# The Ongoing Challenge of Understanding Quantum Mechanics

Written on

The quest to interpret quantum mechanics is fraught with confusion and controversy. In my earlier piece, I delved into the peculiarities of quantum mechanics, culminating with Richard Feynman's observation:

> “Quantum Mechanics is so confusing that I don’t even know if there’s a problem.”

Now, I intend to examine why this conundrum is itself so challenging and why the interpretations surrounding quantum mechanics spark such vigorous debate.

The field is rife with competing interpretations, with varying preferences even among the most esteemed researchers. The question of how to interpret quantum mechanics remains largely unresolved, and discussions are perhaps more vibrant today than ever before.

I will focus primarily on the **_Many Worlds Interpretation_** and the **_Copenhagen Interpretation_**, as they present starkly different views about our universe, leading to astonishing implications. Although Bohmian Mechanics is intriguing, it is somewhat more complex and will not be discussed here. For those interested, I recommend additional resources.

Furthermore, I will explore why the connection between consciousness and quantum mechanics is so appealing to many.

The history of quantum mechanics interpretations is peculiar, revealing that even those within a community regarded as highly rational and critical—namely, theoretical physicists—are susceptible to human errors such as personality cults, politics, and dogma.

Sean Carroll has stated that it is a source of embarrassment for 20th-century physics that it adhered for so long to an outdated interpretation of quantum mechanics, as discussions about alternative interpretations were largely discouraged in its early days.

One notable instance of this is the treatment of Hugh Everett, the originator of the **_Many Worlds Interpretation_**, who effectively became marginalized within the physics community.

However, I will not delve into that narrative here. For those curious, I recommend starting with David Albert's discussion on Sean Carroll’s Mindscape Podcast.

In the remainder of this article, I aim to succinctly explain why the strangeness of quantum mechanics complicates its interpretation.

## The Copenhagen Interpretation

The predominant interpretation of quantum mechanics among modern physicists is still the Copenhagen interpretation, developed by Heisenberg and Bohr in Copenhagen between 1925 and 1927. This was the interpretation presented to me during my introductory course on quantum mechanics.

In my previous article, I concentrated on what defines a quantum measurement and the peculiarities that arise during such measurements.

I introduced the concept of the wave function, which embodies the inherently probabilistic nature of quantum measurements.

> The wave function encapsulates everything we can ascertain about a quantum system's spin and integrates the statistical characteristics of the measurement into reality's framework. A spin wave function might be represented as:

spin = up z (with 50%) + down z (with 50%)

At the heart of the Copenhagen interpretation lies the notion of **_wave function collapse_**.

This concept posits that a quantum system—essentially every object in the universe—remains somewhat indeterminate until it is measured. Following the measurement, it collapses into a more defined state known as an eigenstate of an observable.

In the Copenhagen framework, the observer is perceived as instigating the "collapse" of the wave function since, post-measurement, we only observe a specific outcome rather than the statistical distribution.

## The Collapse of the Wave Function

Starting with the wave function:

spin = up z (with 50%) + down z (with 50%)

Measuring yields two potential results:

- spin collapses to up z (with 50%)

**or**

- spin collapses to down z (with 50%)

### The Challenges of This Model

The difficulty arises in the treatment of the observer within this theory. The observer is not considered a quantum system due to its unique, inexplicable ability to induce wave function collapse.

There is no clear justification for this within the formal structure of quantum physics. Why should a mere passive observer possess this extraordinary property?

**_One potential resolution is to model the observer as a quantum system._**

Since every object in the universe qualifies as a quantum system, there is no compelling reason to exclude the measuring device from this classification. This approach aligns with the standard quantum measurement known as **_von Neumann measurement_**.

We express this relationship through a vector product between quantum states (denoted by a **bold x**), resulting in an entangled state:

total system = (observer measures up spin z) **x** (spin up z)

**_Here, the observer is represented by a wave function, and thus the observer measuring one outcome remains part of the overall system._**

The wave function of the system can be expressed as:

total system = (observer sees up z) **x** up z + (observer sees down z) **x** down z

**_This is not what the individual observer perceives; the observer only witnesses one branch of the wave function!_**

Observers = (observer sees up z) **x** up z **or** (observer sees down z) **x** down z

**_The critical distinction between these two expressions lies in the “+” sign versus the “or” sign._**

In simple terms, if we use **_+_**, both branches remain existent. If we use **_or_**, the wave function collapses to one of the measurement's potential outcomes. Consequently, only one outcome is then real, as posited by the Copenhagen interpretation.

