SPIN-WAVE ARCHITECTURES - Bio-Inspired and Nanoscale Integrated Computing - page 204

The use of spin waves for computation is an entirely new idea. The first
computational architecture utilizing spin waves was for massive entanglement of
distant spin-based qubits in a quantum computer as described in [3, 4]. In this
research, spin waves are used for both information transmission and information
processing. Moreover, the classical type of computing is employed as opposed to
quantum, and the architectures are operable at room temperature.
In the following section, we present three spin-wave architectures: crossbar,
reconfigurable mesh, and fully interconnected cluster. Afterward, we explain our
experimental results.
7.2. SPIN-WAVE ARCHITECTURES
In the following section, after a brief introduction to spin waves, we present three
nanoscale spin-wave architectures: nanoscale crossbar, spin-wave reconfigurable
mesh, and spin-wave fully interconnected cluster. Then, to address the size limitation
of spin-wave architectures, we propose a multiscale hierarchical architecture.
Spin wave is a collective oscillation of spins in an ordered spin lattice around
the direction of magnetization. The phenomenon is similar to the lattice vibration,
where atoms perform oscillation around its equilibrium position. In other words, a
collection of electron spin precessions about the magnetic field is a spin wave [5],
as shown in Figure 7.1. The magnitude of the spin wave is determined by
precession angle. A propagating spin wave changes the local polarization of spins
in the ferromagnetic material. In turn, the change in magnetic field results in an
inductive voltage. Recently published experimental results indicate that an
inductive voltage signal of the order of mV produced by spin waves propagating
through a nanometer thin ferromagnetic film are detectable at the distances of up
to 50 microns at room temperature. Our idea is to use the phase of the spin wave
for both information exchange and information processing [6].
Typically, the speed of the spin wave is 10 4 m/s. In the current experimental
results, the switching frequency is in the order of GHz, but up to the order of THz
is possible. As mentioned above, the attenuation of spin waves is around
50 microns, which makes it a suitable candidate for nanoscale communication.
In the following section, we show how spin waves can be used in implementing
nanoscale architectures.
7.3. SPIN-WAVE CROSSBAR
In this section, a nanoscale crossbar architecture that is interconnected with
ferromagnetic spin-wave buses is introduced [7, 8]. The power consumption of
Figure 7.1. Spin wave: a collective oscillation of spins.