# The Two-State Vector Formalism

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1. Sep 28, 2015

### Hybrid

Within Two-state vector formalism is the universe probabilistic or determined?
I have read into this interpretation, but I cannot figure out which.
Thanks guys

https://en.wikipedia.org/wiki/Two-state_vector_formalism
http://www.tau.ac.il/~yakir/yahp/yh165.pdf
http://www.tau.ac.il/~vaidman/lvhp/m108.pdf
http://arxiv.org/pdf/0706.1347v1.pdf
http://arxiv.org/pdf/quant-ph/0105101v2.pdf
http://arxiv.org/pdf/1406.6382v1.pdf
http://philsci-archive.pitt.edu/4396/1/vaidman_paper_jb_3rd_edit.pdf

2. Sep 28, 2015

### stevendaryl

Staff Emeritus
Well, in your second reference, equation 13.9 clearly gives probabilities for measurement results.

3. Sep 28, 2015

### Hybrid

Thanks I picked up on that as well, however it's irritating to me that the author's didn't just come out and state if it's a realist interpretation or indeterminate. Although it does seem as though retro-causality would imply in-determinism.

4. Jan 12, 2016

### Agrippa

The universe is deterministic according to the TSVF. Both the forwards and backwards evolving wave function evolve in accord with deterministic laws. Since both wave functions come together to constitute reality, reality will "seem" probabilistic if you don't know the backwards evolving wave function.

5. Jan 12, 2016

### atyy

As I understand it, the two-state vector formalism is Copenhagen. The formalism is not a new interpretation, but a re-packaging of Copenhagen to make certain calculations more intuitive. In particular, the formalism is not an interpretation because it does not aim to solve (or dissolve) the measurement problem, unlike real attempts at interpretation such as MWI, BM and Consistent Histories.

6. Jan 12, 2016

### Hybrid

Yes, and I'm aware of this as I've already looked it, although their view of determinism isn't so cut and dry, and leaves much to be desired. They used weak measurements to come to this conclusion which are questionable at best. (http://motls.blogspot.com/2012/09/pseudoscience-hiding-behind-weak.html)

Also I found this tidbit of information perusing around the internet interesting -

"Charles Bennett of IBM’s research laboratories in Yorktown Heights, New York, a specialist on quantum information theory, is not convinced. For a start, he sees the TSVF as only one way of looking at the results. “People in quantum foundations are often so wedded to their own interpretation or formalism that they say it is the only reasonable one, when in fact quantum mechanics admits multiple interpretations, which except for a few outliers are entirely equivalent to one another. The differences are aesthetic and philosophical, not scientific.”

Bennett believes that the findings can be interpreted without any apparent ‘backwards causation’, so that the authors are erecting a straw man. “To make their straw man seem stronger, they use language that in my opinion obscures the crucial difference between communication and correlation. They say that the initial weak measurement outcomes anticipate the experimenter's future choice but that doing so causes no violation of causality because the anticipation is encrypted.” But he thinks this is a bit like an experiment in quantum cryptography in which the sender sends the receiver the decryption key before sending (or even deciding on) the message, and then claims that the key is somehow an ‘anticipation’ of the message. With this in mind, it is not clear whether even an experiment will resolve the issue, since it would come down to a matter of how to interpret the results."

Point being that this is not actual determinism, it's still inherently indeterministic.

Yes, I agree.

After evaluating all the interpretations of quantum mechanics indeterministic consistent histories makes the most sense of things.

Last edited: Jan 12, 2016