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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//F81il 8FFI1il.t.L '11815 8HL?/ Balanced Homodyne System for Casimir Cavities What has not been experimentally measured yet are the sub-vacuum fluctuations and their (negative) energy density inside a Casimir cavity. Marecki [5, 6] theoretically evaluated the use of BHDs for this purpose. He proposed that a BHD can be used to detect and spatially map the sub-vacuum fluctuation region inside a Casimir cavity as well as measure its negative energy density spectrum. Marecki discovered that by exploiting a trick with the subtraction of the output of balanced photodiodes, it is possible to quantify the fluctuations of the quantum field (even in the vacuum[), which uniquely addresses Davies and Ottewill's [54] negative energy detector hypothesis. The quantity of interest (to be measured) is the fluctuations of the quantum electric ( , r , r ) field E;(x,t)Ej(x,t) s (for fields restricted to the frequency w of the local oscillator) , r ) for squeezed and vacuum states, where E,( x,t is the quantum electric field operator '(in ground-state representation and restricted in frequencies) at the point x, t . r represents the time-dependence of E,(x,t), and ( ... )s stands for the expectation value with respect to an arbitrary initial state 5 (vacuum, squeezed, ground state, coherent, thermal, etc.) of the quantum radiation field under study. ( i:,(l,t)EJ(l,t)t is also called a two-point function. In quantum field theory, the expectation value (or matrix element) computed by inserting a product of two quantum operators between two states, usually the vacuum states, is called a two-point function. This quantity suggests a "relation" between two states in the same dynamics, and it expresses the fluctuations of a quantum field. The product of n-operators is called then-point function which expresses the higher moments of the quantum field fluctuations. The goal of the experiment is that a state 5 of the quantum radiation field under study needs to be characterized by its n-point functions. The typical solution in quantum optics is to use well-characterized quantum systems interacting in a simple way with the quantum radiation field. The detection scheme uses the simple model of a PIN junction photodiode in which a single electron interacts with the quantum radiation field under study. This simple interaction means that the state space of the electron can be severely restricted, the interaction is assumed to be linear in the quantum field, and so the Born approximation can be used [5, 6]. The PIN junction model of the photodetection process is an electron in an initial state I0)®S, with its bound-state lo) 'well-localized around a certain point x 11 , that gets excited to the continuum of scattering states Ii) by the quantum field state of interest 5 such that the final states r of the system are lq)@S _-au The excitation is caused by the linear (dipole approximation) interaction with the quantum electric field which is t.tt The symbol (?;· denotes the tensor product of two quantum eigenstates such that Ia 1 , a.,_)= Ia 1 ) @la:) for factorized eigenstates which correspond to independent measurements. 36 UNCLASSIFIED/ ,'1"e11, 81"1"1!11111! l!l!il! a,11alf
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