Computing device of Ising model
A calculation device of the present disclosure is characterized by implementing an item, which expresses a magnetic field, at each site by adding, to the conventional coherent Ising machine, a function for simulating the magnetic field item. Specifically, light having the amplitude of a predetermined sign is input in the conventional coherent Ising machine by dislocating an operation point of the push-pull-type optical modulator. When the operation point is dislocated to a + direction, DOPO (Degenerate Optical Parametric Oscillator) having the same wavelength as that of DOPO of an optical resonator and having a fixed initial phase difference from pump light into which the light is injected considerably tends to oscillate at 0 phase, and becomes reversed when the operation point is dislocated to a minus direction.
1. A computing device of the Ising model, comprising:
a phase sensitive amplifier for causing a parametric oscillation at a phase of 0 or π of a plurality of optical pulses that correspond to a plurality of spins of the Ising model and that have the same oscillation frequency;
an optical pulse measurement unit for measuring the phases and amplitudes of the plurality of optical pulses outputted from the phase sensitive amplifier;
a high-speed computation circuit that calculates, regarding information of the phases and amplitudes of the optical pulses measured by the optical pulse measurement unit as an input, a feedback value based on the interaction regarding an optical pulse that is calculated based on a coupling coefficient of the Ising model and the measured optical pulse to output a feedback signal; and
a modulator that modulates, based on the feedback signal calculated by the high-speed computation circuit, the phases and the amplitudes of a plurality of optical pulses in the same number as the inputted plurality of optical pulses to thereby implement the interaction regarding the optical pulse,
wherein:
the modulator is a push-pull modulator that drives two phase modulators provided in both arm waveguides of a Mach-Zehnder interferometer by signals having the same absolute value and different signs so that the driving operation is performed at a point at which light transmitted through the operating point of the modulator has the minimum intensity, and
during the superposition of the feedback signal, the operating point is shifted in an amount of the voltage corresponding to the applied magnetic field so that a fixed number of light is injected to DOPO (Degenerate Optical Parametric Oscillator) pulses that have the same wavelength as that of DOPO pulses of an optical resonator and that has a fixed difference in an initial phase from pump light.
2. The computing device of the Ising model according to claim 1 , wherein a fixed number voltage is used as a voltage shift of the operating point.
3. The computing device of the Ising model according to claim 1 , wherein the voltage shift of the operating point is provided by a voltage change based on a predetermined function.
4. The computing device of the Ising model according to claim 3 , wherein the voltage change is a linear increase.
5. The computing device of the Ising model according to claim 1 , wherein such a voltage is used that is proportional to DOPO amplitude c i obtained through the measurement of ith pulse (i is a natural number) of the DOPO pulses as a voltage shift of the operating point in the ith pulse.
6. The computing device of the Ising model according to claim 1 , wherein such a voltage is used that is proportional to the absolute value ci of DOPO amplitude obtained through the measurement of ith pulse (i is a natural number) of the DOPO pulses as a voltage shift of the operating point in the ith.
7. The computing device of the Ising model according to claim 1 , wherein as a voltage shift of the operating point in ith DOPO pulse (i is a natural number) of the DOPO pulses, a voltage proportional to the average of the absolute values of DOPO amplitudes obtained through the measurement of all pulses is used when assuming that N is the total number of pulses and “C i ” is DOPO amplitude,
[
Formula
1
]
∑
i
c
i
N
.
8. The computing device of the Ising model according to claim 1 , wherein:
the computing device of the Ising model is configured to operate to satisfy the following formula by simultaneously combining a plurality of configurations from among:
a first configuration using a fixed number voltage as a voltage shift of the operating point;
a second configuration causing a voltage change as a voltage shift of the operating point based on a predetermined function;
a third configuration causing a voltage change as a voltage shift of the operating point based on a predetermined function and the voltage change is a linear increase;
a fourth configuration configured to use a voltage that is proportional to the DOPO amplitude c i obtained through the measurement of the ith pulse as a voltage shift of the operating point in ith DOPO pulse (i is a natural number) of the DOPO pulses; and
a fifth configuration configured to use a voltage that is proportional to the absolute value c i of DOPO amplitude obtained through the measurement of the ith pulse as a voltage shift of the operating point in the ith DOPO pulse (i is a natural number),
[
Formula
2
]
s
i
=
(
-
∑
j
J
i
j
c
j
-
(
Ah
i
+
B
h
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(
t
)
+
C
h
i
c
i
+
D
h
i
❘
"\[LeftBracketingBar]"
c
i
❘
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+
Eh
i
∑
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"\[LeftBracketingBar]"
c
j
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"\[RightBracketingBar]"
N
)
)
r
wherein A, B, C, D, and E are an arbitrary real number.