Reversibility: Reversible
All systems with reversibility: reversible
Systems (10)
Antikythera mechanism
f(x) = astronomical positions, eclipse prediction, Metonic calendar (multi-cycle gear ratios)
A hand-cranked bronze gearwork device built around 150–100 BC — the oldest known analog computer. Turning a single input crank advances 37 meshing gears whose tooth-count ratios encode the periods of ...
Billiard-ball computer
f(x) = reversible boolean logic (Fredkin gate)
Proposed by Fredkin & Toffoli (1982). Balls travel on paths representing wires; presence/absence of a ball encodes a bit. Collisions at path intersections implement logic gates. Logically and thermody...
Gate-based quantum computer
f(x) = unitary quantum computation / quantum algorithms (Shor factoring, Grover search, VQE)
A register of qubits — typically superconducting transmons cooled to ~10 mK — whose state is manipulated by sequences of microwave pulses implementing one- and two-qubit unitary gates. Any computation...
Liquid marble computer
f(x) = boolean logic / reversible gates (AND, XOR, OR, NOT, Toffoli, Fredkin)
Liquid marbles are millimetre-scale droplets coated with hydrophobic powder that makes them roll freely without wetting surfaces. Computation is collision-based: two marbles directed at an intersectio...
MEMS accelerometer
f(x) = Newton's second law (a = F/m) — continuous analog acceleration measurement
A microfabricated proof mass (typically silicon, ~1 μg) suspended by folded-beam springs. Under acceleration, the mass displaces by x = ma/k (Hooke's law + Newton's second law in equilibrium). Displac...
Planimeter
f(x) = area enclosed by an arbitrary plane curve (∮ via Green's theorem)
A two-bar linkage with a tracing point at one end and a measuring wheel mounted on the tracer arm. When the operator traces the boundary of an arbitrary shape, the wheel rolls only in the direction pe...
Quantum gate computer (superconducting qubits)
f(x) = unitary transformations / quantum algorithms
Superconducting qubits manipulated by microwave pulses to perform unitary operations. Quantum gates like Hadamard, CNOT, and phase gates enable quantum algorithms such as Shor's factoring and Grover's...
Resistive sheet (Teledeltos) Laplace solver
f(x) = solutions to Laplace's equation ∇²φ = 0 (electrostatics, heat, groundwater flow)
A sheet of Teledeltos — carbon-coated resistive paper with ~6 kΩ/square resistivity — conducts current that obeys the same Laplace equation as electrostatic potential, steady-state heat conduction, in...
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...
Slide rule
f(x) = logarithm, multiplication, division, roots
Logarithmic scales engraved on sliding rules allow multiplication by physical addition of lengths (log a + log b = log ab). Precision is bounded by engraving quality and human reading resolution — typ...