Realization of a Universal Quantum Gate Set for Itinerant Microwave Photons

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.

Exploring ab initio machine synthesis of quantum circuits

“…Native gate sets for quantum hardware often consist of a limited number of gates, which express hardware constraints like restricted qubit connectivity or a specific set of supported gates, as is the case e.g. for trapped ions [6][7][8][9][10], superconducting qubits [11][12][13][14], and silicon-based hardware [15][16][17][18][19]. Quantum algorithms, on the other hand, are often prescribed in a gate set that fits the properties of the computation [20].…”

Proposal for generating complex microwave graph states using superconducting circuits

“…Compared to the other three types of encoding, generating Fock-basis qubits is the fastest, which makes the generation scheme have higher fidelity. However, singlequbit gates (SQGs) on Fock-basis qubits require first absorbing the photon qubit into a transmon, which maps the photon state to the transmon state, and then applying the gate to the transmon and emitting the photon again [42]. The gate fidelity of this capturing and reemitting protocol is rather limited.…”