arXiv subjects

D. Rodríguez Pérez

Publications and source records attributed to D. Rodríguez Pérez.

4 recordsLinked to original sources

arXiv2025

Repeated ancilla reuse for logical computation on a neutral atom quantum computer

Quantum processors based on neutral atoms trapped in arrays of optical tweezers have appealing properties, including relatively easy qubit number scaling and the ability to engineer arbitrary gate connectivity with atom movement. However, these platforms are inherently prone to atom loss, and the ability to replace lost atoms during a quantum computation is an important but previously elusive capability. Here, we demonstrate the ability to measure and re-initialize, and if necessary replace, a subset of atoms while maintaining coherence in other atoms. This allows us to perform logical circuits that include single and two-qubit gates as well as repeated midcircuit measurement while compensating for atom loss. We highlight this capability by performing up to 41 rounds of syndrome extraction in a repetition code, and combine midcircuit measurement and atom replacement with real-time conditional branching to demonstrate heralded state preparation of a logically encoded Bell state. Finally, we demonstrate the ability to replenish atoms in a tweezer array from an atomic beam while maintaining coherence of existing atoms -- a key step towards execution of logical computations that last longer than the lifetime of an atom in the system.

quant-ph↗

arXiv2024

High-fidelity universal gates in the $^{171}$Yb ground state nuclear spin qubit

Arrays of optically trapped neutral atoms are a promising architecture for the realization of quantum computers. In order to run increasingly complex algorithms, it is advantageous to demonstrate high-fidelity and flexible gates between long-lived and highly coherent qubit states. In this work, we demonstrate a universal high-fidelity gate-set with individually controlled and parallel application of single-qubit gates and two-qubit gates operating on the ground-state nuclear spin qubit in arrays of tweezer-trapped $^{171}$Yb atoms. We utilize the long lifetime, flexible control, and high physical fidelity of our system to characterize native gates using single and two-qubit Clifford and symmetric subspace randomized benchmarking circuits with more than 200 CZ gates applied to one or two pairs of atoms. We measure our two-qubit entangling gate fidelity to be 99.72(3)% (99.40(3)%) with (without) post-selection. In addition, we introduce a simple and optimized method for calibration of multi-parameter quantum gates. These results represent important milestones towards executing complex and general quantum computation with neutral atoms.

quant-ph↗

arXiv2019

Sensitivity for four-body tau-lepton decays at Belle and Belle II experiments

We study the expected sensitivity at Belle and Belle II for four-body $τ^\mp \to X^\pm l^\mp l^\mp ν_τ$ decays where $l=e$ or $μ$ and $X=π$, $K$, $ρ$ and $K^*$ mesons. These decay processes violate the total lepton number ($|ΔL|=2$ ) and they can be induced by the exchange of Majorana neutrinos. In particular, we consider lifetimes in the accessible ranges of $τ_N$ = 5, 100 ps and extract the limits on $|V_{\ell N}|^2$ without any additional assumption on the relative size of the mixing matrix elements. For an integrated luminosity collected of 1 ab$^{-1}$ at Belle, we found significant sensitivity on branching fractions of the order BR($τ^\mp \to X^\pm l^\mp l^\mp ν_τ$) $\sim 10^{-8}$. For an integrated luminosity expected of 50 ab$^{-1}$ and intermediate luminosity of 10 ab$^{-1}$ at the Belle II, we found significant sensitivity on branching fractions of the order BR($τ^\mp \to X^\pm l^\mp l^\mp ν_τ$) $\sim 10^{-9}-10^{-8}$. We use these sensitivities to set limits for the exclusion regions on the parameter space $(m_N, |V_{\ell N}|^2)$ associated with the heavy neutrino; such that for a $|V_{\ell N}|^2 \sim \mathcal{O}(10^{-5})$ at $τ_N = 100$ ps, we find the bounds as $0.140 < m_N < 1.776$ GeV for $τ^- \to X^+ e^- e^- ν_τ$ and $0.245 < m_N < 1.671 $ GeV for $τ^- \to X^+ μ^- μ^- ν_τ$.

hep-ph↗

arXiv2019

Prospects for $τ$ Lepton Physics at Belle II

The Belle II experiment is a substantial upgrade of the Belle detector and will operate at the SuperKEKB energy-asymmetric $e^+e^-$ collider. The design luminosity of the machine is 8$\times10^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ of data, a factor of 50 more than its predecessor. From February to July 2018, the machine has completed a commissioning run and main operation of SuperKEKB has started in March 2019. Belle II has a broad $τ$ physics program, in particular in searches for lepton flavor and lepton number violations (LFV and LNV), benefiting from the large cross section of the pairwise $τ$ lepton production in $e^+e^-$ collisions. We expect that after 5 years of data taking, Belle II will be able to reduce the upper limits on LFV and LNV $τ$ decays by an order of magnitude. Any experimental observation of LFV or LNV in $τ$ decays constitutes an unambiguous sign of physics beyond the Standard Model, offering the opportunity to probe the underlying New Physics. In this talk we will review the $τ$ lepton physics program of Belle II.

hep-ex↗