Applying this reasoning to Schrödinger’s Cat, upon opening the box, there exists only one reality where the cat is either alive or dead. Should we employ the plus sign, the cat exists in a state of both life and death simultaneously.

**_But where exactly is it alive and where is it dead?_**

## Is There More Than One World?

Assuming we employ the plus sign, this “branching” naturally arises from treating the observer as a quantum mechanical system.

The **_total wave function of the world_** splits into various outcomes, leading to different worlds after each measurement!

In one world, the observer measuring the spin sees spin up, while a parallel world could exist where the observer perceives spin down.

**_These two worlds then continue to develop independently!_**

If one treats the entire measurement process as quantum mechanically valid, as there is no substantial reason not to, the **_Many Worlds Interpretation_** seems to emerge more naturally from quantum mechanics' mathematics than the Copenhagen interpretation, as it avoids arbitrary assumptions regarding wave function collapse.

One might assume that a trivial factor like an atom's spin would have minimal impact on the universe's evolution. After all, we do not observe quantum properties in our daily lives.

Yet, a small difference can have profound effects.

**_Let me illustrate with a thought experiment:_**

Imagine a **_quantum casino_** where you gamble on spin measurement outcomes. You wager $100 on each measurement. Since the casino operates as a non-profit, winning nets you $200, while losing yields nothing.

After a night of gambling, suppose you placed bets on 100 spin measurements.

On average, nothing significant occurred—you lost some and won some.

However, if you subscribe to the **_Many Worlds Interpretation_**, you can take solace in the fact that a version of yourself emerged victorious, winning $10,000 and acquiring a new car, while another version is distraught, having gambled away a college fund.

This scenario is not merely theoretical; establishing such a quantum casino could be a fascinating startup venture, and these implications naturally follow from one of quantum mechanics' leading interpretations.

**_Strange, isn’t it?_**

I will pause for a moment to allow you to absorb this, accompanied by a serene image of stones on a beach.

I hope this provides clarity. Now, let's return to the topic of wave function collapse.

## What Triggers the Collapse of the Wave Function? What Justifies the Observer's Special Status?

A critical moment arises when the wave function collapses—this occurs when we observers become cognizant of the measurement's result. In von Neumann’s framework, this is facilitated by “an abstract ego” that represents the measurement result's information content.

Figures such as von Neumann and Wigner emphasize the necessity of incorporating the observer's subjective experience for a comprehensive understanding of quantum mechanics (for a more in-depth examination of von Neumann's theory, see relevant literature).

This leads to the speculation about the elusive role of **_consciousness_** in quantum mechanics.

The ambiguous relationship between consciousness and quantum mechanics has given rise to numerous pseudoscientific claims from figures like Deepak Chopra or the quantum healing community.

**_I do not aim to reopen that debate here._**

While the connection between quantum mechanics and consciousness remains unresolved, some scientifically grounded attempts to connect the two exist (for instance, the psychophysical interpretation).

Nevertheless, without a robust theory of consciousness, it is premature to assert that consciousness possesses the mystical ability to collapse wave functions.

I propose that a different perspective may be more fruitful.

## Quantum Mechanics as an Information Theory

As I previously noted, epistemology (what we know about the world) and ontology (what exists) converge in quantum mechanics. If we define reality as that which we measure through quantum observations, then it follows that reality is influenced by our measurements.

It becomes challenging to separate our role as observers from the objective reality of phenomena.

**_In my view, the most promising (though still not fully developed) approach to resolving quantum mechanics' challenges is to conceptualize it as a theory of information._**

Wheeler famously stated “It from Bit” or “It from Qbit,” while theorists like Carl Friedrich von Weizsäcker have explored the concept of “Urtheorie,” among others.

Information could serve as the fundamental unit of reality, bridging the objective, material aspects of the world with the subjective. This aligns with the long-standing efforts of proponents of Neutral Monism.

Thus, discussing an objective world independent of an observer may be futile, much like Kant demonstrated that a perspective-free view of the world is fundamentally inconsistent.

Perhaps, through this lens, our interactions with quantum objects will become clearer.

Yet, as you can see, clarity remains elusive, which is both exciting and frustrating.

**_Such is the nature of quantum mechanics, and perhaps we should gradually acclimate to this reality!_**