Abstract
The generation of high-fidelity distributed multi-qubit entanglement is a challenging task for large-scale quantum communication and computational networks1,2,3,4. The deterministic entanglement of two remote qubits has recently been demonstrated with both photons5,6,7,8,9,10 and phonons11. However, the deterministic generation and transmission of multi-qubit entanglement has not been demonstrated, primarily owing to limited state-transfer fidelities. Here we report a quantum network comprising two superconducting quantum nodes connected by a one-metre-long superconducting coaxial cable, where each node includes three interconnected qubits. By directly connecting the cable to one qubit in each node, we transfer quantum states between the nodes with a process fidelity of 0.911 ± 0.008. We also prepare a three-qubit Greenberger–Horne–Zeilinger (GHZ) state12,13,14 in one node and deterministically transfer this state to the other node, with a transferred-state fidelity of 0.656 ± 0.014. We further use this system to deterministically generate a globally distributed two-node, six-qubit GHZ state with a state fidelity of 0.722 ± 0.021. The GHZ state fidelities are clearly above the threshold of 1/2 for genuine multipartite entanglement15, showing that this architecture can be used to coherently link together multiple superconducting quantum processors, providing a modular approach for building large-scale quantum computers16,17.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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Acknowledgements
We thank P. J. Duda, A. Clerk and K. J. Satzinger for discussions. We thank W. D. Oliver and G. Calusine at MIT Lincoln Lab for providing the travelling-wave parametric amplifier (TWPA) used in this work. Devices and experiments were supported by the Air Force Office of Scientific Research and the Army Research Laboratory. É.D. was supported by LDRD funds from Argonne National Laboratory; A.N.C. was supported in part by the DOE, Office of Basic Energy Sciences, and D.I.S. acknowledges support from the David and Lucile Packard Foundation. This work was partially supported by the University of Chicago’s MRSEC (NSF award DMR-2011854) and made use of the Pritzker Nanofabrication Facility, which receives support from SHyNE, a node of the National Science Foundation’s National Nanotechnology Coordinated Infrastructure (NSF grant number NNCI1542205), with additional support from NSF QLCI for HQAN (NSF award 2016136).
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Y.Z. designed and fabricated the devices, performed the measurement and analysed the data. H.-S.C. provided help with the measurement. A.B. and É.D. provided help with the infrastructure setup. A.N.C. and D.I.S. advised on all efforts. All authors contributed to discussions and production of the manuscript.
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Zhong, Y., Chang, HS., Bienfait, A. et al. Deterministic multi-qubit entanglement in a quantum network. Nature 590, 571–575 (2021). https://doi.org/10.1038/s41586-021-03288-7
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DOI: https://doi.org/10.1038/s41586-021-03288-7
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Xinhang Shen
Please be aware that quantum mechanics itself is a theory based on the wrong interpretation of the particle-wave duality, which leads to all ridiculous conclusions such as particles entanglement. There is no such thing called wave of probability in nature because "probability" is not a physical substance, but a mathematical concept. The culprit is the wrong theory - special relativity which has denied the existence of aether - a fluid medium filling up the entire visible part of the universe and delivering all electromagnetic forces. The fatal mistake of special relativity is that it uses Lorentz Transformation to have redefined time but still equates the newly defined time and the physical time measured with physical clocks.
We know time is a concept abstracted from the status changes of physical processes such as the change of the view angle of the sun, the increase of the height of a tree, the distance that a car has driven, etc. All the changes of the statuses of physical processes are the products of time and changing rates. The effect of time can only be shown through these status changes, and there is no pure time keeper in the world which does not need the status change of a physical process. A physical clock records the number of cycles of a periodical process and uses this number to indirectly calculate the elapsed time. The number of cycles is the product of time and frequency. In special relativity, when observed from a stationary frame, relativistic time of a moving frame does become shorter but the relativistic frequency of a clock on the moving frame becomes faster to make the product of relativistic time and relativistic frequency unchanged compared with that of the stationary clock. That is, clock time is absolute and independent of reference frames, and relativistic kinetic time dilation won't be found on any physical clock or any other physical process. Time dilation is just the property of the relativistic time, nothing to do with the physical clock. As we all use physical clocks to observe physical phenomena, clock time is the real physical time. Thus, relativistic time is just a fake time without physical meaning and special relativity is wrong.
Ranbir Singh Parmar Replied to Xinhang Shen
Love the contrarian point of view. It certainly helps to see through physical phenomena and its association with formal frameworks.