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This Defense Intelligence Reference Document from the Defense Intelligence Agency is dated 11 January 2011. It was produced in FY 2010 under the Advanced Aerospace Weapons System Applications (AAWSA) Program. It reviews negative, or sub-vacuum, energy found in squeezed light and the Casimir effect, and explains quantum optical homodyne tomography as a way to measure and map that energy in the lab. It proposes balanced homodyne detector arrays that could help detect anomalous aerospace platforms using engineered spacetime propulsion.
“R.G.”1 page
UNCLASSIFIED//FIHl 8FFHil.t.k Wfili IH.k\f
Quadrature components iJ0 are definedt~t~ with respect to a certain reference phase 0
that can be varied experimentally.
The principle scheme of a balanced homodyne detector is depicted in Figure 10. The
signal interferes with a coherent laser beam at a well-balanced SO: SO beam splitter.
The laser light field is called the local oscillator (LO), and it provides the phase
reference 0 for the quadrature measurement. It is assumed that the signal and the LO
have a fixed phase relation, as is the case in most experiments applying homodyne
detection, because both fields are ultimately generated by a common master laser. The
LO should be intense with respect to the signal for providing a precise phase reference.
It is also assumed that the LO is powerful enough to be treated classically, i.e., we
totally neglect the quantum fluctuations of the LO. After the optical mixing of the signal
with the LO, each emerging beam is directed to a linear-response photodiode. The
photocurrents /1 and hare measured, electronically processed, and finally subtracted
from each other. The difference current In = h - /1 is the quantity of interest because
it contains the interference term of the LO and the signal. It is assumed for simplicity
that the measured photocurrents Ii and h are proportional to the photon numbers n 1
and ,12 of the beams striking each detector, which are given by 111 = a;'/1; and
11 2 = &~t &~ in terms of the mode operators a; = 2- 112
( G- au,) and (I~ = 2- 11
='{ (I+ au,) of
the fields emerging from the beam splitter [38]. Here d denotes the annihilation
operator of the signal and aw is the complex amplitude of the LO.
The difference current h 1 is proportional to the difference photon number (assuming
~ ~ ~ sin0 and
J\ = lf '(0) 1H)(0) = -!jsin0+ 1Jcos0, via the quadrature decomposition defined in Sect. IIB-1 and the phase
sh1ft1ng property of the annihilation operator defined 1n Sect. IIIB-1.
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