Algorithm for initializing a generalized fermionic Gaussian state on a quantum computer.

摘要: We present explicit expressions for the central piece of a variational method developed by Shi et al. which extends wave functions that are efficiently computable on classical computers beyond mean-field to generalized Gaussian states [1]. In particular, we derive iterative analytical evaluation expectation values products fermionic creation and annihilation operators in Grassmann variable-free representation. Using this result find closed expression energy functional its gradient general quantum many-body Hamiltonian. simple gradient-descent-based algorithm can be used as an optimization subroutine combination with imaginary time evolution, construction guarantees monotonic decrease each iteration step. Due simplicity circuit implementing state Ansatz, results algorithms discussed here [1] could serve improved, initial computation. [1] Tao Shi, Eugene Demler, J. Ignacio Cirac. Variational study bosonic systems non-gaussian states: Theory applications. Annals Physics, 390: 245-302, 2018.