*Since the early days of quantum mechanics, physicists and philosophers have argued that solving problems of measurement requires appealing to the mind of a conscious observer. That is still the case today, argues Shan Gao.*

Quantum mechanics is a very successful physical theory due to its accurate empirical predictions. But the key puzzle still lies at its core. It’s a matter of measurement. What the Schrödinger equation tells us, that the system described by the wavefunctions can be in a state of superposition and instantiate apparently contradictory properties, and what experience tells us, that such There seems to be an inconsistency when measuring things. For the system, we get one clear result instead of superposition. Using Schrödinger’s thought experiment, quantum mechanics seems to imply that cats are alive and dead at the same time, but we only experience cats living or dead. .

There are several proposed solutions to the measurement problem, including what has come to be known as hidden variable theory, which suggests that the wavefunction is not a complete description of the system, but rather eliminates the superposition state. – world interpretation. This suggests that superposition is expressed across different universes, each with one distinct result. However, since the early days of quantum mechanics, physicists and philosophers have argued that solving measurement problems requires the human mind. To understand why, we need to look more closely at the measurement problem and the proposed solution.

recommended reading

Consciousness has nothing to do with quantum mechanics

Carlo Rovelli

**Formalization of measurement problems**

In 1995 Tim Maudlin gave an exact formulation of the measurement problem. According to this formulation, the problem of measurement results from the discrepancies in the following three claims.

(C1) The wavefunction of a physical system is a complete description of the system.

(C2) The wavefunction always evolves according to linear dynamical equations such as the Schrödinger equation.

(C3) measurement gives a single, clear result.

There are three main approaches to solving the measurement problem formulated in this way. The first approach is to refute the assertion (C1) and add specific hidden variables and corresponding dynamics to explain the unambiguous measurement results. A well-known example is de Broglie and Bohm’s pilot wave theory, or Bohm mechanics. The second approach denies claim (C2) and modifies the linear and deterministic Schrödinger equation by adding specific nonlinear and stochastic evolution terms that account for the dynamic collapse of the wavefunction. , is to explain the clear measurement results. Such theories are called collapse theories. A third approach is to deny the claim (C3) and assume that there are many equally real worlds to accommodate all possible outcomes of the measurement. In this way, we may also be able to explain robust measurements in each world, including ours. This approach is called Everett’s theory or the many-worlds interpretation of quantum mechanics.

___

If you observe the pointer of the measuring instrument pointing to a particular location after taking a measurement, are you really sure that the pointer is actually pointing to that particular location?

___

**Where does the mind fit into quantum mechanics? **

So far, we have not talked about observers and their minds. And quantum mechanics seems to have nothing to do with consciousness. But there are two well-known and interesting predictions of his that quantum mechanics and consciousness are closely related. These two conjectures are both related to decay theory. The first suggests that consciousness causes wavefunction collapse. This conjecture has a long history, dating back to von Neumann (1932), London and Bauer (1939), Wigner (1961), and Stapp (1993). Recently, Chalmers and McQueen (2022) formulated a more rigorous and complete anticipation based on the integrated information theory (IIT) of consciousness. Another claims that the collapse of the wavefunction creates consciousness. This conjecture was proposed by Penrose and Hamerov (1996, 2014), Orchestration goal reduction modelIndeed, many researchers in the field consider these two speculations too radical to be true, but experiments have yet to give a definitive answer.

So does the mind really matter in quantum mechanics? My answer is yes, at least for now. Let me ask you a simple question. If you observe the pointer of a measuring instrument pointing to a particular location after a measurement, are you really sure that the pointer actually points to a particular location? I have to say that I still don’t know if it points to a specific location. In fact, all we know for sure from experience is that we, as observers, obtain a definite record by having a definite mental state of that record after the measurement. It is not known with certainty whether will give really clear results after measurements. For example, if the mental state is randomly determined by his one outcome branch of post-measurement superposition, as in the single-mind theory (Albert and Loewer, 1988), then the Does not indicate position. But the observer will get a clear record after observing the pointer position.

