It's common empirical knowledge that computing generates heat--go ahead, touch the bottom of your MacBook--but a new paper in the journal Nature claims that it doesn't have to. In fact, under the right conditions, theoretical physicists say that deleting data can actually produce negative heat--that is, it can have a cooling effect. That's right, this is a quantum mechanics post. Exit now if you don't want a headache to start the weekend.
The phenomenon here has to do with basic rules about knowledge and the lack of knowledge, and it is rooted firmly in the definition of entropy and how information theory, thermodynamics, and quantum theory define it differently (and also in the same way). But the idea is thus: If it were technologically possible (and it should be, perhaps someday) to quantum-mechanically entangle the bits to be deleted with an observer, the observer could actually withdraw heat from the system while deleting the bits.
This is where the headaches start, and I'm not going to pretend to understand the nuts and bolts here. But conceptually, it comes down to knowledge. In information theory, entropy describes information density. In thermodynamics, entropy describes disorder in systems. What this new paper claims to prove is that in both cases, entropy basically describes a lack of knowledge.
An object doesn't really possess entropy, but rather its entropy is dependent on the observer. So the idea is that if there are two observers deleting data from a memory, and one observer has more knowledge of the data, that observer will perceive the memory has lower entropy, and thus can delete it with less energy expenditure.
Now, enter quantum mechanics. In quantum theory, when calculated from the information theory standpoint entropy can actually be negative. So here's the magic idea: quantum correlations (like entanglement) are stronger than classical correlations. So if an observer has perfect classical knowledge of a memory, then he or she would perceive its entropy as zero. And if the two were quantum-mechanically entangled, the entropy would be perceived as even less--less than zero, or negative entropy.
So with perfect classical knowledge of a system, deletion of data could theoretically happen with no energy at all. And if the deleter of the system has more than complete classical knowledge (i.e., is entangled with the system at the quantum level), then the deletion will actually remove heat from the system.
Right? It's a stretch for the brain but it makes sense conceptually. In the future, such mind-bending could in theory lead to supercomputers with capacities that are not restrained by heat as they are today, allowing them to reach full potential while cooling themselves as they compute. We're a long way from that, but considering the rapid pace at which researchers are learning to manipulate entangled systems, it's certainly not out of the question.
Up next: How to cool your beer with quantum entanglement.
While my lack of knowledge inclines me to be very skeptical I like how these guys think. I can only hope this would lead to computational power or storage utilizing the fabric of space or strong/weak atomic forces.
A stretch for the imagination certainly, but a noble effort thinking radically.
wow. that's mind bending. so basically heat can be removed from computers and also other electronics by deleting data/information and using Quantum entanglement? makes sense.
I can't believe you don't understand this! It's so simple!
I just wonder what the initial heat content would be in a condition of "perfect classical knowledge". My first impression is that the heat content would rise exponentially to attain "perfect classical knowledge", and so reducing this heat by deleting files may in fact provide some cooling, but cooling something increasingly hot as one approaches perfect classical knowledge.
I base this on my understanding that even an error of one part in one billion would very quickly result in having no knowledge at all.
This really is Pointless, and has Zero prospects for practical application.
Let's first work out how to use Quantum E. for something like subspace communication, and do something useful like controlling a Mars Rover (for example) in Real Time.
This seems based on the premise that "quantum correlations (like entanglement) are stronger than classical correlations" and because one (classic) is zero, and the other (entanglement) is stronger, it has to be less than zero. Even if that is so it would logically follow that establishing those stronger correlations (writing the date using entanglement) would also require more energy. As computers generally save more date than they delete I would think they would run hotter rather than cooler.
the people who understand this stuff are crazy smart, i think what they are getting at is an added cooling effect (for free?), not a computer that needs no cooling