Adaptive projected variational quantum dynamics

TL;DR

This paper introduces an adaptive quantum algorithm, Adaptive pVQD, that dynamically grows the variational circuit during time evolution, improving accuracy and efficiency in simulating quantum systems compared to traditional methods.

Contribution

The paper presents a novel adaptive algorithm for variational quantum dynamics that grows the circuit during simulation without auxiliary qubits, enhancing accuracy and scalability.

Findings

Adaptive pVQD outperforms Trotterized circuits in simulations.

The method produces shallower circuits with improved measurement accuracy.

Parallel gate search enables efficient implementation on multiple quantum devices.

Abstract

We propose an adaptive quantum algorithm to prepare accurate variational time evolved wave functions. The method is based on the projected Variational Quantum Dynamics (pVQD) algorithm, that performs a global optimization with linear scaling in the number of variational parameters. Instead of fixing a variational ansatz at the beginning of the simulation, the circuit is grown systematically during the time evolution. Moreover, the adaptive step does not require auxiliary qubits and the gate search can be performed in parallel on different quantum devices. We apply the new algorithm, named Adaptive pVQD, to the simulation of driven spin models and fermionic systems, where it shows an advantage when compared to both Trotterized circuits and non-adaptive variational methods. Finally, we use the shallower circuits prepared using the Adaptive pVQD algorithm to obtain more accurate measurements of physical properties of quantum systems on hardware.