Quantum causal loops + Another step towards room temperature superconductivity

#1
C C Offline
Quantum casual loops
https://www.eurekalert.org/pub_releases/...020921.php

RELEASE: Causal reasoning is ubiquitous - from physics to medicine, economics and social sciences, as well as in everyday life. Whenever we press the button, the bell rings, and we think that the pressing of the button causes the bell to ring. Normally, causal influence is assumed to only go one way - from cause to effect - and never back from the effect to the cause: the ringing of the bell does not cause the pressing of the button that triggered it.

Now researchers from the University of Oxford and the Université libre de Bruxelles have developed a theory of causality in quantum theory, according to which cause-effect relations can sometimes form cycles. This theory offers a novel understanding of exotic processes in which events do not have a definite causal order. The study has been published in Nature Communications.

One of the ways in which quantum theory defies classical intuitions is by challenging our ideas of causality. Quantum entanglement can be used to produce correlations between distant experiments that are known to evade satisfactory causal explanations within the framework of classical causal models. Furthermore, a unification of quantum theory and gravity is expected to allow situations in which the causal structure of spacetime is subject to quantum indefiniteness, suggesting that events need not be causally ordered at all.

Recently, a team of researchers from Oxford and Brussels has developed a theory of causality in quantum theory, in which causal concepts are defined in intrinsically quantum terms rather than pertaining to an emergent classical level of measurement outcomes. This has offered, in particular, a causal understanding of the correlations produced by entangled states. Now, they have generalized the theory to allow causal influence to go in cycles, providing a causal understanding of processes with events in indefinite causal order.

"The key idea behind our proposal is that causal relations in quantum theory correspond to influence through so-called unitary transformations - these are the types of transformations that describe the evolutions of isolated quantum systems. This is closely analogous to an approach to classical causal models that assumes underlying determinism and situates causal relations in functional dependences between variables," says Jonathan Barrett from the University of Oxford.

The main idea of the new study is to apply the same principle to processes in which the order of operations can be dynamical or even indefinite, seeing as a large class of these processes can be understood as arising from unitary transformations, too, just not ones that unfold in an ordinary sequence.

"Previously, processes with indefinite causal order were typically regarded as simply incompatible with any causal account. Our work shows that a major class of them - those that can be understood as arising from unitary processes and which are believed to be the ones that could have a physical realisation in nature - could in fact be seen as having a definite causal structure, albeit one involving cycles," says Robin Lorenz, a corresponding author of the study.

"The idea of cyclic causal structures may seem counterintuitive, but the quantum process framework within which it is formulated guarantees that it is free of logical paradoxes, such as the possibility of going back in time and killing your younger self," explains Ognyan Oreshkov from the Université libre de Bruxelles. "Exotic as they appear, some of these scenarios are actually known to have experimental realisations in which the variables of interest are delocalized in time."

Does this mean that spacetime does not have the acyclic causal structure it is normally assumed to have? Not exactly, since in the mentioned experiments the events that are causally related in a cyclic fashion are not local in spacetime. However, the researchers believe that the causal structure of spacetime itself could become cyclic in this quantum way at the intersection of quantum theory and general relativity, where analogous processes to those realizable in the lab are expected, but with the events being local in their respective spacetime reference frames.


Physicists take another step towards room temperature superconductivity
https://massivesci.com/notes/room-temper...ty-carbon/

INTRO: In a recent study published in Nature, a group of physicists reported superconductivity at room temperature and extreme pressure by adding a third element — carbon — to Eremet’s original compound of hydrogen and sulfur. They chose to use carbon because its strong bonds could help keep a material together once the pressure is released as it does for diamond... (MORE)


https://www.youtube.com/watch?v=uMExoSVKhLE
Reply
#2
Syne Offline
(Feb 11, 2021 09:48 PM)C C Wrote: One of the ways in which quantum theory defies classical intuitions is by challenging our ideas of causality. Quantum entanglement can be used to produce correlations between distant experiments that are known to evade satisfactory causal explanations within the framework of classical causal models. Furthermore, a unification of quantum theory and gravity is expected to allow situations in which the causal structure of spacetime is subject to quantum indefiniteness, suggesting that events need not be causally ordered at all.

No, quantum theory only defies classical causality if you try to artificially and unjustifiably impose classical explanations on quantum behavior. Not having "satisfactory [classical] causal explanations" doesn't even vaguely imply reverse causality, much less causal loops.
Reply
#3
Ostronomos Online
(Feb 11, 2021 09:48 PM)C C Wrote: Quantum casual loops
https://www.eurekalert.org/pub_releases/...020921.php

RELEASE: Causal reasoning is ubiquitous - from physics to medicine, economics and social sciences, as well as in everyday life. Whenever we press the button, the bell rings, and we think that the pressing of the button causes the bell to ring. Normally, causal influence is assumed to only go one way - from cause to effect - and never back from the effect to the cause: the ringing of the bell does not cause the pressing of the button that triggered it.

Now researchers from the University of Oxford and the Université libre de Bruxelles have developed a theory of causality in quantum theory, according to which cause-effect relations can sometimes form cycles. This theory offers a novel understanding of exotic processes in which events do not have a definite causal order. The study has been published in Nature Communications.

One of the ways in which quantum theory defies classical intuitions is by challenging our ideas of causality. Quantum entanglement can be used to produce correlations between distant experiments that are known to evade satisfactory causal explanations within the framework of classical causal models. Furthermore, a unification of quantum theory and gravity is expected to allow situations in which the causal structure of spacetime is subject to quantum indefiniteness, suggesting that events need not be causally ordered at all.

Reality is reversed in time symmetry according to any insight I made while high in 2014.
Reply


Possibly Related Threads…
Thread Author Replies Views Last Post
  Anyons confirmed, quantum computing role + Quantum teleportation achieved C C 3 97 Dec 21, 2020 09:05 PM
Last Post: Zinjanthropos
  The quantum agent + Quantum dream time C C 0 141 Mar 8, 2020 09:13 PM
Last Post: C C
  Correlations can’t imply causation? Not so fast. A primer on causal networks C C 0 276 Oct 19, 2017 06:56 PM
Last Post: C C
  Rebuilding quantum theory + Dark energy from matter + Crossing quantum computer goal C C 2 612 Sep 8, 2017 01:29 AM
Last Post: RainbowUnicorn
  Chemists Are One Step Closer to Manipulating All Matter C C 0 390 May 11, 2017 07:01 PM
Last Post: C C
  Showing lack of causal order in quantum process + Rescuing electronics C C 3 670 Apr 17, 2017 07:14 AM
Last Post: RainbowUnicorn
  Is there room for hermeneutics in math? Leigha 4 543 Oct 7, 2016 12:54 AM
Last Post: Leigha
  Blurring Causal Lines C C 0 447 Mar 3, 2016 05:00 AM
Last Post: C C



Users browsing this thread: 1 Guest(s)