36 | David Albert on Quantum Measurement and the Problems with Many-Worlds
Mar 4, 2019
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David Albert joins the host to discuss the measurement problem in quantum mechanics. They delve into the Many-Worlds interpretation, exploring skepticism towards this theory. The conversation explores historical influences, hidden variables, and rational decision-making in uncertain quantum scenarios.
Quantum measurement problem questions what occurs when observing quantum systems, highlighting the need for separate rules.
Many-Worlds interpretation explains quantum outcomes by branching into parallel universes, challenging traditional views.
Critiques of Many-Worlds theory focus on aligning deterministic branching futures with probabilistic decisions, sparking ongoing debates.
Deep dives
Everett's Many Worlds Interpretation
Everett's Many Worlds Interpretation proposes that the deterministic equations of quantum mechanics lead to a world where every possible quantum outcome branches into a new parallel universe. This interpretation contrasts the traditional chance-based view of quantum mechanics. The theory argues that the appearance of chance or probability is our subjective experience of splitting into different branches, rather than actual probability outcomes.
Criticism of the Many Worlds Interpretation
A significant objection to the Many Worlds Interpretation focuses on the challenge of reconciling the deterministic nature of Everett's theory with the probabilistic nature evident in our empirical observations. Decision theory is often cited in critiques, highlighting that branching preferences cannot be logically deduced from non-branching preferences. This critique questions the coherence of using non-branching preferences to determine actions in branching futures.
Potential Solutions to the Probability Challenge
Efforts to address the probability challenge associated with Everett's theory include arguments from the Oxford school of thought, which suggest that chance-like decisions can emerge in a deterministic universe based on how rational agents would behave. These arguments attempt to align decision-making in branching futures with traditional decision theory, seeking to show that rational actions in deterministic branching worlds mirror ones in probabilistic outcomes.
Significance of Decision Theory in Quantum Interpretations
Decision theory plays a critical role in assessing the validity of interpretations like Everett's Many Worlds theory. The challenge lies in bridging the gap between deterministic branching futures and probabilistic non-branching preferences. Critics argue that the constraints and insights derived from non-branching preferences are insufficient to dictate rational behavior in branching scenarios. The debate over the role of probability in quantum interpretations continues to spark theoretical and philosophical discussions.
Debunking Branching Preferences
The podcast delves into the concept of branching preferences and challenges the idea that non-branching preferences fully dictate one's choices in branching scenarios. Using a financial example involving $100 and $1 distributed across different states, it illustrates how branching scenarios introduce new options that are not solely determined by non-branching preferences. The discussion highlights the misconception that preferences among non-branching cases can exclusively govern choices in branching situations, emphasizing the autonomy and complexity of branching preferences.
Epistemic Uncertainty and Self-Locating Probabilities
Exploring self-locating probabilities, the episode introduces a philosophical conundrum regarding uncertainty in determining personal outcomes within multiverse scenarios. Drawing on examples involving identical states and diverging experiences, it raises questions about assigning probabilities where empirical verification is elusive. The conversation contrasts classical statistical mechanical probabilities with purely indexical facts, indicating the challenge of formulating theories reliant on inherently subjective probabilistic assessments in quantum scenarios.
Quantum mechanics is our best theory of how reality works at a fundamental level, yet physicists still can’t agree on what the theory actually says. At the heart of the puzzle is the “measurement problem”: what actually happens when we observe a quantum system, and why do we apparently need separate rules when it happens? David Albert is one of the leading figures in the foundations of quantum mechanics today, and we discuss the measurement problem and why it’s so puzzling. Then we dive into the Many-Worlds version of quantum mechanics, which is my favorite (as I explain in my forthcoming book Something Deeply Hidden). It is not David’s favorite, so he presents the case as to why you should be skeptical of Many-Worlds. (The philosophically respectable case, that is, not a vague unease at all those other universes.) Support Mindscape on Patreon or Paypal. David Albert received his Ph.D. in physics from Rockefeller University. He is currently the Frederick E. Woodbridge Professor of Philosophy at Columbia University. His research involves a number of topics within the foundations of physics, including the arrow of time (coining the phrase “Past Hypothesis” for the low-entropy state of the early universe) and quantum mechanics. He is the author of a number of books, including Time and Chance, Quantum Mechanics and Experience, and After Physics. Columbia web page Publications at PhilPapers Wikipedia page Videos at Closer to Truth BigThink interview
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