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Re: [nanotech] Re: Quantum Computing

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  • eugene.leitl@lrz.uni-muenchen.de
    ... You can t signal faster than speed of light in a vacuum. It s not just a good idea, it s the law. So, how does FTL come into picture? Why FTL, and not,
    Message 1 of 17 , Jan 31, 2001
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      Bruce Bombere wrote:
      >
      > Magnet tunnel junctions!
      > So, FTL computing is in the works.

      You can't signal faster than speed of light in a vacuum.
      It's not just a good idea, it's the law. So, how does FTL
      come into picture? Why FTL, and not, say, aliens? Or banana
      daiquiris?
    • Andrew
      It s the law eh? Well then there are some people who should be brought up on charges and thrown into jail because they ve broken that law. Last summer a group
      Message 2 of 17 , Jan 31, 2001
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        It's the law eh?  Well then there are some people who should be brought up on charges and thrown into jail because they've broken that law.  Last summer a group of scientists, in Chicago I think, managed to accelerate a light particle faster than the speed of light.  The end result was that the particle was leaving the test chamber before it had finished entering it.  Check back four months ago in the nanotech archives.  We were talking about it for a while.  Personally I was quite amused at all the physicist who were craping their metaphorical pants at the implications of this experiment.
        Andrew

        eugene.leitl@...-muenchen.de wrote:

        Bruce Bombere wrote:
        >
        > Magnet tunnel junctions!
        >  So, FTL computing is in the works.

        You can't signal faster than speed of light in a vacuum.
        It's not just a good idea, it's the law. So, how does FTL
        come into picture? Why FTL, and not, say, aliens? Or banana
        daiquiris?
         


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        "Nanotechnology: solutions for the future."

      • Bruce Bombere
        ... Not that it matters, the distance involved in the magnetic tunnel junctions is not far. Repeal the Law of Gravity! Shop online without a credit card
        Message 3 of 17 , Feb 1, 2001
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          eugene.leitl@...-muenchen.de wrote:
          >
          > Bruce Bombere wrote:
          > >
          > > Magnet tunnel junctions!
          > > So, FTL computing is in the works.
          >
          > You can't signal faster than speed of light in a vacuum.
          > It's not just a good idea, it's the law. So, how does FTL
          > come into picture? Why FTL, and not, say, aliens? Or banana
          > daiquiris?
          >

          Not that it matters, the distance involved in the
          magnetic tunnel junctions is not far.

          Repeal the Law of Gravity!

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        • Bruce Bombere
          ... Marconi s transatlantic radio transmission experiment noted a pre-signal pulse that preceeded the main signal. Radio waves travel through ether, nicht ja?
          Message 4 of 17 , Feb 1, 2001
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            eugene.leitl@...-muenchen.de wrote:
            >
            > Bruce Bombere wrote:
            > >
            > > Magnet tunnel junctions!
            > > So, FTL computing is in the works.
            >
            > You can't signal faster than speed of light in a vacuum.
            > It's not just a good idea, it's the law. So, how does FTL
            > come into picture? Why FTL, and not, say, aliens? Or banana
            > daiquiris?
            >

            Marconi's transatlantic radio transmission experiment noted
            a pre-signal pulse that preceeded the main signal. Radio waves
            travel through ether, nicht ja?

            I think that Nimtz, et al, have also noted this frontal wave.

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          • Mark Gubrud
            No signal has ever been transmitted at a speed greater than the speed of light in vacuum. The experiment you re talking about is no exception. We did discuss
            Message 5 of 17 , Feb 1, 2001
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              No signal has ever been transmitted at a speed greater than the speed of
              light in vacuum. The experiment you're talking about is no exception. We
              did discuss this; apparently you were unable to comprehend the discussion.

