From 5332bcedc5d0fb24d3b0fc488c1b71dcc258bdd6 Mon Sep 17 00:00:00 2001
From: Craig Gidney <craig.gidney@gmail.com>
Date: Sat, 8 Jun 2019 11:08:38 -0700
Subject: [PATCH] Fix conditional incoherent amplitude displays not normalizing
 magnitudes

Fixes https://github.com/Strilanc/Quirk/issues/434
---
 src/gates/AmplitudeDisplay.js       |  4 +++-
 test/gates/AmplitudeDisplay.test.js | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/gates/AmplitudeDisplay.js b/src/gates/AmplitudeDisplay.js
index d76795ce..3068f9d9 100644
--- a/src/gates/AmplitudeDisplay.js
+++ b/src/gates/AmplitudeDisplay.js
@@ -131,7 +131,9 @@ function processOutputs(span, pixelGroups, circuitDefinition) {
     let incoherentUnity = 0;
     for (let i = 0; i < n; i++) {
         incoherentUnity += rawIncoherentKetPixels[i];
-        incoherentKetPixels[i << 1] = Math.sqrt(rawIncoherentKetPixels[i]);
+    }
+    for (let i = 0; i < n; i++) {
+        incoherentKetPixels[i << 1] = Math.sqrt(rawIncoherentKetPixels[i] / incoherentUnity);
     }
     if (isNaN(incoherentUnity) || incoherentUnity < 0.000001) {
         return {
diff --git a/test/gates/AmplitudeDisplay.test.js b/test/gates/AmplitudeDisplay.test.js
index da0b773f..c982125c 100644
--- a/test/gates/AmplitudeDisplay.test.js
+++ b/test/gates/AmplitudeDisplay.test.js
@@ -229,3 +229,15 @@ suite.testUsingWebGL("AmplitudesDisplayIncoherent_hadamard", () => {
     ]);
     assertThat(out.displays[0].data.coherence_measure).isLessThan(0.85);
 });
+
+suite.testUsingWebGL("AmplitudesDisplayIncoherent_conditioned", () => {
+    let stats = CircuitStats.fromCircuitAtTime(
+        Serializer.fromJson(CircuitDefinition, {"cols":[[1,"•","Z"],["•","Amps1"]],"init":["+","+","+"]}),
+        0);
+    let out = stats.toReadableJson();
+    assertThat(out.displays[0].data.incoherentKet).isApproximatelyEqualTo([
+        Math.sqrt(0.5),
+        Math.sqrt(0.5),
+    ]);
+    assertThat(out.displays[0].data.coherence_measure).isLessThan(0.85);
+});