Can decoherence be associated with heat generation?

In summary, the conversation discusses the relationship between decoherence and the generation of heat in a density matrix that is not diagonal in the energy basis. It is mentioned that the production of heat is associated with dissipation, which is independent from decoherence. References are provided for further reading on the topic. However, there is some confusion about the terminology used, specifically regarding the definitions of T1 and T2. It is noted that T2 can be limited by classical dissipation and can affect the coherence time of a system.
  • #1
Prathyush
212
16
This question is inspired by a comment that @thephystudent made where he said that

"The dephasing between the Bragg pulses is not unitary, I believe it can be explicitly written in Lindblad form and generates heat. I believe this Point of view is the same as (among others) the papers of Allahverdyan and Van Nieuwenhuizen cited, but I don't know how far it applies to your work."

The context for this comment is that a density matrix that is not diagonal in the energy basis undergoes decoherence and the off diagonal terms go to zero. Can this type of decoherence be associated with the generation of heat? How does one define heat in such a context?

Any references will be also be much appreciated.
 
Physics news on Phys.org
  • #2
No, the production of heat is associated with dissipation, which is independent from decoherence. See Schlosshauer, Decoherence and the Quantum-to-Classical Transition, Sec. 2.11.
 
  • Like
Likes Lord Jestocost
  • #3
But isn't there some entropy production (supposed the Lindblad operators are choosen appropriately)? I know, entropy is not heat, and you need a temperature measure to define heat via ##T \mathrm{d} S## though.
 
  • #4
vanhees71 said:
But isn't there some entropy production
Yes, since Lindblad equations don't preserve all pure states.
 
  • Like
Likes vanhees71
  • #5
vanhees71 said:
But isn't there some entropy production (supposed the Lindblad operators are choosen appropriately)? I know, entropy is not heat, and you need a temperature measure to define heat via ##T \mathrm{d} S## though.
Heat is associated with thermal entropy, which is a maximal possible entropy under given constraints. The entropy produced by decoherence (Lindblad) is usually not maximal entropy.
 
  • Like
Likes vanhees71
  • #6
Demystifier said:
No, the production of heat is associated with dissipation, which is independent from decoherence. See Schlosshauer, Decoherence and the Quantum-to-Classical Transition, Sec. 2.11.

I don't think that is correct; at least not in the way the terminology is normally used. If you take a regular two-level system and assume no pure dephasing you have T2=2*T1.
Now, T1 will of course depend on the amount of dissipation in the system; and if the TLS is just a resonator you have that this is directly proportional to Q; i.e. the dissipation. I realize that you know this which is why I suspect there is an issue with the terminology here.

Note that when the goal is to maximise the coherence time of a real system (e.g. a qubit) you are in reality very rarely in this limes since T2 is typically limited by things like spectral diffusion etc . However, it is nevertheless true that T2 will ultimately be limited by "classical" dissipation; and in some systems (e.g. superconducting qubits) we are now at a point where we are frequently limited by plain old dissipation.
 
  • #7
@f95toli I don't understand the terminology you are using? What are T1 and T2 ?
 
  • Like
Likes Demystifier

1. What is decoherence and how is it related to heat generation?

Decoherence is a process in which a quantum system loses its coherence and becomes more classical and predictable. This loss of coherence is often associated with the transfer of energy, which can manifest as heat generation in the system.

2. Can decoherence occur without heat generation?

Yes, decoherence can occur without heat generation in certain circumstances. For example, if the quantum system is isolated from its environment, there may be no transfer of energy and therefore no heat generation.

3. What factors contribute to heat generation during decoherence?

The amount of heat generated during decoherence depends on several factors, including the size and complexity of the quantum system, the strength of its interactions with the environment, and the temperature of the environment itself.

4. Is heat generation always a negative consequence of decoherence?

No, heat generation during decoherence is not always a negative consequence. In fact, it can sometimes be a useful tool for controlling and manipulating quantum systems, such as in the field of quantum computing.

5. Can decoherence and heat generation be reversed?

Decoherence and heat generation are irreversible processes, meaning that once they occur, they cannot be reversed. However, there are techniques and strategies being developed to minimize the effects of decoherence and heat generation in quantum systems.

Similar threads

  • General Math
Replies
2
Views
4K
Back
Top