/// <summary>
/// The probabilities of each possible register value indexed by that value.
/// </summary>
public static double[] GetDistribution(this IQuantumState state, Register reg)
{
int regSize = reg.QubitIndexes.Count();
long maxRegValue = (long)Math.Pow(2, regSize);
// probabilities indexed by register value
double[] regProbabilities = new double[maxRegValue];
// go through every probability
for (long i = 0; i < state.Dimension; i++)
{
var basis = new ComputationalBasis(i, state.NumQubits());
var amp = state.GetAmplitude(basis);
if (amp.Magnitude < ComplexExt.Precision)
{
continue;
}
var labels = basis.GetLabels();
var registerLabels = new List <bool>();
foreach (var index in reg.QubitIndexes)
{
registerLabels.Add(labels[index]);
}
long regValue = ComputationalBasis.FromLabels(registerLabels.ToArray()).AmpIndex;
regProbabilities[regValue] += amp.Magnitude * amp.Magnitude;
}
return(regProbabilities);
}
public static string Print(this IQuantumState state, params Register[] registers)
{
var test = state.ToArray().Where(b => b.Magnitude > ComplexExt.Precision);
StringBuilder sb = new StringBuilder();
for (long i = 0; i < state.Dimension; i++)
{
var basis = new ComputationalBasis(i, state.NumQubits());
var amp = state.GetAmplitude(basis);
if (amp.Magnitude < ComplexExt.Precision)
{
continue;
}
sb.Append($"+{(amp.Imaginary == 0 ? amp.Real.ToString("F2") : amp.ToString("F2"))}");
var labels = basis.GetLabels();
foreach (var register in registers)
{
var registerLabels = new List <bool>();
foreach (var index in register.QubitIndexes)
{
registerLabels.Add(labels[index]);
}
long regValue = ComputationalBasis.FromLabels(registerLabels.ToArray()).AmpIndex;
sb.Append($"|{regValue}>");
}
}
return(sb.ToString());
}
public void BasisTests()
{
var b1 = ComputationalBasis.FromLabels("101".ToBits());
b1.AmpIndex.Should().Be(5);
b1.GetLabels().Should().BeEquivalentTo("101".ToBits());
var b2 = ComputationalBasis.FromLabels("001".ToBits());
b2.AmpIndex.Should().Be(1);
b2.GetLabels().Should().BeEquivalentTo("001".ToBits());
var b3 = ComputationalBasis.FromLabels("1001".ToBits());
b3.AmpIndex.Should().Be(9);
b3.GetLabels().Should().BeEquivalentTo("1001".ToBits());
var b4 = ComputationalBasis.FromLabels("00".ToBits());
b4.AmpIndex.Should().Be(0);
b4.GetLabels().Should().BeEquivalentTo("00".ToBits());
}
public IQuantumState Transform(IQuantumState input)
{
if (transform.Dimension > input.Dimension)
{
throw new ArgumentException(nameof(transform.Dimension));
}
var newAmps = new Complex[Dimension];
// foreach basis vector in the state
for (long i = 0; i < Dimension; i++)
{
bool[] basis = new ComputationalBasis(i, NumQubits).GetLabels();
Complex origAmp = input.GetAmplitude(basis);
// apply the subroutine to part of that basis
IQuantumState res = transform.Transform(
new MultiQubit(
applyToQubitIndexes
.Select(index => basis[index] ? Qubit.ClassicOne : Qubit.ClassicZero)
.ToArray()));
// redistribute the result to every possible basis
for (long j = 0; j < transform.Dimension; j++)
{
bool[] subRoutineBasis = new ComputationalBasis(j, transform.NumQubits).GetLabels();
Complex amp = res.GetAmplitude(subRoutineBasis);
for (int indexIndex = 0; indexIndex < transform.NumQubits; indexIndex++)
{
int qubitIndex = applyToQubitIndexes[indexIndex];
basis[qubitIndex] = subRoutineBasis[indexIndex];
}
long ampIndex = ComputationalBasis.FromLabels(basis).AmpIndex;
newAmps[ampIndex] += origAmp * amp;
}
}
// weirder
return(new MultiQubit(newAmps));
}