The transactional interpretation of quantum mechanics is an alternative interpretation of the formalism of quantum mechanics. It was proposed by John Cramer in 1986 and seeks to provide a coherent explanation for the phenomenon of quantum measurement and the nature of wave-particle duality. The interpretation introduces several distinguishing physical assumptions, including:
The Existence of Advanced Waves: In the transactional interpretation, both the usual "retarded" waves (representing the forward flow of time) and "advanced" waves (representing the backward flow of time) are considered as fundamental entities. Advanced waves are often associated with retrocausality, meaning they travel backward in time. These waves are considered to be physically real and are essential for understanding the transactional nature of quantum interactions.
Time Symmetry: The interpretation assumes that the laws of physics are symmetric under time reversal, meaning that they are the same whether time flows forward or backward. This time symmetry is necessary for the consistency of the transactional picture, where information is exchanged between the future and past.
Handshake Model: The transactional interpretation employs a "handshake" model to describe quantum interactions. According to this model, a transaction is initiated by an "offer wave" emitted by the source particle, which travels forward in time. This offer wave interacts with the "confirmation wave" emitted by the receiver particle, which travels backward in time. The interaction between the offer and confirmation waves determines the probabilities of different outcomes and the final state of the system.
Absorber Theory: The interpretation incorporates the idea of "absorber theory," which suggests that particles can be thought of as both emitters and absorbers of waves. In this view, particles emit waves when acting as sources and absorb waves when acting as detectors. This absorber theory helps explain the phenomenon of wave-particle duality and the role of measurement in collapsing the quantum wavefunction.
It's important to note that the transactional interpretation remains a subject of ongoing debate and investigation within the field of quantum foundations. While it introduces novel concepts and physical assumptions to address certain interpretational issues, it has not yet gained wide acceptance within the scientific community. The interpretation's distinguishing assumptions offer an alternative perspective on the nature of quantum phenomena but require further development and empirical evidence to establish their validity.