A quantum emulator is software that imitates quantum behavior on classical hardware such as CPUs or GPUs. It models qubits, gates, and measurements well enough to let engineers test quantum algorithms without needing a real quantum device. Because the emulator runs on ordinary computers, it is limited by classical memory and compute, so it can only scale to small or approximate quantum systems.
In cyber security, quantum emulators matter because they let defenders prototype post-quantum cryptography, benchmark key exchange schemes, and check whether software behaves correctly before new algorithms are deployed. They are also useful for attackers and researchers who want to estimate how much hardware a future quantum attack would need, or to debug quantum workflows that could later be used for cryptanalysis. The main value is practical validation: emulation helps teams find implementation mistakes, compare designs, and measure risk long before real quantum machines are available at useful scale.