Readout Calibration (RCAL)¶
This example illustrates how to generate readout calibration (RCAL) circuits and use them to correct readout errors in other circuits. While this example uses a simulator to execute the circuits, the same procedure can be followed for hardware applications.
The code below generates RCAL circuits for qubits
1, populates their
results using a simulator with readout error, and displays their confusion matrices.
import trueq as tq # generate RCAL circuits to measure the readout errors on qubits [0, 1] circuits = tq.make_rcal([0, 1]) # initialize a simulator with a 20% readout error on every qubit sim = tq.Simulator().add_readout_error(0.2) # run the circuits on the simulator to populate their results sim.run(circuits, n_shots=1000) # display the confusion matrices circuits.fit()
P(0 | 0) = 0.802
P(1 | 1) = 0.798
P(0 | 0) = 0.790
P(1 | 1) = 0.787
If your circuit collection contains RCAL circuits, then that information will be
used automatically to apply readout correction to your circuits when you call
The code below illustrates this for SRB circuits executed on a noisy
simulator with readout error. It also shows how you can view the results with and
without readout correction being applied.
# generate RCAL circuits to measure the readout errors on qubits [0, 1, 2] circuits = tq.make_rcal([0, 1, 2]) # generate SRB circuits to simultaneously characterize a single qubit  and # a pair of qubits [1, 2] with 30 circuits for each random cycle in [4, 32, 64] circuits.append(tq.make_srb([, [1, 2]], [4, 32, 64], 30)) # initialize a noisy simulator with a large 10% readout error sim = tq.Simulator().add_stochastic_pauli(px=0.01).add_readout_error(0.1) # RCAL generally needs more shots than the other protocols because it is estimating # an absolute value rather than a decay over randomizations, thus in this simulation # we use different amounts of shots for SRB and RCAL to populate their results sim.run(circuits.subset(protocol=["RCAL"]), n_shots=50) sim.run(circuits.subset(protocol="RCAL"), n_shots=1000) # plot the exponential decay with readout correction, # where each expectation value (dot) has been compensated circuits.plot.raw()
To avoid performing readout correction during analysis, we can remove all RCAL
circuits from the collection before calling
Notice that the y-intercept is lower than in the plot above.
# plot the exponential decay without readout correction circuits.subset(protocol="SRB").plot.raw()
Total running time of the script: ( 0 minutes 0.942 seconds)