The CPU, the brain of the computer, is the mechanism that executes the programs for various processes, and is composed
of the following parts:
- Arithmetic unit
- Processes the data stored in the register.
- Control unit
- Controls the flow of data and processing.
- Storage device (Register)
- Stores the instructions and data to be processed.
These simple mechanisms are combined to perform what the program wants to do. By programming a variety of processes, we
can achieve general-purpose calculations.
In conventional computers, the performance of the CPU has been improving with the progress of semiconductor
miniaturization, and the overall performance of the CPU has been improving along with it. However, miniaturization is
approaching its physical limit and big performance improvements will not likely be expected anymore. Therefore,
application-specific computers that achieve high performance by specializing in specific processing have been the new
focus. The annealing machine is a type of application-specific computer that focuses on optimization.
Why annealing machines are fast
To solve a problem on a traditional Neumann architecture computer, we had to devise a procedure/algorithm for solving
the problem, write the algorithm as a sequence of instructions for the CPU, and execute the sequence of instructions
sequentially on CPU. It sometimes uses techniques to increase speed by executing multiple instructions in parallel, but
mostly a traditional computer executes an essentially sequential sequence of instructions.
In contrast, an annealing machine defines an abstract physical model (Ising model) and puts the desired combinatorial
optimization problem into this model (mapping). The energy of the model is then varied, and the answer is obtained at
the lowest energy state (ground state).
Compared to the Neumann architecture computer, which performs operations in binary numbers (0/1) and executes processing
sequentially through branching, decision making, and repetition processes, the processing with the Ising model feels
like a natural phenomenon like living things, waves, or wind, and is therefore called natural computing. In other words,
instead of processing the problem sequentially, the convergence behavior of the natural phenomenon itself is used to
process the problem, making it possible to solve the problem at high speed even when the problem gets larger.
Understand the processing of an annealing machine using the Ising model.
How can we imagine the Ising model? Simply put, it is a collection of spins and couplings. A single element in the Ising
model is called a spin, and it can take on two values, +1/-1. Many spins interact with each other and each spin is
subjected to an external force of + or -. It is a model that describes how the set of spins (the Ising model as a whole)
behaves. In a quantum annealing machine, qubits play the role of these spins, and in a CMOS annealing machine,
semiconductor memory and digital circuits are used to solve optimization problems by simulating the behavior of spins.
In the Ising model, as the connected spins interact with each other, there are countless patterns/combinations where the
energy of the entire Ising model is high or low. The combination of the spins when they settle down to the lowest energy
state, i.e., which ones are +1 and which ones are -1, represents the optimal solution of the optimization problem to be
We believe that annealing machines can overcome the barrier that Neumann architecture computers cannot because annealing
machines are application-specific, non-Neumann architecture computers.