Implementations of heralded quantum Toffoli and Fredkin gates assisted by waveguide-mediated photon scattering

Multiqubit quantum logic gates play a critical role in quantum information processing and serve as a stepping stone to implementing a scalable quantum computation. In this paper, based on the photon-scattering property of a four-level emitter coupled to one-dimensional waveguide, we propose two heralded schemes for implementing Toffoli and Fredkin gates simultaneously on polarization and spatial degrees of freedom (DoFs) of two-photon systems. The undesired scattering processes between two photons and waveguide-emitter system can be detected by the single-photon detectors. That is, two multiqubit quantum gates are implemented in a heralded way, and the fidelity of each gate is near to unit in principle under current technical conditions, which ensures the feasibility of the experiment. Moreover, the quantum circuits for the two gates are robust against the decoherence, and require less quantum resource compared with the ones in one DoF only.

Automated summary

In this paper, we propose two heralded schemes for implementing Toffoli and Fredkin gates simultaneously on polarization and spatial degrees of freedom (DoFs) of two-photon systems based on the photon-scattering property of a four-level emitter coupled to one-dimensional waveguide. Undesired scattering processes can be detected by the single-photon detectors. The fidelity of each gate is near to unit in principle under current technical conditions, ensuring the feasibility of the experiment. Moreover, the quantum circuits for the two gates are robust against decoherence and require less quantum resource compared with single DoF gates.