pm.

Then the storm moved in and left us without power.

I have posted yesterday's recording just now.

Below, a summary of the first 30 pages in Terry's book.

The behavior of the NOT gate should be clear:

This is the definition of the control-NOT gate, a two qubit gate:

Two NOT gates in sequence leave the original input unchanged:

The behavior of the PETE box should also be clear:

Here we show that happens if we look at what comes out of a PETE box.

Pete is Pete Shadbolt, the gate is otherwise known as the Hadamard gate.

Two PETE boxes in sequence leave the original input unchanged,

The PETE box with a white ball in its input creates a plus state (a misty state).

The PETE box with a black ball in its input creates a minus state (also a misty state).

Recall our rule: NOT of a superposition of states is the superposition of NOT applied to each state.

This is how the PETE box works on a misty state presented in its input.

The rule is the same: PETE applied to a superposition of states is the superposition of H applied to each state.

So if we don't look we recover the input with a PETE box just like we do with a NOT.

What is the circuit on the left? Can you build it in Qiskit? On the right we have a misty state applied to a C-NOT.

And this is just an exercise producing an entangled state.

Now can you prove this?