Page 79 - Principles and Applications of NanoMEMS Physics

66 Chapter 2

effects of surface roughness, by replacing the flat plate with the mean
stochastic roughness amplitude A, to obtain,

ª § A · 2 º
z
F r () = Fz 0 ()« + 61 ¨ ¸
Cas Cas » , (60)
« © z ¹ »
¬
¼
where A is derived from direct measurements via an Atomic Force
Microscope (AFM).

2.4 Quantum Information Theory, Computing and Communications

The advent of nanoscale fabrication techniques has brought within our
reach the possibility of producing systems whose predominant behavior is
described by quantum mechanics (QM). While the engineering of systems
based on exploting this new physics/technological paradigm is still in its
infancy, this new paradigm is ultimately expected to manifest itself in the
ushering of a ‘new electronics’ technology era. Obviously, this ‘new
electronics’ is expected to change the way in which systems are implemented
to effect the functions of information processing, computing and
communications [100-111]. These functions, in turn, will exploit the
properties of quantum mechanical wave functions. In this section we
introduce key aspects of the fundamental physics on which these functions
are predicated, in particular, we focus on the concepts underpinning quantum
information processing, namely, quantum bits (qubits), quantum
entanglement, the Einstein-Podolsky-Rosen (EPR) State, quantum gates, and
quantum teleportation.
Quantum information is represented by quantum bits or qubits [103].
Qubits are fundamental physical entities, such as a two-level atom, which
may adopt two possible quantum (stationary) states (see Appendix A), say
the mutually orthogonal states 0 and 1 . Due to its quantum nature,
however, the most general state is expressed as,

ψ = a 0 + b 1 , (61)

i.e., as a superposition of both states. Thus, a measurement of the qubit will
2
cause its wavefunction to collapse into the state 0 with probability a , or
2
into the state 1 with probability b . This means that during its time
evolution a qubit may be partly in both the 0 and 1 state at the same