Several katas could have better error messaging:

• Superposition : the test harness could log the actual state of the system after prep vs the expected state before asserting that they are the same (the change would add state prep and logging using DumpMachine to AssertEqualOnZeroState)
• BasicGates : a similar improvement, but a bit more extra code to write a unified test wrapper

Here are some examples:

• Root README is missing machine learning category of samples
• README in algorithms is missing repeat-until-success and sudoku-grover
• [README in diagnostics](https://github.com/microsoft/Quantum/blob/main/samples/diagnostics/RE

What is the expected behavior?

While there is still a distinction between Gate (strictly unitary) and Instruction (not necessarily unitary) we should not only have a to_instruction but also a to_gate on the o

Is your feature request related to a use case or problem? Please describe.
The use case is documentation.

Describe the solution you'd like
Basically something like the docstring used here: https://github.com/quantumlib/Cirq/blob/d58423a3f06dd0a40fd8acfdd006d9a876274a7c/cirq/circuits/qasm_output.py#L86

**What is the urgency from your perspective for this issue? Is it blocking impo

Did you find a doc bug or broken link that needs to be fixed?

English Qiskit Docs: https://qiskit.org/documentation/release_notes.html#id187
Korean Qiskit Docs: https://qiskit.org/documentation/locale/ko_KR/release_notes.html#id155

We probably might want to generate the version history table in all docs.

To get this codebase up to standard, we need to add type hints. At the very least, perhaps we should start insisting that all new code has type hints added, but moreover we need to add typing to the code that currently exists.

This is a pretty large project, but luckily it can be done incrementally - I believe at this point it's a stretch goal for v1, if anyone wants to help it would be much ap

Running travis lint gives a bunch of warning. Like for instance, sudo : required is no longer needed, and Travis migrated to a new architecture. So the travis.yml file needs to be updated.

https://blog.travis-ci.com/2018-10-04-combining-linux-infrastructures

For example, pylint would have caught ProjectQ-Framework/ProjectQ#19 via an undefined variable warning.

What is the expected enhancement?

>>> from qiskit.aqua.operators import I, X
>>> (0 * X + I) == I
False  # should be True

A possible solution would be to add a ``SummedOp.chop_summands(threshold=0)

It would be nice to allow users to set a custom value for the tensorflow dtype if they are really pushing their simulations (and aware of the memory tradeoffs). This would be a very straightforward feature to add, most likely by adjusting backend_options to accept a dtype argument or something similar

See, e.g., the discussion below:

You could change this line https://github.com/XanaduAI

There seems to be confusion between 'schedule' and 'scheduler' throughout sources and doc. They seem to be used interchangeably, which seems confusing. Is a "schedule" the same as a "scheduleR"?

For example, consider the following code snippet in src/compressor/compressor.lisp:

  (let ((lschedule (make-lscheduler)))
    ;; load up the logical schedule

The variable lschedule and