AAWSAP DIRD, High-Frequency Gravitational Wave Communications, April 2010

This Defense Intelligence Reference Document, DIA-08-1004-005, is dated 6 April 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications program. It reviews proposed laboratory generators and detectors for high-frequency gravitational waves. It favors a piezoelectric approach for proof-of-concept tests, IR-excited molecules for an operational transmitter and the Li-Baker detector as the receiver. It estimates about 1.9 million bits per second over 7,000 km through the Earth and discusses timing standards and interplanetary navigation uses.

From the source:Release of 2026-09-18 Incident: 4/6/10, 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 examines whether high-frequency gravitational waves could serve as a communications medium while avoiding the attenuation that limits radio-frequency systems. The report surveys proposed transmitter and detector concepts, argues that gravitational-wave communications could support secure point-to-point links, timing standards, and interplanetary navigation, and gives particular attention to laboratory generator concepts and the Li-Baker detector as possible building blocks for such a system. The document makes clear, however, that the entire concept depends on capabilities that had not been demonstrated in practice, including laboratory-scale generation and reliable detection of usable high-frequency gravitational-wave signals. It is an exploratory systems-oriented review built around a future communications concept.

UNCLASSIFIED/ /iiOR OiiiilCI OL lallili QPIL¥
where L1x is the position uncertainty, LJp is the momentum uncertainty, and n is
Planck's reduced constant. Thus measuring x disturbs p, which in turn disturbs future
measurements of x
Llx(dt) = Llx(O) + dt[L1p(O)/m] (4)
where Llx(O) is the initial position uncertainty is, Llp(O) is the initial momentum
uncertainty, dt is the time of the future measurement, and m is the mass of the system
under measurement. E/c2 may be substituted for mass in an energy only system. This
is depicted in Figure 13.
To summarize, the quantum effects of measurements on future measurements is
quantum back action. Therefore the Standard Quantum Limit defines the lower
sensitivity limit for all measurement instruments, including gravitational-wave
detectors, according to the Heisenberg uncertainty principle. Detectors cannot avoid
quantum back action, however the use of higher energies in the detection process can
change the relative scale and impact of back action, and the use of squeezed states can
shift the relative distribution of back action into states not involved in measurement.
TIME t= 0
"A---+----,'• :
I
I
''~ ~ Ap(O) > li/2
Al((O)
A~(qt) =ox(dt) + Slt[Ap(O) / m]Measurement of x drives down All.{0) Therefore ApjO) drives up Ax(£1t)which drives up Ap(O)
Quantum Back Action:
x dt) measurement affected
l1Y, earlier x(O) measurement
\
\
I
I
I I
I I
ox dt) ---.: ~
I I
TIME t= dt
Figure 13. Quantum Back Action as a Mechanism for Creating the Standard Quantum Limit
Calculating the Standard Quantum Limit (SOU
A method for calculating the Standard Quantum Limit (SQL) is introduced in this
section. The calculation of coherent versus stochastic SQL is compared and contrasted.
Important terms of the SQL calculation are described, including the impact of contained
energy levels within the detector on SQL, and the sources of Quality Factor and its
effect on SQL. Calculating the Standard Quantum Limit (SQL)
UNCLASSIFIED/ /FOR OiiiilCl,.k 1!191!!! tJflti
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