While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum ga...While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum gates engaging multiple qubits are used.In the noisy intermediate-scale quantum(NISQ)era where a universal error correction is still unavailable,this strategy is particularly appealing since it can significantly reduce the computational resources required for executing quantum algorithms.In this work,we experimentally investigate a three-qubit ControlledCPHASE-SWAP(CCZS)gate on superconducting quantum circuits.By exploiting the higher energy levels of superconducting qubits,we are able to realize a Fredkin-like CCZS gate with a duration of 40 ns,which is comparable to typical single-and two-qubit gates realized on the same platform.By performing quantum process tomography for the two target qubits,we obtain a process fidelity of86.0%and 81.1%for the control qubit being prepared in|0>and|1>,respectively.We also show that our scheme can be readily extended to realize a general CCZS gate with an arbitrary swap angle.The results reported here provide valuable additions to the toolbox for achieving large-scale hardware-efficient quantum circuits.展开更多
基金supported by the Key-Area Research and Development Program of Guangdong Province(No.2018B030326001)the National Natural Science Foundation of China(Nos.12074166 and 12004162)the Guangdong Provincial Key Laboratory(No.2019B121203002).
文摘While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum gates engaging multiple qubits are used.In the noisy intermediate-scale quantum(NISQ)era where a universal error correction is still unavailable,this strategy is particularly appealing since it can significantly reduce the computational resources required for executing quantum algorithms.In this work,we experimentally investigate a three-qubit ControlledCPHASE-SWAP(CCZS)gate on superconducting quantum circuits.By exploiting the higher energy levels of superconducting qubits,we are able to realize a Fredkin-like CCZS gate with a duration of 40 ns,which is comparable to typical single-and two-qubit gates realized on the same platform.By performing quantum process tomography for the two target qubits,we obtain a process fidelity of86.0%and 81.1%for the control qubit being prepared in|0>and|1>,respectively.We also show that our scheme can be readily extended to realize a general CCZS gate with an arbitrary swap angle.The results reported here provide valuable additions to the toolbox for achieving large-scale hardware-efficient quantum circuits.
