Loophole in the laws of thermodynamics?

[aggle-rithm]

http://www.physorg.com/news/2011-06-quantum-knowledge-cools-entropy.html

In the case of perfect classical knowledge of a computer memory (zero entropy), deletion of the data requires in theory no energy at all. The researchers prove that "more than complete knowledge" from quantum entanglement with the memory (negative entropy) leads to deletion of the data being accompanied by removal of heat from the computer and its release as usable energy. This is the physical meaning of negative entropy.

Renner emphasizes, however, "This doesn't mean that we can develop a perpetual motion machine". The data can only be deleted once, so there is no possibility to continue to generate energy. The process also destroys the entanglement, and it would take an input of energy to reset the system to its starting state. The equations are consistent with what's known as the second law of thermodynamics: the idea that the entropy of the universe can never decrease. Vedral says "We're working on the edge of the second law. If you go any further, you will break it."

This certainly SEEMS legit, but it's a little unsettling to see the same kind of language used here as is used frequently by woos ("quantum entanglement" and "determined by the observer"). I know these are legitimate terms, but I see them misused so often.

I guess the problem I have is how the article suggests that the "observer" is a human being. Quantum computing would need to work regardless of whether it's being observed or not.

Or would the 200 GB batch processing job not exist until we view the data the next day...?

ETA: I realize the article isn't claiming that entropy is being reduced in a closed system...it's just being moved from one place to another. If I understand it correctly, the big deal is that it's possible to do it in a way that we've never considered before.

 

[CaveDave]

I was under the impression that "observer" as used in Physics has nothing to do with humans, conciousness, or any other mundane meaning; I think it just means something along the lines of "leaves a measurable effect behind", but I am often mistaken.

Dave

ETA:

Sol? Zig? Shad? DD? TT? Matt? Cuddles? (TOO many others to list or recall)?

 

[Dilb]

"Observer" in physics means something like "a system with a large number of degrees of freedom, which interact strongly enough to cause decoherence; and we're not interested in keeping track of it's state".

I think "observer" is a very poor choice of words to describe what is happening. From the article

In measuring entropy, one should bear in mind that an object does not have a certain amount of entropy per se, instead an object's entropy is always dependent on the observer. Applied to the example of deleting data, this means that if two individuals delete data in a memory and one has more knowledge of this data, she perceives the memory to have lower entropy and can then delete the memory using less energy.

This is talking about two different situations, not two people observing the same operation. Let me rephrase:

Data does not have a certain amount of entropy independent of other data. To delete data from an object would ordinary require generating heat. However, if you have a second object with a copy of the data, i.e. you have complete knowledge of the data, you can delete it without generating heat.

The research then goes on to find:
By having the data entangled with a copy outside the object, the information can be deleted while removing heat from the system. In this way entangled data is "more than complete knowledge" of the original data.

The fact that negative entropy systems exist has been known for over a century. What's new is that it's being applied to information theory.

 

[aggle-rithm]

I guess the real trick is going to be finding a practical application for this knowledge. Seems like a non-trivial problem, but these guys have proved pretty clever in the past.

 

[Darwin123]

http://www.physorg.com/news/2011-06-quantum-knowledge-cools-entropy.html
I guess the problem I have is how the article suggests that the "observer" is a human being. Quantum computing would need to work regardless of whether it's being observed or not.

Observer does not mean 'human being' or even 'consciousness', whatever that is. However, a general definition of 'observer' is not currently available. As a rule of thumb, it is often interchanged with the phrase 'measuring instrument'. However, the definitions of 'measuring instrument' is rather elastic.

There is some research being done to define 'observer' in a useful way. I consider this real science, in that it is useful to engineers. However, it is still a branch of philosophy because it involves the way people know things. I consider it a branch of metrology. Metrology is the study of measurement.

There subject within quantum mechanics called 'decoherence theory'. It is also referred to as 'quantum Darwinism'. There, formal definitions of 'measurement' are developed consistent with the rules of quantum mechanics. It is sometimes considered an alternative to the 'Copenhagen interpretation'.

