Quantum Computing without Quantum Computers: Database Search and Data Processing Using Classical Wave Superposition

Abstract: Quantum computing is an emerging field of science which will eventually lead us to new and powerful logic devices with capabilities far beyond the limits of current transistor-based technology. There are certain types of problems which quantum computers can solve fundamentally faster than the tradition digital computers. There are quantum algorithms which require both superposition and entanglement (e.g. Shor algorithm). But neither the Grover algorithm nor the very first quantum algorithm due to Deutsch and Jozsa need entanglement. Is it possible to utilize classical wave superposition to speedup database search? This interesting question was analyzed by S. Lloyd. It was concluded that classical devices that rely on wave interference may provide the same speedup over classical digital devices as quantum devices. There were several experimental works using optical beam superposition for emulating Grover algorithm. It was concluded that the use of classical wave superposition comes with the cost of exponential increase of the resources. Since then, it is widely believed that the use of classical wave superposition for quantum algorithms is inevitably leading to an exponential resources overhead (number of devices, power consumption, precision requirements). In this work, we describe a classical Oracle machine which utilizes classical wave superposition for database search and data processing. We present experimental data on magnetic database search using spin wave superposition. The data show a fundamental speedup over the digital computers without any exponential resource overhead. We argue that in some cases the classical wave-based approach may provide the same speedup in database search as quantum computers.