We propose a scheme for a ground-code measurement-based quantum computer, which enjoys two major advantages. First, every logical qubit is encoded in the gapped degenerate ground subspace of a spin-1 chain with nearest-neighbor two-body interactions, so that it equips built-in robustness against noise. Second, computation is processed by single-spin measurements along multiple chains dynamically coupled on demand, so as to keep teleporting only logical information into a gap-protected ground state of the residual chains after the interactions with spins to be measured are turned off. We describe implementations using trapped atoms or polar molecules in an optical lattice, where the gap is expected to be as large as 0.2 or 4.8 kHz, respectively.
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http://dx.doi.org/10.1103/PhysRevLett.101.010502 | DOI Listing |
Nat Commun
January 2025
Joint Center for Quantum Information and Computer Science (QuICS), University of Maryland & NIST, College Park, MD, USA.
Quantum computers are now on the brink of outperforming their classical counterparts. One way to demonstrate the advantage of quantum computation is through quantum random sampling performed on quantum computing devices. However, existing tools for verifying that a quantum device indeed performed the classically intractable sampling task are either impractical or not scalable to the quantum advantage regime.
View Article and Find Full Text PDFPhys Rev Lett
October 2024
Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, Canada.
Quantum states picked from nontrivial symmetry-protected topological (SPT) phases have computational power in measurement-based quantum computation. This power is uniform across SPT phases, and is unlocked by measurements that break the symmetry. Except at special points in the phase, all computational schemes known to date place these symmetry-breaking measurements far apart, to avoid the correlations introduced by spurious, nonuniversal entanglement.
View Article and Find Full Text PDFIn Vivo
October 2024
Department of Medical Physics, Osaka Heavy Ion Therapy Center, Osaka, Japan.
Background/aim: In the pencil beam scanning carbon-ion radiotherapy, spot positions are arranged in three dimensions throughout the entire target region. Therefore, dose deviations can occur due to spot position errors in the target. However, performing three-dimensional measurements for routine patient-specific quality assurance (PSQA) is difficult because a simple measurement method has not been established.
View Article and Find Full Text PDFNature
October 2024
California Institute of Technology, Pasadena, CA, USA.
Enhancing the precision of measurements by harnessing entanglement is a long-sought goal in quantum metrology. Yet attaining the best sensitivity allowed by quantum theory in the presence of noise is an outstanding challenge, requiring optimal probe-state generation and read-out strategies. Neutral-atom optical clocks, which are the leading systems for measuring time, have shown recent progress in terms of entanglement generation but at present lack the control capabilities for realizing such schemes.
View Article and Find Full Text PDFPhys Rev Lett
August 2024
NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan and NTT Research Center for Theoretical Quantum Information, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
There are two types of universality in measurement-based quantum computation (MBQC): strict and computational. It is well known that the former is stronger than the latter. We present a method of transforming from a certain type of computationally universal MBQC to a strictly universal one.
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