Set of two-qubit gates for near-term quantum algorithms

Demonstration of the tunable coupling between gmon qubits.

Quantum algorithms offer a dramatic speedup for computational problems in material science and chemistry. However, any near-term realizations of these algorithms will need to be optimized to fit within the finite resources offered by existing noisy hardware.

Here, taking advantage of the adjustable coupling of gmon qubits, researchers demonstrated a continuous two-qubit gate set that can provide a threefold reduction in circuit depth as compared to a standard decomposition.

They implemented two gate families: an imaginary swap-like (iSWAP-like) gate to attain an arbitrary swap angle, θ, and a controlled-phase gate that generates an arbitrary conditional phase, ϕ.

Using one of each of these gates, they were able to perform an arbitrary two-qubit gate within the excitation-preserving subspace allowing for a complete implementation of the so-called Fermionic simulation (fSim) gate set.

The paper has been published in Physical Review Letters.