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Does the threshold estimation of the surface code not need a fault-tolerant setup?

I think technically, if you want to ensure Fault-Tolerance, indeed you need Shor/Steane/Knill error correction. e.g. in the surface code case, you need weight-4 cat state to do syndrome measurement ...
AndyLiuin's user avatar
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Does the threshold estimation of the surface code not need a fault-tolerant setup?

Is this still a fault-tolerant scheme? Can't an error in an ancilla spread to multiple data qubits and cause a logical error? Why would "fault tolerance" hinge on whether or not an error in ...
Craig Gidney's user avatar
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explain_detector_error_model_errors complains "no single circuit error had these exact symptoms"

That method is for turning the detection events of a single dem error into possible circuit errors causing that dem error. It doesn't do general decoding, as that is way way harder. So it doesn't work ...
Craig Gidney's user avatar
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Obtaining and Applying XX and ZZ Parity in Stim for Controlled Paulis

Stim's supported gates documentation includes the gate MXX and the gate MZZ which are exactly the two-qubit parity measurement ...
Craig Gidney's user avatar
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Does the threshold estimation of the surface code not need a fault-tolerant setup?

What does it mean to have a fault-tolerant setup? This has been done most rigorously for distance 3 codes, in which case a sufficient condition for a gate to be fault tolerant is that it should ...
DaftWullie's user avatar
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having REPEAT with circuit append

Multiplying a circuit by an integer larger than 1 turns it into a circuit with a loop, so you can do: circuit += loop_body_circuit * repeat_count or, if you ...
Craig Gidney's user avatar
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Calculating the weights of error mechanisms in stim

The key thing to realize is that the 15 cases within DEPOLARIZE2 are disjoint whereas the error mechanisms in a detector error model are independent. So they can't ...
Craig Gidney's user avatar
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What is TICK layer in stim

In Stim, TICK is an instruction that does nothing except indicate the passage of time. Conceptually, ticks split the circuit up into steps. Ticks have no effect on ...
Craig Gidney's user avatar
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Motivation for simulating multiround syndrome extraction circuits for quantum error correction code

A single round of noise ("code capacity") is a good model for a perfect sender transmitting to a perfect receiver over a noisy quantum channel. It's a bad model for a quantum computer built ...
Craig Gidney's user avatar
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Motivation for simulating multiround syndrome extraction circuits for quantum error correction code

This paper is a good read. The key point is that measurement is also a noisy process, so you cannot fully trust your extracted syndrome at any round. If you consider that you sometimes incorrectly ...
AG47's user avatar
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Parallelizing decode_to_edges_array (PyMatching)

You'll either have to make the pymatching.Matching after creating the child processes, or add pickling support to pymatching. We'd certainly take that as a ...
Craig Gidney's user avatar
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Efficiently Generating Expectation Values of Operators Using Stim

You can use the flip simulator to efficiently sample how often the current error set anticommutes with each observable. That tells you how often they're flipped. Then the tableau simulator can be used,...
Craig Gidney's user avatar
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