Support for circuit repeats in cirq-web

[seunomonije]

Describe the issue

Repeats in circuits cause issues in cirq-web. This can be fixed by:

1. Adjusting the code on the Python side where we serialize and build the 3D symbols for the Typescript to detect operations inside of a repeating block.
2. Introducing some symbol or sprite on the Typescript side that points to the Moment(s) that the user wants repeated. Similar to how a qubit is added, we can create a unique mesh that lives outside of the circuit and surrounds the moment(s) that are being repeated.

For starters, it might be best to only show a bracket. Eventually it would be nice to have the option to expand out the repetitions.

A patch could also just ignore the repeat and show the moment.

Explain how to reproduce the bug or problem

When running a circuit with repeats (for brevity, this stim circuit is invalid):

stim_circuit = stim.Circuit("""
REPEAT 999 {
    TICK
    H 2 11 16 25
    DEPOLARIZE1(0.001) 2 11 16 25
    TICK
    CX 2 3 16 17 11 12 15 14 10 9 19 18
    DEPOLARIZE2(0.001) 2 3 16 17 11 12 15 14 10 9 19 18
    TICK
    CX 2 1 16 15 11 10 8 14 3 9 12 18
    DEPOLARIZE2(0.001) 2 1 16 15 11 10 8 14 3 9 12 18
    TICK
    CX 16 10 11 5 25 19 8 9 17 18 12 13
    DEPOLARIZE2(0.001) 16 10 11 5 25 19 8 9 17 18 12 13
    TICK
    CX 16 8 11 3 25 17 1 9 10 18 5 13
    DEPOLARIZE2(0.001) 16 8 11 3 25 17 1 9 10 18 5 13
    TICK
    H 2 11 16 25
    DEPOLARIZE1(0.001) 2 11 16 25
    TICK
    MR 2 9 11 13 14 16 18 25
    SHIFT_COORDS(0, 0, 1)
    DETECTOR(2, 0, 0) rec[-8] rec[-16]
    DETECTOR(2, 2, 0) rec[-7] rec[-15]
    DETECTOR(4, 2, 0) rec[-6] rec[-14]
    DETECTOR(6, 2, 0) rec[-5] rec[-13]
    DETECTOR(0, 4, 0) rec[-4] rec[-12]
    DETECTOR(2, 4, 0) rec[-3] rec[-11]
    DETECTOR(4, 4, 0) rec[-2] rec[-10]
    DETECTOR(4, 6, 0) rec[-1] rec[-9]
}
""")
cirq_circuit = stimcirq.stim_circuit_to_cirq_circuit(stim_circuit)
print(cirq_circuit)
cirq_web.Circuit3D(cirq_circuit).generate_html_file(
    file_name="stim_circuit_viewer.html",
    open_in_browser=True,
)

Cirq-web does not display any meaningful information.

However, when removing the repeat code:

stim_circuit = stim.Circuit("""
    TICK
    H 2 11 16 25
    DEPOLARIZE1(0.001) 2 11 16 25
    TICK
    CX 2 3 16 17 11 12 15 14 10 9 19 18
    DEPOLARIZE2(0.001) 2 3 16 17 11 12 15 14 10 9 19 18
    TICK
    CX 2 1 16 15 11 10 8 14 3 9 12 18
    DEPOLARIZE2(0.001) 2 1 16 15 11 10 8 14 3 9 12 18
    TICK
    CX 16 10 11 5 25 19 8 9 17 18 12 13
    DEPOLARIZE2(0.001) 16 10 11 5 25 19 8 9 17 18 12 13
    TICK
    CX 16 8 11 3 25 17 1 9 10 18 5 13
    DEPOLARIZE2(0.001) 16 8 11 3 25 17 1 9 10 18 5 13
    TICK
    H 2 11 16 25
    DEPOLARIZE1(0.001) 2 11 16 25
    TICK
    MR 2 9 11 13 14 16 18 25
    SHIFT_COORDS(0, 0, 1)
    DETECTOR(2, 0, 0) rec[-8] rec[-16]
    DETECTOR(2, 2, 0) rec[-7] rec[-15]
    DETECTOR(4, 2, 0) rec[-6] rec[-14]
    DETECTOR(6, 2, 0) rec[-5] rec[-13]
    DETECTOR(0, 4, 0) rec[-4] rec[-12]
    DETECTOR(2, 4, 0) rec[-3] rec[-11]
    DETECTOR(4, 4, 0) rec[-2] rec[-10]
    DETECTOR(4, 6, 0) rec[-1] rec[-9]
""")
cirq_circuit = stimcirq.stim_circuit_to_cirq_circuit(stim_circuit)
print(cirq_circuit)
cirq_web.Circuit3D(cirq_circuit).generate_html_file(
    file_name="stim_circuit_viewer.html",
    open_in_browser=True,
)

The circuit is handled properly.

Tell us the version of Cirq where this happens

1.6.0

[seunomonije]

Addressed in #7541