              On Thu, 1 Feb 2001, Andrew wrote:

              > It's the law eh? Well then there are some people who should be brought
              > up on charges and thrown into jail because they've broken that law.
              > Last summer a group of scientists, in Chicago I think, managed to
              > accelerate a light particle faster than the speed of light. The end
              > result was that the particle was leaving the test chamber before it had
              > finished entering it. Check back four months ago in the nanotech
              > archives. We were talking about it for a while. Personally I was quite
              > amused at all the physicist who were craping their metaphorical pants at
              > the implications of this experiment.
              > Andrew
              >
              > eugene.leitl@...-muenchen.de wrote:
              >
              > > Bruce Bombere wrote:
              > > >
              > > > Magnet tunnel junctions!
              > > > So, FTL computing is in the works.
              > >
              > > You can't signal faster than speed of light in a vacuum.
              > > It's not just a good idea, it's the law. So, how does FTL
              > > come into picture? Why FTL, and not, say, aliens? Or banana
              > > daiquiris?
              > >
              > >
              > > Yahoo! Groups Sponsor
              >
              >
              > Do you know the name you want? Enter the domain name
              > below and press GO!
              > www. [Yahoo! Domains]
              >
              > >
              > > The Nanotechnology Industries mailing list.
              > > "Nanotechnology: solutions for the future."
              >
            • Bruce Bombere
              ... Yeah, but. My original semi-tongue in cheek observation was regarding computing using magnetic tunnel junctions. Not vacuum. Chandra Bose used
              Message 6 of 17 , Feb 1, 2001
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                Mark Gubrud wrote:
                >
                > No signal has ever been transmitted at a speed greater than the speed of
                > light in vacuum. The experiment you're talking about is no exception. We
                > did discuss this; apparently you were unable to comprehend the discussion.
                >

                Yeah, but. My original semi-tongue in cheek observation was
                regarding computing using "magnetic tunnel junctions."
                Not vacuum. Chandra Bose used dialectrics thusly years ago.

                http://www.compu-web.com/ftl.htm

                Superluminal tunneling (faster than light transmission of
                signals) was first observed at the University of Cologne
                with micro-wave photons. Soon thereafter these experiments
                were duplicated and validated at the University of Berkeley
                and Vienna.

                For theoretical physics the implication is that there exist
                spaces devoid of time.

                Prof. Dr. Nimtz present experiment takes it's inspiration
                from an experiment by Jagadis Chandra Bose, an Indian
                physicist born in 1858. Bose's successful public
                demonstration of remote signaling with radio waves in 1895
                predate Marconi's experiments by two years.

                In 1897 Bose carried out experiments with semiconductors at
                frequencies as high as 60 GHz and was in the opinion of Sir
                Neville Mott, Nobel Laureate in 1977, at least 60 years
                ahead of his time.

                The new experiment of Prof. Nimtz explores total internal
                reflection of micro waves inside a dielectric prism, and the
                effect and characteristics of a small air gap between two
                identical prisms.

                One known effect of quantum tunneling is the propagation of
                photons at speeds much faster than light.

                Prof. Nimtz explaining the tunneling effect on the
                dielectric prism. The modulation of the microwave is approx.
                1Ghz. and has a wavelength of 3cm. The gap between the
                prisms is 5cm, and tunneling takes place.

                Prof. Nimtz: "The waves enter on the left and are being
                reflected totally on the first wall. Only when the distance
                between the two prisms is not too great the can signal
                tunnel through the gap. It looks as if this gap here is the
                tunnel barrier.

                When we increase the gap the signal intensity received at
                the other end decreases. This has already been shown by Bose
                in 1897. But the time in which the signal traverses the
                tunnel has not been reliably measured until now."

                Speeds measured on this device exceeded 9x the speed of
                light, within the frame of reference of this tunnel. The
                speed is achieved by the staggered effect of repeated change
                from Perspex to air.

                Perspex to air. Bose 1897 diagram looks like the prism set-up
                that Nimtz uses.

                Anyway, any news of new carbon bonding methods or configurations?
                More unusual carbons? C82 metalo-bonding?

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              • Mark Gubrud
                No signals and no energy and no matter can propagate faster than c, the speed of light in vacuum. This fact is so fundamental that in theoretical work one
                Message 7 of 17 , Feb 2, 2001
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                  No signals and no energy and no matter can propagate faster than c, the
                  speed of light in vacuum. This fact is so fundamental that in theoretical
                  work one usually assigns the value c=1, i.e. c represents the conversion
                  constant between familiar units of time and space.

                  Claims of "faster than light" signaling or motion are always based on
                  smoke-and-mirrors physics. If you go out to the edges of what is known,
                  you can make speculations and hypotheses and no one can contradict you.
                  Alternatively, you can stick to what is known, but use verbal sleight of
                  hand to suggest what you do not claim outright.

