A universal quantum computer may be emulated by a classical computing system that uses an electronic signal of bounded duration and amplitude to represent an arbitrary initial quantum state. The initial quantum state may be specified by inputs provided to the system and may be encoded in the signal, which is derived from a collection of phase-coherent coherent basis signals. Unitary quantum computing gate operations, including logical operations on qubits or operations that change the phase of a qubit, may be performed using analog electronic circuits within the quantum computing emulation device. These circuits, which may apply a matrix transformation to the signals representing the initial quantum state, may include four-quadrant multipliers, operational amplifiers, and analog filters. A measurement component within the quantum computing emulation device may produce a digital signal output representing the transformed quantum state. The gate operation(s) performed may be selected from among multiple supported operations.