No cloning theorem

• There is no unitary transform that allows us to copy a qbit

  • No analog in classical reversible logic
  • Consequences
    • No wired OR’s
    • All gates have fanin and fanout of 1

• Illustration: Copy a bit using CNOT

  • Two entangled bits are identical
  • When we read one, we collapse the state of the other
    • We lose the hidden information
  • The two entangled qbits carry only 1 bit of information

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