Superluminal communication: Difference between revisions
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===A communication system using quantum entanglement=== |
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A(lice) and B(ob) are measuring corresponding particles from pairs of quantum mechanically entangled photons - so-called Bell-couples. |
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The distance between the transmitter and the source are suitably much shorter than between the source and the receiver, so with synchronized watches the transmitter will detect its twin particle before the other twin reaches the receiver. |
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The transmitter can change its measuring setup by inserting a mirror or not – choice situation, T (1) or T (0). It keeps its choice for an agreed period – for instance 1 / 300.000 sec. |
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The receiver has a fixed preset setup. It should by measuring its part of the pairs with at least 99% probability, guess the Transmitters choice. |
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As the exchange between the entangled particles takes place instantaneous it will for a growing distance between A and B create superluminal communication. |
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How the transmitter and the receiver should be building up is still to discussion. [[User:UChr|UChr]] ([[User talk:UChr|talk]]) 19:32, 25 May 2011 (UTC) |
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==References== |
==References== |
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Revision as of 19:32, 25 May 2011
Superluminal communication is the term used to describe the hypothetical process by which one might send information at faster-than-light (FTL) speeds.
Some theories and experiments include:
- Group velocity > c experiments
- Evanescent wave coupling
- Tachyons
- Quantum non-locality
According to the currently accepted theory, three of those four phenomena do not produce superluminal communication, even though they may give that appearance under some conditions. As for tachyons, their existence remains hypothetical; even if their existence were to be proven, attempts to quantize them appear to indicate that they may not be used for superluminal communication, because experiments to produce or absorb tachyons cannot be fully controlled.[1]
If wormholes are possible, then ordinary subluminal methods of communication could be sent through them to achieve superluminal transmission speeds. Considering the immense energy that current theories suggest would be required to open a wormhole large enough to pass spacecraft through it may be that only atomic-scale wormholes would be practical to build, limiting their use solely to information transmission. Some theories of wormhole formation would prevent them from ever becoming "timeholes", allowing superluminal communication without the additional complication of allowing communication with the past.[citation needed]
The no cloning theorem prevents superluminal communication via quantum cloning. However, this does not in itself prevent faster-than-light or superluminal communication, since it is not the only proposed method of such communication [1]. But, consider the EPR thought experiment, and suppose quantum states could be cloned. Alice could send bits to Bob in the following way:
If Alice wishes to transmit a '0', she measures the spin of her electron in the z direction, collapsing Bob's state to either |z+>B or |z->B. If Alice wishes to transmit a '1', she measures the spin of her electron in the x direction, collapsing Bob's state to either |x+>B or |x->B. Bob creates many copies of his electron's state, and measures the spin of each copy in the z direction. If Alice transmitted a '0', all his measurements will produce the same result; otherwise, his measurements will be split evenly between +1/2 and -1/2. This would allow Alice and Bob to communicate across space-like separations, potentially violating causality. But violation of causality is not sufficient as proof of no superluminal communication. So superluminal communication remains an open issue.[2]
A communication system using quantum entanglement
A(lice) and B(ob) are measuring corresponding particles from pairs of quantum mechanically entangled photons - so-called Bell-couples.
The distance between the transmitter and the source are suitably much shorter than between the source and the receiver, so with synchronized watches the transmitter will detect its twin particle before the other twin reaches the receiver.
The transmitter can change its measuring setup by inserting a mirror or not – choice situation, T (1) or T (0). It keeps its choice for an agreed period – for instance 1 / 300.000 sec.
The receiver has a fixed preset setup. It should by measuring its part of the pairs with at least 99% probability, guess the Transmitters choice.
As the exchange between the entangled particles takes place instantaneous it will for a growing distance between A and B create superluminal communication.
How the transmitter and the receiver should be building up is still to discussion. UChr (talk) 19:32, 25 May 2011 (UTC)
References
- ^ Feinberg, Gerald (1967). "Possibility of Faster-Than-Light Particles". Physical Review. 159 (5): 1089–1105. doi:10.1103/PhysRev.159.1089.
- ^
Jensen, Raymond (2006). "Is Faster-than-Light Communication Possible?" (PDF). Space Technology and Applications International Forum (STAIF-2006). AIP Conference Proceedings 813. pp. 1409–1414. ISBN 0735403058.
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