Thermodynamics: The energy consumed by pure information

All electrical equipment requires energy because they output energy. Light bulbs produce light to illuminate the room. Microwaves generate microwave radiation to heat the meal. The car produces the car to accelerate itself and passengers. Basically, each electrical device has an energy input, and then outputs a part of the useful energy, and the other part of the energy is scattered on things such as friction, vibration and heat.

But the computer processor is different, and its function is not to light up, heated a certain thing or move around. When we ask it to calculate 123 by 456, we do not expect any useful energy. What we want is to let it manipulate the information, turn a set of 0 and 1 and give us the answer. So does this mean that the energy used by the processor is scattered? If we have a way to eliminate these energy losses, can the computer processor run without energy?

It turns out that the answer is negative, because the information itself also has its own energy cost, which is set by the principle of a Landor limit. This principle stipulates that the minimum energy required to flip the information is equal to 0.96 × 10^-23t scorched ear, where T is the temperature. In this article, we will see where this limit comes from.

Logic door

First of all, we must ask, how do computers work in physics? This is the land of logic doors, which is the basic construction block of all computers. Its principle is very simple, accepts two inputs, each input is 1 or 0, and then generates an output of the same form, which is also 1 or 0.

There are many types of logic doors, which are used for different purposes, and each has different input and output modes. We can connect different types of logic doors, connect the output to the input of another door, and then connect to another. In this way, we have a logical network. The larger the network, the more complicated it can be answered. It is enough to build it, and in the end we can ask: What is the maximum value of less than 1 billion, and even what is the best way to cook rice?

This is what the modern computer owns: a network composed of hundreds of millions of logical doors, all of which work together to process the complex information given.

Entropy increase principle

So what does these logical doors have to do with energy and information? Back to a single logic door, we need to consider the number of input and output combinations that it can have. Enter two bit, each bit can be independent of 1 or 0, we have a total of four possibilities. The output is simpler. Because the door is only output, there are only two possible output states: 1 or 0.

When we start talking about the state, a person named Bolzmann becomes very interested. Bolzman is one of the earliest people who use the concept of entropy. The more state he can be in a system, the higher the entropy. A very famous law in physics is the second law of thermodynamics. It pointed out that the total entropy of the system can only increase or remain unchanged, and it will never decrease. In the 1870s, Bolzman wrote the equation of entropy: s = Kʙ (LNW), where Kʙ is the so -called Boltzmann constant, and W is the status of the system. Let's apply it to the logical door we said above.

There are four possible input states into the formula, and the entropy we get is KʙLn4; there are two possible states after executing, which gives KʙLn2 entropy. After the operation, the entropy of the door has actually decreased. In order not to violate the second law of thermodynamics, it must generate a compensation increase in some ways so that the total entropy will not decrease.

Landor Extreme

Specifically, the change of the unit heat of the door is multiplied by the temperature of the system. The release of this heat ensures that the total entropy of the entire system will not become smaller. Therefore, we have Lan Doul limits, and we need to consume the minimum energy running on the logic door. In 1961, physicist Lan Douer first proposed the limit when working in IBM.

It is worth noting that we don't have to know the actual working principle of the logic door. It is not important to use a transistor or photon. What we know is that if the output state is less than the input state, the physical law guarantees it must consume certain energy. This is why Landor's limit is sometimes said to the energy value of the information itself.

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Source: Vientiane experience

Edit: Lezi Superman

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