Square root of 2 the square root of two, with a reasonable small denominator, the fraction (≈ 1.4142857) is sometimes used. The sequence in the OEIS gives the numerical value for the square root of two, truncated to 65 decimal places: The Babylonian clay tablet YBC 7289 (c. 1800–1600 BC) gives an approximation of in four sexagesimal figures, , which is accurate to about six decimal digits, and is the closest possible three-place sexagesimal representation of : Another early close approximation is given in ancient Indian mathematical texts, the Sulbasutras (c. 800–200 BC) as follows: "Increase the length [of the side] by its third
Square root of a matrix linear map is completely positive if and only if it is of the form where "k" ≤ "nm". Let {"E"} ⊂ C be the "n" elementary matrix units. The positive matrix is called the "Choi matrix" of Φ. The Kraus operators correspond to the, not necessarily square, square roots of "M": For any square root "B" of "M", one can obtain a family of Kraus operators "V" by undoing the Vec operation to each column "b" of "B". Thus all sets of Kraus operators are related by partial isometries. In quantum physics, a density matrix for an "n"-level quantum system