'Measurement' in quantum Darwinism is an interaction between two quantum objects: the measuring instrument, the system and the 'environment'. The environment is complex in that it has many degrees of freedom (quantum numbers) and unknown phase information. The system being 'measured has only a few degrees of freedom which are mindlessly copied onto the environment by an interaction which characterizes the measurement. The interaction has to satisfy certain conditions.

The theory of quantum Darwinism is somewhat mathematical. It does not assume that there is any system that is completely classical in behavior, including the environment. The uncertainty in quantum measurements come from the fact that the environment is so very complex, with more quantum numbers than can be counted. Hence, there is no consciousness or human required in a quantum measurement. The theory is abstract but quantifiable. Predictions made with quantum Darwinism have been confirmed by experiment.

I recommend looking up 'decoherence theory' and 'quantum Darwinism'. I thin you will find what I think you are looking for in this theory.

 

[3point14]

I always figured it was because, in order to measure something, one needs to trap a bit of it, bounce something off it (probably light) or in some other way use up or influence the thing being measured.

On a macro scale this matters not a jot but on a quantum scale when measuring a single photon (for example) as soon as it's hit the photographic plate it's gone, the measuring uses up the object.

How wrong am I?

 

[Nonpareil]

Observer does not mean 'human being' or even 'consciousness', whatever that is. However, a general definition of 'observer' is not currently available. As a rule of thumb, it is often interchanged with the phrase 'measuring instrument'. However, the definitions of 'measuring instrument' is rather elastic.

There is some research being done to define 'observer' in a useful way. I consider this real science, in that it is useful to engineers. However, it is still a branch of philosophy because it involves the way people know things. I consider it a branch of metrology. Metrology is the study of measurement.

There subject within quantum mechanics called 'decoherence theory'. It is also referred to as 'quantum Darwinism'. There, formal definitions of 'measurement' are developed consistent with the rules of quantum mechanics. It is sometimes considered an alternative to the 'Copenhagen interpretation'.

'Measurement' in quantum Darwinism is an interaction between two quantum objects: the measuring instrument, the system and the 'environment'. The environment is complex in that it has many degrees of freedom (quantum numbers) and unknown phase information. The system being 'measured has only a few degrees of freedom which are mindlessly copied onto the environment by an interaction which characterizes the measurement. The interaction has to satisfy certain conditions.

The theory of quantum Darwinism is somewhat mathematical. It does not assume that there is any system that is completely classical in behavior, including the environment. The uncertainty in quantum measurements come from the fact that the environment is so very complex, with more quantum numbers than can be counted. Hence, there is no consciousness or human required in a quantum measurement. The theory is abstract but quantifiable. Predictions made with quantum Darwinism have been confirmed by experiment.

I recommend looking up 'decoherence theory' and 'quantum Darwinism'. I thin you will find what I think you are looking for in this theory.

You have a real problem with reviving threads that have been dead for more than a year.

 

[Floyt]

I always figured it was because, in order to measure something, one needs to trap a bit of it, bounce something off it (probably light) or in some other way use up or influence the thing being measured.

On a macro scale this matters not a jot but on a quantum scale when measuring a single photon (for example) as soon as it's hit the photographic plate it's gone, the measuring uses up the object.

How wrong am I?

To add my ounce of half-remembered factoid from listening to Einstein's biography - the observer effect is not thought to have any connection to "measurement disturbance". I believe that was an interpretation that was common for some time, but is now regarded as wrong. Situations can be set up where knowledge of the system is acquired without interaction with the system, and it still pops up.

Now, someone correct me

 

[Modified]

The equations are consistent with what's known as the second law of thermodynamics: the idea that the entropy of the universe can never decrease.

That's not really true is it? The entropy of the universe could decrease, even on a long time scale, it's just unlikely enough to be effectively impossible.