The Takeaways:
- Quantumology agrees (with quantum cosmology) that the principles of quantum mechanics can be applied to the entire universe to help us understand its origins and evolution.
- The “theory of everything” is the theory of the universe. We can begin with particle physics and/or with quantum cosmology, and the two are not mutually exclusive — otherwise there is no base to apply quantum physics to the entire universe. Since they each have pros and cons, the best approach is to work with both.
- Some argue that information loss is inevitable when breaking the whole down to its parts, and the only way to describe the universe is to look at the universe itself. The “monism” thinking overlooks the quantum “state delicacy” and falsely limits quantum information loss to when the universe is decomposed. There are numerous occasions where quantum information is subject to loss, which is what the term “decoherence” describes. It is also operationally difficult to adhere to this reasoning.
- The old tenet “from all things One” has limited value today because the universe at the beginning of the Big Bang was unlikely to be just one thing but infinitely condensed, hot and superpositioned states of multiple particles.
- Similarly, “from One all things” does not tell us that the Big Bang is itself a superposition of a historical event and an ongoing process, rendering the universe a superposition of matter and energy in space-time dimensions.
- Even though quantum physicists insist there is nothing “spooky” about anything in quantum physics, they have yet to come up with a solid explanation of quantum entanglement.
This is the second in the quantumology series. I will introduce key concepts in quantum physics in a way that is easy to understand — something easier said than done, requiring cutting down deep but not coming out dry, creating one’s own way of saying things by reading widely of others.
It is also more interesting and meaningful to embed fundamental knowledge within debates, like the one between quantumology and quantum cosmology.
Understanding Quantum Cosmology
My concept of quantumology bears similarity with the so called “Theory of everything.” An interesting and the latest discussion of such a theory comes from the German theoretical physicist Heinrich Päs in a 2023 book The One, which does not break theoretical ground but does campaign enthusiastically for quantum cosmology.
It makes sense to first learn what quantum cosmology is.
According to ChatGPT, quantum cosmology is “a branch of theoretical physics that seeks to understand the origins and evolution of the universe using the principles of quantum mechanics. It implies that the universe as a whole should be treated as a quantum system and that the laws of quantum mechanics should be applied to the entire universe.”
However, ChatGPT reminds us that quantum cosmology is still “theoretical and still a developing field, and the interpretation of the nature of reality and the universe is still a subject of ongoing research and debate among scientists and philosophers.”
A Three-Thousand-Year-Old Idea
With the above background in mind, let’s consider Päs in more detail. The author starts by contending that “while we almost always adopt quantum mechanics to describe specific observations and experiments, we usually don’t apply it to the entire universe.”
We should, says Päs, because “once quantum mechanics is applied to the entire cosmos, it uncovers a three-thousand-year-old idea: that underlying everything we experience there is only one single, all-encompassing thing—that everything else we see around us is some kind of illusion.”
One way to prove the validity of a single fundamental “thing,” according to Päs, is to realize that the Newtonian physics is having a crisis “that forces us to reconsider what we understand as ‘fundamental’ in the first place. Right now, the most brilliant particle physicists and cosmologists are alienated by experimental findings of extremely unlikely coincidences that so far defy any explanation.”
Päs then argues that “(q)uantum cosmology implies that the fundamental layer of reality is made neither of particles nor of tiny, vibrating, one-dimensional objects known as ‘strings,’ but the universe itself — understood not as the sum of things making it up but rather as an all-encompassing unity.” At its core, the theory of everything simply says that “all is One.”
Reasoning Behind Monism
The argument for the “monism” (i.e., a single unity of reality) moves head-on with the argument that quantum physics is all about tiny things at subatomic level and should stay there. To prove its fault, Päs travels to the other extreme by proposing that the “most fundamental description of the universe has to start with the universe itself.”
More specifically, Päs suggests that we should “turn our quest for a theory of everything upside down —to build up on quantum cosmology rather than on particle physics or string theory (currently the most popular candidate for a quantum theory of gravitation).”
I want to summarize his reasoning in three points. First of all, quantum physics is naturally, inherently and fundamentally linked to quantum cosmology, just like Heraclitus told us three thousand years ago that “from all things One.” There is no need to wait for quantum mechanics in particles to (slowly) grow into the universe, because quantum cosmology describes the universe just like quantum mechanics does for particles.
Secondly, “from all things One” naturally leads to Heraclitus’s other tenet of “from One all things” because if everything goes to “One” in the end, “One” must also be the starting point.
This is like drawing a perfect circle, where the starting point must meet the ending point.
