Probing Quantum States over Spacetime through Interferometry

Area of Science:

• Quantum Information Theory
• Relativistic Quantum Mechanics
• Spacetime Physics

Background:

• A consistent definition of quantum states across spacetime is needed for relativistic quantum theory.
• Current formalisms struggle to unify concepts across space and time.

Purpose of the Study:

• To establish an operational meaning for multipartite quantum states across arbitrary spacetime regions.
• To develop a unified framework for quantum states in both space and time.
• To explore the implications for quantum non-Markovianity and distinguishing quantum dynamics.

Main Methods:

• Causally agnostic measurements, implementable independently of causal relations.
• Interferometry and scattering circuit techniques.
• Unification of density operator, quantum state over time (QSOT), and process matrix formalisms.

Main Results:

• Demonstration that causally agnostic measurements merge density operator, QSOT, and process matrix formalisms.
• Identification of mixed states in the temporal setting as key to modeling quantum non-Markovianity.
• Discovery of spatiotemporal correlations enabling the distinction of certain quantum dynamics under time-reversal symmetry.

Conclusions:

• The developed framework provides a unified approach to quantum states across spacetime.
• The formalism offers new insights into quantum non-Markovianity and the distinguishability of quantum dynamics.
• Spatiotemporal correlations can serve as a resource for discriminating quantum processes.