"We show that emergence of nonclassical single-mode
light from an optomechanical cavity is followed by noncausal
behavior in the linear response of the cavity. The
nature of emergence of noncausal behavior is independent
from the length (boundary conditions) and the type
of the cavity. Anomaly in the linear response emerges due
to the noncausal matching of the incident and reflected
waves at the front interface of the cavity. Emergence
of noncausal behavior is shown to be strongly related
with the possibility of faster-than-light communication
between the source and potential.
The result of the present paper is intimately related
with the outcomes of the following studies. Holstein-
Primako mapping for nonclassical fields [18], wormhole
representation of entanglement in 4D space [10{13], discussion
on the constituents of the vacuum [15, 16], mathematical
equivalence of faster-than-light source-potential
communication to violation of causality among fields
(Sec. IV) and superluminal reference frames in Relativity
[9].
If vacuum indeed has constituents [15, 16], ensemble
of these constituents must be superfluid, since high energetic
photons from Crab Nebula reaches the observers
undamped [17]. Holstein-Primako mapping of
N -particle (N large) states to single-mode photon states
[18] restricts the particles to occupy the (exchange) symmetric
Dicke states [21, 22]. Hence, if vacuum has constituents
{generating photons as quasiparticles { these
constituents are restricted to symmetrized states. We already
know that collisions (interactions) in symmetrized
particles (such as Bose-Einstein condensates) are responsible
for the induction of superfluid rather than creating
damping, see p. 2 in Ref. [23].
The emergence of violation of causality {due to faster than
light communication via entanglement{ may also be
related with the theory of relativity. Maxwell equations
are consistent with relativity [7, 8]. In relativity, for a reference
frame moving with v > c , the order of events may
change [9], resulting in violation of causal behavior. Even
though the fields (electric/magnetic and gravitational)
are the quantities we observe in typical experiments, potentials
are more fundamental quantities in quantum mechanics,
see discussion in Chapter 2.6 of Ref. [6].