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In-Depth Information
Excitation
Detection
+1V
−
1V
Figure
9.4.
Encoding the information in the phase of the spin-wave.
The one-bit NOT gate can be obtained measuring the inductive voltage, V
out
,
at the output line produced by spin waves excited by the input line. Taking
t
m
=
p
g/v
ph
(where g is the distance between the contacts and v
ph
is the spin-wave
phase velocity), and V
ref
=0 V, we achieve the required logic correlation [7]. At
this t
m
, the spin waves are detected with 180
1
phase difference comparing to the
original phase as shown in Figure 9.4.
Next, the two-bit AND gate can be realized when t
m
=2
p
g/v
ph
, and V
ref
=V
1
(in Table 9.2, V
1
=10mV). Two spin-wave packets coming in phase enhance the
amplitude of the produced inductive voltage, and cancel each other when coming
out of phase. The nonzero reference voltage is needed to avoid the effect caused by
the finite size of the detecting ACPS line. The OR gate can be realized by analogy,
taking t
m
=2
p
g/v
ph
and V
ref
=
V
1
. In Table 9.2, the input/output correlations
are summarized for different NOT, AND, and OR logic gates as shown in [8].
Extending the same idea, a two-bit NAND gate can be implemented when
t
m
=
p
g/v
ph
and V
ref
=
V
1
. Similarly a two-bit NOR gate can be realized when
t
m
=
p
g/v
ph
and V
ref
=V
1
. Table 9.3 shows the input/output correlations for
NAND and NOR gates.
To realize XOR and XNOR gates, we need two reference voltages, V
ref1
and
V
ref2
. In these two gates, we define the output to be in state ''1'' if the detected
output voltage is between V
ref1
and V
ref2
and in state ''0'' if it is greater than V
ref1
or less than V
ref2
. For both gates, V
ref1
=V
1
and V
ref2
=
V
1
. For an XOR gate
TABLE 9 . 2 . Truth Table for AND and OR Gates [6]
AND
OR
V
ref
=0.5mV
V
ref
=
0.5mV
Input voltage
Logic
state
Output
voltage
Logic
state
Input voltage
Logic
state
Output
voltage
Logic
state
+1 V +1 V
1
1 +27mV
1
+1 V +1 V
1
1 +27mV
1
+1 V
1 V
1
0
0mV
0
+1 V
1V 1 0
0mV
1
1 V +1 V
0
1
0mV
0
1 V +1 V
0
1
0mV
1
1V
1V 0
0
27mV
0
1V
1V 0 0
27mV
0
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