Efficient Hamiltonian engineering

We propose a novel and efficient scheme to engineer arbitrary (local) many-body Hamiltonians by interleaving the free evolution of a fixed system Hamiltonian with layers of single-qubit Pauli or Clifford gates. These sequences are constructed by solving a linear program (LP) which minimizes the total evolution time. The target Hamiltonians that can be engineered by our method are only limited by the locality of the Pauli terms in the system Hamiltonian. We then construct an efficient relaxation of this LP with a classical runtime that depends on the number of Pauli terms in the Pauli decomposition of the system Hamiltonian and is thus a low-degree polynomial in the number of qubits in practice. With our method, it is also possible to engineer Hamiltonians if only partial knowledge of the system Hamiltonian is available, which can be used to cancel unknown unwanted Pauli terms. We show the classical efficiency of our method by engineering an arbitrary two-body Hamiltonian on a 2D square lattice with $225$ qubits in only $60$ seconds. We also provide numerical simulations of our method modelling an ion trap device with an Ising Hamiltonian and engineering a general Heisenberg Hamiltonian. Moreover, we address dominant error sources in practical applications.