Realization of a Universal Quantum Gate Set for Itinerant Microwave Photons

TL;DR

This paper demonstrates a deterministic, non-post-selected universal quantum gate set for itinerant microwave photons using superconducting circuits, enabling advanced quantum networking capabilities.

Contribution

It introduces the first non-post-selected, deterministic microwave photon-photon gate using superconducting circuits, combining controlled absorption, re-emission, and single-qubit gates.

Findings

Achieved 75% fidelity for single-qubit gates.

Achieved 57% fidelity for two-qubit gates.

Limited mainly by radiation loss and decoherence.

Abstract

Deterministic photon-photon gates enable the controlled generation of entanglement between mobile carriers of quantum information. Such gates have thus far been exclusively realized in the optical domain and by relying on post-selection. Here, we present a non-post-selected, deterministic, photon-photon gate in the microwave frequency range realized using superconducting circuits. We emit photonic qubits from a source chip and route those qubits to a gate chip with which we realize a universal gate set by combining controlled absorption and re-emission with single-qubit gates and qubit-photon controlled-phase gates. We measure quantum process fidelities of $75\,\%$ for single- and of $57\,\%$ for two-qubit gates, limited mainly by radiation loss and decoherence. This universal gate set has a wide range of potential applications in superconducting quantum networks.