Draw `qml.cond`: Part 2; `qml.map_wires` correctly maps nested tape wires #4901

mudit2812 · 2023-11-29T20:41:19Z

Context:
This PR follows up on adding support for qml.cond with qml.draw by fully allowing users to draw multiple conditional operators that are conditioned on multiple mid-circuit measurements. While implementing this, I tried to use qml.map_wires on the tape being drawn (which was eventually scrapped as it's too messy to use with nested tapes), and found out that nested tapes were not handled by map_wires correctly.

An example of what drawings can look like is shown here:

def circuit():
    qml.RX(0.5, 0)
    qml.RX(0.5, 1)

    m0 = qml.measure(0, reset=True, postselect=1)
    m1 = qml.measure(1)
    qml.cond(m0 & m1, qml.MultiControlledX)(wires=[1, 2, 3, 0], control_values="110")
    qml.cond(m1, qml.PauliZ)(2)

    m2 = qml.measure(1)
    qml.CNOT([3, 2])
    qml.cond(m0, qml.ctrl(qml.SWAP, control=[1, 2], control_values=[True, False]))(wires=[0, 3])
    qml.cond(m2 & m1, qml.PauliY)(0)

    qml.Toffoli([3, 1, 0])

    m3 = qml.measure(3, postselect=0)
    qml.cond(m3, qml.RX)(1.23, 3)
    qml.cond(m3 & m1, qml.Hadamard)(2)

    return qml.expval(qml.PauliZ(0) @ qml.PauliZ(2))

print(qml.draw(circuit)())

0: ──RX(0.50)──┤↗₁│  │0⟩──────╭X────────────╭SWAP──Y─╭X────────────────────┤ ╭<Z@Z>
1: ──RX(0.50)───║─────────┤↗├─├●─────┤↗├────├●─────║─├●────────────────────┤ │     
2: ─────────────║──────────║──├●──Z───║──╭X─├○─────║─│───────────────────H─┤ ╰<Z@Z>
3: ─────────────║──────────║──╰○──║───║──╰●─╰SWAP──║─╰●──┤↗₀├──RX(1.23)──║─┤       
                ╚══════════║═══╬══║═══║══════╝     ║      ║    ║         ║         
                           ╚═══╩══╩═══║════════════╬══════║════║═════════╣         
                                      ╚════════════╝      ║    ║         ║         
                                                          ╚════╩═════════╝

Description of the Change:

Update when fillers are used for drawing bit lines.
Update unicode character used when two bit lines cross over.
Removed use of defer_measurements in qml.draw. Now, QNodes won't defer measurements unconditionally, rather only when expansion_strategy=device is used, although this is only true for the new device API.
Update map_wires to correctly append mapped nested tapes to the parent tape.

Benefits:

qml.draw works fully with mid-circuit measurements!
qml.map_wires works with nested tapes

Possible Drawbacks:

Related GitHub Issues:

github-actions · 2023-11-29T20:41:36Z

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

A one-to-two sentence description of the change. You may include a small working example for new features.
A link back to this PR.
Your name (or GitHub username) in the contributors section.

timmysilv

curious as to why you were testing with nested tapes? we try to avoid them in general. It might even be preferred to not add more support for them, and instead start removing support? don't feel super duper strong about it, but figured I'd mention it.

pennylane/drawer/draw.py

mudit2812 · 2023-11-30T15:05:54Z

curious as to why you were testing with nested tapes? we try to avoid them in general. It might even be preferred to not add more support for them, and instead start removing support? don't feel super duper strong about it, but figured I'd mention it.

