1. Quantum Interfaces Karl Svozil Vienna University of Technology Svozil@tuwien.ac.at

2. Context Automaton logic: automaton uncertainty relation vs. quantum complementarity Relativity theory & Conventionality Intrinsic undecidability Interpretation of quantum mechanics

3. Why consider interfaces? Proposal of new information flux quantity New approach to quantum measurements Generalizations to virtual reality New approach to old questions such as, „why is there classical information if a priori there is merely quantum information?“ Metaphysical speculations

4. Perspective „Reality push:“ Oberserver is confronted with a perpetual inbound data stream „Reality pull:“ at the same time, the observer acts within the very system he is acted upon. Information is exchanged via interfaces or cartesian cuts Information is formalized by symbols Measurement process is modeled as an information exchange between object and observer

5. Conventionalism Implicit or explicit assumptions about information received Relativity theory: one-to-one transformation and invariance of the speed of two-way signalling yields Lorentz-type transformations (Alexandrov‘s theorem; KS „Relativizing Relativity“) Quantum theory: desiderata of organizing data (Jayne‘s principle, Summhammer‘s principle,...) Oberver uses „knowables“ to (re)construct „reality“

6. Interface An interface is an entity forming the common boundary between two parts of a system, as well as a means of information exchange between those parts. By convention, one part of the of the system is called „observer“ and the other part „object.“ Information between the observer and the object via the interface is exchanged by symbols. Any such information exchange is called „measurement.“

7. „ Alice and Bob behind a curtain“

8. Types of interfaces Classical scenario I: defined in a classical system, for which the symbols are classical states. Quasi-classical scenario II: defined in a quantum system, whereby the symbols exchanged are effectively classical states encoded by classical bits. Quantum scenario III: defined in a quantized system. The quantum symbols exchanged are quantum states.

9. Quantum interface (scenario III) A uniform quantum system with unitary, and thus reversible, one-to-one evolution. What is called ``measurement'' is merely an exchange of quantum information. the observer can ``undo'' a measurement by proper input of information. Irreversibility through the practical (not principal) impossibility to reconstruct a certain states: ``Information flows off fast‘‘ Effective many-to-one state evolution.

10. Analogy in statistical physics: irreversibility through many-to-one mapping of microstates onto macrostates

11. Principle of Information conservation Throughout temporal evolution, the amount of (classical) information measured in bits is conserved. The information flow density j is the total amount of information passing per unit time through a surface. Assume that the cut is on a closed surface A c surrounding the object. The conservation law of information requires the following continuity equation to be valid Quantum eraser Experiment suggests reconstruction at 6 10^7 bits/sec.

12. Virtual reality as a quantum double Reversible automata: a finite set S of states, a finite input alphabet I, a finite output alphabet O, temporal evolution function :S×I  S, output function :S×I  O. The combined transition and output function U is reversible and thus corresponds to a permutation: U:(s,i)  ((s,i),(s,i))

13. Metaphysics: test of transcendence Step I: The conscious observer measures some quantum observable and „is aware of'' the measurement result. Step II: Reconstruction of the original quantum state, including the „unthinking“ of the observer. Step III: The observer predicts/guesses the measurement result. Step IV: The measurement is „re-done“ and the result is compared with the observer's prediction in step III.

14. Summary & Outlook Quantum measurements are pricipally reversible (1-1). Quantum measurements are practically irreversible (many-to-one). Hierarchisation of intrinsic observers Physics in terms of „knowables“

15. URLs http://tph.tuwien.ac.at/~svozil/publ/interf ace.htm http://tph.tuwien.ac.at/~svozil/publ/interf ace.htm http://tph.tuwien.ac.at/~svozil/publ/interf ace.ps http://tph.tuwien.ac.at/~svozil/publ/interf ace.ps http://tph.tuwien.ac.at/~svozil/publ/qi.ht m http://tph.tuwien.ac.at/~svozil/publ/qi.ht m http://tph.tuwien.ac.at/~svozil/publ/qi.ppt

16. Final Quote Er nennt sich heimlich des ausgelassensten Dentisten der Galaxie, doch weiß er natürlich nichts von den wahren Verhältnissen. [[English translation: Secretly he calls himself the most flamboyant dentist of the galaxy, but of course he does not realize the true circumstances.]] (Erich Christian Schreibmüller, 1983)