  There is no self adjoint time operator defined in quantum mechanics. However,
time intervals can be defined in several ways and can also be probed
experimentally. Our interest in this work is traversal time and signal
propagation time. According to Copenhagen interpretation of quantum mechanics
the two should be the same but the issue is not settled yet in regimes where
they can be negative. We use Argand diagram and Burgers circuit to show that
the correct traversal time and the correct signal propagation time can be
identically negative implying signal can be propagated in negative time. Some
other physical consequences are discussed.
