Here's a research plan for the NSA: 1. Build a quantum computer; in parallel with 2. Find a small (but not too small) black hole to cool it with. (3. Then move it to Bluffdale?) There, we found the money to "invest" in a huge space program... At 12:58 PM 9/16/2015, Mike Stay wrote:
Anything advanced enough to colonize the galaxy will radiate waste heat into a black hole. http://www.weidai.com/black-holes.txt
Advanced civilizations probably have extensive cooling needs. Computing and communication equipment both work better at lower temperatures. A cooler computer means a faster computer with lower energy needs, and a cooler transceiver has lower thermal noise. Since these equipment cannot operate with perfect efficiency, they will need to eliminate waste heat.
It's not too difficult to cool a system down to the temperature of the cosmic background radiation. All you need to do is build a radiator in interstellar space with a very large surface area, and connect it with the system you're trying to cool with some high thermal-conductance material.
However, even at the cosmic background temperature of T=3K, erasing a bit still costs a minimum of k*T*ln 2 = 2.87e-23 J. What is needed is a way to efficiently cool a system down to near absolute zero. I think the only way to do it is with black holes.
Black holes emit Hawking radiation at a temperature of T=h*c^3/(16*pi*G*M). With the mass of the sun, the temperature of a black hole would be about 10^-8 K. At this temperature, erasing a bit costs only about 10^-31 J. If you build an insulating shell outside the event horizon of a black hole, everything inside the shell would eventually cool down to the temperature of the black hole. However, it would not be necessary to build a complete shell around a black hole in order to take advantage of its low temperature. For example you can simply point the radiators of your black hole orbiter toward the black hole and insulate the side facing away from the black hole.
If it's true that the only efficient way to cool material down to near absolute zero is with black holes, we should expect all sufficiently advanced civilizations to live near them. However this prediction may be difficult to test since they would have virtually no radiation signatures.