@timmysilv I wasn't adding any tests using nested tapes. When I mapped wires in tape_text, it caused the already existing nested tape tests to fail. As for adding more support for nested tapes, I think we should do so until we actually mark it as a deprecated feature. In my opinion, if we're going to stop supporting something, we should be verbose about it. I do agree that we need to get rid of them though.

mudit2812 · 2023-11-30T15:39:48Z

[sc-49288]

codecov · 2023-11-30T15:51:44Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e734949) 99.65% compared to head (b82d0a8) 99.65%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4901      +/-   ##
==========================================
- Coverage   99.65%   99.65%   -0.01%     
==========================================
  Files         387      387              
  Lines       35051    34784     -267     
==========================================
- Hits        34931    34663     -268     
- Misses        120      121       +1

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timmysilv

looks fantastic. won't worry about the nested tapes in this PR, but will maybe get back to them. fwiw, in the past, test with nested tapes have been marked (I think by me..) as xfail

lillian542

I offer you a tiny spelling/typo correction, a rocket ship and an approval 🚀

tests/drawer/test_draw.py

Co-authored-by: lillian542 <38584660+lillian542@users.noreply.github.com>

…ires (#4901) **Context:** This PR follows up on adding support for `qml.cond` with `qml.draw` by fully allowing users to draw multiple conditional operators that are conditioned on multiple mid-circuit measurements. While implementing this, I tried to use `qml.map_wires` on the tape being drawn (which was eventually scrapped as it's too messy to use with nested tapes), and found out that nested tapes were not handled by `map_wires` correctly. An example of what drawings _can_ look like is shown here: ```python def circuit(): qml.RX(0.5, 0) qml.RX(0.5, 1) m0 = qml.measure(0, reset=True, postselect=1) m1 = qml.measure(1) qml.cond(m0 & m1, qml.MultiControlledX)(wires=[1, 2, 3, 0], control_values="110") qml.cond(m1, qml.PauliZ)(2) m2 = qml.measure(1) qml.CNOT([3, 2]) qml.cond(m0, qml.ctrl(qml.SWAP, control=[1, 2], control_values=[True, False]))(wires=[0, 3]) qml.cond(m2 & m1, qml.PauliY)(0) qml.Toffoli([3, 1, 0]) m3 = qml.measure(3, postselect=0) qml.cond(m3, qml.RX)(1.23, 3) qml.cond(m3 & m1, qml.Hadamard)(2) return qml.expval(qml.PauliZ(0) @ qml.PauliZ(2)) print(qml.draw(circuit)()) ``` ``` 0: ──RX(0.50)──┤↗₁│ │0⟩──────╭X────────────╭SWAP──Y─╭X────────────────────┤ ╭<Z@Z> 1: ──RX(0.50)───║─────────┤↗├─├●─────┤↗├────├●─────║─├●────────────────────┤ │ 2: ─────────────║──────────║──├●──Z───║──╭X─├○─────║─│───────────────────H─┤ ╰<Z@Z> 3: ─────────────║──────────║──╰○──║───║──╰●─╰SWAP──║─╰●──┤↗₀├──RX(1.23)──║─┤ ╚══════════║═══╬══║═══║══════╝ ║ ║ ║ ║ ╚═══╩══╩═══║════════════╬══════║════║═════════╣ ╚════════════╝ ║ ║ ║ ╚════╩═════════╝ ``` **Description of the Change:** * Update when fillers are used for drawing bit lines. * Update unicode character used when two bit lines cross over. * Removed use of `defer_measurements` in `qml.draw`. Now, `QNode`s won't defer measurements unconditionally, rather only when `expansion_strategy=device` is used, although this is only true for the new device API. * Update `map_wires` to correctly append mapped nested tapes to the parent tape. **Benefits:** * `qml.draw` works fully with mid-circuit measurements! * `qml.map_wires` works with nested tapes **Possible Drawbacks:** **Related GitHub Issues:** --------- Co-authored-by: lillian542 <38584660+lillian542@users.noreply.github.com>

