# Why does Landauer define erasure of information as resetting

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1. Apr 22, 2016

### voila

Hi. I hope this is the right forum for the question.

Landauer's principle says that the erasure of one bit of information (1 or 0) requires kBTln2 of heat production. When he talks about erasure, it means "resetting back to 0 (or 1)" after measuring. He says something along "this is needed as to not to bias the device". I guess this means "for the device to perform a measure, it needs to previously be in a given state". So that if you need to measure 0's and 1's, it intrinsically needs to be restored to 0 before each new measure. Why?

2. Apr 27, 2016

### Greg Bernhardt

Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?

3. Apr 27, 2016

### rcgldr

4. Apr 28, 2016

### voila

I have an answer to the question, but still there's something quite open to me. Erasure means resetting so that it doesn't interfere the device operation. For example, if a device with a one bit memory controls a door and is instructed to "OPEN DOOR whenever a measure gives 1", it wouldn't work if it wasn't resetted to 0.

The right side of the red line is the resetting procedure, which resets a bit to 0 no matter what its state is. Calculations have shown this procedure implies, on average, a work of W=kTln2 on the particle (particle is brownian, and so disippates it into heat).

The left side is what Bennett proposed for a measure of a bit of information, saying measurement requires no work done. Worry not about the procedure he thought of, the important part is that it can be represented as a double well potential being modulated like is indicated next to the figure.

...Notice something similar? I find both modulations of the potential to be quite the same, yet the left one is an example of no expenditure of energy and the right one is just the opposite. What am I missing?

Edit: "Medida" means measurement.

#### Attached Files:

• ###### Doble pozo medida Bennet-Borrado de Landauer.png
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5. Apr 30, 2016

### Dominik Tugend

6. Apr 30, 2016

### voila

Yes, I know. A process where the memory of the device takes a state (1 or 0 if its a one bit memory) which corresponds to a given physical variable of the system being measured.