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Paper 1
Superconducting processor design optimization for quantum error correction performance
Xiaotong Ni, Ziang Wang, Rui Chao, Jianxin Chen
- Year
- 2023
- Journal
- arXiv preprint
- DOI
- arXiv:2312.04186
- arXiv
- 2312.04186
In the quest for fault-tolerant quantum computation using superconducting processors, accurate performance assessment and continuous design optimization stands at the forefront. To facilitate both meticulous simulation and streamlined design optimization, we introduce a multi-level simulation framework that spans both Hamiltonian and quantum error correction levels, and is equipped with the capability to compute gradients efficiently. This toolset aids in design optimization, tailored to specific objectives like quantum memory performance. Within our framework, we investigate the often-neglected spatially correlated unitary errors, highlighting their significant impact on logical error rates. We exemplify our approach through the multi-path coupling scheme of fluxonium qubits.
Open paperPaper 2
Entanglement in XYZ model on a spin-star system: Anisotropy vs. field-induced dynamics
Jithin G. Krishnan, Harikrishnan K. J., Amit Kumar Pal
- Year
- 2023
- Journal
- arXiv preprint
- DOI
- arXiv:2307.15949
- arXiv
- 2307.15949
We consider a star-network of $n=n_0+n_p$ spin-$\frac{1}{2}$ particles, where interaction between $n_0$ central spins and $n_p$ peripheral spins are of the XYZ-type. In the limit $n_0/n_p\ll 1$, we show that for odd $n$, the ground state is doubly degenerate, while for even $n$, the energy gap becomes negligible when $n$ is large, inducing an \emph{effective} double degeneracy. In the same limit, we show that for vanishing $xy$-anisotropy $γ$, bipartite entanglement on the peripheral spins computed using either a partial trace-based, or a measurement-based approach exhibits a logarithmic growth with $n_p$, where the sizes of the partitions are typically $\sim n_p/2$. This feature disappears for $γ\neq 0$, which we refer to as the \emph{anisotropy effect}. Interestingly, when the system is taken out of equilibrium by the introduction of a magnetic field of constant strength on all spins, the time-averaged bipartite entanglement on the periphery at the long-time limit exhibits a logarithmic growth with $n_p$ irrespective of the value of $γ$. We further study the $n_0/n_p\gg 1$ and $n_0/n_p\rightarrow 1$ limits of the model, and show that the behaviour of bipartite peripheral entanglement is qualitatively different from that of the $n_0/n_p\ll 1$ limit.
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