## Fundamental Quantum Effects

## Interference swapping
When quanta scatter from two slits, they interfere in a characteristic two-slit
interference pattern. This is a quantum experiment, but let’s make it even more
quantum by replacing the two slits with a single quantum slit in a superposition
of two locations. Do we get characteristic two-slit interference? No!
Depending on the quanta and the slits, we may get no interference pattern or
we may get a new kind of interference pattern that is characteristic of interference
from a single superposed slit. |
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#### Aharonov-Casher effect

Neutral atoms have magnetic moments, so they should display an effect dual
to the Aharonov-Bohm effect: a neutral particle with a magnetic moment diffracting
around a line of charge should acquire a topological phase. Controversy over this effect
has not completely subsided, but recent work makes precise the meaning of “duality” and
what is dual between the Aharonov-Bohm and Aharonov-Casher effects.

[D. Rohrlich, Duality in the Aharonov-Bohm and Aharonov-Casher Effects,
J. Phys. A: Math. Theor. 43 (2010) in press.]

## Other fundamental aspects of quantum mechanics
The quest for a simpler, clearer basis for quantum mechanics –
a new and more physical set of axioms – leads to such new concepts as
“weak” values of quantum operators, “modular” variables, and time reversal symmetry. |
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