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Foil theories, sometimes called mathematically rigorous science fiction, describe ways the world could have been were it not quantum mechanical. Our understanding of quantum theory has been deepened by contrasting it with these alternatives. So far, observers in foil theories have only been modeled implicitly, for example via the recorded probabilities of observing events. Even when multi-agent settings are considered, these agents tend to be compatible in the classical sense that they could always compare their observations. Scenarios where agents and their memories are themselves modeled as physical systems within the theory (and could in particular measure each other, as in Wigner's friend experiment) have not yet been considered. In this workshop, we will investigate which foil theories allow for the existence of explicit observers, and whether they allow for paradoxes in multi-agent settings such as those found in quantum theory. We will also investigate which interpretations of quantum theory would equally well interpret the foil theories, and which interpretations are truly quantum. We will gain a deeper understanding of how this can happen by discussing appropriate definitions observers in these theories and seeing how such observers learn about their environment.
Sponsorship for this workshop has been provided by:
- Giulio Chiribella, University of Oxford
- Lidia del Rio, ETH Zurich
- Thomas Galley, University College London
- Markus Mueller, Perimeter Institute & Institute for Quantum Optics and Quantum Information, Vienna
- Renato Renner, ETH Zurich
- Jess Riedel, Perimeter Institute
- Carlo Maria Scandolo, University of Oxford
- Ruediger Schack, Royal Holloway University of London
- Rob Spekkens, Perimeter Institute
- Joel Wallman, University of Waterloo
- Giulio Chiribella, University of Oxford
- Thomas Galley, University College London
- Ravi Kunjwal, Perimeter Institute
- Markus Mueller, Perimeter Institute & Institute for Quantum Optics and Quantum Information, Vienna
- Renato Renner, ETH Zurich
- Jess Riedel, Perimeter Institute
- Nitica Sakharwade, Perimeter Institute
- Carlo Maria Scandolo, University of Oxford
- Ruediger Schack, Royal Holloway University of London
- David Schmid, Perimeter Institute
- John Selby, Perimeter Institute
- Rob Spekkens, Perimeter Institute
- Joel Wallman, University of Waterloo
Monday, April 2, 2018
Time |
Event |
Location |
10:00 – 10:30am |
Registration |
Reception |
|
WHAT IS QUANTUM |
|
10:30 – 11:30am |
Jess Riedel, Perimeter Institute |
Bob Room |
11:30 – 12:00pm |
Coffee Break |
Bistro – 1st Floor |
12:00 – 1:00pm |
Discussion 1 |
Bob Room |
1:00 – 2:30pm |
Lunch |
Bistro – 1st Floor |
2:30 – 3:30pm |
Thomas Galley, University College London |
Bob Room |
3:30 – 4:00pm |
Coffee Break |
Bistro – 1st Floor |
4:00 – 5:00 pm |
Discussion 2 |
Bob Room |
Tuesday, April 3, 2018
Time |
Event |
Location |
|
INFORMATION ACQUSITION |
|
10:30 – 11:30am |
Markus Mueller, Perimeter Institute and Institute for Quantum Optics and Quantum Information, Vienna |
Bob Room |
11:30 – 12:00pm |
Coffee Break |
Bistro – 1st Floor |
12:00 – 1:00pm |
Discussion 3 |
Reflecting Lounge |
1:00 – 2:30pm |
Lunch |
Bistro – 1st Floor |
2:30 – 3:30pm |
Markus Mueller, Perimeter Institute and Institute for Quantum Optics and Quantum Information, Vienna |
Bob Room |
3:30 – 4:00pm |
Coffee Break |
Bistro – 1st Floor |
4:00 – 4:30pm |
Discussion 4 |
Reflecting Lounge |
Wednesday, April 4, 2018
Time |
Event |
Location |
|
FOILS AND OTHER MODELS |
|
10:30 – 11:30am |
Rob Spekkens, Perimeter Institute |
Bob Room |
11:30 – 12:00pm |
Coffee Break |
Bistro – 1st Floor |
12:00 – 1:00pm |
Discussion 5 |
Reflecting Lounge |
1:00 – 2:00pm |
Lunch |
Bistro – 1st Floor |
2:00 – 3:30pm |
Colloquium |
Time Room |
3:30 – 4:00pm |
Coffee Break |
Bistro – 1st Floor |
4:00 – 5:30pm |
Joel Wallman, University of Waterloo |
Bob Room |
Thursday, April 5, 2018
Time |
Event |
Location |
|
PARADOXES & INTERPRETATIONS |
|
10:30 – 11:30am |
Renato Renner, ETH Zurich |
Bob Room |
11:30 – 12:00pm |
Coffee Break |
Bistro – 1st Floor |
12:00 – 1:00pm |
Discussion 6 |
Reflecting Lounge |
1:00 – 2:30pm |
Lunch |
Bistro – 1st Floor |
2:30 – 3:30pm |
Lidia del Rio, ETH Zurich |
Bob Room |
3:30 – 4:00pm |
Coffee Break |
Bistro – 1st Floor |
4:00 – 5:00pm |
Ruediger Schack, Royal Holloway University of London |
Bob Room |
6:00 – 8:00pm |
Banquet |
Bistro – 2nd Floor |
Friday, April 6, 2018
Time |
Event |
Location |
|
CAUSALITY? |
|
10:30 – 11:30am |
Giulio Chiribella, University of Oxford |
Bob Room |
11:30 – 12:00pm |
Coffee Break |
Bistro – 1st Floor |
12:00 – 1:00pm |
Discussion 7 |
Reflecting Lounge |
1:00 – 2:30pm |
Lunch |
Bistro – 1st Floor |
2:30 – 3:30pm |
Carlo Maria Scandolo, University of Oxford |
Bob Room |
3:30 – 4:00pm |
Coffee Break |
Bistro – 1st Floor |
4:00 – 5:00pm |
Wrap Up and Good-Bye |
Bob Room |
Giulio Chiribella, University of Oxford
Agents, Subsystems, and the Conservation of Information
