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

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

UNCLASSIFIED/ /iiOR OiiiilCI O L lallili QPIL¥
same frequency, direction and phase. This situation is termed "synchro-resonance."
These PPF detection photons a are generated as the EM wave propagates along its z­
axis path, which is also the path of the GWs, as shown in Figure 12.
The magnetic field is in the y-direction. According to the Li-Effect, the PPF detection
photon flux (also called the "Poynting Vector") moves out along the x-axis in both
directions.
The signal (the PPF) and the noise, or background photon flux (BPF) from the Gaussian
beam have very different physical behaviors. The BPF (background noise photons) are
from the synchro-resonant EM Gaussian beam and move in the z-direction, whereas the
PPF (signal photons) move out in the x-direction along the x-axis.
The PPF signal can be intercepted by electromagnetic-interference-shielded microwave
receivers located on the x-axis (isolated from the synchro-resonance Gaussian EM field,
which is along the z-axis). In addition, isolation is further improved by cooling the
microwave receiver apparatus to greatly reduce thermal noise background (Baker,
Stephenson and Li, 2008a).
The resultant efficiency of detection of HFGWs is very much greater than from the
inverse Gertsenshtein effect, which has been exploited in some previously proposed
HFGW detectors and found to have insufficient sensitivity to HFGWs (Eardley, et al.,
2008). The amplitude of the PPF has space accumulation dependence-that is, it is
proportional to the length of the wave overlap. This is because the GWs (gravitons) and
EM waves (photons) have identical propagation velocities, so that the two waves
overlap synchronously and coherently throughout and their interaction is cumulative
(Boccaletti et al., 1970; Delogi and Mickelson, 1977). This is the synchro-resonant
condition or Li-effect. This means that for maximum signal, the interaction overlap
coupling must be as long as possible. It should be noted that the identification of this
coupling or Li-effect, upon which the Li-Baker HFGW detector is based, is not so new
that it is untested in the literature. At least nine peer-reviewed research publications
concerning the theory have appeared following Li, Tang and Zhao (1992), including
those by Li and Tang (1997), Li et al. (2000), Li, Tang and Shi (2003), Li and Yang
(2004), Li and Li (2006), Li and Baker (2007), Li, Baker and Fang (2007), Baker,
Stephenson and Li (2008a), and Li et al. (2008).
2.2.3 Quantum Back-Action Limit
The Standard Quantum Limit (SQL) will be introduced and reviewed in this section
(Stephenson, 2009b), and design of the Li-Baker HFGW Detection System will also be
reviewed to understand how the SQL might limit the sensitivity of this new type of GW
detector.
Review of the Standard Quantum Limit
The Standard Quantum Limit (SQL) is often defined as "The limit on measurement
accuracy at quantum scales due to back-action effects." But what is "back-action"? (See
Kippenberg and Vahala, 2008.) From Clerk (2008) the Heisenberg Uncertainty Principle
is
(&') X (Lip) > fl/2
(3)
UNCLASSIFIED/ /FOR CiiiilCl.t..k 1!191!!! tJfltf
16