Distributed Quantum Computation Assisted by Remote Toffoli Gate

Ming‐Xing Luo, Yun Deng, Xiaojun Wang

Distributed quantum computation requires that quantum operations may be acted on remote logical qubits. We investigate the possibility of the distributed quantum computation for nonlocal photons assisted by cavity quantum electrodynamics. We first give a compact circuit for the controlled-NOT gate on a remote two-photon system. For the Toffoli gate, we introduce two circuits for a bipartite system with one photonic Einstein-Podolski-Rosen (EPR) entanglement. Two EPR pairs are required for a tripartite system. These Toffoli gates cost a half of entanglements required in the previous teleportation-based quantum computation. These elementary gates may be combined flexibly up to special decompositions of joint system in large-scale quantum applications.

Ming‐Xing Luo

Moein Sarvaghad-Moghaddam, Mariam Zomorodi Moghadam

Abstract In distributed quantum computation, quantum remote-controlled gates are used frequently and applied on separate nodes or subsystems of a network. One of the universal and well-known controlled gates is the n-qubit controlled-NOT gate, especially Toffoli gate for the case of three qubits, which are frequently used to synthesize quantum circuits. In this paper, we considered a more general case, an n-qubit controlled-U gate, and present a general protocol for implementing these gates remotely with minimum required resources. Then, the proposed method is applied to implement a Toffoli gate in bipartite and tripartite systems. In this method, we considered cases in which a group of qubits belongs to one subsystem of the network. Then, we improved its consumption resources.

Harry Buhrman, Hein Röhrig

XiangQi LU, YiLiu WANG, MengFan CHEN +3 more

Implementing three-qubit Toffoli gates nonlocally plays an important role in quantum communication networks and distributed quantum computation. Most of previous protocols for implementing quantum Toffolis gate consider only implementing Toffoli gates with one degree of freedom. In this paper, we present a scheme for parallel implementation of nonlocal Toffoli gates in polarization and spatial-mode degrees of freedom assisted by quantum dots inside a double-side optical microcavity. Alice and Bob let photons traverse the double-side optical microcavity sequentially and perform single-particle measurements on electron spin in quantum dots and the entangled photons. Charlie performs single-particle measurements and applies the corresponding unitary operation in polarization and spatial-mode degrees of freedom according to Alice and Bob’s measurement results. Alice and Bob can implement hyper-parallel nonlocal Toffoli gates by performing unitary operations according to Charlie’s measurement result. This protocol has the advantage of having high channel capacity by the hyperentangled state as the quantum channel.

Juan Carlos Boschero, Niels M. P. Neumann, Ward van der Schoot +2 more