Exactness: Heuristic
All systems with exactness: heuristic
Systems (8)
Biological brain
f(x) = general intelligence / perception, memory, reasoning, motor control
The human brain contains ~86 billion neurons connected by ~10¹⁵ synapses. Each neuron integrates thousands of synaptic inputs and fires a spike when its membrane potential crosses threshold — a leaky ...
Coherent Ising machine (OPO network)
f(x) = Ising Hamiltonian ground state / combinatorial optimization (MAX-CUT, QUBO)
A network of degenerate optical parametric oscillator (DOPO) pulses circulating in a fiber ring cavity. Each pulse can oscillate in one of two phase states (0 or π), encoding a spin. Measurement-feedb...
Coupled oscillator network (Kuramoto / XY model)
f(x) = MAX-CUT / graph partitioning (approximate)
A network of identical oscillators — pendula, LC circuits, or CMOS ring oscillators — coupled to their neighbours by springs or resistive links. The Kuramoto model describes how each oscillator's phas...
DishBrain (in-vitro neural culture)
f(x) = closed-loop sensorimotor control / game-playing (via biological learning)
~800,000 human iPSC-derived or mouse cortical neurons are plated onto a high-density multi-electrode array (HD-MEA). The DishBrain system (Kagan et al., 2022, Neuron) embeds the culture in a simulated...
Memristive Hopfield network optimizer
f(x) = optimization via chaotic annealing / transient dynamics
Memristive circuits implementing Hopfield network topology where the intrinsic nonlinearity of memristors creates transient chaotic annealing processes. The chaotic dynamics enable escape from local m...
Physarum polycephalum (slime mold)
f(x) = Steiner tree / shortest transport network (approximate)
The plasmodial slime mold extends filaments toward nutrient sources and progressively reinforces paths that carry more flow, pruning inefficient routes. Toshiyuki Nakagaki showed it reproduces the Tok...
Quantum and quantum-inspired annealers
f(x) = Ising model energy minimization / QUBO optimization
Quantum and quantum-inspired systems for solving combinatorial optimization problems through annealing processes. Includes true quantum annealers (D-Wave) using superconducting qubits and quantum-insp...
Rubber-band Steiner tree
f(x) = Euclidean Steiner minimum tree (approximate)
Elastic bands stretched between pins hammered into a board relax under tension to a state of minimum total length. Because each band pulls with a force proportional to its extension, the equilibrium c...