Mark  Repeat from Mark  Undo to Mark  Redo to Mark       Undo  Redo    Undo Set  Redo Set    Undo All  Redo All

The banner at the top shows a Title, a button to Load from file (file type .qco) a sequence of operations (example), and a button to pop up a window showing the running history of operations.

Below the banner is a set of buttons for various quantum operations. Clicking a button selects its operation. When a selected operation requires the specification of one or more qubits, it is highlighted until the requisite number of qubits is selected.

Below the buttons is a set of qubits (initially a single qubit) numbered starting at 0, with each qubit shown above its number as a vertical bar whose height indicates the probability that it will be read as a 1.

For operations that require the specification of one or more qubits, the qubits can be clicked; if more qubits must be specified, the already-selected qubits are highlighted. Some operations allow all (remaining) qubits to be selected; the All button performs that function.

Below the qubits is shown the actual state of the quantum computer as a set of amplitudes, one for each conventional bit configuration, and labeled in binary (big-endian) or hex (little-endian) with that bit configuration. The squared magnitudes of all the amplitudes sum to 1. Each amplitude is a complex number, and is shown as a partially filled in unit circle with a white-and-gray radial line showing the phase. The radius of the filled-in portion of the circle is the magnitude of the amplitude, so the filled-in area is the probability of the corresponding bit configuration. The length of the white portion of the phase line is a sigmoid function of the probability, allowing a more precise differentiation of probabilities close to 0 or 1.

Description of operations
Mark	place a mark in the history so that subsequent operations can be handled as a group
Repeat from Mark	perform the sequence of operations starting with the last mark
Undo to Mark	undo the sequence of operations starting with the last mark
Redo to Mark	redo the sequence of operations that were undone.
Undo	undo the last operation
Redo	redo the operation just undone
Undo Set	undo a sequence of the same operation applied to multiple qubits
Redo Set	redo a sequence of the same operation applied to multiple qubits
Undo All	undo all operations
Redo All	redo all operations
+qubit	add a qubit, initialized to Hadamard(0)
Read	read a qubit, causing it to be either 0 or 1.
Clear	read a qubit, and if the result is 1, apply Not.
Hadamard	apply a Hadamard gate to a qubit, i.e., the amplitude of 0 becomes the normalized sum of the amplitudes of 0 and 1, while the amplitude of 1 becomes the normalized difference of the amplitudes of 0 and 1.
Not	apply a Not gate to a qubit, i.e., invert the qubit, i.e., swap the amplitudes of 0 and 1
Y	apply a Y gate, i.e., swap the amplitudes of 0 and 1 then rotate 0 by -pi/2 and 1 by pi/2.
Pi/2	apply a Pi/2 gate to a qubit, i.e., rotate the amplitude of 1 by pi.
Pi/4	apply a Pi/4 gate to a qubit, i.e., rotate the amplitude of 1 by pi/2.
Pi/8	apply a Pi/8 gate to a qubit, i.e., rotate the amplitude of 1 by pi/4.
Not/2	apply "half" a Not gate to a qubit. (Applying this twice is the same as applying Not once.)
Negate0	negate the amplitude of the 0 state of a qubit.
CNot	apply Controlled Not gate to a pair of qubits, i.e., invert the second qubit if the first is 1.
Swap	swap a pair of qubits.
Swap/2	apply "half" a Swap gate to a pair of qubits.
iSwap	like swap, but rotate the phase of the 01 and 10 states by pi/2.
iSwap/2	apply "half" an iSwap gate to a pair of qubits.
CCNot	apply a Toffoli gate to a triple of qubits, i.e., invert the third qubit if the first two are 1.
CSwap	swap the second and third qubits if the first is 1.
NotIf0	apply Not to selected qubit if all other qubits are 0.
QFT	apply Quantum Fourier Transform to selected qubits. Select lo order then hi order qubit.
Negate	negate the amplitude of the selected bit configuration. Select by clicking a state circle.

Example of a file containing one step of Grover's Algorithm:

Grover(5,0xa)
+qubit
+qubit
+qubit
+qubit
+qubit
Clear 5
Mark
Not 1
Not 3
NotIf0 5
Pi/2 5
NotIf0 5
Not 1
Not 3
Hadamard 0
Hadamard 1
Hadamard 2
Hadamard 3
Hadamard 4
NotIf0 5
Not 5
Pi/2 5
Not 5
NotIf0 5
Hadamard 0
Hadamard 1
Hadamard 2
Hadamard 3
Hadamard 4
Mark