Simulating complex systems on a computer improves our understanding of natural phenomena and helps to develope new technology. Yet, some systems are beyond the simulation capabilities of even the most advanced supercomputers. Quantum simulators could overcome this challenge and greatly impact quantum chemistry, material science, condensed matter, and high-energy physics. While general-purpose quantum computers promise to more broadly revolutionize computing, they are still in their infancy, while quantum simulators can already tackle some task-specific problems. This is achieved by following a different approach than computer-based simulators, by using one quantum system to directly mimic the evolution of another, target system. The weakness in this strategy is that it lacks flexibility. This project aims to expand the capabilities of quantum simulation by introducing programmable analog quantum simulators which combine the ease of directly mimicking a system evolution, with the flexibility of engineering the simulator dynamics via logic gates. In addition, the project will develop novel metrics to evaluate performance and to acquire the most comprehensive information about the simulated system.
To achieve these goals, the researchers will employ a hybrid approach, combining evolution under the natural Hamiltonian (as in analog quantum simulators) with periodic control (collective quantum gates) to engineer a Floquet Hamiltonian approximating the interaction models of interest. As the simulation performance should be assessed on large (scalable) quantum systems not accessible to classical simulators, the project will validate the quantum control protocols experimentally, devising experimentally accessible metrics that can characterize the many-body dynamics, such as out-of-time ordered correlations and Loschmidt echoes. The systems used as quantum simulators will include quasi-1D nuclear spin chains, nuclear spins in 3D crystals, and spin impurities in diamond. There are several advantages of using spin systems to address these questions over synthetic matter systems such as cold atoms and ions. First, the system directly maps to typical spin Hamiltonians studied theoretically and it can build upon the long tradition of magnetic resonance investigation of condensed matter physics. In addition, these spin systems allow exploring broader regimes than cold atoms and ions, for example high-temperature conditions, and conditions that are well beyond what can be simulated exactly, such as large, 3D systems, and open systems interacting with a well-defined environment. Exploring the out-of-equilibrium dynamics of such rich spin systems will bring forward a host of new physical phenomena, as it will be demonstrated with a few paradigmatic examples of quantum spin models. A particular focus of the project is on investigating quantum thermalization or its absence due to localization or prethermalization, a key question in the quest to exploit many-body systems for quantum applications.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
