Quantum Emulation

Overview

Quantum emulation is the technique of running software on classical hardware (CPUs or GPUs) that reproduces the behavior of a quantum processing unit. For workloads up to approximately 35–40 qubits, classical emulation can replicate QPU results completely error-free, because the quantum state vector for a small qubit count fits within available classical memory. This makes emulation the preferred development and testing environment: developers can iterate on quantum algorithms without consuming scarce, expensive QPU time and without introducing hardware-induced errors.

The practical limit of classical emulation is determined by memory scaling: the quantum state vector for an n-qubit system requires 2^n complex amplitudes, so memory footprint grows exponentially with qubit count. At ~35 qubits, this fills a large-memory classical server; beyond 40 qubits, emulation becomes impractical on conventional hardware. This threshold neatly aligns with current QPU sizes (100–250 qubits), meaning the emulation regime covers the algorithm development phase while QPUs are required for production-scale quantum workloads.

Dell's HQCC reference architecture includes Accelerated vQPU Servers specifically for emulation, positioned as the development and small-problem layer within the hybrid stack.