So for now we have to assume some kind of psychophysical connection in quantum theory. Without assumptions about the relationship between the mind and quantum mechanics, we cannot even test the predictions of quantum theory. This is because the measurement is made by the observer in the final analysis, and the measurement ends only when the result is consciously perceived by the observer. This motivates a more basic formulation of the observer measurement problem (Gao, 2019). This demonstrates the incompatibility of her three assumptions:

(A1) The observer’s mental state is determined by the wave function.

(A2) The wavefunction always evolves according to linear dynamical equations such as the Schrödinger equation.

(A3) Observer measurements yield a single mental state with a clear record.

This formulation of the measurement problem emphasizes the important role of psychophysical connections in the cause of the problem. This new formulation allows us to look at solutions to measurement problems from a new angle. In particular, his three principal realist quantum theories of Baomian mechanics, Everett’s theory and collapse theory correspond to three different forms of psychophysical connection. In fact, the physical states that may determine the observer’s mental state include (1) the wavefunction in decay theory, (2) specific branches of the wavefunction in Everett theory, and (3) his three types of There is only one. Other hidden variables such as particle composition in Bohm mechanics.

___

Despite major advances in neuroscience and quantum technology, quantum mechanics and consciousness remain two mysteries of our time.

___

As an optimist, I believe we will eventually know the form of psychophysical connection and which quantum theory is true. is one of the basic reasons I justify. *for now*Another deeper reason is that the forms of psychophysical connectivity envisioned by quantum theory must be consistent with current scientific and philosophical understandings of the conscious mind. Analysis of the observer’s mind may help determine which quantum theory is wrong.

Take Bohm mechanics for example. In Bormian mechanics, the physical state that determines the result of a measuring device and the mental state of an observer is not the wave function, but the arrangement of the Bormian particles. These particles have only position and velocity in three-dimensional space, no mass, no charge, and no interaction with each other (unless their wavefunctions are entangled). An interesting question then arises. Could these Bohmian particles constitute a consciousness-producing brain? Or, put another way, does the observer have Bohmian mechanics consciousness?

recommended reading

What the Nobel Prize Wrong About Quantum Mechanics

Tim Maudlin

A basic premise in neuroscience and philosophy of mind is that parts of a system must be tightly coupled together to enable the generation of a conscious mind. A typical example is the Integrated Information Theory of Consciousness, which is one of the leading theories of consciousness. According to that theory, consciousness requires the grouping of elements within a system that have physical causal relationships, and the level of consciousness of a system is described by the integrated information of the system. The mathematical quantity Φ. A system with strong element coupling has a high Φ, and a system with weak element coupling has a small Φ. Our brains have a very high Φ and are therefore very conscious. In contrast, a system is 0 if there are no connections to any component of the system. This means that the system is completely unaware.

Now let’s move on to the important issues. What if our brains consisted of nothing but Bormian particles? Could this Bormian brain produce a conscious mind? Answering this question requires both neuroscience and the philosophy of mind. We need a common assumption in That is, our consciousness is generated by the activity of some quasi-classical systems, such as neurons in the brain, without quantum entanglement. In this case, the effective wavefunctions of these quasi-classical systems are product states. That is, each system has its own effective wave function or wave flux, and the motion of its Bormian particles is guided only by its wave flux.

Then it can be argued that such a Bohf brain cannot generate a conscious mind. Since there is no connection between the and the system as a whole, the Bohmian brain has a Φ of 0 and thus no conscious experience. Do not consolidate information.

___

Without assumptions about the relationship between the mind and quantum mechanics, we cannot even verify the predictions of quantum theory.

___

The Bormian mechanics example above shows that the mind actually matters in quantum mechanics for now. According to our current understanding of consciousness, our bains cannot consist solely of Baumian particles, as they are incapable of creating the conscious mind that we have.

Despite major advances in neuroscience and quantum technology, quantum mechanics and consciousness remain two mysteries of our time. In my view, a careful and thorough investigation of possible relationships between them is not only necessary, but even urgent, in order to unravel these two mysteries. We hope this article will inspire more people to join us in our quest for the ultimate reality of the universe.