Here's a great piece of scientific word salad:
"we believe coherence and entanglement are operationally equivalent but conceptually different".
phys.org
Huh?
I'm trying to look at the reality, which is that coherence has a well defined mathematical meaning, whereas no one really knows what entanglement is
Here's some more annoying word salad courtesy of Google AI:
"Entangled wave functions are considered relatively stable, meaning that the correlation between entangled particles remains strong even when separated over large distances, as long as they are not significantly disturbed by external influences like environmental noise; however, this stability is not absolute and can be disrupted by decoherence mechanisms, which can cause the entanglement to degrade over time".
Hello? What is a "decoherence mechanism"? No one really knows. lol - "external mechanisms like environmental noise" - lmao
Shall we try to make some sense of this mumbo jumbo? Let's. Word salad in politics is bad enough, but in science it's downright embarrassing.
What is coherence?
Coherence is defined as:
C^2 = (Sxy)^2 / SxxSyy
Where S is the spectral density, which is the Fourier transform of the correlation. So Sxx is related to the autocorrelation, while Sxy describes the cross correlation.
Correlation "of what"? Where do we find coherence?
Well, lasers are the low hanging fruit. A laser generates a "highly coherent" beam of light. The beam of light consists of waves that are all the same frequency, whose phases all line up. Therefore we have monochromaticity and we have constructive and destructive interference. If the waves are all the same frequency and they have a fixed and invariant phase relationship, one can consider the STABILITY of the light beam as it traverses space and time
Rather than blaming "environmental noise", we can look at Heisenberg's uncertainty in an open system. Which would encompass both environmental noise and self noise, along with transfers of energy and information between the system and the bath.
So we could look at light, but entanglement also occurs in electrons and quarks, in atoms and even molecules. Maybe even in large gravitational objects like planets and stars and black holes. Still, lasers are easier, and cheaper too.
Let's do the fundamentals. A qubit has a spin state, the spin can be either up or down. A superposition is a combination of spin states, much like a pair of coupled oscillators. We have a wave function for the up state and a wave function for the down state, and generally they will be "coherent" because they have the same frequency and a stable phase relationship.
You can disrupt the coherence by altering the stability of either, for example you can pump the laser beam into an optical fiber and vibrate the fiber, so you get additional frequencies and additional phase relationships that affect the stability of the spectral densities. Another trick is, you can make a "measurement" by putting a detector in the path of the light beam, and it's intuitive that any such osculation would affect the stability of the light waves.
None of this explains why coherence becomes entanglement, nor does it explain how you get varying degrees of coherence from conjugate wave functions. The word salad people claim they understand it, but they don't. The topological types claim they can explain it but they can't.
en.wikipedia.org
en.wikipedia.org
"we believe coherence and entanglement are operationally equivalent but conceptually different".
Physicists find quantum coherence and quantum entanglement are two sides of the same coin
(Phys.org)—Quantum coherence and quantum entanglement are two landmark features of quantum physics, and now physicists have demonstrated that the two phenomena are "operationally equivalent"—that is, equivalent for all practical purposes, though still conceptually distinct. This finding allows...
Huh?
I'm trying to look at the reality, which is that coherence has a well defined mathematical meaning, whereas no one really knows what entanglement is
Here's some more annoying word salad courtesy of Google AI:
"Entangled wave functions are considered relatively stable, meaning that the correlation between entangled particles remains strong even when separated over large distances, as long as they are not significantly disturbed by external influences like environmental noise; however, this stability is not absolute and can be disrupted by decoherence mechanisms, which can cause the entanglement to degrade over time".
Hello? What is a "decoherence mechanism"? No one really knows. lol - "external mechanisms like environmental noise" - lmao
Shall we try to make some sense of this mumbo jumbo? Let's. Word salad in politics is bad enough, but in science it's downright embarrassing.
What is coherence?
Coherence is defined as:
C^2 = (Sxy)^2 / SxxSyy
Where S is the spectral density, which is the Fourier transform of the correlation. So Sxx is related to the autocorrelation, while Sxy describes the cross correlation.
Correlation "of what"? Where do we find coherence?
Well, lasers are the low hanging fruit. A laser generates a "highly coherent" beam of light. The beam of light consists of waves that are all the same frequency, whose phases all line up. Therefore we have monochromaticity and we have constructive and destructive interference. If the waves are all the same frequency and they have a fixed and invariant phase relationship, one can consider the STABILITY of the light beam as it traverses space and time
Rather than blaming "environmental noise", we can look at Heisenberg's uncertainty in an open system. Which would encompass both environmental noise and self noise, along with transfers of energy and information between the system and the bath.
So we could look at light, but entanglement also occurs in electrons and quarks, in atoms and even molecules. Maybe even in large gravitational objects like planets and stars and black holes. Still, lasers are easier, and cheaper too.
Let's do the fundamentals. A qubit has a spin state, the spin can be either up or down. A superposition is a combination of spin states, much like a pair of coupled oscillators. We have a wave function for the up state and a wave function for the down state, and generally they will be "coherent" because they have the same frequency and a stable phase relationship.
You can disrupt the coherence by altering the stability of either, for example you can pump the laser beam into an optical fiber and vibrate the fiber, so you get additional frequencies and additional phase relationships that affect the stability of the spectral densities. Another trick is, you can make a "measurement" by putting a detector in the path of the light beam, and it's intuitive that any such osculation would affect the stability of the light waves.
None of this explains why coherence becomes entanglement, nor does it explain how you get varying degrees of coherence from conjugate wave functions. The word salad people claim they understand it, but they don't. The topological types claim they can explain it but they can't.
Coherence (physics) - Wikipedia
