Question about entanglement and spacetime

[SchrodingersRat]

Hi everyone, this is my first post.

As anyone interested in physics I am somewhat familiar with the concept of entanglement. Also I have read that contrary to what most people think about this phenomenon, the particles involved are not always exactly synchronized but one can actually seem to be ahead of the other in time (time in the sense of what you measure with a clock). This would be hard to explain in a Newtonian-like formulation of physics but as they say this is not necessarily a problem with GR.

A question I have thought about regarding this, and one I am sure someone would have come up with an experiment to test, is how this effect changes with distance. That is, does the degree of de-synchronization compared to clocks increase linearly with distance? And are there other factors that can affect this behavior?

Also, is the de-synchronization different for every entangled particle pair or is there some form of correlation in every pair with roughly the same two positions? The first would seem to fit better with the rest of modern physics, but I my knowledge of QM is not that deep yet.

 

[PeroK]

Hi everyone, this is my first post.

As anyone interested in physics I am somewhat familiar with the concept of entanglement. Also I have read that contrary to what most people think about this phenomenon, the particles involved are not always exactly synchronized but one can actually seem to be ahead of the other in time (time in the sense of what you measure with a clock).

I have no idea what you mean by this. A system of particles in an entangled state is described by a single state that cannot be decomposed into a separate state for each particle.

 

[DrChinese]

Hi everyone, this is my first post.

A question I have thought about regarding this, and one I am sure someone would have come up with an experiment to test, is how this effect changes with distance. That is, does the degree of de-synchronization compared to clocks increase linearly with distance? And are there other factors that can affect this behavior?

Also, is the de-synchronization different for every entangled particle pair or is there some form of correlation in every pair with roughly the same two positions? The first would seem to fit better with the rest of modern physics, but I my knowledge of QM is not that deep yet.

Entangled systems are not "synchronized" as you imagine. They follow a set of rules that can be difficult to understand for the beginner. Generally: time and distance are not factors. Interaction with other quantum particles or systems is a factor. Entanglement can be full (maximal) or partial. Entanglement can occur on some bases (such as spin) but not on others (such as momentum). And entanglement can be between 2, 3, or more particles.

There are literally thousands of experiments in the canon on entanglement.

 

[PeterDonis]

Hi everyone, this is my first post.

Hi, and welcome to PF!

the particles involved are not always exactly synchronized but one can actually seem to be ahead of the other in time

It would help if you could give some specific references to where you have read this.

However, I suspect what you are referring to is descriptions of experiments on pairs of entangled particles in which measurements are made on the particles at spacelike separated events--that is, it would be impossible for a light signal to travel from one measurement to the other. For spacelike separated measurements, their time ordering is frame-dependent--they can happen at the same time in one frame, but in other frames measurement A can happen before measurement B, or measurement B can happen before measurement A.

What this means from a physics perspective is not that the particles or the measurements on them get "desynchronized", but that the time ordering of the measurements cannot matter--in other words, the measurement results cannot depend on the order in which the measurements are made. (In more technical language, physicists will say that the measurements must commute.) That puts strong constraints on the types of physical models that can match the experimental results.

 

[SchrodingersRat]

Hi, and welcome to PF!


It would help if you could give some specific references to where you have read this.

However, I suspect what you are referring to is descriptions of experiments on pairs of entangled particles in which measurements are made on the particles at spacelike separated events--that is, it would be impossible for a light signal to travel from one measurement to the other. For spacelike separated measurements, their time ordering is frame-dependent--they can happen at the same time in one frame, but in other frames measurement A can happen before measurement B, or measurement B can happen before measurement A.

What this means from a physics perspective is not that the particles or the measurements on them get "desynchronized", but that the time ordering of the measurements cannot matter--in other words, the measurement results cannot depend on the order in which the measurements are made. (In more technical language, physicists will say that the measurements must commute.) That puts strong constraints on the types of physical models that can match the experimental results.

I feel a bit stupid now, but I don´t remember where I read this except that it was on the internet. Are you saying that there is not desynchronization but rather that it is not possible to determine in which order the measurements were made? Also I know that there is a phenomenon referred to as time-like quantum entanglement, could you tell briefly how it works and how it relates to regular entanglement?

 

[PeroK]

I feel a bit stupid now, but I don´t remember where I read this except that it was on the internet. Are you saying that there is not desynchronization but rather that it is not possible to determine in which order the measurements were made? Also I know that there is a phenomenon referred to as time-like quantum entanglement, could you tell briefly how it works and how it relates to regular entanglement?

In Special Relativity there is no absolute time. In particular, there is no universal simultaneity. Events that happen in the same place have a definite order. Events may however be "spacelike" separated, which means they have no definite order. It makes no sense to say which one absolutely happened first.

 

[SchrodingersRat]

I know that you cannot measure absolute time in relativistic physics. But by desynchronization I mean what could be described as how close a "spacelike" separation is to being a "lightlike" separation.

 

[SchrodingersRat]

Actually I found an article that answered these questions nicely. I´m sorry for taking up people´s time.