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This Defense Intelligence Reference Document, dated 30 March 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under its Advanced Aerospace Weapon System Applications Program. It reviews quantum entanglement, nonlocality and EPR experiments, and asks whether nonlocal quantum effects could carry observer-to-observer signals faster than light. The paper describes proposed experiments and an example of real-time Earth control of a Mars rover. It concludes that there is no compelling answer yet and that experimental tests are needed.
From the source: Release of 2026-09-18 Incident: 3/30/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD reviews quantum entanglement and nonlocality with a focus on whether those phenomena might be usable as a means of faster-than-light communication between observers, especially for real-time space operations over interplanetary distances. The report surveys the relevant quantum experiments and no-signal theorems, then examines proposed communication schemes based mainly on momentum-entangled photons, including scenarios involving superluminal and retro-causal signaling. However, it repeatedly acknowledges that the central question remains unresolved experimentally, and it gives substantial attention to the coherence-versus-entanglement tradeoff and other features of standard quantum mechanics that may prevent usable signaling even if non-local correlations are experimentally validated. Overall, the document is an exploratory analysis of whether quantum nonlocality could conceivably support a practical communications application rather than a demonstration of prospective utility.
B Source Slit Detector UNCLASSIFIED/ /FOR OFFICIAL tt.!I!! 8HL'f when the coincidence requirement is relaxed. This may be explain ed by the action of coherence-entanglement complementarity, as discussed in the next section. V. Coherence-Entanglement Complementarity As discussed above, the finite extent of the source is expected to limit the possibility of observing a two-slit interference pattern, which would be the "signal" if nonlocal commun ication were possible. Figure 6 shows schematically (not to scale) this "thick source" effect. The source volume on the left is the region of the nonlinear crystal that is illuminated by the UV pump-laser beam directed along the u axis. The source volume is a cylinder a few mm thick and a mm or so in radius with a center point C. The source cylinder is assumed to be tilted at an angle 0 with respect to the horizontal z axis on which the slit system and detector plane are symmetrically centered. We note that 0 = 0° in the Ghost Interference experiment and 0 = 28.2° in the Dopfer experiment. A horizontal distance Lxs away from the source is a two-slit system, a pair of apertures a with center-to-center separation d. Light passing through the slit system travels a horizontal distance Lsd and is detected at detector plane at position x,. System Plane Volume Figure 6. Thick-Source Effect (not to scale): Waves arriving at the two slits from points A and B at the extrema of the source volume may have sig nificant path length and phase differences, while waves from the central point C are in phase at the slits. If the point of photon production is off the z axis, there will be a path length difference between waves relative to C as they arrive at the two slits . In Figure 6, waves from points A and B could have path length differences greater that half a wavelength and phase differences greater than 180°. Roughly speaking, this shifts the interference pattern relative to waves created at central point C so that maxima become minima and vice versa. The net effect of averaging over all points in the source volume would therefore be to wash out the two-slit interference pattern. That two-slit interference pattern must be observed unambiguously, because it is the "signal" that would be used in any nonlocal communication. This operability is quantified by an observable called "visibility," which is related to the peak-to-valley ratio of the interference pattern. The constancy of the relative phase at the two slits for photons arriving from various parts of the source is called "coherence" and ensures a high visibility. It should be clear that a point-like source has perfect coherence, wh ile a source with a large solid angle as UNCLASSIFIED/ ,,roA &FFISIAL 1:181! 8HL'I" 10
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