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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.
UNCLASSIFIED//F811. 8FFll!lllit 1!1!11! 9IU:!Y they are extremely vulnerable to quantum decoherence. Quantum decoherence is caused by linear losses, and it is the main reason why the extremely strange quantum phenomena allowed in quantum theory are very difficult to observe in practice. However, the good news is that investigators have successfully controlled or suppressed quantum decoherence to such a high degree that Schr6dinger cat states were experimentally observed and measured using optical homodyne tomography [55, 56]. Figure 7 shows the experimentally reconstructed Wigner functions for two Schr6dinger cat states that have different amplitude values ±qo. The observed peaks at ±qo seen in the figure are of small magnitude, so investigators euphemistically call these "SchrOdinger kitten states." As seen in the figure, the interference structure halfway between the peaks displays the quantum superposition of both amplitudes, showing rapid oscillations with a frequency given by the distance 21qol of the superimposed amplitudes. Also seen in the figure is that the two reconstructed Wigner functions become negative (i.e., negative "probabilities"), indicating the nonclassical behavior of SchrOdinger cat/kitten states. Beam Splitters A very important device that is used to demonstrate the quantum nature of light is the simple optical beam splitter. A large number of strange quantum effects have been experimentally observed by splitting or recombining photons using a small cube of glass. The beam splitter also serves as a theoretical model for other linear optical devices such as interferometers, semitransparent mirrors, dielectric interfaces, wave- guide couplers, and polarizers. The beam splitter model can also be used to account for the effect of absorption, mode mismatch, and other linear losses. An ideal beam splitter is a reversible, lossless device in which two incident beams of light may interfere to produce two emerging beams [38]. For example, a dielectric interface inside a cube or plate of glass splits a light beam into two. This situation may be reversed by sending the two beams back to the cube (or plate) where they interfere constructively to restore the original beam. However, if the phases of the two beams are changed, then their mutual interference generates two emerging beams in general. So four beams might be involved, two incident light modes and two outgoing light modes, and the splitting of just one beam is a special case. Therefore, the most general theoretical beam splitter model is a four-port device, which is simply a "black box" with two input and two output ports having certain mathematical and physical properties [38]. See Figure 8 for a schematic of an ideal lossless four-port beam splitter. The beam splitter is quantum mechanically described by a simple unitary transformation operator (or matrix), based on an analog transformation matrix in classical optics/H* which mathematically transforms the two input light modes into the two output light modes. This operator is unitary, which reflects the fact that a lossless beam splitter conserves energy and that the total light mode intensity at a1 + a;a2 is an invariant quantity. Since the incoming and the outgoing light modes are both independent bosonic modes, their annihilation operators must satisfy the following '"' In classical optics, the components of the transformation matrix of a real beam splitter are simply the transmissivity and reflectivity, which account for the transmission and reflection probabilities of photons passing through the glass cube or plate. 24 UNCLASSIFIED/ ,'F811. 8FFll!lllit l!llili e,11,1/'
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