Quantum

Optimal four-copy detection of the three-tangle and its fault-tolerant cost

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Based on a feed excerpt; full article content has not been acquired. Source evidence retrieved 21/10/2026, 04:13:25 UTC.

Briefings

A new arXiv preprint (2610.27260) identifies the statistically optimal one-sided four-copy detector for the three-tangle, achieving a click probability of τ₃²/48. This contrasts with previous constructions that required 16/3 times more repetitions. The study constructs ancilla-free implementations using 15 CNOT gates and an 11-CNOT variant with 96% efficiency. In fault-tolerant settings, these results reveal a tradeoff between statistical efficiency and circuit cost, with explicit resource estimates provided for Steane and [[8,3,2]] codes.

Key points

• The optimal one-sided four-copy detector for the three-tangle achieves a click probability of τ₃²/48.
• Previous four-copy constructions require asymptotically 16/3 times more experimental repetitions to achieve the same efficiency.

Context

The three-tangle (τ₃) is a measure of genuine tripartite entanglement used to distinguish GHZ-type from W-type entanglement in pure three-qubit states. This research addresses the tradeoff between statistical efficiency and implementation cost in detecting this specific entanglement measure.

Limitations

The evidence is an untrusted arXiv preprint (2610.27260v1) with no experimental data or validation. Results are theoretical and subject to future revision. No specific authors, dates, or quotes are provided in the source text.

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