Square Root Day September 9, 1981 (9/9/81). Gordon remains the holiday's publicist, sending news releases to world media outlets. Gordon's daughter set up a Facebook group where people can share how they were celebrating the day. One suggested way of celebrating the holiday is by eating square radishes, or other root vegetables cut into shapes with square cross sections (thus creating a "square root"). Square Root Day occurs on the following dates each century: The number of years between consecutive Square Root Days in a century are consecutive odd numbers: 3, 5, 7, 9, 11, 13, 15, 17. This illustrates the fact that
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