But how about drawing a circle in a piecemeal fashion, where we start with multiple arcs and then connect them into a circle? Two problems there. First of all, connecting multiple arcs (i.e., the parts) is error-prone and two, the result cannot be a perfect circle (i.e., the whole). The only efficient way for a perfect circle is to make the ending point also the starting point — the universe, that is.
The Problem of Info Loss
Everything so far is philosophy, but Päs’ third (and the last) point offers the key arguments against starting from particle physics to quantum cosmology due to two fundamental challenges.
The first is information loss going from the “whole” to the “parts.” Päs proves his point using nothing else but quantum mechanics, which says “it is, in general, impossible to decompose an object without losing some essential information. Particle physicists strive for a fundamental description of the universe, one that discards no information. But if we take quantum mechanics seriously, this implies that, on the most fundamental level, nature cannot be composed of constituents.”
This is essentially saying that if we want to avoid information loss we must start from — and stay with — the “whole,” never going down to any “parts” below the “whole.”
This goes back to my earlier metaphor of drawing a perfect circle, where the starting and ending points must meet.
The above “monist” thinking overlooks the quantum “state delicacy” and falsely limits quantum information loss to when the universe is decomposed. But information loss is everywhere possible. This is what the term “decoherence” describes. I will discuss more in another post.
For now, it’s important to remember that quantumology can begin with particle physics and/or quantum cosmology, and the two are not mutually exclusive — otherwise there is no basis to apply quantum physics to the entire universe. Since they each have pros and cons, the best approach is to work with both.
Entanglement & Complete Darkness
If information loss from decomposition is bad, the second problem with entanglement is even worse. Here according to Päs we enter a space of complete darkness: “In quantum systems, objects get so completely and entirely merged that it is impossible to say anything at all about the properties of their constituents anymore. This phenomenon is known as ‘entanglement.’”
The idea is similar to information loss: Losing the capability of saying anything about the parts or constituents, entanglement forces us to stick with Heraclitus’s dogma “from all things One” (i.e., to start from — and to stay with — the One or the universe.)
The Incidence of Entanglement
Believing in a universal reach of quantum mechanics is one thing, justifying that universe can only be described by universe itself is another. Some statements in Päs’ book are only partly correct (or mostly incorrect).
One easy example is how common entanglement is. Päs’ claim stands out that quantum objects are “completely and entirely merged,” making it “impossible to say anything at all about” its parts.
Päs does not tell us whether he believes all quantum objects are entangled or just some of them, although he does tell us (in the same paragraph) that “Apply entanglement to the entire universe and you end up with Heraclitus’s dogma ‘From all things One.’”
I wonder just how common entanglement is. The following ChatGPT answer is both important and straightforward.
“No, not all particles are entangled with others… In general, entanglement is a relatively rare event, and most particles in the universe are not entangled. To observe entanglement, one typically has to perform experiments in a controlled laboratory setting, where the conditions for entanglement can be carefully engineered. In these experiments, entanglement can be created, measured, and manipulated, allowing researchers to study the properties and implications of this phenomenon in more detail.”
It sounds like we have a long way to go before we can apply entanglement to the entire universe. In another post, I will argue that entanglement is more common than proven in the experiment — but for a different reason.
An arguably bigger issue is what exactly entanglement does. Is it like what Päs said that entanglement makes it impossible to know its constituents? Let’s move on to that claim. But first, let’s begin with the Big Bang theory.
Rethinking “the One” & “All Things” in Light of the Big Bang.
Heraclitus’s tenets “from One all things” and “from all things One,” sometimes referred to as the “Unity of Opposites,” sound appealing, as it implies that once we figure out what “One” is, we are done with describing the entire universe.
The only problem is that Heraclitus, a Greek philosopher from the 5th century BCE, did not see the age of quantum physics nor the Big Bang theory, and could not possibly see the dynamics and complexity with both “the One” and “all things.”
Heraclitus may see the two tenets as two sides of the same coin, but we can break them apart. An intuitive interpretation of “from all things One” is to trace backward to the history or origin of the Universe, while “from One all things” goes forward on how the One has been shaping everything in the Universe as we know it.
The two are not the same in the ontological and epistemological senses because the Big Bang theory — the most widely accepted theory or the prevailing cosmological model that explains the origin and evolution of the universe — says so.
According to the Big Bang model, the Universe started from a state of singularity that had an infinitely high density and temperature, then underwent rapid expanding and cooling. Expansion caused matter and energy to spread out, leading to the formation of galaxies, stars, and planets.
The Big Bang itself is in a superposition of a historical event and also an ongoing process with which our Universe arrives here and now from the initial state of singularity. Bear in mind that singularity was when and where the laws of physics broke down and the concept of time itself did not exist. As a result, we cannot pinpoint the time or place for singularity.
