Quantum-Logic Gate between Two Optical Photons with an Average Efficiency above 40%

TL;DR

This paper presents a new quantum-logic gate platform achieving over 40% efficiency for two optical photons, surpassing previous records, and demonstrating multi-photon entanglement, advancing optical quantum information processing.

Contribution

The authors introduce a novel scheme combining atom-cavity systems and Rydberg EIT to achieve high-efficiency optical CNOT gates, surpassing the long-standing efficiency record.

Findings

Achieved a 41.7% average efficiency in optical CNOT gate.

Extended the scheme to multi-target qubits and generated entangled states of up to five photons.

Demonstrated potential for high-efficiency quantum information processing.

Abstract

Optical qubits uniquely combine information transfer in optical fibers with a good processing capability and are therefore attractive tools for quantum technologies. A large challenge, however, is to overcome the low efficiency of two-qubit logic gates. The experimentally achieved efficiency in an optical controlled NOT (CNOT) gate reached approximately 11% in 2003 and has seen no increase since. Here we report on a new platform that was designed to surpass this long-standing record. The new scheme avoids inherently probabilistic protocols and, instead, combines aspects of two established quantum nonlinear systems: atom-cavity systems and Rydberg electromagnetically induced transparency. We demonstrate a CNOT gate between two optical photons with an average efficiency of 41.7(5)% at a postselected process fidelity of 81(2)%. Moreover, we extend the scheme to a CNOT gate with multiple target qubits and produce entangled states of presently up to five photons. All these achievements are promising and have the potential to advance optical quantum information processing in which almost all advanced protocols would profit from high-efficiency logic gates.