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? 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] -- 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.