Dividing the world into subsystems is an important component of the scientific method. The choice of subsystems, however, is not defined a priori. Typically, it is dictated by our experimental capabilities, and, in general, different agents may have different capabilities. Here we propose a construction that associates every agent with a subsystem, equipped with its set of states and its set of transformations. In quantum theory, this construction accommodates the traditional notion of subsystems as factors of a tensor product, as well as the notion of classical subsystems of quantum systems. We then restrict our attention to systems where all physical transformations act invertibly. For such systems, the future states are a faithful encoding of the past states, in agreement with a requirement known as the Conservation of Information. For systems satisfying the Conservation of Information, we propose a dynamical definition of pure states, and show that all the states of all subsystems admit a canonical purification. This result extends the purification principle to a broader setting, in which coherent superpositions can be interpreted as purifications of incoherent mixtures. As an example, we illustrate the general construction for subsystems associated with group representations.
Thomas Galley, University College London
Compatibility of implicit and explicit observers in quantum theory and beyond
The observer is implicitly present in the measurement postulates of quantum theory. However the observer can also be modeled as a quantum system interacting with other quantum systems. A theory where every action implicitly undertaken by an agent (such as a measurement or preparation) can be explicitly modeled as non-classical systems interacting is called a universal theory. By modifying the measurement postulates of quantum theory (and preserving the other postulates) we create theories where the observer can still be explicitly modeled as a pure quantum state, but where the implicit observer is different. We argue that any modification of the measurement postulates of quantum theory gives a theory which is not universal. That is to say there are certain actions implicitly carried out by an agent which cannot be explicitly modeled.
Markus Mueller, Perimeter Institute and Institute for Quantum Optics and Quantum Information, Vienna
From observers to physics via algorithmic information theory I & II
Motivated by the conceptual puzzles of quantum theory and related areas of physics, I describe a rigorous and minimal “proof of principle” theory in which observers are fundamental and in which the physical world is a (provably) emergent phenomenon. This is a reversal of the standard view, which holds that physical theories ought to describe the objective evolution of a unique external world, with observers or agents as derived concepts that play no fundamental role whatsoever.
Microcanonical thermodynamics in general physical theories
Microcanonical thermodynamics studies the operations that can be performed on systems with well-defined energy. So far, this approach has been applied to classical and quantum systems. Here we extend it to arbitrary physical theories, proposing two requirements for the development of a general microcanonical framework. We then formulate three resource theories, corresponding to three different choices of basic operations. We focus on a class of physical theories, called sharp theories with purification, where these three sets of operations exhibit remarkable properties.
Agents, Subsystems, and the Conservation of Information
Dividing the world into subsystems is an important component of the scientific method. The choice of subsystems, however, is not defined a priori. Typically, it is dictated by our experimental capabilities, and, in general, different agents may have different capabilities. Here we propose a construction that associates every agent with a subsystem, equipped with its set of states and its set of transformations.
QBism and Wigner's friend
Inadequacy of modal logic in quantum settings
Quantum theory cannot consistently describe the use of itself
Representing transformations
Motility of the internal-external cut as a foundational principle
From observers to physics via algorithmic information theory II
From observers to physics via algorithmic information theory I
Motivated by the conceptual puzzles of quantum theory and related areas of physics, I describe a rigorous and minimal “proof of principle” theory in which observers are fundamental and in which the physical world is a (provably) emergent phenomenon. This is a reversal of the standard view, which holds that physical theories ought to describe the objective evolution of a unique external world, with observers or agents as derived concepts that play no fundamental role whatsoever.
Compatibility of implicit and explicit observers in quantum theory and beyond
The observer is implicitly present in the measurement postulates of quantum theory. However the observer can also be modeled as a quantum system interacting with other quantum systems. A theory where every action implicitly undertaken by an agent (such as a measurement or preparation) can be explicitly modeled as non-classical systems interacting is called a universal theory.
Pages
Scientific Organizers:
- Lidia del Rio, ETH Zurich
- Matthew Pusey, University of Oxford
- Ana Belen Sainz, Perimeter Institute