…4930) **Context:** This PR adds support for drawing the collection of mid-circuit measurement statistics with `qml.draw`. An example is shown below: ```python def circ(): qml.Hadamard(0) m0 = qml.measure(0) qml.Hadamard(1) m1 = qml.measure(1) qml.Hadamard(2) m2 = qml.measure(2) qml.Hadamard(3) qml.measure(3) qml.cond(m0, qml.PauliX)(0) qml.cond(m0 & m1, qml.PauliY)(1) return qml.expval(m2), qml.sample([m1, m2]) print(qml.draw(circ)()) ``` ``` 0: ──H──┤↗├──────────────────────────X────┤ 1: ──────║───H──┤↗├──────────────────║──Y─┤ 2: ──────║───────║───H──┤↗├──────────║──║─┤ 3: ──────║───────║───────║───H──┤↗├──║──║─┤ ╚═══════║═══════║═══════════╩══╣ ╚═══════║══════════════╩═╡ ╭Sample[MCM] ╚════════════════╡ <MCM> ╰Sample[MCM] ``` **Description of the Change:** * Refactor `tape_text` to only run through one loop containing all layers, not separate loops for op layers and measurement layers. The logic inside the loop has been adjusted accordingly. I also added big block comments to make the separation between different steps more obvious. * Add helpers to `tape_text.py` to add grouping symbols and labels for mid-circuit measurement statistics correctly. * Update `drawable_layers` to find layers for mid-circuit measurement statistics correctly. This included adding a new helper to recursively find layers for terminal measurements that use measurement values. * The bit map is now initialized with `None` values before everything else, and this is used to keep track of which mid-circuit measurements are used. Mostly a refactor to tidy up the code. * Remove code from `draw_mpl` that deferred measurements unconditionally for qnodes with mid-circuit measurements. This code was removed from `qml.draw` in #4901 and `qml.draw_mpl` is now updated as well. * The example in the `iterative_qpe` docstring was written before we had advanced mid-circuit measurement support and drawing capabilities, so I updated the example as well. **Benefits:** * We can draw mid-circuit measurement statistics! * Code related to the text drawer is slightly more readable. **Possible Drawbacks:** **Related GitHub Issues:** --------- Co-authored-by: Tom Bromley <49409390+trbromley@users.noreply.github.com> Co-authored-by: Christina Lee <christina@xanadu.ai> Co-authored-by: Matthew Silverman <matthews@xanadu.ai>

mudit2812 added 3 commits November 29, 2023 14:36

Updated tests; added full support for drawing conditions

a0aee02

Removed defer_measurements from draw

8357ef7

Merge branch 'master' into draw-mcm-3

160c572

Added test for map_wires with nested tape

7cc70e4

mudit2812 marked this pull request as ready for review November 29, 2023 20:49

Removed qnode test

06615ab

mudit2812 requested a review from a team November 29, 2023 20:52

Updated changelog

bd737cd

timmysilv reviewed Nov 29, 2023

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pennylane/drawer/draw.py Outdated Show resolved Hide resolved

mudit2812 added 2 commits November 30, 2023 09:38

Fixed tests

f5c4b9a

Fixed tests again

a80b26f

mudit2812 added 3 commits November 30, 2023 10:09

Updated changelog

6e5aea8

Fixed drawer test mocking

b3bf77c

Merge branch 'master' into draw-mcm-3

ad96e76

timmysilv approved these changes Dec 1, 2023

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mudit2812 requested a review from a team December 1, 2023 18:04

lillian542 approved these changes Dec 1, 2023

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mudit2812 and others added 2 commits December 1, 2023 15:52

Apply suggestions from code review

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Co-authored-by: lillian542 <38584660+lillian542@users.noreply.github.com>

Merge branch 'master' into draw-mcm-3

b82d0a8

mudit2812 merged commit 6ad2de6 into master Dec 1, 2023

mudit2812 deleted the draw-mcm-3 branch December 1, 2023 22:09

mudit2812 mentioned this pull request Dec 13, 2023

Support drawing mid-circuit measurement statistics with qml.draw #4930

Merged

albi3ro mentioned this pull request Jan 19, 2024

Use appropriate names in circuit drawings of qml.cond #2806

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Draw `qml.cond`: Part 2; `qml.map_wires` correctly maps nested tape wires #4901

Draw `qml.cond`: Part 2; `qml.map_wires` correctly maps nested tape wires #4901

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Draw qml.cond: Part 2; qml.map_wires correctly maps nested tape wires #4901

Draw qml.cond: Part 2; qml.map_wires correctly maps nested tape wires #4901

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Draw `qml.cond`: Part 2; `qml.map_wires` correctly maps nested tape wires #4901

Draw `qml.cond`: Part 2; `qml.map_wires` correctly maps nested tape wires #4901

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