Multi-Copy Protocols for Imaginary-Time Evolution and Ground-State Preparation

The ability to implement imaginary-time evolution and prepare ground states is a central goal of quantum computation and simulation. Using multiple copies of the system, controlled-SWAP operations (or more general SWAP-generated unitaries), and real-time evolution under the system Hamiltonian, we present protocols that approximate imaginary-time dynamics with different performance guarantees and resource requirements. We provide numerical results for a heuristic variant and benchmark it against a protocol with provable convergence. Finally, we propose an implementation in cold-atom platforms that can complement existing ground-state preparation techniques and is compatible with near-term experiments.