That said, the Big Bang is generally considered to have taken place around 13.8 billion years ago, and will continue to expand for billions of years to come.
Which Universe Are We Talking About?
Here is the problem we face: The Universe as we know it today had a starting point (i.e., when it broke off from singularity more than 13 billion years ago), but is far away from reaching its ending point yet, as we are still in the middle of the Big Bang expanding, perhaps only halfway through it. See this article for an interesting, non-technical discussion of it.
This means we can figure out the One as the starting point but not “all things” in the end — unless we treat the Universe today as one of the “moving ends.”
Let’s look at some numbers to better understand the issue. The recent finding shows that our Universe is actually expanding 73 plus or minus 1 kilometer per second per megaparsec, which predicts the size of the universe will double in about 10 billion years. To get a better sense, the universe at one minute ago would be (73*60=4,380 KM) smaller than the universe of this minute, or the universe one hour ago was 73*60*60=262,800 KM smaller than this hour or the universe of yesterday was 73*60*60*24=6,307,200 KM smaller than today.
The earlier problem of “information loss” identified by Päs seems applicable here: Using the universe at any earlier time always means a loss of essential information for describing the universe of this moment, simply because the sizes, matter and energy of the earlier Universes do not match that of today.
It’s much easier for Heraclitus to say, “One is all, and all is One,” as he had no idea how fast the universe moves and grows. We on the other hand do not have the luxury of making such a highly simplified statement, given we now know the Universe is still expanding as we speak, which means we are dealing with an almost endless number of timepoints. Which Universe, or perhaps more accurately, the Universe at which timepoint should we use to describe is a big question.
Saying “only universe can describe the universe” helps little, because the One will lead to numerous universes as time goes on, or a continuously growing universe. Only today’s universe can describe itself, not the One from yesterday — unless you don’t care about losing essential information.
Is the “One” Really Just One?
Let’s now return to “from all things One,” which as I said earlier is concerning about going back to find out exactly what the One is. The simple answer is that it is dynamic and complex — most likely not one but multiple particles.
From the quantum wavefunction we know the particle at the very beginning of the universe — assuming we are capable of going back all the way to the beginning, which according to this article is far from being a sure thing — may have multiple states superpositioned, each state having a different probability of existence. In that sense, the “One” was not a single state of a single particle but multiple particles, each with multiple states, so condensed in the singularity that made all laws of physics fail to work. It eventually triggered the Big Bang explosion to create the universe we know today.
Recent research points out the universe may have conflict at the heart of cosmology, which explains why there is a discrepancy between “two different telescopes to study the structure of the Universe at different cosmic epochs. One facility, called the South Pole Telescope (SPT), looks at the earliest possible light, emitted a mere 380,000 years after the Universe began. At that time, the Universe was 0.003% its current age.”
“The second facility is called the Dark Energy Survey (DES)… This telescope can image galaxies from the current day to as far back as eight billion years ago.” If the Big Bang theory is right, we should use the earlier SPT to predict the later DES. In reality, there is about 10% discrepancy between them.
What Entanglement Really Means
After learning what the One and all things in the universe are, we are ready to return to the earlier question of what exactly entanglement means or whether Päs is right to say that entanglement makes it impossible to know constituents.
I copied the original Päs claim and then asked ChatGPT if it was right. Here is the answer I received: “The statement is partially correct…, it is not entirely true that it is impossible to say anything at all about the properties of the constituents anymore, as it is possible to extract some information about the system by doing measurements, and also by studying the properties of the subsystems of the entangled systems.”
This sounds like “plain vanilla” because it can lead to different interpretations. For example, knowing “it is possible to extract some information about the system by doing measurements” is not enough. We need more specific information.
So, I asked ChatGPT a more “pointed” question: “Does entanglement mean if I know the state of one particle, I know the state of another (entangled) particle?” This is not a random inquiry but inspired by my previous impression learned from elsewhere, which differs from Päs’ “impossibility” thesis.
The answer I received this time is confirmative: “If two particles are entangled, then knowing the state of one particle can give you information about the state of the other particle, but it does not mean that you know the state of the other particle with certainty.”
This is good news because it confirms my previous impression but disagrees with Päs. In fact, based on my reading in the past, even the uncertainty part of the above ChatGPT answer is not entirely right, as sometimes entanglement can make the state of the unmeasured particle known with certainty.
For example, this article of stackexchange.com says “Quantum Entanglement means that when you have two entangled particles, and you will measure one particle’s spin … and second particle will definitely have opposite spin or in other words in you know state of one of two entangled particles you will definitely know state of the other entangled particle” (emphasis added).
