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arXiv:1801.03782 · npj Quantum Information

16-qubit IBM universal quantum computer can be fully entangled

Yuanhao Wang, Ying Li, Zhang-qi Yin, Bei Zeng

Published Sep 21, 2018• 148 citations
arXivHTMLPDF

Abstract

Abstract Entanglement is an important evidence that a quantum device can potentially solve problems intractable for classical computers. In this paper, we prepare connected graph states involving 8 to 16 qubits onibmqx5, a 16-qubit superconducting quantum processor accessible via IBM cloud, using low-depth circuits. We demonstrate that the prepared state is fully entangled, i.e., the state is inseparable with respect to any fixed partition.

DOI
10.1038/s41534-018-0095-x

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Abstract Entanglement is an important evidence that a quantum device can potentially solve problems intractable for classical computers. In this paper, we prepare connected graph states involving 8 to 16 qubits onibmqx5, a 16-qubit superconducting quantum processor accessible via IBM cloud, using low-depth circuits. We demonstrate that the prepared state is fully entangled, i.e., the state is inseparable with respect to any fixed partition.
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Abstract The ability to generate large‐scale entanglement is an important progenitor of quantum information processing capability in noisy intermediate‐scale quantum (NISQ) devices. In this paper, the extent to which entangled quantum states over large numbers of qubits can be prepared on current superconducting quantum devices is investigated. Native‐graph states on the IBM Quantum 65‐qubit ibmq_manhattan device and the 53‐qubit ibmq_rochester device are prepared and quantum readout‐error mitigation (QREM) is applied. Connected entanglement graphs spanning each of the full devices are detected, indicating bipartite entanglement over the whole of each device. The application of QREM is shown to increase the observed entanglement within all measurements, in particular, the detected number of entangled pairs of qubits found within ibmq_rochester increases from 31 to 56 of the total 58 connected pairs. The results of this work indicate full bipartite entanglement in two of the largest superconducting devices to date.
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Abstract As quantum computing technology slowly matures and the number of available qubits on a QPU gradually increases, interest in assessing the capabilities of quantum computing hardware in a scalable manner is growing. One of the key properties for quantum computing is the ability to generate multipartite entangled states. In this study, aspects of benchmarking entanglement generation capabilities of noisy intermediate‐scale quantum (NISQ) devices are discussed based on the preparation of graph states and the verification of entanglement in the prepared states. Thereby, entanglement witnesses that are specifically suited for a scalable experiment design are used. This choice of entanglement witnesses can detect A) bipartite entanglement and B) genuine multipartite entanglement for graph states with constant two measurement settings if the prepared graph state is based on a two‐colorable graph, e.g., a square grid graph or one of its subgraphs. With this, it is experimentally verified that a bipartite entangled state comprising all qubits can be prepared on a 127‐qubit IBM Quantum superconducting QPU, and genuine multipartite entanglement can be detected for states of up to 23 qubits with quantum readout error mitigation.
Quantum computers have the potential to revolutionize information technology as we know it by solving certain relevant and interesting problems, using fundamentally fewer resources (number of computational steps) compared with even the fastest supercomputers. While critical aspects of quantum computing are being demonstrated in laboratories across the world, a fully functional and practical quantum computer is still many years away. It therefore becomes of great interest to discover applications of small-scale quantum computers which are the subject of current theoretical and experimental research. In order to facilitate access to small quantum computers, IBM recently announced the IBM Quantum Experience which provides access to a 5-qubit quantum processor as a stepping stone for the community as a whole to continue learning and discovering the full potential of quantum computing.
Abstract A quantum processor might execute certain computational tasks exponentially faster than a classical processor. Here, using superconducting quantum circuits we design a powerful universal quantum processor with the structure of symmetric all-to-all capacitive connection. We present the Hamiltonian and use it to demonstrate a full set of qubit operations needed in the programmable universal quantum computations. With the device the unwanted crosstalk and ZZ -type couplings between qubits can be effectively suppressed by tuning gate voltages, and the design allows efficient and high-quality couplings of qubits. Within available technology, the scheme may enable a practical programmable universal quantum computer.