Major Areas of Opportunity - Implications of Emerging Micro-and Nanotechnologies - page 45

through a material transformation (typically an absorption changing the electronic
state of a dye such as bacteriorhodopsin. 66 Although the information density for
holographic storage is often quoted in Gbit/cm 2 for comparison with conventional
storage, holography is inherently a volumetric technique with intrinsic units of
Gbit/cm 3 . Holographic storage is inherently analog and requires extensive elec-
tronics to retrieve digital information. Intensive research efforts to develop holo-
graphic information storage have yet to produce a commercial result.
Communications
Communications are a critical aspect of information technology. The Air
Force's requirements are for very large aggregate bandwidths between large
numbers of time-varying platforms with free-space optical, microwave, or RF
connectivity. The overall system must be both dynamic and reconfigurable. Plat-
forms will continuously move into and out of the system as a result of operations.
The total amount of data will become staggering as large numbers of complex
sensors (e.g., multispectral focal plane arrays) are fielded. Two consequences are
immediately evident: (1) it will be necessary to provide a hierarchical structure to
ensure that time- and command-critical messages are prioritized and (2) the sen-
sors must be intelligent, with the capability of drawing inferences from raw data
and transmitting condensed information and of switching to a more voluminous
raw data stream as critical data fusion requirements demand. Discussion of these
systems aspects is deferred to the next section, “Signal and Information Processing
and Data Fusion.” Here, the hardware aspects of communications are discussed.
Secure Communications
An emerging benefit of some of the physics of nanotechnology is communi-
cations security and secrecy. The application of certain quantum principles al-
lows communications to be made perfectly secure in the sense of not allowing a
message to be listened to without detection. One can prepare the quantum states
of individual photons, e.g., polarization, in such a way that the “no cloning
theorem” prohibits their being read without detection yet allows a “quantum
repeater” to relay the signal to a distant source. Since such a scheme can be
jammed, it does not seem attractive for general secure communications. How-
ever, it may have considerable value in periodically distributing the keys needed
to decode encrypted messages sent by more conventional means. Of particular
interest to the Air Force would be the use of such a secure form of communica-
tion to send encryption keys to satellites. Research on sources of single photons
on demand and single photon detectors might be valuable.
Hardware aspects of communication will be enhanced by miniaturization
trends in general simply through the introduction of denser and faster digital
electronics. Advances in miniaturization will directly affect hardware design for