Why isn't this a way to transfer information faster than light using quantum entanglement?

Question

Suppose Alice and Bob have entangled particles A and B that are very far apart. Alice uses Particle A to send information through its spin along the x axis, and Bob uses Particle B to receive this information.

To start, Alice measures Particle A's spin perpendicular to the x axis:

and continually measures it along axes that gradually closer to the desired spin state along the x axis. The more measurements taken to get to the desired state, the better, since that reduces the chance of an error occurring at some point.

Once Alice has reached the desired spin state for Particle A, Bob measures the spin of Particle B.

The images I've given show Particle A being measured with spin to the right, then being rotated counterclockwise, but it doesn't always have to be like this. It could be measured with spin left or right and rotated clockwise or counterclockwise, depending on whether Alice wants to set it to up or down.

This process is repeated at regular intervals so that Alice and Bob can make measurements at the right time without communicating, and there are other pairs of entangled particles in case some of them do get misaligned.

Ignoring the logistics of actually setting up a system like this, what keeps this from working?

Comments in this answer to another thought experiment said that quantum entanglement doesn't last that long. Is that why this system fails too?

Answer 1

Once you measure an entangled state, the "entangledness" gets destroyed and they start behaving like regular spin particles. This is one of the biggest impediments in building quantum computers; they rely heavily on entangled states and a stray photon or something can accidentally cause one of the particles in the quantum computer to get measured which thus destroys the quantum state.

Answer 2

There is a fatal flaw in your reasoning.

You begin by having Alice measure the spin in the horizontal direction. But she cannot force it to go to the right. Maybe it went to the left ! Impossible to predict which way it went.

Now she starts turning it counterclockwise. You assume it turned to point up, but maybe it turned to point down. Then she measures on the vertical axis. She was able to choose which direction it turned, and by what amount . But since she can't choose where it started from, she can't choose which vertical direction it will be measured. Hence no possibility to send a signal to Bob faster than light.