Native three-body interaction in superconducting circuits

TL;DR

This paper demonstrates how a superconducting circuit with three non-linear oscillators can naturally implement strong three-body qubit interactions, enabling fast quantum gates with high fidelity.

Contribution

It introduces a superconducting circuit design that realizes native three-body interactions and analytically accounts for all Josephson junction contributions.

Findings

Achieves average gate fidelities above 99.5%.

Operation times are on the order of a nanosecond.

Provides an analytical method for including all cosine contributions.

Abstract

We show how a superconducting circuit consisting of three identical, non-linear oscillators in series considered in terms of its electrical modes can implement a strong, native three-body interaction among qubits. Because of strong interactions, part of the qubit-subspace is coupled to higher levels. The remaining qubit states can be used to implement a restricted Fredkin gate, which in turn implements a CNOT-gate or a spin transistor. Including non-symmetric contributions from couplings to ground and external control we alter the circuit slightly to compensate, and find average fidelities for our implementation of the above gates above $ 99.5\% $ with operation times on the order of a nanosecond. Additionally we show how to analytically include all orders of the cosine contributions from Josephson junctions to the Hamiltonian of a superconducting circuit.