Skip to content

Commit 371224c

Browse files
committed
remove call to absent files in message passing.md
1 parent 3bdf3c5 commit 371224c

File tree

1 file changed

+0
-11
lines changed

1 file changed

+0
-11
lines changed

docs/src/Tutorials/Message Passing.md

Lines changed: 0 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -247,7 +247,6 @@ lines!(ax, x, x, color = :black)
247247
f
248248
249249
```
250-
![phi](./../assets/images/phi.png)
251250

252251
Trying to plot this function with the $\tanh$ versus plotting this function with the exponentials makes the numerical instability of the $\tanh$ apparent. Fortunately, the exponential form makes it apparent that it is not only symmetric about $y = x$, but also that the function is dominated by smaller values of $x$:
253252

@@ -751,7 +750,6 @@ lines!(noise, FER, color = :red)
751750
scatter!(noise, FER, color = :red)
752751
current_figure()
753752
```
754-
![CSS_FER_test](./../assets/images/CSS_FER_test.png)
755753

756754

757755
TODO REDO THIS FUNCTION
@@ -772,7 +770,6 @@ ax2 = Axis(fig2[1, 2], xlabel = "Iteration Number", ylabel = "Number Of Times Co
772770
barplot!(ax1, collect(keys(X_iters_15)), X_values, bar_width = 1)
773771
barplot!(ax2, collect(keys(Z_iters_15)), Z_values, bar_width = 1)
774772
```
775-
![CSS_test_iters](./../assets/images/CSS_test_iters.png)
776773

777774
The overwhelming majority of convergeneces, for both $X$ and $Z$, occurred within one or two iterations. This is plausible for a couple of reasons. First, note that all variable nodes have degree four but all check nodes have degree nine! This is large for an LDPC code. For low error rates when errors are sparsely distributed over 254 qubits, it may be common that a single check node does not connect to more than one inncorrect variable node and the degrees are high enough to immediately flip any bit.
778775

@@ -805,8 +802,6 @@ false
805802

806803
Rerunning the simulation without using Bayes' Theorem returns almost symmetric $X$ and $Z$ iteration counts. For completeness, we include both runs on a single plot. The first blue point on the left is due to a single convergence error and the spike on the left further shows that direct sampling is either not appropriate for this error rate or it has not been sampled enough times for accuracy.
807804

808-
![CSS_FER_Bayes_test](./../assets/images/CSS_FER_Bayes_test.png)
809-
810805
## Example 2: Single-Shot Decoding With Metachecks
811806
Next we're going to look at two single-shot decoding schemes. We will call the paper [quintavalle2021single](@cite) scheme one and [higgott2023improved](@cite) scheme two. We encourage the reader to check out both papers directly for details. Briefly, both schemes will consider data errors, as in the previous example, plus additional measurement errors (on the syndrome values). The code family we will look at has an extra matrix, $M$, with the property that $Ms = 0$ for any valid syndrome $s$ of the code. Then assuming that the measurement error $s_e$ didn't take us from a valid syndrome to another valid syndrome, $M(s + s_e) = Ms_e \neq 0$. Whether or not this happens depends on the properties of the classical code with $M$ as its parity-check matrix. To correct the syndrome, we decode using the Tanner graph based on $M$. Then we will use the corrected syndrome to decode the stabilizers.
812807

@@ -1220,14 +1215,8 @@ julia> check_weights(X_meta_L)
12201215

12211216
By distance eight, scheme one was difficult to run without a cluster. We did not attempt distance nine with this scheme. This is problematic for many reasons, the most important of which is that many code families do not "settle in" to their asymptotic behaviors until distances much higher than this (although the exact distance depends on the decoder being used). For example, for the surface codes under minimum-weight perfect-matching (MWPM), anything below distance 20 is considered the small-code regime (compare this to distance seven for the same code family using trellis decoding).
12221217

1223-
![CSS_Single_Shot_test](./../assets/images/CSS_Single_Shot_test.png)
1224-
12251218
Logical errors were equally distributed among the cosets and only occurred on odd-distance codes.
12261219

1227-
1228-
1229-
1230-
12311220
julia> x = -20:.05:20; y = [abs(atanh(tanh(x)) - x) for x in x]; y2 = [exp(2abs(x)) / 2^56 for x in x]; plot(x, [replace(y, 0.0 => 1e-21) y2], ylims = (1e-20, 1), yscale = :log10, linewidth = 0.5, label = ["abs(atanh(tanh(x)) - x)" "exp(2abs(x)) / 2^56"])
12321221

12331222
p = 1 - 1/(1 + exp(LLR)) if LLR = log(p / (1 - p))

0 commit comments

Comments
 (0)