Add sampling overhead table and expand/update cutting explanation #342
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I will likely keep tweaking this, and I still plan to further expand the explanation document a bit (either before or after this PR is merged -- doesn't matter to me), but this is already a substantial contribution and is in a good place, essentially ready for review. The most convenient way to review it probably is to either build it locally or to download the artifact from the Docs CI run. (Click on the docs run, then click "Summary", then click "html_docs.") |
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@caleb-johnson and @ibrahim-shehzad: Requesting your review. Any comments are truly welcome, but just remember this doesn't need to be perfect before we merge; we can always iterate on it later. |
Co-authored-by: Ibrahim Shehzad <[email protected]>
following discussion at #342 (comment)
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| There are three settings to consider for circuit cutting. The first is where only local operations (LO) [i.e., local *quantum* operations] are available. The other settings introduce classical communication between the circuit executions, which is known in the quantum information literature as LOCC, for `local operations and classical communication <https://en.wikipedia.org/wiki/LOCC>`__. The LOCC can be either near-time, one-directional communication between the circuit executions (the second setting), or real-time, bi-directional communication (the third setting). | ||
| There are `three settings <https://research.ibm.com/blog/circuit-knitting-with-classical-communication>`__ to consider for circuit cutting. The first is where only local operations (LO) [i.e., local *quantum* operations] are available. The other settings introduce classical communication between the circuit executions, which is known in the quantum information literature as LOCC, for `local operations and classical communication <https://en.wikipedia.org/wiki/LOCC>`__. The LOCC can be either near-time, one-directional communication between the circuit executions (the second setting), or real-time, bi-directional communication (the third setting). |
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Should we mention here we only support Case 1?
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I see we mention it below
Follow up to #342 (comment)
It's actually very similar to the one at the top of the explanation #342 (comment)
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| Circuit cutting as a quasiprobability decomposition (QPD) | ||
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| Quasiprobability decomposition is a technique which can be used to simulate quantum circuit executions that go beyond the actual capabilities of current quantum hardware while using that same hardware. It forms the basis of many error mitigation techniques, which allow simulating a noise-free quantum computer using a noisy one. Circuit cutting techniques, which allow simulating a quantum circuit using fewer qubits than would otherwise be necessary, can also be phrased in terms of a quasiprobability decomposition. No matter the goal, the cost of the quasiprobability decomposition is an exponential overhead in the number of circuit executions which must be performed. In certain cases, this tradeoff is worth it, because it can allow the estimation of quantities that would otherwise be impossible on today's hardware. | ||
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| To perform circuit cutting, one must partition (“cut”) the graph representing a quantum circuit into smaller pieces, which are then executed on available hardware. The results of the original circuit must then be reconstructed during post-processing, resulting in the desired quantity (e.g., the expectation value of a joint observable). | ||
| There are two types of cuts: gate cuts and wire cuts. Gate cuts, also known as "space-like" cuts, exist when the cut goes through a gate operating on two (or more) qubits. Wire cuts, also known as "time-like" cuts, are direct cuts through a qubit wire, essentially a single-qubit identity gate that has been cut into two pieces. In CKT, a wire cut is represented by introducing a new qubit into the circuit and moving remaining operations after the cut identity gate to the new qubit; see :ref:`wire cutting as move`, below. |
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Super minor point: I realize that using space-like cuts for gate cuts and time-like cuts for wire cuts is common in the cutting literature but I find this terminology very confusing. This is because if we think of time as flowing horizontally, from left to right in a quantum circuit, a space-like cut should be a ''vertical'' cut (since space-like cuts give you ''constant time slices'') which would be more analogous to a wire cut. Do we need to use the ''space-like/time-like cut'' terminology? Alternatively, I could consider getting rid of my relativity baggage :).
Co-authored-by: Ibrahim Shehzad <[email protected]>
Co-authored-by: Ibrahim Shehzad <[email protected]>
ibrahim-shehzad
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I think we may just be able to ignore the contention I raised in this comment (since the literature uses this terminology). Overall, this looks good to me, thanks for putting this together.
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* Add sampling overhead table * typos * Fix heading level * Rearrange table * Fix some Sphinx cross references * Fix Sphinx LaTeX expressions * Add link to IBM blog post on LOCC cutting * Tweaks to intro * Lots of progress * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> * Rephrase LOCC vs dynamic circuits following discussion at #342 (comment) * Removed `PauliList` limitation, lifted by #523 Follow up to #342 (comment) * Rephrase circuit cutting intro #342 (comment) * Remove circuit cutting graph It's actually very similar to the one at the top of the explanation #342 (comment) * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> --------- Co-authored-by: Ibrahim Shehzad <[email protected]> (cherry picked from commit 299c849) # Conflicts: # test/cutting/qpd/test_qpd.py
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…ckport #342) (#553) * Add sampling overhead table and expand/update cutting explanation (#342) * Add sampling overhead table * typos * Fix heading level * Rearrange table * Fix some Sphinx cross references * Fix Sphinx LaTeX expressions * Add link to IBM blog post on LOCC cutting * Tweaks to intro * Lots of progress * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> * Rephrase LOCC vs dynamic circuits following discussion at #342 (comment) * Removed `PauliList` limitation, lifted by #523 Follow up to #342 (comment) * Rephrase circuit cutting intro #342 (comment) * Remove circuit cutting graph It's actually very similar to the one at the top of the explanation #342 (comment) * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> * Update docs/circuit_cutting/explanation/index.rst Co-authored-by: Ibrahim Shehzad <[email protected]> --------- Co-authored-by: Ibrahim Shehzad <[email protected]> (cherry picked from commit 299c849) # Conflicts: # test/cutting/qpd/test_qpd.py * Fix conflict --------- Co-authored-by: Jim Garrison <[email protected]>
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This adds a sampling overhead table.
I should triple check it.I may push other improvements to the cutting explanation to this branch, too.EDIT: I've added many other improvements, too.
Fixes #293.
Fixes #373.