Frauchiger & Renner / newby question

Jun 2019
1
0
I am trying to understand Frauchiger & Renner's (2018) paper but it's been thirty years since I studies quantum physics at college.

There's one step I just can't get.

Fbar gets tails, and Wbar gets the result OK. Why?

Wbar is measuring the state of Fbar's lab against a basis that is the subtraction: (wave function for heads) - (wave function for tails).
So if Fbar gets tails, I expected Wbar to get fail.
Probably I don't understand what it means to use a basis that subtracts one wave function from another.

I am sure this must be a dumb question, but can anyone help me?

Reference
"Quantum theory cannot consistently describe the use of itself"
Daniela Frauchiger & Renato Renner
DOI 10.1038/s41467-018-05739-8
Nature Communications
 

topsquark

Forum Staff
Apr 2008
2,936
611
On the dance floor, baby!
I am trying to understand Frauchiger & Renner's (2018) paper but it's been thirty years since I studies quantum physics at college.

There's one step I just can't get.

Fbar gets tails, and Wbar gets the result OK. Why?

Wbar is measuring the state of Fbar's lab against a basis that is the subtraction: (wave function for heads) - (wave function for tails).
So if Fbar gets tails, I expected Wbar to get fail.
Probably I don't understand what it means to use a basis that subtracts one wave function from another.

I am sure this must be a dumb question, but can anyone help me?

Reference
"Quantum theory cannot consistently describe the use of itself"
Daniela Frauchiger & Renato Renner
DOI 10.1038/s41467-018-05739-8
Nature Communications
Unless I've missed it I have no access to this paper. Please either post a copy or describe the system you are refering to.

-Dan
 
Oct 2017
536
256
Glasgow
I downloaded a copy, so ill read it tonight and provide some feedback. However, I'm not really an expert in QM (I only understand basic University level QM)
 
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topsquark

Forum Staff
Apr 2008
2,936
611
On the dance floor, baby!
I downloaded a copy, so ill read it tonight and provide some feedback. However, I'm not really an expert in QM (I only understand basic University level QM)
Really? Could you send me the link? I couldn't find it online. (Probably hidden in plain sight, knowing me. I'm terrible at web searches.)

-Dan