A quantum circuit consisting of parameterized gates RX(theta), RY(theta) and RZ(theta), represents a unitary transformation \(U(\theta)\) that transforms the initial quantum state into an Ansatz state \(|\psi(\theta)\rangle\).

Hardware Efficient Ansatz#

Qibochem provides a hardware efficient ansatz that simply consists of a layer of single qubit rotation gates followed by a layer of two-qubit gates that entangle the qubits. For the H2 case discussed in previous sections, a possible hardware efficient ansatz can be constructed as such:



Placeholder for hardware-efficient ansatz example

Unitary Coupled Cluster Ansatz#

The Unitary Coupled Cluster ansatz [1] [2] is a variant of the popular gold standard Coupled Cluster ansatz [3] of quantum chemistry. The unitary coupled cluster wave function is a parameterized unitary transformation of a reference wave function, of which a common choice is the Hartree-Fock wave function.

\[|\psi_{\mathrm{UCC}}\rangle = U(\theta)|\psi_{\mathrm{ref}}\rangle\]


Placeholder for UCCD example