THE universe puts a fundamental limit on communication and studying this limit may help researchers unify the two pillars of modern physics.
Seth Lloyd, an information theorist at the Massachusetts Institute of Technology, and his colleagues, have combined ideas from quantum mechanics and relativity to show that there is a maximum possible rate of transmitting information. Fortunately, it鈥檚 pretty fast.
They started with the Bekenstein bound, an idea developed by Jacob Bekenstein at the Hebrew University of Jerusalem in Israel, who showed that at a quantum scale there is a limit to how much information can be encoded with a given amount of energy. And relativity sets two limits of its own: you cannot send matter or radiation faster than light, and you cannot compress it any more densely than a black hole. But it is theoretically possible to send a message almost as dense as a black hole at almost the speed of light.
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Putting it all together, the team found a simple formula for the maximum information rate. Bekenstein himself has recently worked out the same formula, but his reasoning applies only under special circumstances according to the MIT researchers.
The rate depends on how much power you have to use and the volume of space available to squeeze the message into. If you have 1 watt of power and a 1-square-metre pipe, for example, the limit is about 1052 bits per second. Cranking up the power to a megawatt, you would get 1055 bits per second.
That may sound ludicrously fast, but if the bandwidth available to internet users keeps increasing at its current rate, we would hit this barrier in about 250 years. 鈥淚nterestingly, that is also the point at which Moore鈥檚 law requires computers to consist of black holes,鈥� Lloyd says.
It is not clear, of course, whether we will ever be able to code information so efficiently and fling super-dense material at near the speed of light. But this work may have more fundamental significance: it might be useful in telling us how these two theories can finally be unified into a single theory of quantum gravity.