How to perform a measurement in acqdp?

[gtaifu]

There are two classes (Measurement and PureMeas) in circuit.py. Since this simulator is based on tensor-network and density matrix, the effect of a measurement can be represented as a density-matrix update. To my understanding, this is the method acqdp adopts.

In some cases, we are only interested in the state vector update, where a measurement collapses the state vector and returns a single bit representing the measurement result. How could we do this in acqdp?

Thanks!

[cupjinhuang]

Hello gtaifu,

We have added two methods measure and collapse in acqdp.circuit.Circuit.

The method measure of a circuit takes an argument specifying the index of the qubit to be measured, and returns a random measurement result and the corresponding conditional quantum state. Two optional arguments include remove_qubit, indicating whether the qubit being measured is to be removed from the system, and collapse, indicating whether the returned conditional state still preserves the tensor network structure.

The method collapse evaluates a quantum circuit as a tensor network, and replace the tensor network structure with the value of it. Doing this simplifies the quantum circuit and makes state vector update more efficient. collapse now only supports quantum circuits that are states, i.e. quantum operators with no input wires.

Please let us know if those functionalities meet your need.

[gtaifu]

@cupjinhuang thank you! I think it should work for us. I will integrate it into our open-source simulation platform (pyqcisim). If there is any question, I will return to you!