Another example is an article from California Institute of Technology Science Exchange, which says very vividly that “The beauty of entanglement is that just knowing the state of one particle automatically tells you something about its companion, even when they are far apart.”
Still, let’s make sure we get it completely right. So, my final question asks for an example of entanglement. ChatGPT faithfully responded, first with quick background on the famous “double-slit experiment:”
“A double-slit experiment involves shining light through two small slits in a barrier, creating an interference pattern on a screen behind the barrier. This experiment demonstrates the wave-particle duality of light, as the pattern is characteristic of a wave interference, but the light behaves as particles when observed.”
To be honest, a double slit experiment is best shown as a diagram. Unfortunately, ChatGPT is a text-based AI model, so images or diagrams are out of the question. A few good images however can be found on this website of Indiana University https://iu.pressbooks.pub/openstaxcollegephysics/chapter/youngs-double-slit-experiment/, which show not only the process of “double slit experiment” but interference in constructive and destructive patterns.
Without spending too much time on double slit experiments, ChatGPT did a good job telling us how entanglement will impact the state of measured and unmeasured particles:
“Now, imagine that you have a pair of entangled electrons, and you sent one of the electrons through the double-slit, and you measure the position of the electron on the other side. You will find that the other electron has a definite position, even though it has not been measured. This is because the state of the second electron is entangled with the state of the first electron, so measuring the state of one electron affects the state of the other, even if they are far apart.”
These words are more in line with my own knowledge but disagree with Päs. It basically says knowing the state of a measured particle helps us know the state of another unmeasured — but entangled — particle. Simply put, entanglement is our friend, not foe, in learning the unmeasured part of the world.
Knowledge Gaps on Entanglement
Our knowledge of entanglement is still limited and insufficient to answer one or a few deep questions.
An obvious question is how exactly entanglement works. ChatGPT faithfully responded to this question of mine: “How to explain that knowing the state of one entangled particle leads to immediate knowledge of the state of another particle?”
This time ChatGPT did a mediocre job, offering little new information and simply repeating what entanglement is: “the state of an entangled particle can be described only in relation to the state of the other particle. Therefore, measuring the state of one particle gives you immediate knowledge of the state of the other particle.”
However, ChatGPT responded better to my follow up question: “Does entanglement mean there is only one state shared by entangled particles?” I must admit this is another pointed question to get to the link between entanglement and superposition, to be discussed later.
ChatGPT says this time: “No, entanglement does not mean that there is only one state shared by entangled particles. Instead, entangled particles share a set of possible states, known as a superposition of states… When a measurement is made on one of the entangled particles, the state of the particle collapses into one of the possible states in the superposition, and the state of the other particle becomes correlated with it, meaning that the other particle is instantaneously ‘forced’ into the corresponding state in the superposition. This correlation between the states of entangled particles is what allows for the transfer of information between them, even at large distances.”
Thanks for this answer that clarifies entanglement is not correlation with one state (e.g., both particles are spinning up or both spinning down) but about superposition of multiple states. What is not clear however is how and why measuring the state of one particle will magically “force” the particle to change its state.
So here is my next follow up question: How is the other particle instantaneously “forced” into the corresponding state in the superposition? This time ChatGPT again talks less intelligently: “The instant change in state of the other particle in entanglement is often referred to as ‘spooky action at a distance’… According to quantum mechanics, the other particle is not directly influenced by any physical force, but its state is correlated with the first particle in such a way that it instantaneously changes its state when the first particle’s state is measured. This correlation is described by the mathematical concept of entanglement, which is a fundamental aspect of quantum mechanics and is widely accepted by the physics community.”
Widely accepted it may be, widely understood it is certainly not.
The problem in my view is that although quantum physicians have argued that entanglement is nothing “spooky,” it has yet to come up with a solid theory to explain it. We know entanglement does not require direct influence nor communication, and no communication means no transmission of information across space and time, which in turn means entanglement does not require higher speed than light (i.e., relativity remains solid), we just don’t know how entanglement really works.
ChatGPT is honest on this: “While entanglement has been widely observed and is a well-established concept in quantum mechanics, it is still not fully understood from a fundamental perspective. The correlation between the states of entangled particles is described by the mathematical formalism of quantum mechanics, but a complete physical explanation for this phenomenon is still a subject of active research and debate in the physics community.”
“Many scientists believe that a full understanding of entanglement and its implications for our understanding of the nature of reality may require a deeper theory that goes beyond quantum mechanics. Some interpretations of quantum mechanics, such as the many-worlds interpretation, attempt to provide a framework for understanding entanglement and other quantum phenomena, but these interpretations are still the subject of ongoing discussion and debate.”