Better representation of state vectors

[nils-wittemeier]

Visualization

Adds a draw() method with three visualization modes to QuantumStateVector

from quri_parts.core.state import QuantumStateVector
import numpy as np

amp = np.sqrt(1/2)
state = QuantumStateVector(1, [amp, -amp])

state.draw(output="bloch")       # Bloch sphere
state.draw(output="qsphere")     # Q-sphere (multi-qubit phase/probability view)
state.draw(output="hinton")      # Hinton diagram of the density matrix

• bloch: Visualizes the state as a point on the Bloch sphere. For multi-qubit states, reduced single-qubit states are shown via partial trace.
  

• qsphere: Global view of a multi-qubit state in the computational basis. Dot size = probability, color = phase of each basis state.
  

• hinton: Hinton diagram of the density matrix. Square size encodes magnitude, color (white/black) encodes the sign of real/imaginary parts.
  

Text/Latex Representation

Adds text/latex representation of QuantumState, which uses mpmath to find expressions for floating point coefficients.

from quri_parts.core.state import QuantumStateVector
import numpy as np

amp = np.sqrt(1/2)
state = QuantumStateVector(1, [amp, -amp])

state.draw()
state.draw(output="latex_source")
state.draw(output="latex") 

|0> amp=0.707107 prob=0.5
|1> amp=-0.707107 prob=0.5
\frac{\sqrt{2}}{2}|0\rangle + -\frac{\sqrt{2}}{2}|1\rangle
<IPython.core.display.Latex object>

Jupyter notebooks will automatically render the LaTeX object as formatted math when evaluating a cell.

[github-actions]

🚀 Deployed on https://deploy-preview-512--quri-parts.netlify.app

[NaoQunaSys]

This is a very useful feature! Until now, when I wanted to display LaTeX in a Jupyter Notebook, I had to convert it into Qiskit and implement it like below, so I'm glad to see it supported natively.

from quri_parts.qiskit.circuit import convert_circuit as convert_circuit_qiskit
qc_qiskit = convert_circuit_qiskit(qc) # qc is a QuantumCircuit Object
return Statevector(qc_qiskit).draw('latex')

[ThomasenQunasys]

Oh, I'm sorry, I forgot to approve this. I've already gone over the changes earlier LGTM.