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 Post subject: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 1:57 am 
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Scientists have for some years been able to 'teleport' quantum states from one place to another. Now Seth Lloyd and his MIT team say that, using the same principles and a further strange quantum effect known as 'postselection', it should be possible to do the same backwards in time. Lloyd told the Technology Review: "It is possible for particles (and, in principle, people) to tunnel from the future to the past."

Postselection is a vital part of the nascent science of quantum computing. In traditional computing, if a user needs to determine which set of variables in an equation leads to the answer being true, the computer must try every combination until it hits upon one that works. In quantum computing, due to the weird parallel behaviour of subatomic particles, it seems to be possible to simplify the procedure by running all possible variations simultaneously, and selecting only the combinations that make the answer true.

Professor Lloyd and his team say that, by combining teleportation and postselection, it would be possible to carry out the quantum teleportation effect in reverse; that is, to decide after the teleportation what the quantum state must have been before it. This works as postselection allows you to dictate which quantum states can be teleported, limiting what state it can have been in before the teleportation. The state of the particle post-teleportation has therefore, in effect, travelled back in time.

Dr Richard Low, a quantum computing scientist from the University of Bristol, says: "You could think of it as postselection affecting the history of the particle, sending the state back in time."

Unlike previous theories of teleportation, this apparently avoids the "grandfather paradox" - or, to Back to the Future fans, the Marty McFly problem. If you go back and change time, and accidentally end up killing your own grandparent, you create a paradox - you will not be born, so you cannot go back and affect time. Even with subatomic particles, this is still a problem: upon travelling back in time, the particle could somehow destroy its earlier self or move it, thus preventing it from travelling.

However, because of the probabilistic nature of quantum mechanics, Prof Lloyd's method seems to avoid this. Anything caused by the time travel must have had a finite probability of happening anyway, so paradoxical impossibilities are out.

Further, this time travel method does not involve bending spacetime, unlike other proposed systems. At the moment, the only conditions known that would bend spacetime sufficiently exist in black holes, which would be impractical at best.

http://www.telegraph.co.uk/science/7904 ... ravel.html

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 2:37 am 
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What, like this???
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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 3:16 pm 
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I miss paradox, I was really GOOD at it :(

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 4:23 pm 
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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 4:24 pm 
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No, wait, you said paraDOX.... :DOH!

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 4:26 pm 
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I have this album :shock:

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 4:26 pm 
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aussie_aussie_oi_oi wrote:
Scientists have for some years been able to 'teleport' quantum states from one place to another. Now Seth Lloyd and his MIT team say that, using the same principles and a further strange quantum effect known as 'postselection', it should be possible to do the same backwards in time. Lloyd told the Technology Review: "It is possible for particles (and, in principle, people) to tunnel from the future to the past."
Even if this is possible, we couldn't travel more than perhaps a few seconds back, for security reasons. Before we can travel both ways in time (which I'm confident will never ever happen[*]) time travel is out of the question.

Yay! I just went back 10 seconds!!!!!

---------------------------
[*] The future doesn't exist.

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 4:30 pm 
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The future is not set, there is no fate but what we make! :fyi:

That being said, time travel into the future IS possible.....the current rate is one second per second.....and if we could figure out a way to travel at about 3/4 the speed of light, we could travel into the future at a much faster rate. Everyone who has studied Relativity Theory has heard of the 'twins paradox'

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 6:19 pm 
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Doom wrote:
The future is not set, there is no fate but what we make! :fyi:

John? Is that you?

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 6:20 pm 
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I was betting on this: http://www.youtube.com/watch?v=1lrjs7eq2JI (NAR)

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Sun Jul 25, 2010 10:13 pm 
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Greetings:

My wife needs this:knowing what dress to take back,and not missing the sale price.

by(e)carg

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Mon Jul 26, 2010 8:26 am 
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I happen to know that this is possible and already happens. I watch Dr. Who.

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 Post subject: Re: Quantum time machine 'allows paradox-free time travel'
PostPosted: Mon Jul 26, 2010 8:59 am 
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I grow weary of the snake oil claims made by quantum physicists hawking their latest-and-greatest theory du jour. :?

In other words, *yawn*, call me when you've actually done something.

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