Error at First Access to Quantum-Circuit.COM using QPS Client about quantum-circuit

[perak]

@claudefalbriard is your qvm running? It should be running in another terminal, with following command:

qvm -c -S

[perak]

By the way, not related to this issue: there is a problem with FireFox - it doesn't show scrollbars in some pages, will be fixed. If you notice please report (in a new issue). Thanks 👍

[falbriard]

Thanks for the quick support. Indeed the process started with the command: qvm -c -S fixed the browser connectivity. After starting the process I get a log as followed:

127.0.0.1 - [2019-01-17 11:15:08] "POST /qvm HTTP/1.1" 200 12 "-" "python-requests/2.21.0"
[2019-01-17 11:19:57 [INFO]] [127.0.0.1 Session:2] Got "multishot" request from API key/User ID: NIL / NIL
[2019-01-17 11:19:57 [INFO]] [127.0.0.1 Session:2] Making qvm of 2 qubits
[2019-01-17 11:19:57 [INFO]] [127.0.0.1 Session:2] Running experiment with 1 trial on PURE-STATE-QVM
[2019-01-17 11:19:57 [INFO]] [127.0.0.1 Session:2] Finished in 3 ms
127.0.0.1 - [2019-01-17 11:19:57] "POST /qvm HTTP/1.1" 200 12 "-" "python-requests/2.21.0"

and at the browser console ouput log:
[[0]]

Question: For [ run ] where do I get the probability value for the two qubits that are part of my circuit, as shown at the simulation screen?

Yet another suggestion: A clear output window button could be helpful.

Thanks for clarification.

[perak]

@falbriard all looks good now :)

Browser console output shows measurement (looks like you have "measurement" gate on single qubit, thus you have single number as output: [[0]]).

Currently, qps-client is set to return output from measurement, it doesn't print probabilities. That functionality is planned but not implemented yet (idea is to have similar screen like "Simulate -> Browser" screen).

[perak]

(print probabilities is supported by Forest SDK/QVM but qps-client is not set to print that)

[falbriard]

Thanks so much, problem isolated and fixed.
I've manually updated the QASM code to generate two classical registers for storing the results of the measurements on two entangled qubits. Here is what I've done:

Result:
[[0 0]]

QASM Code:
OPENQASM 2.0;
include "qelib1.inc";
qreg q[2];
creg r[2];
h q[0];
cx q[0], q[1];
measure q[0] -> c[1];
measure q[1] -> r[1];

As previously tested the result is OK. Both of qubits flip its state together in an aleatory result.

Suggestion: The creation of a additional classical register could eventually be automated by a "drag" of the measurement arrow, to a point below the existing registers, much the way as CNOT is creating a second qubit.

[perak]

@falbriard it is possible to manipulate registers via Drag & Drop interface. Please see following video:

https://www.youtube.com/watch?v=4SfnwMr2aWg

There is green "plus" at the right side of the screen, next to word "Registers" (when no gate is selected) which allows you to add registers.

[falbriard]

Sorry, my fault, watched in the wrong screen corner. This is perfect and gives the control. thanks. Please close this issue, its solved. Will enjoy this tool, specially for training and education.

[perak]

Great, closing first issue! Glad you like it! Enjoy!