Gate Visualizer

This program is a calculator-looking application that aims to help visualizing quantum gates on a Bloch sphere. It is a visualization tool for single qubit rotations on a Block sphere.

Unfortunately, The visualize_transition() function has been deprecated and will be removed in the 2.0.0 release. This function had a number of limitations which limited its utility to only very specific use cases and did not fit in with the rest of the Qiskit visualization module.

Gates

The following lists all the single-qubit gates that are implemented.

• $X$: flips the state of the qubit. circuit.x()
• $Y$: rotates the state vector about the $y$-axis. circuit.y()
• $Z$: flips the phase by $\pi$ radians along circuit.z()
• $R_x$: performs a parametrized rotation about the $x$-axis. circuit.rx()
• $R_y$: performs a parametrized rotation about the $y$-axis. circuit.ry()
• $R_z$: performs a parametrized rotation about the $z$-axis. circuit.rz()
• $S$: rotates the state vector about the $z$-axis by $\frac{\pi}{2}$ radians. circuit.s()
• $T$: rotates the state vector about the $z$-axis by $\frac{\pi}{4}$ radians. circuit.t()
• $S_d$: rotates the state vector about the $z$-axis by $-\frac{\pi}{2}$ radians. circuit.sdg()
• $T_d$: rotates the state vector about the $z$-axis by $-\frac{\pi}{4}$ radians. circuit.tdg()
• $H$: the Hadamard gate that creates the state of superposition. circuit.h()

For $R_x$, $R_y$, and $R_z$, the input angle $\theta$ of rotation is only allowed for the range of values $\theta \in [-2\pi, 2\pi]$.

At one instance, only ten operations can be visualized.

Important Change

The function qiskit.visualization.visualize_transition() was not working well with qiskit.QuantumCircuit.initalize() and was treating it as a quantum gate itself that was to be animated. To solve this, we can modify the code of the function qiskit.visualization.visualize_transition(). Specifically, we can add an argument in the function that accounts for the starting position and feed it into the starting_pos variable.

The function initially is

    def visualize_transition(circuit, trace=False, saveas=None, fpg=100, spg=2):

and then becomes

    def visualize_transition(circuit, trace=False, saveas=None, fpg=100, spg=2, initial_state=[0, 0, 1]):

after adding the argument initial_state=[0, 0, 1] to the end.

Additionally, somewhere in that function is a definition for the variable starting_pos. Initially, the variable was defined as

    starting_pos = _normalize(np.array([0, 0, 1]))

and then becomes

    starting_pos = _normalize(np.array(initial_state))

which is fed as an argument to the function visualize_transition().

This is a very easy solution but requires some local editing of the qiskit files.