                  If you want to claim that _something_ can move faster than light, it's
                  easy. There is no reason why you could not set the timers in a string
                  of blinking lights so that the blinking would appear to propagate down the
                  string at faster than c. This is not FTL signaling because the timers
                  were pre-set; everything was determined in advance rather than an actual
                  signal propagating down the string. Similarly, if the blades of a very
                  long scissors are closing, the point of intersection can move arbitrarily
                  fast. This is not FTL signaling again because everything was determined
                  in advance. If you tried to signal by squeezing and releasing the handle
                  of the scissors, the blades would bend and the motion would propagate down
                  the blades at the a velocity (much) less than c.

                  The two kinds of FTL claims that have come up recently both involve games
                  played with pulses of light. Basically, if you have a long pulse, and in
                  passing through a short apparatus it emerges with it's center "advanced"
                  relative to where it would be if it had traversed the same length of
                  vacuum, you can then claim that its velocity in the apparatus was greater,
                  perhaps much greater, than c. However, this is just a verbal game.

                  All pulse generators have limited bandwidth. This means that the pulse
                  will be made up only of frequencies in a limited band. A band-limited
                  pulse never has a definite beginning or end; rather, it typically has a
                  leading edge that begins with an exponential buildup, followed by a region
                  of roughly linear slope, followed by a flattening. There is a peak or a
                  broad plateau around the center of the pulse. The the trailing edge,
                  typically a mirror image of the leading edge, ending in an exponential
                  decay to zero. Like this:

                  *******
                  ***** *****
                  ** **
                  * *
                  * *
                  ** *
                  ***** *****
                  ********* ****************

                  Shifting such a pulse forward is a simple matter of amplifying the leading
                  edge and attenuating the trailing edge. There are a lot of ways this can
                  be done without seeming to force it too much. You can make an amplifier
                  powered by a battery that runs down as the pulse runs through it. That is
                  essentially what was done in the experiment with the cesium cell which had
                  been pumped to a high-energy state, so that the weak signal at the leading
                  edge of the pulse caused the cesium to emit light like a laser, and thus
                  fall to its low-energy state, so that it then absorbed light from the
                  trailing edge.

                  In the tunneling experiments, the entire pulse is attenuated, but the
                  leading parts are attenuated less than the remainder, so that again the
                  center of the pulse is shifted forward.

                  Why isn't this forward-shifting really faster than light propagation?
                  Because the actual signal does not arrive any sooner than it would have
                  anyway. But we have to say what this means. If the pulse does not have
                  any definite beginning, when exactly does it arrive? If we are interested
                  in detecting the signal as soon as possible, the answer is not necessarily
                  the center of the pulse. We could set some threshold, say, half way up
                  the slope, and have our detector tell us the signal has arrived when that
                  threshold is reached. If we set the threshold lower, we'll get the
                  signal sooner. But we also have to consider the presence of noise. We
                  can always reach our threshold of detection sooner if we just amplify the
                  signal, but we'll be amplifying noise along with it. That's the problem
                  with these schemes. You can amplify the leading edge, attenuate the
                  trailing edge, or do both, but you never reach a given signal-to-noise
                  ratio at any velocity greater than c. That's what the people who try to
                  pass this off as "FTL" never bother to tell you.
                • Ed Minchau
                  ... necessarily ... way up ... when that ... noise. We ... amplify the ... problem ... noise ... try to ... Furthermore, according to the Nyquist sampling
                  Message 8 of 17 , Feb 19, 2001
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                    --- In nanotech@y..., Mark Gubrud <mgubrud@s...> wrote:
                    > If we are interested
                    > in detecting the signal as soon as possible, the answer is not
                    necessarily
                    > the center of the pulse. We could set some threshold, say, half
                    way up
                    > the slope, and have our detector tell us the signal has arrived
                    when that
                    > threshold is reached. If we set the threshold lower, we'll get the
                    > signal sooner. But we also have to consider the presence of
                    noise. We
                    > can always reach our threshold of detection sooner if we just
                    amplify the
                    > signal, but we'll be amplifying noise along with it. That's the
                    problem
                    > with these schemes. You can amplify the leading edge, attenuate the
                    > trailing edge, or do both, but you never reach a given signal-to-
                    noise
                    > ratio at any velocity greater than c. That's what the people who
                    try to
                    > pass this off as "FTL" never bother to tell you.

                    Furthermore, according to the Nyquist sampling criteria, you need to
                    receive two "pulses" to be certain that you have received one at the
                    desired wavelength; again, slower than c.

                    :) ed
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