In this talk, I will describe an on-going work where we start from a generic 0+1-dimensional system with a generalized free field
and construct the corresponding bulk field. This is a generalization of Hamilton-Kabat-Lifschytz-Lowe (HKLL) construction. The
difference is that our construction applies to generic boundary theories with generalized free fields, and does not rely on
knowledge about the bulk geometry. More specifically, we discretize the boundary time and obtain the bulk dual theory in large $N$
limit in the form of a Gaussian quantum circuit.