Error in Sampler counts

#1

Hi!

I’m running some simple tests in the QPU with Sampler. When I read the results, I get more counts than the number of samples I have assigned. Here is the code that I’m using:

rx_test = (pcvl.Circuit(2)
           .add(0, BS.Rx(theta= np.pi ))
           .add(0, BS.Rx(theta= np.pi )))

remote_qpu = pcvl.RemoteProcessor("qpu:ascella", token_qcloud) 
remote_qpu.with_input(pcvl.BasicState([1, 0]))
remote_qpu.set_circuit(rx_test)

sampler = Sampler(remote_qpu)

nsample = 10000
remote_job = sampler.sample_count(nsample)#['results']
remote_job

{'results': BSCount(int, {|1,0>: 106145, |0,1>: 25}),
 'physical_perf': 0.007833302204987094,
 'computed_circuit': <perceval.components.linear_circuit.Circuit at 0x7fe085ea9670>,
 'computed_input': |1,0,0,0,0,0,0,0,0,0,0,0>,
 'final_mode_number': 2}

The sum of counts in results should be 10000, but I get 106170, which is 96170 more counts than my parameter nsample

Is there any error in my code? Or another way of using Sampler?

Thanks for the help!

#2

Hello Victor,

We’re currently improving the way we control our hardware to be accurate to the sample, when asking for a specific count. However, as of today, we acquire slices of 1 second worth of samples and return them all, so if your job requires a lot less than 1s of acquisition, you’ll get a lot more samples than required. Your code is alright, the issue is on us and we’re about to fix it.

Thanks,
Eric

#3

Hi Eric,

Thanks for the answer!
When is the issue expected to be solved?

#4

Hi Victor,

I’m not sure as we need to test a lot before releasing. I’d say not before October.

Best wishes,
Eric