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quil-lang / quil

Specification of Quil: A Practical Quantum Instruction Set Architecture
https://quil-lang.github.io/
Apache License 2.0
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Clarification: Standard function definitions #62

Open MarquessV opened 1 year ago

MarquessV commented 1 year ago

The Quil spec references the cis function in an example for DEFGATE:

The definition of CAN can be written as the following Quil matrix definition:

DEFGATE CAN(%alpha, %beta, %gamma):
    (cis((%alpha+%beta-%gamma)/2)+cis((%alpha-%beta+%gamma)/2))/2, 0, 0, (cis((%alpha-%beta+%gamma)/2)-cis((%alpha+%beta-%gamma)/2))/2
    0, (cis((%alpha+%beta+%gamma)/(-2))+cis((%beta+%gamma-%alpha)/2))/2, (cis((%alpha+%beta+%gamma)/(-2))-cis((%beta+%gamma-%alpha)/2))/2, 0
    0, (cis((%alpha+%beta+%gamma)/(-2))-cis((%beta+%gamma-%alpha)/2))/2, (cis((%alpha+%beta+%gamma)/(-2))+cis((%beta+%gamma-%alpha)/2))/2, 0
    (cis((%alpha-%beta+%gamma)/2)-cis((%alpha+%beta-%gamma)/2))/2, 0, 0, (cis((%alpha+%beta-%gamma)/2)+cis((%alpha-%beta+%gamma)/2))/2

If I understand correctly: cis, sin,cos,exp, andsqrt` are all standard functions that can be used in (at least) gate definitions, but they don't appear in the spec outside of the above example. It would be nice to document their existence, where they can be used, and if they are treated like other keywords.

stylewarning commented 1 year ago

Great idea. By the way, CIS(x) is $e^{ix}$.