Waveguide Variational Quantum Algorithms

Variational Quantum Algorithms (VQAs) [1], which make use of a classical optimizer to train a parametrized quantum circuit (PQC), have emerged as the leading proposal to leverage state-of-the-art quantum computers. However, they are still subjected to important constraints, such as scalability problems, undesired interactions between qubits and a limited connectivity, which motivate the search of new resources when designing PQCs. In this work we capitalize on the long-range interactions naturally appearing between quantum emitters coupled to waveguide-QED setups [2-4] as a resource for designing a novel class of PQCs, which we benchmark against other hardware-agnostic PQCs. Remarkably, these long-range interactions introduce entanglement between qubits in a controlled way, which allows an efficient classical training while reducing the gate count and noise impact. Our results suggest that such waveguide-mediated interactions can be a useful resource when designing VQAs.

[1] M. Cerezo et al., Nature Review Physics 3, 625-644 (2020).

[2] D. E. Chang et al., Rev. Mod. Phys. 90, 031002 (2018).

[3] Eunjong Kim et al., Physical Review X 11, 011015 (2021).

[4] Tamara Dordevic et al., Science 373 , 1511-1514 (2021).