Instantaneous Communications Using Entangled States

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Discussion Overview

The discussion revolves around the concept of instantaneous communication using entangled states in quantum mechanics. Participants explore the implications of entanglement on communication, particularly in the context of general relativity and the potential for faster-than-light messaging through quantum entanglement and measurement techniques.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether instantaneous communication could be achieved through time-shifted measurements of entangled particles, suggesting a scenario involving Alice and Bill where pre-measured states could allow for message transmission.
  • Another participant asserts that entanglement ceases with the first measurement, indicating that no further changes can maintain entanglement, thus challenging the feasibility of the proposed communication method.
  • There is a repeated emphasis that while two particles may remain entangled, the act of measurement disrupts this entanglement, which is a point of contention among participants.
  • Participants discuss the nature of the states of entangled particles, noting that while the relationship between particles can be known, the individual values are random, which complicates the idea of using entanglement for communication.

Areas of Agreement / Disagreement

Participants express disagreement regarding the implications of entanglement on communication. Some believe that entanglement can be utilized for instantaneous messaging, while others argue that measurement disrupts this possibility. The discussion remains unresolved with competing views on the nature of entanglement and its implications for communication.

Contextual Notes

Participants reference a book on entanglement, which appears to influence their understanding of the topic. There are unresolved assumptions about the nature of measurements and the conditions under which entanglement persists or ceases.

SkyLeach
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Hey all. I know it's been a long time since I have posted, but I just finished reading Entanglement: The Greatest Mystery in Physics, by Amir D. Aczel and I had a question concerning the conclusion of the work.

He made the claim that GR was not violated by entanglement since messages could not be transmitted due to the impossibility of predicting the spin of an entangled particle before measurement, and that after spin was detected you had to transmit the message of it's state via a conventional channel.

My question was if instantaneous communication could be achieved by using time-shifted measurement of states.

Let's say that Bill is on the Earth and Alice is traveling to Mars in a manned space capsule. Before launch sophisticated as-yet unrealized equipment to quickly measure the spin of entangled particles was installed with a few hundred or thousand entangled particles mated between matching equipment at Houston and in the spacecraft . Before launch, Bill measured the states of his particles, communicated the states to Alice, and Alice mesured her states and verified pairs of opposites. The equipment then continuously monitors the states of the pairs in both Bill and Alice's equpment. After Alice leaves Earth, bill needs to send her a message and does so by altering the states of his particles in a predertimined ordered fassion. Wouldn't Alice's mated pairs also alter states in a predictable fassion, or would the possible states to which they are altered not be deterministic? Obviously if this is possible QE could be used to transmit messages at infinite speed, eliminating the need for time delay in communications, interferrance, etc...
 
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No as the book indicates entanglement ends with the ‘first’ measurement by A or B, there is no changing of a state that remains entangled. Just one measure that ends that entanglement.
 
RandallB said:
No as the book indicates entanglement ends with the ‘first’ measurement by A or B, there is no changing of a state that remains entangled. Just one measure that ends that entanglement.
what about teleportation of states? The book also said that when two particles are entangled they are always entangled.
 
SkyLeach said:
The book also said that when two particles are entangled they are always entangled.
Until one measure ends that entanglement.(even if you don't see or record the measurement, if it hits something unlike a mirror - like the side of a container)
 
SkyLeach said:
what about teleportation of states? The book also said that when two particles are entangled they are always entangled.

The state is essentially the relationship of the particles... not the individual values themselves. So you can know the states are identical or orthogonal (as the case may be) but since the values themselves are random, it won't do much for you.
 

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