3 research outputs found
Hilbert Space Fragmentation and Subspace Scar Time-Crystallinity in Driven Homogeneous Central-Spin Models
We study the stroboscopic non-equilibrium quantum dynamics of periodically
kicked Hamiltonians involving homogeneous central-spin interactions. The system
exhibits a strong fragmentation of Hilbert space into four-dimensional
Floquet-Krylov subspaces, which oscillate between two disjointed
two-dimensional subspaces and thus break the discrete time-translation symmetry
of the system. Our analytical and numerical analyses reveal that fully
polarized states of the satellite spins exhibit fragmentations that are stable
against perturbations and have high overlap with Floquet eigenstates of
atypically low bipartite entanglement entropy (scar states). We present
evidence of robust time-crystalline behavior in the form of a period doubling
of the total magnetization of fully polarized satellite spin states that
persists over long time scales. We compute non-equilibrium phase diagrams with
respect to a magnetic field, coupling terms, and pulse error for various
interaction types, including Heisenberg, Ising, XXZ, and XX. We also discuss
possible experimental realizations of scar time crystals in color center,
quantum dot, and rare-earth ion platforms.Comment: 17 pages, 9 figures, 1 tabl
Protocol for nearly deterministic parity projection on two photonic qubits
Photonic parity projection plays a significant role in photonic quantum
information processing. Non-destructive parity projections normally require
high-fidelity Controlled-Z gates between photonic and matter qubits, which can
be experimentally demanding. In this paper, we propose a nearly deterministic
parity projection protocol on two photonic qubits which only requires stable
matter-photon Controlled-Phase gates. The fact that our protocol does not
require perfect Controlled-Z gates makes it more amenable to experimental
implementation.Comment: 12+6 pages, 11 figure
Extracting perfect GHZ states from imperfect weighted graph states via entanglement concentration
Photonic GHZ states serve as the central resource for a number of important
applications in quantum information science, including secret sharing, sensing,
and fusion-based quantum computing. The use of photon-emitter entangling gates
is a promising approach to creating these states that sidesteps many of the
difficulties associated with intrinsically probabilistic methods based on
linear optics. However, the efficient creation of high-fidelity GHZ states of
many photons remains an outstanding challenge due to both coherent and
incoherent errors during the generation process. Here, we propose an
entanglement concentration protocol that is capable of generating perfect GHZ
states using only local gates and measurements on imperfect weighted graph
states. We show that our protocol is both efficient and robust to incoherent
noise errors.Comment: 8 pages, 5 figure