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Equation 27 · Part 2 · Error Correction Is the Whole Problem in Quantum Computing

Symbol d

PL(d)  ≈  A(ppth)⌊(d+1)/2⌋,P_L(d) \;\approx\; A \left( \frac{p}{p_{\mathrm{th}}} \right)^{\left\lfloor (d+1)/2 \right\rfloor} ,
dd

What this part means

d is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

d is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

The passage around this formula

The practical form of the promise is a scaling law. Below threshold, the logical error rate per round of a distance- d code falls approximately as PL(d)  ≈  A(ppth)⌊(d+1)/2⌋P_L(d) \;\approx\; A \left( \frac{p}{p_{\mathrm{th}}} \right)^{\left\lfloor (d+1)/2 \right\rfloor} . so that each increase of the code distance by two multiplies the protection by a factor conventionally written

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