The difference between classical and quantum correlations

[sciencejournalist00]

I believe it is an important topic for us to learn about. There are frequent mistakes, people confuse many times classical correlations with quantum entanglement on their blogs and forums and only peer-reviewed papers give the true answers.

Classical correlations exist between the quanta of a single mode generated with resonance, like in the case of lasers and musical instruments.

They are called Coherent Gaussian Beams, appear when the individual waves of a pulse are in phase (0 degrees phase difference) and are described by different equations from the ones that describe quantum entanglement.

If classical correlations and quantum entanglement were the same, you would just have to use a single laser device to generate billions of entangled photons, without use of beam splitter or nonlinear crystals. But they aren't.

While I know about the difference between quantum and classical correlations, I do not know how to distinguish them in practice.

Can you please give some examples of interactions that create these types of correlations for each case, so that everyone may have in future a template to follow in their experiments?

1. Classical correlations: resonant excitations...
2. Quantum correlations: parametric fluorescence, double decay...

 

[eljose79]

Hello,

Thank you for bringing up this important topic. it is crucial for us to have a clear understanding of the differences between classical correlations and quantum entanglement. I completely agree with you that only peer-reviewed papers can provide accurate information on this subject.

To answer your question, let me first explain the difference between classical correlations and quantum entanglement. Classical correlations refer to the relationship between two or more systems that can be described by classical physics, such as Newtonian mechanics. These correlations are based on the properties of individual particles and do not involve any quantum effects.

On the other hand, quantum entanglement refers to a phenomenon where two or more particles are intrinsically connected and their behavior is linked, regardless of the distance between them. This phenomenon is based on the principles of quantum mechanics and cannot be explained by classical physics.

Now, let's look at some examples of interactions that create these types of correlations:

1. Classical correlations: Resonant excitations in classical systems, such as lasers and musical instruments, can create classical correlations. For example, when two musical instruments are tuned to the same frequency and played simultaneously, the sound waves from each instrument will be in phase and produce a coherent sound.

2. Quantum correlations: There are several ways to create quantum correlations, such as parametric fluorescence and double decay. In parametric fluorescence, a photon from an excited atom is split into two entangled photons. In double decay, a particle decays into two particles that are entangled. These types of correlations cannot be created in classical systems and are unique to quantum systems.

In conclusion, classical correlations and quantum entanglement are fundamentally different phenomena. Classical correlations exist in classical systems, while quantum entanglement is a purely quantum phenomenon. I hope this helps to clarify the distinction between the two and provides a template for future experiments. Thank you for your interest in this topic.