On Wed, Jul 18, 2012 at 6:05 PM, Aaron Meurer <[email protected]> wrote: > On Wed, Jul 18, 2012 at 6:40 PM, Brian Granger <[email protected]> wrote: >> On Wed, Jul 18, 2012 at 12:13 PM, Aaron Meurer <[email protected]> wrote: >>> In my branch where I'm fixing expand, I've moved the base _eval_expand >>> functions to Expr. The result is that for expand to work on an >>> object, it must be rebuildable via obj.func(*obj.args). >>> >>> There are two classes in the quantum module that came up where this >>> doesn't work. One is OracleGate, which is built like OracleGate(2, >>> lambda qubits: qubits == IntQubit(2)), which produces the .args ((0, >>> 1), lambda qubits: qubits == IntQubit(2)) (in general, the first >>> argument n is converted to range(n)). The second is WGate, which >>> works like WGate(3), which produces the .args (2, 1, 0) (in general, >>> an argument n produces reversed(range(n))). >>> >>> I was able to change OracleGate to accept its args without ambiguity. >>> If the first argument is an integer, it does what it does now. If >>> it's a tuple, succeed if it's of the form of range(N) for some N. >>> >>> WGate cannot be fixed like this, though, because there is ambiguity >>> for WGate(0), which can be construed as either WGate(1) or WGate() >>> (range(1) or range(0)). >>> >>> Since I know very little about quantum computing and Grover's >>> algorithm, I'd like to know what the best way to fix this is. The >>> options are see are: >>> >>> - Make WGate(0) be construed as range(1). Currently WGate(0) doesn't >>> work, which leads me to believe that you can't have a gate with 0 >>> quibits. This would not require breaking the current API, but might >>> be confusing (?). >> >> You need to have at least 1 qubit for it to make sense. WGate(0) >> should really raise a ValueError. > > Right. WGate(0) would be the rebuild of WGate(1) (if that makes sense). > >> >>> - Break the API. Since any kind of break would be equally disruptive, >>> I would suggest moving to just storing n in .args, and constructing >>> reversed(range(n)) on the fly when it's needed. Alternately, we could >>> store (reversed(range(n)),), which would make it similar to >>> OracleGate. >> >> Yes, let's to that. Just make a property that returns >> reversed(range(n)) and use that when needed. > > OK. What should it be called? .quibits I guess. Should OracleGate > (and maybe others?) also be changed? I would call it target_qubits and OracleGate should have the same thing.
Cheers, Brian > Aaron Meurer > >> >> Does this answer your questions? >> >> Cheers, >> >> Brian >> >> >>> Aaron Meurer >> >> >> >> -- >> Brian E. Granger >> Cal Poly State University, San Luis Obispo >> [email protected] and [email protected] -- Brian E. Granger Cal Poly State University, San Luis Obispo [email protected] and [email protected] -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
