The Space-Communication Implications of Quantum Entanglement and Nonlocality

This Defense Intelligence Reference Document, produced under the Advanced Aerospace Weapon System Applications (AAWSA) Program in 2010, provides a technical assessment of the potential for using quantum entanglement and nonlocality to facilitate space-based communication. The author notes that current space communication is severely limited by the speed of light, resulting in significant time delays for interplanetary operations. The paper investigates whether quantum phenomena could provide a mechanism for superluminal or retrocausal signaling, which would theoretically allow for real-time control of remote assets like Mars rovers.

The document begins by reviewing the history of quantum nonlocality, referencing the foundational work of Einstein, Podolsky, and Rosen (EPR), and the subsequent experimental tests of Bell's inequalities. It examines the 'no-signal' theorems, which generally assert that nonlocal quantum correlations cannot be used to transmit information. However, the author explores whether these 'proofs' are tautological or if they might be circumvented under specific experimental conditions, such as those involving momentum-entangled photons.

Several experimental setups are analyzed, including the 1995 Ghost Interference experiment and the 1998 Dopfer experiment. The author discusses the concept of 'coherence-entanglement complementarity,' suggesting that there is a trade-off between the two that complicates the transmission of nonlocal signals. The document also explores the 'transactional interpretation' of quantum mechanics as a framework for understanding these interactions.

Furthermore, the paper addresses the potential for retrocausal communication and the associated 'bilking paradoxes' that arise when information is sent back in time. It suggests that such paradoxes might be avoided by ensuring that communication intervals are spacelike rather than timelike. Finally, the document considers the possibility that nonlinear quantum mechanics, as proposed by Steven Weinberg and others, could provide a path to nonlocal signaling, though it notes that experimental evidence for such effects has been elusive. The document concludes that the question of whether nonlocal communication is possible remains an experimental one, and that further testing is required to determine if the limits of coherence and entanglement can be overcome.