  Quantum simulation can help us study poorly understood topics such as
high-temperature superconductivity and drug design. However, existing quantum
simulation algorithms for current quantum computers often have drawbacks that
impede their application. Here, we provide a novel hybrid quantum-classical
algorithm for simulating the dynamics of quantum systems. Our approach takes
the Ansatz wavefunction as a linear combination of quantum states. The quantum
states are fixed, and the combination parameters are variationally adjusted.
Unlike existing variational quantum simulation algorithms, our algorithm does
not require any classical-quantum feedback loop and by construction bypasses
the barren plateau problem. Moreover, our algorithm does not require any
complicated measurements such as the Hadamard test. The entire framework is
compatible with existing experimental capabilities and thus can be implemented
immediately.
