MilestoneTheory & algorithmsConfirmed

Wootters and Zurek show that unknown quantum states cannot be copied

Oct 28, 1982

William Wootters and Wojciech Zurek publish a proof that quantum mechanics forbids a device that can perfectly copy an arbitrary unknown quantum state. The restriction applies to all quantum systems, not just photons.

Why it matters

Quantum information cannot be backed up by simply making exact copies, a fundamental constraint on how quantum computers store and protect data.

William K. Wootters · Wojciech H. Zurek

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Related

• Bennett and Brassard propose BB84, a way to share secret keys using photons (Dec 1984)
• Peter Shor shows quantum information can be protected from errors (Oct 1, 1995)