Entangling four logical qubits beyond break-even in a nonlocal code

• URL: http://arxiv.org/abs/2406.02666v2
• Date: Mon, 5 Aug 2024 21:35:58 GMT
• Title: Entangling four logical qubits beyond break-even in a nonlocal code
• Authors: Yifan Hong, Elijah Durso-Sabina, David Hayes, Andrew Lucas,
• Abstract summary: Quantum error correction protects logical quantum information against environmental decoherence. We encode the GHZ state in four logical qubits with fidelity $ 99.5 pm 0.15 % le F le 99.7 pm 0.1% $ (after postselecting on over 98% of outcomes) Our results are a first step towards realizing fault-tolerant quantum computation with logical qubits encoded in geometrically nonlocal quantum low-density parity check codes.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum error correction protects logical quantum information against environmental decoherence by encoding logical qubits into entangled states of physical qubits. One of the most important near-term challenges in building a scalable quantum computer is to reach the break-even point, where logical quantum circuits on error-corrected qubits achieve higher fidelity than equivalent circuits on uncorrected physical qubits. Using Quantinuum's H2 trapped-ion quantum processor, we encode the GHZ state in four logical qubits with fidelity $ 99.5 \pm 0.15 \% \le F \le 99.7 \pm 0.1\% $ (after postselecting on over 98% of outcomes). Using the same quantum processor, we can prepare an uncorrected GHZ state on four physical qubits with fidelity $97.8 \pm 0.2 \% \le F\le 98.7\pm 0.2\%$. The logical qubits are encoded in a $[\![ 25,4,3 ]\!]$ Tanner-transformed long-range-enhanced surface code. Logical entangling gates are implemented using simple swap operations. Our results are a first step towards realizing fault-tolerant quantum computation with logical qubits encoded in geometrically nonlocal quantum low-density parity check codes.

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