state_output

guppylang.std.debug.state_output(tag, *args) → None

Report the quantum state of the specified qubits.

This is a debugging function that works only when the program is executed on a supported simulator.

Guppy does not in general respect the order of function calls in the source code, it is constrained by the dataflow of the program. Whilst two state_output`s are guaranteed to execute in source-code order, function calls such as “pure quantum” gates that act on disjoint qubits can slide past each other. This can interact badly with entanglement since the guppy compiler does not know which qubits are entangled together. That is, a gate on a qubit may execute before (or after) a `state_output on another (potentially entangled) qubit, even when the gate occurs after (resp. before) the state_output in the source code. which can lead to unexpected results. To avoid this, use the barrier() command to ensure that all operations on a set of qubits are completed before the state is output.

Parameters:

• tag – A string literal representing the tag of the state output.

• args – The qubits whose quantum state is to be reported. The order they are given in corresponds to the order in which the state will be reported.