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Equation 19 · Error Correction Is the Whole Problem in Quantum Computing

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pthp_{\mathrm{th}}

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pthp_{\mathrm{th}}

Symbol p_th

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subscript

subscript

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The threshold theorem is the reason the field exists. Stated informally: if the physical error rate per operation is below some constant pthp_{\mathrm{th}} determined by the code, the noise model and the fault-tolerant circuit construction, then an arbitrarily long quantum computation can be performed with arbitrarily small error, at an overhead that grows only polylogarithmically in the size of the computation. Knill, Laflamme and Zurek established resilient computation under a constant error rate [ 5 ] , and Aharonov and Ben-Or gave the constant-error-rate construction in a form that has become the standard citation [ 6 ] .

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