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Implement fromBlochVector #26

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Implement fromBlochVector #26

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7235f2f
Implement fromBlochVector
marwahaha Sep 13, 2020
c398f47
Add variable declarations
marwahaha Sep 17, 2020
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15 changes: 14 additions & 1 deletion Q/Q-Qubit.js
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Original file line number Diff line number Diff line change
Expand Up @@ -286,8 +286,21 @@ Object.assign( Q.Qubit, {
},
fromBlochVector: function( x, y, z ){

// converting back to a Qubit (a, b) only maintains the relative phase between a and b
// for convenience, I will assume a is real.

//basically from a Pauli Rotation
// this neat trick comes from considering the density matrix if a = r and b = s + ti:
// ( r*r rs-rti )
// ( rs+rti s*s+t*t )

// compare that with the density matrix in https://en.wikipedia.org/wiki/Bloch_sphere

const
aReal = ( 0.5 + 0.5 * z ) ** 0.5,
a = new Q.ComplexNumber( aReal, 0 ),
b = new Q.ComplexNumber( x / 2 / aReal, y / 2 / aReal )

return new Q.Qubit( a, b )
}

})
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